Rio Grande Plains

(Tamaulipan Brushlands)

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The Rio Grande (Tamaulipan) Plains has traditionally been interpreted by Texas workers as one of the state's vegetational (= land resource) areas. Some of Texas' vegetational areas like the Pineywoods, Blackland Prairies, Coastal Prairies and Marshes, and Post Oak Savanna were based on vegetation. Other land resource areas including the High Plains, Rolling Plains, Edwards Plateau, Trans-Pecos Basin and Range, and Rio Grande Plains were based on general--and often popularized--notions of geology, especially physiographic provinces and units thereof0. The land resource or vegetational area of Rio Grande Plains or, sometimes, South Texas Plains (as well as the whole Tamaulipan unit which also includes land in Mexico) is strictly speaking part of the West Gulf Coastal Plain physiographic province (Feneenman, 1938, ps. 100-120). The West Gulf Coastal Plain province extends to the Balcones Escarpment so that a clear delination exist between the Coastal Plain and the southeastern portion of the Edwards Plateau (which is in Great Plains physiographic province). Other distinctions between the Rio Grande Plains and other land resource or vegetational areas cannot be drawn so easily from physiographic provinces. The Lampasas Cut Plain, Grand Prairie, CrossTimbers, Blackland Prairie, and Pineywoods are also in the Western Gulf Coastal Plain.

As such, criteria for distinctions among and within vegetational areas must include (also on basis of definition) the key criterion of vegetation. Even the inclusion of and definition as to vegetation does not handily or readily define the Rio Grande Plains because vegetation of this designated area is considerably diverse. Even at larger-than-local spatial scale native plant communities of the Rio Grande Plains include several map units of natural vegetation (Kuchler, 1964; Kuchler in Garrison et al., 1977) as well as smaller vegetational units too small and scattered to be mapped conveniently. There are, of course, always arbitrary aspects to designation and description of vegetation not to mention objectives of, disciplinary perspectives of , and value judgments in Vegetation Science.

The physiographic province of Western Gulf Coastal Plain has geologic variables that further confound description and classification of natural vegetation in the Rio Grande Plains even over relatively small mapping space. The southern apex of this vegetational area includes the Rio Grande Embayment (Fenneman, 1938, p. 102) which is distinct from the rest of South Texas Plains.

Historically, the Rio Grande Plains of Texas has been interpreted as including the mesquite-acacia savanna (Andropogon-Setaria-Prosopis- Acacia), mesquite-live oak savanna (Andropogon- Prosopis-Quercus), and ceniza shrub (Leucophyllum-Larrea-Prosopis) designated in the USDA Forest Service version of Kuchler units of Potential Natural Vegetation (Garrison et al., 1977) as numbers 54, 55, and 38, respectively. Additionally, there are various forms of gallary and floodplain forests along the Rio Grande that are too small or local for mapping units of the size used by Kuchler (1964, in Garrison et al., 1977) but that are nonetheless forest cover (hence, range) types.

Range types of the Rio Grande Plains were treated below based on the "units of vegetation" or the "physiogonomic types" (Kuchler, 1964, p. 3) recognized by Garrison et al. (1977) and as consistent as possible with rangeland cover types described by the Society for Range Management (Schiflet, 1994) and forest cover types recognized by the Society of American Foresters (Eyre, 1980).

Location note and clarification- Much of contemporary Rio Grande Plains range vegetation is dominated by naturalized introduced (agronomic or domestic) grass species, most notably King Ranch bluestem (Andropogon ischaemum= Bothriochloa ischaemum var. songarica), buffelgrass (Pennisetum ciliare), and Lehmann's lovegrass (Eragrostis lehmanniana). Other important introduced grass species that have naturalized, at least at local spatial scales, in parts of the Rio Grande Plains include common bermudagrass (Cynodon dactylon), dallisgrass (Paspalum dilatum), kleingrass (Panicum coloratum), blue panicgrass (P. antidotale), and guineagrass (P. maximum).

Throughout the Tamaulipan Plains these introduced (exotic or alien) species--as either single species or in various combinations--were (still are, though at much lower incidences than previously) planted and used as either1) intensively managed tame pasture (agronomic or domestic field crops) or 2) extensively managed, introduced range, especially on severely depleted rangeland and former crop fields. In a third category, 3)--and now much more widespread situation--these introduced species naturalized to some degree or the other and either "took over" ranges or, at least, became plentiful over considerable acreages of range.

Ranges and pastures with introduced (= agronomic, domestic, domesticated, tame) grass species in these three general situations were covered in the chapter entitled, Introduced Forages- Grasses under the Grasslands heading.

Range plant communities featured in this chapter of Range Types of North America were dominated and comprised primarily of native range plant species. In some cases, the featured range vegetation had cover and density of some of these naturalized species ranging from infrequent, individual plants to substantial proportions of current and otherwise natural range plant communities.

Mixed Grass-Woody Legume Savanna

1. Rio Grande (= South Texas) Plains brush type— Degree and extent of woody vs. grass-dominated vegetation of the Rio Grande Plains is a long-debated subject. That woody plant cover has increased substantially at expense of original (pre-Columbian) grass cover due to 200 plus years of overgrazing and consequent reduction or complete cessation of fires is not contested by any knowledgeable, rational range student. It is the quantitative increase that is debated. Currently the prevalent consensus seems to be that the regional climax vegetation is a tall-shrub/short-midgrass savanna dominated by species of Acacia, mesquite (Prosopis glandulosa), guayacan (Porlieria augustifolia), lotebush (Ziziphus obtusifolia), white brush (Aloysia gratissima) in an open, woody upperstory and an open grassy understory of species ranging from tall grasses like seacoast bluestem to short grasses like curly mesquite and buffalo grass with numerous mid-grasses like silver bluestem, Paspalum species, windmill grasses (Chloris species), Arizona cottontop (Trichachne californica), tanglehead (Heteropogon contortus), the widespread pink pappusgrass (Pappophorum bicolor), and tobosagrass. Curly mesquite and red grama (Bouteloua trifida) are major species under continued close- and overgrazing as in this shot on a clay loam range site; tobosagrass is a less common dominant. The most common brush species represented here are blackbrush (Acacia rigidula) and guajillo (A. berlandieri) but huisache (A. farnesiana), guayacan, lotebush, and mesquite are common.Not pristine, but typical Fair to Good range condition class.

Texas A&M Rio Grande Plains Experimental Ranch, Maverick County, Texas. May. FRES No. 32. (Texas Savanna Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion.

*Note: In the classification of North American biotic communities by Brown et al. (1998) the Tamaulipan Plains was mapped as Tamaulipan Thornscrub (the biotic community, fourth hierarchial level) in which the potential natural vegetation would be Mixed Deciduous Series (fifth level) almost all of which is now Mesquite Disclimax Series due to range retrogression.

 

2. That the South Texas Plains is today one of Earth’s great brush patches is reflected in terms ranging from Tamaulipan Brushlands to simply “the brush country”. This gravely ridge range site is an Acacia complex dominated by blackbrush, guajillo, and screwbean or huischillo (A. tortuosa), and this is likely the climax plant community. This vegetation is often regarded as guajillo ridge and mixed brush uplands. It is a major vegetation subtype of this brush-grass savanna.

Chaparrosa Ranch, Zavalla County, Texas. May. FRES No. 32 (Texas Savanna Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mesquite Disclimax Series of Brown et al (1998). Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion, 31c (Griffith et al., 2004).

 

3. South Texas mixed brush type— Another community of the varied Rio Grande Plains is this range vegetation subtype dominated by guayacan, Berlandier wolfberry (Lycium berlandieri), and Texas persimmon (Diospyros texana). Bluewood or brasil (Condalia obovata) is a widely scattered associate. The herbaceous understory which should be abundant on this sandy loam range site is limited to red grama, pappusgrass, and the toxic leather-stem or rubber-plant (Jatropha dioica), a unique subshrub.

Chaparrosa Ranch, Zavalla County, Texas, May. FRES No. 32 (Texas Savanna Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia) variant; this cover type is extremely diverse with numerous subtypes. Mesquite Disclimax Series of Brown et al. (1998). Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion, 31c (Griffith et al., 2004).

 

4. Vegetation typical of much of the Rio Grande Plains under better management (not just a brush patch) and likely also characteristic of the original legume shrub—mixed prairie savanna.Robust huisache scrub as a savanna with a properly utilized herbaceous understory of silver bluestem, tanglehead, Arizonia cottontop, curly mesquite, red grama, buffalograss, pink pappusgrass, big sandbur or grassbur (Cenchrus myosuroides), and plains bristlegrass (Setaria macrostachya = S. leucopila).

Live Oak County, Texas.February.FRES No. 32 (Texas Savanna Ecosystem).K-54 (Mesquite-Acacia Savanna).Another variant of SRM 728 (Mesquite-Granjeno-Acacia). Huisache form of Mesquite Disclimax Series of Brown et al. (1998). Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion, 31c (Griffith et al., 2004).

 

5. Rio Grande Plains Mesquite-Huisache and Mixed Prairie Savanna—Current degree of use is heavy, but except for Texas wintergrass (Stipa leucotricha) and annual forbs like redstem filaree (Erodium cicutarium) forage species are dominant.Sparse mesquite and huisache with good cover of conspicuous proper grazing management.Most green plants are the introduced and naturalized bromes, rescuegrass (Bromus catharticus = B. unioloides) and Japanese chess (B. japonicus), that are being utilized during the winter/early spring seasons.

Atascosa County, Texas.February.Variant of SRM 728 (Mesquite-Granjeno-Acacia). Mesquite Disclimax Series of Brown et al. (1998). Southern Texas Plains- Texas Tamaulipan Thornscrub Ecoregion, 31c (Griffith et al., 2004).

 

6. South Texas-Tamaulipan Plains Shrub Savanna- With exception of the naturalized buffelgrass (Pennisetum ciliare), the tufts of grass in center foreground and at right margin, this is a classic composite shot of what is likely the climax or potential natural vegetation of the Rio Grande Plains. This relict area was sheltered from livestock grazing long enough to recover from range retrogression. It is a savanna of silver bluestem; multi-flower or four-flower trichloris (Trichloris pluriflora); plains bristlegrass (Setaria lecupila); numerous grama species including, hairy, Texas, red, and (rarely) sideoats; red and purple threeawns; buffalograss; with rare individuals of pink pappusgrass and little bluestem as a species-rich understory in a diverse shrub layer that includes guayacan or Texas porlieria (Guaiacum aungstifolium), huisachillo or twisted acacia (Acacia tortuosa= A. schaffneri according to some authors), allthorn goatbush or amargosa (Castela texana), Berlandier wolfberry, tomatillo or cilindrillo (Lycium berlandieri), Spanish dagger (Yucca treculena) plus of course the ever-present honey mesquite and huisache which are rare on this relict site (but which dominate the depleted range on the horizon which appears as a thin green line).

Live Oak County, Texas, October (after a severe drought). FRES No. 32 (Texas Savanna Ecosystem), K- 54 (Mesquite-acacia savanna), SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of the climax form of Tamulipan Thornscrub biotic community of Brown et al. (1998). Southern Texas Plains-Texas-Tamaulipan Thornscrub Ecoregion, 31c (Griffith et al., 2004).

 

7. Rio Grande Plains shrub-grass savanna- The Tamaulipan savanna or brushlands as it likely appeared before three- plus centuries of overgrazing (by every species of livestock imaginable), fire suppression, trade routes, oil-gas development, etc. This is a closer view of the remarkably diverse range plant community shown in the previous landscape shot. Specific Gramineae species in the foreground include tumble windmillgrass (Chloris verticillata), plains bristlegrass, silver bluestem, red threeawn, slender grama (Bouteloua repens= B. filiformis), needle grama (B. aristidoides), and bufflegrass. The two conspicuous shrubs are: guayacan (shorter shrub on left) and amargosa (taller shrub on right). Live Oak County, Texas, October (after severe drought). FRES No. 32 (Texas Savanna Ecosystem), K-54 (Mesquite-Acacia Savanna), SRM 728 (Mesquite-Granjeno-Acacia). Mixed Decicuous Series of Brown et al. (1998). Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion, 31c (Griffith et al., 2004).

The South Texas Chaparral or Rio Grande Plains "brush country"-- Texas-Tamaulipan Thornscrub Ecoregion 31c; Kuchler No. 54 (Mesquite-Acacia Savanna) -- is remarkably diverse with several range subtypes and numerous range sites, notwithstanding the monotous appearance of a mostly brush-infested landscape. Apparent homogenity of general appearance (physiogonomy and structure) of the south Texas shrubland may be a reason why the Society for Range Mangement (Shiflet, 1994) described only the Mesquite-Granjeno-Acacia rangeland cover type (SRM 728) for this farflung range area. (Another reason for this paucity of cover type titles and descriptions is likely that nobody saw fit to "write them up" or submit them for incluision in the official societal publication.) Nonetheless, there are many different range plant communities that comprise Rio Grande Plains range vegetation.

Many (probably most) of these range types, including some subtypes and variants of SRM 728, are disturbance climax types. This fact alone allows for essentially limitless variations in range vegetation. There are, however, undoubtedly other range cover types that are climax vegetation especially when interpreted from the Tanslian polyclimax perspective. This includes cover types (or, probably the most precise designation, subtypes) within what has been called generally the "mixed brush type".

Two of the more common forms, types, or, according to Scifres (1980, p. 32), subtypes of Rio Grande Plains shrublands (South Texas Chaparral) are: 1) guanjillo-ridges and mixed-brush uplands and 2) hardlands vegetation (Scifres, 1980, ps. 32-34). Examples of these two range cover types (= subtypes) were given immediately below.

8. The following four photographs of range vegetation portrayed the typical guajillo ridges and mixed brush uplands type (= subtype) of the generic "mixed brush type" of the South Texas Chaparral. Scifres (1980, ps. 32-33) described this rangeland vegetation as comprised of "almost pure stands" of guajillo on shallow, stoney soils like gravelly ridges or rock outcrops with downslope gradations of vegetation into various range communities distinguished and dominated by various Acacia species such as twisted acacia and blackbrush as well as honey mesquite, granjeno or spiny hackberry, and lotebush along with less common species including Berlandier wolfberry, javelina bush (Condalia ericoides= Microrhamnus ericoides), cenizo (Leucophyllum frutescens), agarito (Berberis trifoliolata= Mahonia trifoliolata), Yucca spp., and whitebrush or beebush (Aloysia lycioides= A. ligustrina= A. gratissima= Lippia lycioides), the latter of which often forms "dense, almost pure stnnds" on deeper, more fertile soils like those of bottomlands.

Some of the most common grasses included Chloris and Paspalum species (Scifres, 1980, p. 31). Thomas (in Gould, 1962, p. 11) listed genera and, less commonly, species of grasses as to sandy loam, clay and clay loam, and saline soils. Gould (1975, p. 11) more or less followed the descriptions of Thomas (in Gould, 1962) but in even more abbreviated form. Based on usually brief reference accounts by various authors it appeared that grasses on range types and sites of the Rio Grande Plains brush ranges were less distinctive and diagnostic than major woody species.

"Conspicuous by their absence" (rarity would be a more precise description) were honey mesquite and huisache, the sterotypic dominants over much of the "brush country" of the Rio Grande Plains. In fact, the remarkable rarity of these two ubiquous woody legumes strongly suggsted that this was not an example of the typical brush-infested deteriorated range. Dominance by guajillo and cenizo was consistent with relative scarcity of mesquite and huisache and with the description cited above from Scifres (1980, ps. 32-34) in which it was concluded that "... the vegetation, even before the coming of of the white man, was low-growing brush of a variety of species" though "...such low-growing woody plants have increased in density with the activities of civilization (Scifres, 1980, p. 32).

 

8. Guajillo-mixed brush uplands- On this stoney ridge-sandy loam soil habitat a mixed shrub form of South Texas Chaparral was co-dominated by guajillo and cenizo (dark-green, compound-leafed shrub at right and grey or silvery shrub at left background, respectively). Major associate species was whitebrush (light-brown, largely leafless shrub in foreground), but also present was broom snakeweed (Gutierrezia sarthrae), Torrey croton (Croton torreyanus= C. incanus). Grasses were very sparse. Most common Gramineae species were shortspike windmillgrass (Chloris subdolichostachya) and silver bluestem. The most common forb was the annual species Texas croton or tinajera (Croton texensis).

Live Oak County, Texas. October, autumnal aspect. FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub subdivision (biotic community) of Brown et al. (1998). Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion 31c (Griffith et al., 2004).

 

9. A diverse brush patch- Another view of range vegetation in the example of the guajillo ridges and mixed brush uplands subtype presented in the preceding slide. In addition to guajillo, cenizo, whitebrush, broom snakeweed, and Torrey croton visible in that photograph, this sample included Spanish dagger, Texas persimmon (Diospyros texana), and agarito. Cover and density of grass species were also greater than in the "photo-plot" of the preceding slide.

Live Oak County, Texas. October, autumnal aspect. FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub subdivision (biotic community) of Brown et al. (1998). Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion 31c (Griffith et al., 2004).

 

10. Chaparral thicket in South Texas Plains- This third view of range vegetation on a guajillo ridges and mixed brush upland subtype "sported" more of the conspicuous Texas persimmon (shrubs with white-barked trunks or shoots) along with guajillo, cenizo, whitebrush, Torrey croton, agarito plus some blackbrush and granjeno or spiny hackberry (= Celtis pallida, Celtis spinosa var. pallida, Celtis tala var. pallida), and shrubby blue sage (Salvia ballotrifolia). The most common grasses (and these were "few and far between") were silver bluestem and shortspike windmillgrass. Potential grass species were those that were present in strips of grassland vegetation maintained by mechanical treatment which was presented in the immediately succeeding photograph.

Live Oak County, Texas. October, autumnal aspect. FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion 31c (Griffith et al., 2004).

 

11. Will the real Rio Grande Plains savanna vegetation "please stand up"?- A swath through an otherwise dense stand of shrubs on a guajillio ridge-mixed brush uplands range type had been maintained by shredding (mechanical control by use of shredder or rotary mower). Was the mechanically maintained grassland or the otherwise-present shrubland the real climax vegetation. Or was climax (= potential natural vegetation) a savanna of varying plant community structure but of a botanical composition made up of all native species (woody and hebvaceous species)?

Dominant grasses in the swath of grassland were shortspike windmillgrass and silver bluestem. Also present was little bluestem, perennial threeawns of the Aristid purpurea complex, buffalograss, curly mesquite, reverchon bristlegrass (Setaria reverchonnii), plains bristlegrass (S. leucopila), hairyseed paspalum (Paspalum publiflorum), and, rarely, tanglehead (Heterpogon contortus).

Live Oak County, Texas. October, autumnal aspect. FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion 31c (Griffith et al., 2004).

9. The following set of three photographs depicted the hardlands vegetation subtype of the Rio Grande Plains general mixed brush type. In describing this range vegetation Scifres (1980, p. 34) specified that the shallow soils of this subtype had calcareous deposits close to their surfaces. Dominant shrubs included blackbrush, guajillo, twisted acacia, and other Acacia spp. while other common woody species included granjeno or spiny hackberry, cenizo, lotebush, and knifeleaf condalia (Condalia spathulata). Woody shrubs present in lesser proportions included Berlandier wolfberry, javelina bush, agarito, Texas persimmon, cactuses, Yucca spp., and and lime prickly ash (Zanthoxylum fagara).

The extremely limited density, cover, and relative proportions of mesquite and huisache suggested that this range plant community was not just another example of an overgrazed, underburned, gone-to-brush, degraded range. While density and cover of woody plants had almost assuredly increased from pre-Columbian conditions (this was afterall Texas with its several centuries tradition of overuse and overgrazing of ranges), this "photo-quadrant" sample probably represented an example of more-or-less natural Rio Grande Plains savanna on a shallow caliche habitat.

The various references cited above for guajillo ridges and mixed brush uplands subtype also applied for the hardlands subtype with specific Gramineae species obviously varying by range site.

 

12. Hardlands Rio Grande chaparral- An extremely shallow, primarily clay soil that was overlaid by an interrupted calcareous layer (caliche) provided an edaphic environment conducive to development of a remarkably diverse range plant community. Guajillo and cenizo were the most abundant species, but there were not obvious dominants. Rather this example of the hardlands chaparral subtype of "mixed brush" was mostly an "equal parts" mixture of knifeleaf condalia, Berlandier woldberry, cilindrillo or tomatillo, javelina bush, granjeno, agarito, Spanish dagger, blackbrush, myrtle-croton or southwest bernardia (Bernardia myricifolia), and the cactus known variously as Texas or Englemann or Lindheimer pricklypear (Opuntia englemannia var. lindheimeri= O. lindheimeri) as well as guajillo and cenizo.

There was an herbaceous understorey made up almost exclusively of buffalograss. There was--not surprising-- a DYC (damn yellow composite), bristleleaf dogweed (Dyssodia tenuiloba= Thymophylla tenuiloba= Boebera tenuiloba).

Live Oak County, Texas. October, autumnal aspect. FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion 31c (Griffitth et al., 2004).

 

13. Rio Grande Plains mixed shrub-shortgrass savanna- Range vegetation portrayed here represented the deciduous shrub-mixed prairie savanna in something resembling what was interpreted by prominent ecologists (Kuchler, 1964, p. 61; Scifres, 1980, ps. 30-34) as natural or climax vegetation. Shrubs were almost certainly somewhat more plentiful than in the virgin vegetation, but this was about as good an approximation as can usually be found. The herbaceous understorey was a consociation of buffalograss. Past overgrazing may have greatly reduced less grazing-tolerant grasses like little bluestem, silver bluestem, sideoats grama, pink pappusgrass, and bristlegrasses leaving an herbaceous layer consisting exclusively of a shortgrass species. Buffalograss might likely have been the predominant --though not the only-- grass even in pristine condition on this shallow clay soil.

Physiogonomy, species composition, and range community structure appeared to approach what was described as virgin range vegetation. This example of the hardlands subtype of Rio Grande Plains savanna matched closely the description of Class 2 of the Texaas Savanna Ecosystem given by Garrison et al. (1977, p. 40). The range vegetation presented in this present photograph and in the close-up photograph immediately below matched closely the vegetation in the photograph used by Kuchler (1964, p. 61) as an example of the potential natural vegetation. The example shown by Kuchler (1964, p. 61) was of range vegetation that obviously was on deeper soil and-- as evidenced by presence of numerous very young mesquite saplings-- that had been recently invaded by the dominant, defining species.

Live Oak County, Texas. October, autumnal aspect. FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub subdivision (Brown et al., 1998). Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion 312c (Griffith et al., 2004).

 

14. Interior of hardlands subtype of Rio Grande Plains mixed shrub chaparral- Close-in view of Tamaulipian Thornscrub vegetation that developed on a caliche outcrop, shallow, clay soil in South Texas Plains vegetational area. Herbaceous layer was a consociation of buffalograss. It was likely that taller, less grazing-tolerant grasses like little bluestem, silver bluestem, sideoats grama, and plains bristlegrass had been reduced to near elimination by overgrazing, but there was no scientific proof of such range retrogression. Conspicuous shrubs were nopal or Texas or Lindheimer pricklypear and Spanish dagger. Other woody species included granjillo, Berlandier wolfberry, agarito, knifeleaf condalia, cenizo, granjeno or spiny hackberry, and javelina bush.

Live Oak County, Texas. October, autumnal aspect. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion 31c (Griffith et al., 2004).

 

15. (In)famous "Texas brush country"- Show in these three slides and several slide/caption units below were some views of contemporary anthropogenic brush vegetation and some component plant species in the northwestern Rio Grande Plains of south Texas. The first two of these three images presented in this unit showed the overall or synopsis view of the classic "south Texas mixed brush type", a man-made range type resulting from various combinations of overgrazing, underburning, cultivation, transportation, (i.e. road-building), species introduction, and climate change (not necessarily in this order of cause and maintenance). Major range plant species in these two slides (in approximate order of cover) were the shrubs: blackbrush, guajillo, Lindheimer pricklypear (Opuntia lindheimeri), granjeno or spiny (or desert) hackberry (= Celtis pallida, Celtis spinosa var. pallida, Celtis tala var. pallida), guayacan, honey mesquite, Spanish dagger or Torrey yucca (Yucca treculeana= T. torreyi), tasajillo (Opuntia leptocaulis), cenizo (leucophyllum frutescens), and leatherstem (Jatropha dioica). Most abundant forbs were bristleleaf dogweed (Dyssodia tenuifolia) and western ragweed (Ambrosia psilostachya). Grasses were limited but the main species included Hall's panicgrass (Panicum hallii subsp. hallii), red grama (Bouteloua trifida), and silver bluestem (Andropogon saccharoides= Bothriochloa saccharoides).

The third image presented a closer-in view of fewer plant species including Lindheimer's pricklypear, blackbrush, guajillo, guayacan, leatherstem, western ragweed, Hall's panicgrass, red grama, and silver bluestem.

This range vegetation was an example of the Rio Grande mixed brush-grass savanna that had gone mostly to shrub cover (ie. gone to Hell brush).

Yes, the vast majority of Texas range--in all vegetational or land resource areas--is brush-infested (Scifres, 1980, ps. xi, 3. 9), but unless otherwise specified, in Texas "brush country" means the Rio Grande or South Texas Plains. This is the epitome of brush invasion and noxious range plant communities.

Furthermore, it has been shown by many studies and now widely recognized that grassland or grass-shrub savanna range in the Rio Grande Plains that through human action (or inaction) has been converted to brush woodlands that become "steady states" much like the pre-Columbian climax grasslands or shrub savannahs (Hamilton et al., 2004, p. 6). Actually, it was relatively early in Range Management education and our understanding of range degradation that the static nature of Rio Grande Plains brushlands was described and regarded as human-induced vegetation. Specifically, this more-or-less permanent state of retrogression became textbook knowledge by the second edition of the classic McGraw-Hill text, Plant Ecology (Weaver and Clements, 1938). These two giants of early plant succession wrote that while this range vegetation "... has all the appearance of a true climax", "[a] study of the effects of fire and graxing... and succession makes it clear that ... it is really a proclimax associes that has greatly increased in extnet during the historical period" (Weaver and Clements, 1938, p. 537).

The "proclimax associes" was terminology of the then-prevalent Clementsian monoclimax theory. In this context, the Rio Grande Plains brush community was most specifically a "disturbance climax" or, simply, "disclimax" (Clements, 1936, p. 70; Weaver and Clements, 1938, ps. 86-88). The term "disturbnce climax" clearly indicated that such plant communities were here for the duration (as the expression goes) barring human intervention--what Weaver and Clements (1938, ps. 247-249) termed "reaction" and "coaction" (as in grazing and fire)--to counteract the previous and typically still prevailing human disturbance. "The damage once done, it can only be repaired by man turning to the use of coactionand reaction for constructive rather than destructiv effects" (Weaver and Clements, 1938, p. 249).

"Brush-dominated rangelands will not revert to productive rgrasslands or savannas if livestock grazing is reduced or even totally eliminated. The conversion of woodlands back to grasslands requires sustained human intervention, including brush removal (with reseeding in many cases), maintenance or follow-up control practices, and proper livestock grazing management" (Hamilton et al, 2004, p. 6). This was the amplified echo of Weaver and Clements (1938) textbook two-thirds of a century earlier.

It was not written or implied to just take the cows off and the virgin vegetation will return (at least not in human time scale).

The question becomes, Will it be cost-effective to resort to the Herculean efforts that will be required to restore some semblance of the former grasslands and savannas? Perhaps the question should be rephrased, Will it be cost effective to keep the range, to pay taxes on the land without some degree of restoration?

Anyway, the following set of slides and captions presented some scenes from one of the worst brush patches on the planet. (Enjoy, or otherwise.)

Duval County, Texas. Early October, autumnal aspect. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Clay Flat range site (Natural Resources Conservation Service, 2011), Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion 31c (Griffith et al., 2004).

 

16. Another part of the same brush patch- Two more "photo plots" of the Rio Grande Plains range plant community introduced in the preceding three-slide/caption set. In these two slides honey mesquite comprised more of the woody plant cover. Otherwise range vegetation still consisted largely of guajillo, blackbrush, Lindheimer pricklypear, granjeno or spiny hackberry, guayacan, Spanish dagger or Torrey yucca, guayacan, tasajillo, cenizo, and leatherstem. Forbs and grasses were more limited than in the range vegetation seen in the immediately preceding photographs but still consisted of bristleleaf dogweed, Hall's panicgrass, and red grama plus the additional grass species of Reverchon's panicgrass(Panicum reverchonii) or Reverchon's bristlegrass (Setaria reverchonii) and the naturalized buffelgrass (Pennisetum ciliare).

Duval County, Texas. Early October, autumnal aspect. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Clay Flat range site (Natural Resources Conservation Service, 2011), Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion 31c (Griffith et al., 2004).

 

17. Another view of the Rio Grande Plains mixed brush type- This "photo plot" showed plant cover and density of a a local brush community dominated by blackbrush, guajillo, and Lindheimer's pricklypear in the same brush patch described in the two immediately preceding slide/caption sets. An example of the ultimate disturbance climax of the Tamaulipan Plains, what had once been largely a grass-shrub savanna with large areas of open grassland.

Duval County, Texas. Early October, autumnal aspect. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Clay Flat range site (Natural Resources Conservation Service, 2011), Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion 31c (Griffith et al., 2004).

 

18. Red cattle in black brush- White-faced Brahman-based cows and calves curiously peering out from the edge of a typical example of Rio Grande Plains or Tamaulipian Plains scrub (scrubland= shrubland) in the western portion of what is known also as the South Texas Plains. This shrub community was dominated by blackbrush (Acacia rigidula) with honey mesquite as the associate species. Granjeno or, the less common English colloquial name, spiny hackberry (Celtis pallida) was the third most abundant woody plant species based on relative foliar or canopy cover. A commonly used general designation for this "brush country" vegetation is Tamaulipian Thornscrub. Blackbrush-dominated thornscrub is one of the more common subtypes or forms of this thornscrub range cover type.

This two photographs shown here and the four slides shown in the next two slide/caption sets presented this particular shrub stand or local shrubland community from the edge of a local South Texas Plains grassland. This grassland was a form of mixed prairie in Fair range condition class. The dominant grass species was white tridens (Tridens albescens) with curly mesquite (Hilaria belangeri), pink pappusgrass (Pappophorum bicolor), naturalized King Ranch bluestem (Andropogon ischaemum= Bothriochloa ischaemum var. songarica), Reverchon's panicgrass or Reverchon's bristlegrass, slimspike windmill grass (Chloris andropogonoides), and naturalized bermudagrass (Cynodon dactylon) as other major grasses. Forbs, other than common broomweed (Gutierrezia draculoides), were of no consequence (essentially absent).

Atascosa County, Texas. Early October, autumnal aspect. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Clay Pan Prairie range site (Soil Conservation Service, 1980), Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion 31c (Griffith et al., 2004).

19. White bovine faces with white bark of black brush- Cows and calves of predominately Hereford X Brahman breeding accentuated this local stand of blackbrush-dominated Tamaulipian Thornscrub in the western Rio Grande Plains or Tamaulipian Plains of south Texas. Honey mesquite and granjeno or spiny hackberry ccomprised most of the rest of the woody cover. A relict of mixed prairie in Fair range condition class (described immediately above and below) was at this outer edge of an extensive thornscrub community.

Atascosa County, Texas. Early October, autumnal aspect. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Clay Pan Prairie range site (Soil Conservation Service, 1980), Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion 31c (Griffith et al., 2004).

 

20. An example of what it could be (once was except for being better back then)- South Texas Plains mixed prairie along the perimeter of the blackbrush-dominated scrub presented immediately above. Periodic mowing (rotary shredding) had maintained this grassland that was alternatively dominated by white tridens in some microsites or curly mesquite in other microhabitats. Other important grasses included pink pappusgrass, slimspike windmillgrass, naturalized King Ranch bluestem, Reverchon's panicgrass or Reverchon's bristlegrass, and naturalized bermudagrass. An occasional plant of common or annual broomweed represented the forbs.

This mixed prairie was in Fair range condition class with most of the major climax (decreaser) grass species absent, at least for all managerial purposes. The potential decreasers that were effectively absent included (among others) silver bluestem (Andropogon saccharoides= Bothriochloa saccharoides= B. laguroides), two-flower trichloris (Trichloris crinita) and four-flower trichloris (T. pluriflora), plains bristlegrass (Setaria leucopila), sideoats grama (Bouteloua curtipendula), and vine mesquite (Panicum obtusum). It was notable that the introduced bufflegrass which is widely naturalized throughout the Rio Grande Plains was also absent from this local grassland.

The land surface or microtopography of this clay-soil mixed prairie was a form of gilgi commonly called "hog wallow". This pattern of microrelief is more common in the Texas Blackland Prairie, but it also occurs on some of the more clayey soils of the Rio Grande Plains such as that seen here. Alternate shrinking and swelling of high-clay content soils is regarded as the main factor responsible for this phenomenon.

This local mixed prairie was a mere remnant--and it only in Fair range condition class--of the once-vast grassland of the Rio Grande Plains. As a remnant of that former grassland that had been converted to a brush disclimax this remaining mixed prairie could be viewed as relict vegetation. The Society for Range Management (Kothmann (1974) efined relict as "a remnant or fragment of a flora that remains from a former period when it was more widely distributed". It is often assumed that relict vegetation is a its state of potential natural vegetation (typically, climax). In this instance, range vegetation of this mere fragment of the former climax Rio Grande Plains prairie was far from climax, but even if it was only inFair range condition class did serve as enough of a vegetational benchmark to show that grassland and not anthropogenic shrubland (ie. brush) was the ecological potential.

Incidentally, the Spanish term chaparral has frequently been applied to Rio Grande Plains brush fields. Given that California chaparral and various types of climax shrubland such as Arizona or interior chaparral are climax scrub types and traditionally have been formally designated as chaparral (Shiflet, 1994), the use of chaparral in reference to Tamaulipian Thornscrub or Rio Grande Plains mixed shrub community was avoided in this publication. South Texas Plains or Tamaulipian Plains mixed brush is another proper and less ambiguous dsignation. Brush is an appropriate title given that range vegetation with excessive--in excess of that of the climax vegetation--woody cover is brush and not (in contrast to California and Arizona chaparral cover types) climax shrubland.

It is brush, dammit. Almost all successional evidence indicates that climax plant communities of the Rio Grande Plains is either grassland with site-specific patches of climax scrub or a grass-shrub savanna. The earliest accounts of explorers and, later, of frontier travelers (see Inglis, 1964) proved this (at least about as conclusively as it is possible to descriptively reconstruct the Pre-Columbian range vegetation).

Atascosa County, Texas. Early October, autumnal aspect. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Clay Pan Prairie range site (Soil Conservation Service, 1980). Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion 31c (Griffith et al., 2004).

 

21. Fair sward- The turf of the local Rio Grande Plains mixed prairie that was introduced and described in the three immediately preeding slide/caption sets. The species composition of this local grassland was comprised of either white tridens or curly mesquite (depending on microsite) as the dominant (white tridens was dominant on more moist microsites) and with pink pappusgrass, slimspike windmillgrass, naturalized King Ranch bluestem, Reverchon's panicgrass or Reverchon's bristlegrass, and naturalized bermudagrass making up almost all of the remaining cover. For whatever reasons, naturalized buffelgrass was not present. There were a few plants of annual broomweed although none were in this "photo plot".

The microtopography of this grassland was a form of gilgi commonly known as "hog wallow". Seasonal shrinking and swelling of this high-clay content soil is the believed to be the main factor that causes this microrelief. White tridens was dominant in depressions of the gilgi (bottoms of the "hog wallows") of this grassland surface whereas curly mesquite was dominant on the slightly higher and substantially drier small ridges and areas farther from the depressions ("hog wallows").

Atascosa County, Texas. Early October, peak standing crop. Clay Pan Prairie range site (Soil Conservation Service, 1980). Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion 31c (Griffith et al., 2004).

 

22. Another and but less dense ptach of blackbrush scrub- Another Rio Grande Plains shrubland (mixed brush) community dominated by blackbrush and with honey mesquite and granjeno or spiny hackberry as associate species plus Brazil, bluewood, or Brazilian bluewood (Condalia obovata= C. hookeri); Texas paloverde or border paloverde (Cercidium texanum= Parkinsonia texana), Texas or Lindheimer's pricklepear, and tasajillo or Christmas cholla as other major shrub species.

This stnd of mixed brush was somewhat more open (had less woody plant or crown cover) than the blackbrush-dominated vegetation described above. Consequently, there was also greater herbaceous cover, almost all of which was grass, in this stand of Tamaulipian Thornscrub. The major grasses (in this relative rank of composition based on herbaceous cover): curly mesquite, pink pappusgrass, purple threeawn (Aristida purpurea), slimspike windmillgrass, red grama, and the two naturalized exotics, King Ranch bluestem and buffelgrass. Forbs were, for practical purposes, absent.

Cover of lichen in crowns of shrubs, especially blackbrush, was extensive (lichen species were treated below).

Atascosa County, Texas. Early October, autumnal aspect. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Shallow range site (Soil Conservation Service, 1980). Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion 31c (Griffith et al., 2004).

 

23. "Purty brushy"- Veteran vaqueros would describe thick brush like that seen here with descriptions like the one given (plus lots of explictives). This is the sort of thorn scrub characteristic of "south Texas brush country". This image was a more detailed "photo plot" of interior of the patch of blackbrush-dominated disclimax scrub described in the immediately preceding two- slide/ caption set. Blackbrush was the dominant range plant, but it was accompanied by honey mesquite; granjeno or spiny hackberry; Brazil, bluewood, or Brazilian bluewood; and Texas paloverde or border paloverde.

Grasses, which were not discernible in this slide, included curly mesquite, pink pappusgrass, slimspike windmillgrass, purple threeawn, and red grama.

Various lichen species were very abundant in the crowns of these shrubs, in particular blackbrush. (Lichen species were presented below.)

Atascosa County, Texas. Early October, autumnal aspect. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Shallow range site (Soil Conservation Service, 1980). Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion 31c (Griffith et al., 2004).

 

24. Partnerships on blackbrush- Three species of lichen on limbs of blackbrush growing in the stand of blackbrush-dominated mixed brush presented in the two immediately preceding slide/caption sets. Identifiable species were a crottle or skull lichen (Parmelia perforata), a foliose lichen; cartilage lichen (Ramalina calicaris= Parmeila calicaris), a fruticose lichen; and slender-orange-bush (Teloschistes exilis), fruticose lichen. All these species are in family, Teloschistaceae and order, Lecanorales, although there is some controversy regarding taxonomic treatment of these lichens.

Atascosa County, Texas. Early October, autumnal aspect.

 

25. Skulls and cartlidge on white bark of blackbrush- Limbs of blackbrush covered by the foliose crottle or skull lichen and the fruticose cartilage lichen. These two lichen species, which were growing on blackbrush shown immediately above, were presented at closer camera distance to show general morphology of these range plants. (This old-taxonomy schoool rangeman regarded every "botanical being"--algae, fungus, lichen, bryophyte, and spermatophyte--as range plants.)

Atascosa County, Texas. Early October, autumnal aspect.

 

26. Silver in blackbrush- Female silver garden spider (Argiope argentata) in her web at terminal end of blackbrush leaders. This species, which is also called the silver argiope, is widespread and common (by spider standards anyway) in the Rio Grande Plains. The specific epithet, argentata, is Latin in reference to the English word, silver. Farther to the north the more common and slightly larger sister spider species is the golden or yellow garden spider (Argiope aurantia).

 

27. Natural versus brush-infested- Two range plant communities on the same lowland habitat ( Clay Flat range site): 1) native Rio Grande Plains mixed prairie at peak standing crop (foreground) and 2) degraded, brush-infested mixed prairie (background). There were three prominent layers of herbaceous vegetation (and there was not a woody component) in the natural grassland. A tallgrass layer or zone was comprised almost exclusively by alkali sacaton ((Sporobolus aeroides). A midgrass layer or intermediate zone consisting of slimspike or, sometimes, bluestem windmillgrass (Chloris andropogoides), the dominant midgrass species; pink pappusgrass; and Reverchon's panicgrass or Reverchon's bristlegrass (in that relative order based on cover and shoot density). A shortgrass layer was made up exclusively of curly mesquite (Hilaria belangeri).

The relict grassland was preserved as an unusually wide state highway right of way on which routine cutting by rotary shredders had permitted this three-herbaceous-layer mixed prairie to thrive while preventing establishment of shrub or tree species. Yes, there was a well-maintained barbed wire fence hidden from view right behind the tall, dense grass cover of the relict mixed prairie. This was the condition and "instructural forum" known as a fenceline contrast.

The deteriorated, brush-invaded grassland in the background had these same species, including large areas dominateed by alkali sacaton, but the native slimspike windmillgrass, along with alkali sacaton , pink pappusgrass, Reverchon's panicgrass or Reverchon's bristlegrass, and curly mesquite were "overwhelmed" by the two introduced and now naturalized species, King Ranch bluestem and bufffelgrass. Of most ecologican and managerial significance, however, was excessive woody cover most of which was honey mesquite with Texas or Lindheimer's pricklypear and whitebrush or beebush (Aloysia gratissima) as associate woody (shrub) species.

Taken overall, this Clay Flat range site in the northwestern Rio Grande Plains had about as much relative grass cover (relative to brush cover) as any range that this rangeman could find in an all day-drive throughout this area. (Actually, a three-day reconnaissance survey throughout the western Rio Grande or Tamaulipan Plains produced the same situation except, as ahown below even more brush in some areas.) Based on historic accounts by explorers, freighters, and common travelers, this entire Rio Grande Plains region was once a mosaic of grassland, grass-shrub savanna, and local dense woody patches. For roughly the last two centuries most of it was converted to "brush country" under influence by the white man (various Caucasian or Caucasoid races and nationalities versus Mongoloid racial stock of the American Indians). (More discussion on this phenomenon below.)

Anyway, it's Texas "brush country" range when this is the closest to clearest (limited woody cover even if not free of shrubs and trees) there is.

Dimmit County, Texas. Early October, autumnal aspect. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Clay Flat range site (Soil Conservation Service, 1985c), Southern Texas Plains- Texas-Tamaulipan Thornscrub Ecoregion 31c (Griffith et al., 2004).

 

28. Dominant (sole representative) of the tall zone- Alkali sacaton (Sporobolus aeroides) constituted the tallgrass layer of a climax mixed prairie that had developed on a Clay Flat range site in the northerwestern Rio Grande Plains. From perspective of height morphology, alkali sacaton defies descriptions like tallgrass or midgrass species because height of individuals of this species varies greatly depending upon, among other factors, soil characteristics, especially water content and water holding capacity. Gould (1975, ps. 299-300) described height of alkali sacaton in Texas as varying from about one and a half to five feet. Plants in these images that were growing on a high-clay, variably high- water content soil varied from two and a half to slightly over three feet in height. In the range plant community of which these plants made a distinctive herbaceous layer above those of midgrasses and a shortgrasses, alkali sacaton grew as a tallgrass form (a tallgrass ecotype).

Undoubtedly, there is considerable genotypic and ecotypic variation among individual plants and populations, respectively, in this widely distributed species. Plus, there is bound to be phenotypic plasticity and, hence, morphological variation in the same genotype from one year to the next in this cespitose perennial. Perhaps in some drought years shoots of these alkali sacaton genotypes did not grow to typical tallgrass height. Most likely, however, their shoots will still be above those of most midgrass plants so there would still be a layer above plants of pink pappusgrass and Reverchon's panicgrass or Reverchon's bristlegrass.

Alkali sacaton is widely throughout western North America occurring in all seventeen western range states and British Columbia and extending as far east as Missouri and Arkansas plus a few sporatic populations in New York.

Alkali sacaton is generally regarded as a cespitose or tufted species (Correll and Johnston, 1979, p. 219)--as is the case for all Sporobolus species--but the bunchgrass habit of alkali sacaton is not as pronounced as it is in most bunchgrass species.

Dimmit County, Texas. Early October; peak standing crop, grain-ripe phenological stage.

 

29.Tops of a tall form- A large open panicle of almost two feet in length (first slide) and a portion of that panicle showing its branching pattern (second slide) of alkali sacaton that comprised a tallgrass layer in a climax mixed prairie that formed on a Clay Flat range site in the northwestern Rio Grande or Tamaulipan Plains. As is the case for all the Sporobolus species, the fruit is, strictly speaking, an achene and characteristically very smalll (tiny would be an appropriate adjective).

Gould (1975, p. 286) explained that in Sporobolus species the seed coat does not adhere to the ovary wall instead separating when moist or wet. Hence, achene is a closer dsignation for Sporobolus fruit.

Alkali sacaton is on the plant lists of both the Society for Range Management International Identification Contest (Stubbendieck, et al., 1992, ps. 136-137) and the Texas Section, Society for Range Management, State identification Contest (Hatch and Pluhar, 1993, ps. 105-106). Society

Dimmit County, Texas. Early October; grain-ripe phenological stage.

 

30. Sward of the short layer- A grassy carpet of the highly stoloniferous curly mesquite (Hilaria belangeri) that made up the shortgrass layer in a climax mixed prairie that developed on a Clay Flat range site in the northwestern Rio Grande Plains. Curly mesquite is one of the most important shortgrass species in the Lone Star State. A good description of this eragrostoid or chlorcoid native was provided by Silveus (Gould (1975, ps. 368-369)

Correll and Johston (1979, p. 252) remarked that curly mesquite is more common on calcareous soils.

Dimmit County, Texas. Early October; grain-ripe phenological stage.

 

31. Instructive examples- Specimens shown at scale of whole aboveground plant (first slide) and scale of portions of stolons (second slide) of curly mesquite growing on a Clay Flat range site in the northwestern Rio Grande Plains. Curly mesquite is on the master plant lists of both the Society for Range Management International Identification Contest (Stubbendieck, et al., 1992, ps. 96-97) and the Texas Section, Society for Range Management, State identification Contest (Hatch and Pluhar, 1993, ps. 79-80).

Dimmit County, Texas. Early October; grain-ripe phenological stage.

 

32. Both reproductive options- Sexual and asexual modes on the same plant of curly mesquite growing on a heavy clay soil (Clay Flat range site) following a wet summer in the northwestern Rio Grande Plains. On these stolons, both the crankshaft-resembling rachis (with spikelets all shattered) and well-developed plant modules or clonal units (daughter or sister plants) were presented on what seemed to be a "very happy"--and certainly reproprductively fulfilled--plant.

Dimmit County, Texas. Early October; grain-ripe phenological stage.

 

33. Another bout of the reproductive options- Stolons of curly mesuite with both grain-ripe inflorescences (sexual reproduction) and modules or clonal units (asexual reproduction) produced on a clay soil in the Rio GrandePlains.

Dimmit County, Texas. Early October; grain-ripe phenological stage.

 

34. Flat-out flowering- Inflorescences of slimspike or, sometimes, bluestem windmillgrass and pink pappusgrass produced on a Clay Flat range site in the northwestern Rio Grande Plains. These midgrasses were major species of the middle herbaceous layer of a mixed prairie that developed on a light-textured or "heavy" soil. The tallgrass layer consisted of alkali sacaton while the shortgrass or lower herbaceous zone was comprised exclusively of curly mesquite.

This remnant of Rio Grande Plains mixed prairie had been maintained or preserved on a highway right of way by routine shredding. On adjoining and untreated (no burning, chemical or mechanical practices) naturalized buffelgrass and King Ranch bluestem were major grasses along with lesser cover of the climax native grasses, plus brush cover of honey mesquite, Texas or Lindheimer's pricklypear, and whitebrush.

Zavala County, Texas. Early October, peak standing crop.

 

35. Much closer to natural- An example of a quasi- (semi-, sub-, whatever) potential natural Rio Grande Plains grass-shrub savanna range shown as to its physiogonomy, structure, and composition on a dry, shallow, rocky habitat (Gravelly Ridge range site) in the northern (northwestern) Rio Grande Plains. This is in the semiarid precipitation zone. The dominant woody species was guajillo or Berlandier's acacia (Acacia berlandieri). Other woody species included cenizo or Texas purple sage (Leucophyllum frutescens), the shrub in right-center in this slide, blackbrush, spiny or desert hackberry (more commonly, granjeno), and, at the more eastern edge of its range, creosotebush (Larrea tridentata).

There was a rich array of grass species including Wright's threeawn (Aristida wrightii), lovegrass tridents (Tridens eragrostoides), slim tridens (T. elongatus= T. muticus var. or subsp. elongatus), pink pappusgrass, and red grama. Forbs were rather limited with common or annual broomweed being the most abundant with Texas palafox (Palafoxia texana) and paperflower (Psilostrophe gnaphalodes) "next in line" cover-wise.

Range vegetation shown here (and seen to better detailed advantage below) was most likely considerably higher in woody plant cover than the climax or pre-Columbian vegetation. This range plant community was, to some degree, a disturbance climax, yet in between brush (excessive woody cover so as to be at noxious proportions) the herbaceous layer was close to composition of what studies indicated was climax or potential natural cover. Successional status of this deteriorated savanna range would be high Fair to, maybe, low Good range condition class. The range plant community presented here and, in greater detail, immediately below was clearly closer to Indian or pre-whiteman vegetation than most of the brush patches shown above.

As is always the case, however, analysis and interpretation of range vegetation must be site-specific. It has been this rangeman's observation that in the Rio Grande or Tamaulipian Plains grass-shrub savannah, brush invasion (increase to "unnatural" high levels of woody plant--mostly shrub--cover) has, in genera, been proportionately greater on the more productive range sites. For example, range deterioration (range plant community retrogression), including brush infestation as well as reduction in grass cover, is usually more advanced on Clay Flat and Clay Pan Prairie range sites than on the Gravelly Ridge range site presented here and in several slides that follow.

Zavala County, Texas. Early October, autumnal aspect at peak standing crop. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Gravelly Ridge range site (Soil Conservation Service, 1976). Southern Texas Plains- Northern Nueces Alluvial Plains
Ecoregion 31a (Griffith et al., 2004).

 

36. Closer to natural up closer- Structure and composition of the Rio Grande Plains grass-shrub savanna range that was introduced in the immediately preceding slide/caption set. This range vegetation developed on one of the more harsh environments in the northern Rio Grande Plains. This Gravelly Rddge range site was characterized by a stoney, shallow soil making for a relatively xeric habitat and low range productivity. To make for an even harsher or more xeric environment, this range was in the semiarid zone.

This range vegetation included excessive woody cover (as could best be determined from historic and ecological literature), but this disclimax was nowhere as extreme a brush patch as almost all of present day Rio Grande Plains vegetation. If viewers could mentally remove about half of the woody cover seen here (a healthy visual "compromise") they would have a good idea of the "original" or "virgin" vegetation of the Rio Grande Plains grass-shrub savanna. An overall rating of range condition clas for this degraded range would be Fair to being generous, Good.

Shrub species ahown in the first of these two slides included the dominant guajillo or Berlandier's acacia, cenizo or Texas purple sage, blackbrush, granjeno (=spiny or desert hackberry, and creosotebush. Important grasses were lovegrass tridents, slim tridens, Wright's threeawn, pink pappusgrass, and red grama. Annual or common broomweed was the most common forb (foreground, first of these two slides). This first slide served as a larger "photoplot" or "photo-transect" (a bigger scale view) of this grass-shrub savanna.

The second slide was a "nested photoplot" of or from the right foreground of the first "photoplot". Guajillo was in front of granjeno with both shrubs beside Wright's threeawn, slender tridens, lovegrass tridens, red grama, pink pappusgrass, and common (annual) broomweed. Yes, all those species were present in foreground (in front of shrubs) of the second slide, although they are not distinguishable at this size and after scanning and then posting as a jpegs.

Thus, please advance to the next slides ...

Zavala County, Texas. Early October, autumnal aspect at peak standing crop. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Gravelly Ridge range site (Soil Conservation Service, 1976). Southern Texas Plains- Northern Nueces Alluvial Plains
Ecoregion 31a (Griffith et al., 2004).

37. Herbaceous savanna species- Grass cover in the Rio Grande Plains grass-shrub savanna range presented in the two immediately peceding slid/caption sets. Grass species in the first of these two "photoplots" were slim tridens, lovegrass tridens, Wright's threeawn, and pink pappusgrass. The two accompanying species were annual or common broomweed and paperflower.

Grass species--both of which are bunchgrasses or cespitose grasses--featured in the second "photoplot" were slim tridens (left) and Wright's threeawn. Behind these two individual plants there was cover of pink pappusgrass, slim tridens, and common broomweed (left to right, respectively).

These two slides presented typical or composite samples of the herbaceous layer or zone of a degraded range in Fair to, at best, Good range condition class.

Zavala County, Texas. Early October, autumnal aspect at peak standing crop. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Gravelly Ridge range site (Soil Conservation Service, 1976). Southern Texas Plains- Northern Nueces Alluvial Plains
Ecoregion 31a (Griffith et al., 2004).

 

38. Amid the brush- Two species of native grasses on a guajillo or Berlandier's acacia-dominated grass-mixed shrub savanna. Slim tridens (in front) and pink pappusgrass (behind) growing on the Gravelly Ridge range treated in the three immediately preceding slide/caption sets. This was a degraded range in high Fair to, perhaps, low Good range condition class.

Zavala County, Texas. Early October, autumnal aspect at peak standing crop.

 

39. Natural or is it semi-natural (kinda, sorta, maybe)- A second example of a South Texas or Tamaulipan Plains grass-shrub savanna in the semiarid northern Rio Grande Plains on a Gravelly Ridge range site. Like the preceding example (and most of the examples before it, regardless of range site), this range plant community was a disclimax (disturbance climax). It was a "safe bet" that such Rio Grande Plains brush (noxious woody plants due to successionally excessive cover)-dominated vegetation was at a steady successional state or permanent disequilibrium in human time scale.

The stage of vegetational disequilibrium on this range and the one discussed immediately above was not as great a departure from climax or the pre-Columbian vegetation as most of the south Texas "brush country". Specifically, the herbaceous component or zone of these ranges did not appear to be as "far removed" from that of the "virgin vegetation" as was the tremendous increase in cover, density, etc. of the woody component.

Woody plant species (most were shrub species and of mature shrub size and habit) included guajillo or Berlandier's acacia, the dominant shrub, cenizo or Texas purple sage, blackbrush, granjeno (=spiny or desert hackberry), and guayacan (Porlieria angustifolia= Guaiacum angustifolium). Of course, on the Rio Grande Plains there is almost always a good representation of cactus species, especially Texas or Linheimer pricklypear.

The Important grasses were lovegrass tridents, slim tridens, pink pappusgrass, sideoats grama, pinhole bluestem (Andropogon perforatus= Bothriochloa barbinodis var. perforata), Wright's threeawn, slimspike windmillgrass, and red grama. Annual or common broomweed was the most abundant forb while silver bladderpod (Lesquerella argyraea) was the second most common (had second greatest foliar cover) forb.

This photograph presented a general view of this range plant community whereas the next two slides provided more detail as to outward appearance (physiogonomy) as well as species composition and structure.

Uvalde County, Texas. Early October, autumnal aspect at peak standing crop. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Gravelly Ridge range site (Soil Conservation Service, 1976). Southern Texas Plains- Northern Nueces Alluvial Plains
Ecoregion 31a (Griffith et al., 2004).

 

40. On closer look- Interior of the grass-mixed shrub (guajillo was dominate) savanna on a Gravelly Ridge range site that was introduced in the preceding slide. The two images shown here presented the physiogonomy, structure, and species composition at smaller spatial scale, hence greater detail of the range plant community. In addition to the dominant guajillo or Berlandier's acacia, shrub species included cenizo or Texas purple sage, blackbrush, granjeno (=spiny or desert hackberry), and guayacan.

The herbaceous layer(s) or component included the major grasses lovegrass tridents, slim tridens, pink pappusgrass, sideoats grama, pinhole bluestem, Wright's threeawn, slimspike or bluestem windmillgrass, and red grama. The two most common forbs were common (annual) broomweed and silver bladderpod.

Uvalde County, Texas. Early October, autumnal aspect at peak standing crop. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Gravelly Ridge range site (Soil Conservation Service, 1976). Southern Texas Plains- Northern Nueces Alluvial Plains
Ecoregion 31a (Griffith et al., 2004).

 

41 Where it was really dense- A part of the semiarid Rio Grande Plains grass-shrub savanna range that developed on a Gravelly Ridge range site and which was shown and described in the two immediately preceding slide/caption units. This image was the fourth "photoplot" or "photoquadrant" of that degraded range that was in overall high Fair to, possibly, low Good range condition class. This fourth slide presented a local range plant community of that savanna that was a disturbance climax at the most advanced stage of range retrogression in regards brush invasion. Range condition class shown here would do well to reach Poor. In fact, in the condition class system traditionally used by the Bureau of Land Management vegetation seen here was in the Very Poor class.

This disclimax vegetation had the same shrub species mentioned above (guajillo, cenizo, blackbrush, granjeno, and guayacan) except at greater plant density and crown (foliar) cover, plus the shrubby composite known variously as gumhead and tatalencho (Gymnosperma glutinosum) or, apparently based on an earlier binomial name of Selloa glutinosa, sticky sGumhead was represented in this "photoquadrant" by the distinctive, yellow-flowered, low shrub in right-center foreground. The shrub to its immediate left was one individual of the dominant shrub, guajillo. The lighter-colored shrub in right background was cenizo or Texas purple sage.

This plant assemblage did have some patches of herbaceous vegetation including such grasses as those listed above: lovegrass tridents, slim tridens, pink pappusgrass, sideoats grama, pinhole bluestem, Wright's threeawn, and red grama. Likewise, the annual composite called common broomweed was present with the grass species. Common broomweed and gumhead are in tribe, Astereae.

Uvalde County, Texas. Early October, autumnal aspect at peak standing crop. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Gravelly Ridge range site (Soil Conservation Service, 1976). Southern Texas Plains- Northern Nueces Alluvial Plains
Ecoregion 31a (Griffith et al., 2004).

 

42. Then and now shots- Classic fenceline contrast of range vegetation on a Gravelly Ridge range in the semiarid zone of the northern Rio Grande or Tamaulipian Plains. Woody plants had obviously been removed (a considerable number of years before these images) from the fenceline in obvious preparation for fence construction. It was not known to this author if the cleared fenceline had been maintained by brush treatments, such as shredding or herbicide application, or if it remained free of woody cover as a result on the single clearing operation. The latter alternative seemed more plausible. There was no evidence of herbicide application because there were no dead shrub shoots.

All range vegetation presented in the first of these two slide was on a livestock range. In the second slide, plant cover to left of the fence was on this same livestock range whereas the smaller portion of plant cover (exclusively herbaceous) to right of the fence was on a highway right of way. Range vegetation on this right of way was the subject of the rest of the slide/caption units in this part of the Rio Grande Plains chapter.

The herbaceous (almost exclusively grass cover) vegetation was "covered" in detail in immediatelslimspike or bluestem windmillgrass, y following slide/caption sets. Major grasses were slim tridens, pink pappusgrass, pinhole bluestem, sideoats grama, Wright's threeawn, slimspike or bluestem windmillgrass, and lovegrass tridens. Woody vegetation was dominated by guajillo or Berlandier's acacia. Other woody (shrub not tree) species included cenizo or Texas purple sage, blackbrush, granjeno (= spiny or desert hackberry), and guayacan.

Uvalde County, Texas. Early October, autumnal aspect at peak standing crop. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Gravelly Ridge range site (Soil Conservation Service, 1976). Southern Texas Plains- Northern Nueces Alluvial Plains
Ecoregion 31a (Griffith et al., 2004).

 

43. Where woody plant growth was controlled- These two views and the three in the next two slide/caption units were on highway right of way that was contiguous (adjoining) to the plant community (ies) of the disclimax savanna range featured in the three immediately preceding slide/caption units. On the adjoining grazed-as-far-back as-anyone-can-remember livestock range, native grasses had, to a substantial degree, given way to brush (noxious range plants based on cover far in excess of the imagined or reconstructed climax vegetation). The preceding four slides showed that this brush invasion varied locally across the livestock range.

In the two slides presented in this unit, there was no woody plant cover because apparently it had been 1) periodically controlled by mowing/shreddingor, 2) not recovered since removal by highway construction, or 3) some combination thereof. (Chemical control seemed unlikely to have been applied.)

No, mechanical shredding is not "natural". God did not have Indians running shredders over the pre-Columbian vegetation, but Indians certainly mimicked Mother Nature and were masters of fire; they were the original prescribed burners. Indians left no written records, but the earliest remaining written accounts of Rio Grande Plains vegetation such as those of the first literate travelers, explorers, merchants, etc. clearly document that the climax vegetation of this region was grassland and grass-shrub savanna not an Acacia-Prosopis-Celtis shrubland.

(More discussion in this regard was presnted below. For now it was sufficient to state that the grassland vegetation existing on this roadway margin was a vegetational relict, a remnant range plant community that at least was an approximation of the climax vegetation.)

This range vegetation consisted exclusively of herbaceous species and almost exclusively of grass species with only occasional plants of forb species. Grasses in the first of these two images consisted primarily of pinhole bluestem, pink pappusgrass, and slim tridens. Red grama was the principle minor grass species. The grey-colored plants in the immediate foreground of this first "photoplot" was silver bladderpod. The other forb species was common or annual broomweed.

Range vegetation in the second image was a local stand of pink pappusgrass with a few "strays" of slim tridens and lovegrass tridens. Pink pappusgrass is a major--often the climax dominant--grass over much of the Rio Grande plains grassland and grass-mixed shrub savanna. This important decreaser grass--along with other range plant species on the Gravelly Ridge range site--was given exclusive treatment below.

Woody plant cover in the background was that of the conterminous livestock range. If viewers look closely they can see wooden (cedar) fence posts against the backdrop of brush. A fence separated the brush-infested range from the highway right of way. This is an opportunistic or de facto controlled experiment (brush control on right of way versus no brush control on livestock pasture, this latter of which is the experimental control meaning, in research terminology, no treatment). This fenceline contrast (see again, the immediately preceding two-slide/caption unit) spoke more than any words.

Uvalde County, Texas. Early October, autumnal aspect at peak standing crop. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Gravelly Ridge range site (Soil Conservation Service, 1976). Southern Texas Plains- Northern Nueces Alluvial Plains
Ecoregion 31a (Griffith et al., 2004).

 

44. The most probable climax range vegetation- Two more slides of the herbaceous vegetation of a Gravelly Ridge range site on a remnant of relict grassland. These two "photoplots" presented examples of the climax range plant community based on the most reliable knowledge currently available. The major grasses in the first slide were (in approximate order of foliar cover) Wright's threeawn, slim tridens, pinhole bluestem, sideoats grama, pink pappusgrass, and lovegrass tridens. Red grama, a common component grass in this grassland community, was sparse in these two "photoplots". The principal forb was silver bladderpod.

Grass cover shown in the second slide was almost all sideoats grama, pinhole bluestem, and slim tridens (in that rank based on foliar cover). There were no forbs in this second "photoplot".

For this shallow, rocky habitat in the semiarid northern Rio Grande Plains the potential natural vegetation is grassland comprised of cespitose midgrass species of the Eragrostoideae and Panicoideae, the two major warm-season grass subfamilies, with widely scattered shrubs primarily of the Mimosoideae subfamily of the Leguminosae.

Uvalde County, Texas. Early October, autumnal aspect at peak standing crop. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Gravelly Ridge range site (Soil Conservation Service, 1976). Southern Texas Plains- Northern Nueces Alluvial Plains
Ecoregion 31a (Griffith et al., 2004).

 

45. What most of it should look like- A "photoplot" of representative climax vegetation for grassland on a shallow, rocky habitat in the smiarid northern Rio Grande Plains. Obviously this local range plant community was exclusively herbaceous (specifically, grass) plants. The principal species were sideoats grama pinhole bluestem, and slim tridens (in that relative rank based on foliar cover).

Crowns of two plants of guajillo or Berlandier's acacia were visible in the background to present a representative sample of the climax vegetation for this Gravelly Ridge range site.

Uvalde County, Texas. Early October, autumnal aspect at peak standing crop. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Gravelly Ridge range site (Soil Conservation Service, 1976). Southern Texas Plains- Northern Nueces Alluvial Plains
Ecoregion 31a (Griffith et al., 2004).

 

46. Composite quadrant- "Photoquadrant" of grass sward on the relict vegetation that developed on a Gravelly Ridge described in this segment of Rio Grande Plains range plant communities. All plants in this image were grasses. The two major species were pink pappusgrass and slimspike or bluestem windmillgrass. Slim tridens was a distant third species (based on cover) in this "photoplot".

Uvalde County, Texas. Early October; peak standing crop, autumnal aspect.

 

47. Another (and more specific) plot- "Photoquadrant" of the grass component of a relict semiarid grass-mixed shrub Rio Grande Plains savanna on a Gravely Ridge range site. Major grass species were slim tridens, pink pappusgrass, red grama, and lovegrass tridens. Slim spike or bluestem windmillgrass and sideoats grama were minor grass species. (By the way, in this relict range vegetation all grasses were native species.)

There was also considerable cover of the annual composite, common broomweed (especially noticable in the sedond slide). Visible in the first of these two slides (upper right corner) was the base of a plant of guajillo or Berlandier's acacia, representing the dominant shrub on adjoining degraded range.

Uvalde County, Texas. Early October; peak standing crop, grain-shatter phenological stage.

 

48. Tops of some of the top ones- Base of panicle (peduncle) of slim tridens (rear) and portion of constrictd panicle of pink pappusgrass (front) on a remnant of climax (or near-climax) grassland or grass-shrub savanna depending on interpretation on a Gravelly Ridge range site in the semiarid northwestern Rio Grande Plains of south Texas.

Uvalde County, Texas. Early October; peak standing crop, grain-shatter phenological stage.

 

49. If not a kings, a prince- Examples of pink pappusgrass (Pappophorum bicolor) growing on a relict tract of Rio Grande Plains mixed prairie (or, perhaps, regarded as grass-shrub savanna) that developed on a Gravelly Ridge range site in the semiarid zone. The shoots of these specimens were just starting to show senescence with spikelets entering the grain-ripe to grain-shatter stages. Height of shoots was roughly two and a half feet (though clearly below a yard or meter height). Although ecological site descriptions listed pink pappusgrass as a "tallgrass" species (Natural Resources Conservation Service, undated; available online) that call was obviously a so-called grave error.

Regardless of general designation, pink pappusgrass is a cespitose species, often of comparatively large plants of mid-height, that is a climax dominant--hence, decreaser--on various range sites in the Rio Grande Plains. It is a very distinctive (and in this rangeman's opinion, beautiful) grass species. In fact, pink pappusgrass is one of the characteristic and defining species of the Tamaulipan Plains grasslands and savannahs.

Pink pappusgrass has a biological or species range extending from Texas to Arizona and south into Tamaulipas and Durango (Correll and Johnston, 1979, p. 251). In Texas, pink pappusgrass grows in the Coastal Prairies and Marshes, Edwards Plateau, and Trans Pecos Basin and Range vegetational areas as well as the Rio Grande Plains (Gould, 1975, ps. 378-379) though it is in the latter that it reaches its greatest ecological and economic importance.

Pink pappusgrass is on the master list of the Texas Section, Society for Range Management Range Plant Identification Contest (Hatch and Pluhar, 1993, ps. 158-159). These authors listed forage value of pink pappusgrass as Poor for wildlife and Fair for livestock., but a lot of range workers in the Rio Grande Plains would take issue with such low ratings and and elevate them to Fair and Good, respectively. Everitt et al. (2011, p. 200) also rated pink pappusgrass as "fair forage for livestock". It seemed likely that the latter authors got their forage rating either from the same source as Hatch and Pluhar (1993, p. 159) or directly from these authors.

The Natural Resources Conservation Service E.”Kika” de la Garza Plant Materials Center and Texas A&M University System cooperatively released a selection of pink pappusgrass named Maverick Germplasm that was a composite of seven collections from the Rio Grande Plains.

Uvalde County, Texas. Early October; peak standing crop, grain-shatter phenological stage.

 

50. More purple than pink- Two constricted panicles (upper image) and branching pattern of constricted panicle (lower image) of pink pappusgrass which is in Gramineae subfamily, Eragrostoideae (= Chlorcoideae).

Uvalde County, Texas (first slide) and Frio County, Texas (second slide). Early October; peak standing crop, grain-shatter phenological stage.

 

51. Sorta pink, but more like tan- Up-close views of ripe-grain spikelets of pink pappusgrass. For morphological details, including of spikelets, see Silveus (1933, 152-153, 155), Hitchcock and Chase (1950, ps. 225-226), and Gould (1975, p. 378).

Atascosa County, Texas. Early October; peak standing crop, grain-shatter phenological stage.

 

52. Just a closer peek- Branches of the contracted panicle of pink pappusgrass showing spikelets. For a good summary treatment of pink pappusgrass see Leithead et al. (1971, ps. 130-131) and Everitt et al. (2011, ps. 199-200).

Duval County, Texas (first slide) and Atascosa County, Texas (second slide). Early October; peak standing crop, grain-shatter phenological stage.

 

53. Slender not skinny- Two plants of slim tridens (T. elongatus= T. muticus var. or subsp. elongatus) growing on a relict remnant of semiarid grass-savanna on a Gravelly Ridge range site in the northwestern Rio Grand Plains. These two specimens provided good examples of the cespitose (tufted or bunched) habit of slim tridens. Cespitose grass species are known as bunchgrasses.

This relict range plant community appeared to be in Good--perhaps even high Good--range condition class. Typically, slim tridens has been considered to be an increaser species (Leithead et al., 1971, p. 201), but, of course, successional status is always range site-specific. Range site specificity includes variation as the relative proportions of increasers and specific increaser species in the potential natural (climax) vegetation.

From this relict range vegetation and that of neighboring range plant communities it was apparent to this range observer that slim tridens can comprise a relatively high percentage (say, upwards of 15 to 20%) of climax cover on harsh habitats such as this Gravelly Ridge range site.

Uvalde County, Texas. Early October; peak standing crop, grain-shatter stage of phenology.

 

54. Slender on slim-pickin's- Three representative plants of slim tridens, a cespitose eragrostoid grass, that was a local dominant on a remnant tract of relict range vegetation that had developed on a Gravelly Ridge range site. These plants were growing on the remnant of Rio Grande Plains grassland or a grass-mixed shrub savanna (in the semiarid zone) that was presented at larger scale above.

As a general rule, slim tridens is an increaser species (Leithead et al., 1971, p. 201) though, of course, exact successional status of any plant species is range site-specific and, also, specific to experience and judgment of the range examiner. On harsh habitats, such as the Gravelly Ridge range site treated herein, slim tridens was an increaser whereas pink pappusgrass, pinhole bluestem, and sideoats granma were (are) decreasers. Notwithstanding this, high cover and density of slim tridens bespoke to the higher quality condition (probably Good range condition class) of this relict Rio Grande Plains grassland.

Slim tridens is--as shown in this segment--often a major forage species, especially on harsher habitats where growing season drought is a "way of life" for range plants.

Uvalde County, Texas. Early October; peak standing crop, grain-shatter phenological stage.

 

55. The skinny of slim- Portions of panicles and spikelets of slim tridens, one of the local dominant grasses on relict semiarid mixed prairie or, depending on interpretation, grass-shrub savann that developed on a Gravelly Ridge range site in the northwestern Rio Grande Plains. This range plant community was probably in high Good range condition class with slim tridens contributing considerable cover and herbage yield on this range.

It seemed reasonable that slim tridens could be expected to contribute up to 15 or, even, 20% of the standing crop of climax (or near-climax) vegetation on shallow, stoney soils in the semiarid zone.

Uvalde County, Texas. Early October; grain-shatter stage of phenology.

 

56. One that makes rangemen look twice- Large plant (first slide) and its lower shoot portion (second slide) of lovegrass tridens (Tridens eragrostoides) growing on a Gravelly Ridge range site in the northwestern part of the Rio Grande Plains. This is not a common grass nor one that has received much attention (and the first statement probably explained the second), though it was covered in the classic, first book devoted to all Texas grasses (Silveus, 1933, ps. 128-129) and, in later comprehensive treatments including Gould (1975, ps. 207-209). This latter agrostologist commented that lovegrass tridens was "most frequent in brushy grasslands" and "usually growing in patial shade" in the Rio Grande Plains (Gould, 1975, p. 209).

In contrast to these observations, specimens on the Gravelly Ridge range site treated here were growing in full-sun and on a remnant tract of Rio Grande Plains mixed prairie far from any woody cover. In this relict range vegetation lovegrass tridens was associated primarily with pinhole bluestem and sideoats grama and secondarily with "its generic cousin", slim tridens.

A good treatment of lovegrass tridens for the Rio Grande Plains was that of Everitt etal. (2011, ps. 277) who designated this species as having good forage value for livestock and, therefore not surprising, a decreaser.

Uvalde County, Texas. Early October; grain-shatter stage of phenology.

 

57. Closer looks at one that can confuse at first- Second specimen of lovegrass tridens shown as the entire aboveground portion (first slide) and upper part of panicle (second slide) that grew on a Gravelly Ridge range site in the northern Rio Grande Plains.

The common name of this grass is an apt one. On first examining this plant, rangemen (including this one) think it is a lovegrass, one of the Eragrostis species, if they see the panicle inflorescence or, if they "hone in on" the curled basal leaves, sideoats grama.

Treatment of lovegrass tridens in the literature is sparse. Response of lovegrass tridens to grazing has probably been limited to range site descriptions most of which were not published (other than in-house) for use in range condition and trend analysis by agencies like the Soil Conservation Service. Current ecological site descriptions by the Natural Resources Conservation Service are, in some aspects more detailed, but as of this writing quite limited. For example, there are Natural Resources Conservation Service ecological site descriptions for the similar Shallow Ridge site, but not for the Gravelly Ridge ecological site.

On the Shallow Ridge ecological site, the description listed both slim and lovegrass tridens as "shortgrass" species that were members of the Native Mid/Shortgrass Prairie Community of the Grassland State in the displayed state-and-transition model (Natural Resources Conservation Service, undated; available online).

The designation of "shortgrass" for these two Tridens species was obviously wrong as these grasses are clearly midgrass species being of approsimately the same height--even, slightly taller)--than sideoats grama (at least on shallow-soil range sites). A shortgrass species common to this area of the Rio Grande Plains (though on clay soils) is curly mesquite. Likewise (and as clarified above) the designation of pink pappusgrass as a tallgrass is in error as this species is also a midgrass-- and it is no more than a foot or so taller than the Tridens species.

Uvalde County, Texas. Early October; grain-shatter stage of phenology.

 

58. Four examples with three awns- Four individual plants (= unique or distinct genotypes) of Wright's threeawn (Aristida wrightii= A. purpurea var. wrightii). Three of these four example specimens (those presented in the first, second and fourth slides) were growing on a Gravelly Ridge range site. The other specimen (in third slide) was growing on a Shallow range site. This selection of specimens was representative or typical of Wright's threeawn having preferences for harsh, especially xeric (eg. shallow, rocky, droughty), habitats.

Aristida species present taxonomic quandries with long-recognized groups, sections, (or by whatever else designation was applied to these systematic units) within the genus. Historically, a group of six to ten closely related (based on morphological features) perennial Aristida species were placed in a group known as Purpureae. The most recent comprehensive coverage (at time of this composition) of this group was that of Allred (1984). For New Mexico, Allred and Ivey (2012, ps. 633-634) "lumped" five former or existing Aristida species, including A. wrightii, as taxonomic varieties of A. purpurea. This group of taxa (varieties) has become known as the A. purpurea complex.

Successional status (as for instance designations of decreaser, increaser,or invader) of the perennial threeawn species is, if anything, more problematic than their taxonomic status. Traditionally, rangemen have interpreted perennial Aristida species (like those in the A. purpurea complex) as being invaders on almost all range sites. This has been expecially the case for range site descriptions by the Soil [currently Natural Resources] Conservation Service as published in county soil surveys or, when used for more detailed range analysis, agency (office) range site descriptions. This situation would also apply to the more detailed and more recent ecological site descriptions; that is, if and when completed.

Admittedly, under most management conditions the Aristida species are some of the least palatable range grasses for both livestock and wildlife. Forage value does not, however, always correspond to successional status. Yes, it does to the extent that more palatable or, from the animal end of things, more preferred species do decline under improper grazing management (eg. overgrazing) before the less palatable (preferred) species do. Decrease, increase, or invade responses under excessive grazing stress often follows responses to other disturbances such as drought and/or critically timed fire. Even this (at least by itself) does not suffice to place species on the successional scale extending from first seral stage to climax.

The fact is that Aristida species like A. wrightii= A. purpurea var. wrightii are quite frequently major component species of climax range plant communities as evidenced by their comparatively high cover and density on relict range vegetation such as that presented above. In his classic monograph, Plant Indicators Clements (1920, ps. 142) specified that in its southern extent in Texas and western portion in New Mexico and Arizona climax shortgrass plains grasslands includes A. purpurea. The Desert Plains (semidesert) grassland was the Aristida-Bouteloua Association (Clements, 1920, ps. 144-149) of which A. purpurea was a frequent dominant in the climax or, often, subclimax grassland vegetation.

Relegating perennial threeawns, like those in the A. purpurea complex, as being invaders is painting with much too broad a successional brush even in the broad expanses of the Rio Grande Plains. Successional status of Wright's threeawn is even more site-specific than midgrass species like sideoats grama and silver bluestem which are often dominants in relict range vegetation of the Tamaulipan Plains Region.

Uvalde, Astacosa, and Zavala Counties, Texas (for first and second, third, and fourth slides, respectively). Early October; peak standing crop.

 

59 Wright on top- Inflorescences (panicles) of Wright's threeawn with the characteristic long awns of the lemma of one-flowered spikelets. Hitchcock and Chase, 1950, p. 460) describe the Aristida spikelet. It is the often sharp-tipped lemma that terminates with a trifid awn that gives the general common of "threeawn" to this group of grasses that in some areas such as in the southeastern United States is known as "wiregrass".

Either way, the Aristida species are not generally palatable to grazing animals (nor are most plants of such size as to produce large amounts of herbage), but as noted by Hitchcock and Chase (1950, p.460) some can be important forage sources when shoots are still immature. This would be before the sometimes mechanically injurious sharp-calluse and "treble-hook" awns develop.

It is the long a panicles (15 centimeters or more) with multi-flowered branches (Hitchcock and Chase, 1950, p. 463; Allered and Ivey, 2012, p. 634) that distinguish Wright's threeawn (at whatever taxonomic level it is recognized) from other taxa in the A. purpurea group.

Zavala County, Texas. Early October; grain-shedding stage.

 

60. Typically small, low-ranked, and frequently present- Red grama (Bouteloua trifida) growing on a Gravelly Ridge range site (first slide) and a Clay Flat range site (second slide) in the northwestern Rio Grande Plains. This shortgrass species is usually short in stature, say five to ten inches (Hitchcock and Chase, 1950, p. 542; Leithead et al., 1976, p. 67), and common--frequently dominant--on deteriorated ranges from northern Mexico across to southern California and north to Utah and Colorado (Hitchcock and Chase, 1950, p. 542;

Red grama is one of the most common ecological invaders on deteriorated ranges in the Rio Grande Plains and Edwards Plateau (in the Edwqrds Plateau especially in southern and western portions). Red grama sometimes grows in single-species stands, which is about the only situation in which it is a key species (Leithead et al., 1976, ps. 66-67). If there ever was a "universal invader" (a species that is an ecological invader species on almost or almost all habitats) it would be red grama. For example, in the Uvalde County, Texas soil survey (Soil Conservation Service, 1976) red grama was listed as an invader on 20 of 21 range sites!

Notwithstanding its successional rank as invader and generally low forage value (given its small size and, hence, limited herbage production), red grama produces fairly nutrition forage when young and it is eatern by all livestock species (Leithead et al., 1976, p. 67). Even more importantly frrom a long-term range conservation perspective, red grama is valuable as a range cover crop to prevent or, at least, reduce soil erosion. Although red grama is a short-lived perennial and, frequently, ephemeral in a single growing season (Leithead et al., 1976, p. 67) it is a more reliable feed source and cover crop than annual grass species.

Invaders--at least the native species--do provide ecosystem functions and are valuable range plants (albeit much less valuable than the decreaser and increaser species). Invaders of native species are often pioneer or early colonizing species in the process of secondary plant succession by which degraded lands like overgrazed ranges, cutover forests, and old fields (abandoned croplands) return to whatever the potential natural vegetation on such derelict land is.

The red grama specimens shown here in the immediately following slides were all unusually large plants having the rare "pleasure" of a wet growing season. Some of these plants were 15 inchesor more tall and of such shoot numbers as to be more like midgrass species such as sideoats grama.

No' the second image did not show to any good extent what it was supposed to show, anamely one extra large specimen of red grama.This image was totally botched up by an Epson Perfection 700 scanner. Never buy Epson products. Epson scanners apparently scan randomly at varying intensities so all images are proverbial "pigs in a poke". It is a wonder that the customer gets as many good or decent images as he does. Your photographer/author invested in a scanner that was billed as the top of its line. Now he is stuck with it. Furthermore, the company provides very little post-sales service. One of those companies that survives by clever advertising and then finding and selling to one-time customers. "There's a sucker born every minute" (attributed to numerous individuals but no proof of any specific person having uttered the wellknow phrase).

Anyway, other scanners would likely be no better. Apparently there has simply not been enough market demand for scanners to encourage (financially justify) any company to come out with a professional grade machine. We do the best we can with we have. "Make do" and "make it last" are two great dictums.

Uvalde County, Texas and Duval County, Texas (for first and second slide, respectively). Early October; peak standing crop, grain shatter stage of phenology.

 

61. "The better to see you, my dear"- Two extra-large specimens of red grama shown as all shoots (first slide) and close-up of upper, sexual shoots (second slide) growing on a shallor, rocky soil (Gravelly Ridge range site). These robust individuals had grown in a wet year and were both taller (15 inches or more) and more productive of tillers than was typical. They made for more easily seen examples, plus they demonstrated that red grama can produce large quantities of herbage available for forage.

In a recommended summary coverage of red grama, Everitt et al. (2011. p. 65) concluded that while red grama was "poor value to livestock and wildlife" it "responds rapidly following rainfall". In other words, this is an opportunistic species and one that ranchers can use opportunistically. Beats bare, eroding soil and hungry, bawling cattle.

Red grama is an opportunistic species, both from ecological and economic aspects. Yes, in good years other more ecologically and economically valuable species (decreasers and increasers) will outproduce invaders, red grama, BUT on many depleted ranges (or under prolonged drought) invaders like red grama might be the only species available. Under such conditions forage-producing, soil-protecting invaders are all the more valuable.

Zavala County, Texas. Early October; peak standing crop, grain-shatter phenological stage.

 

62. Signs of plenty on bad range in a good year- Upper shoots on a large red grama plant (first slide) and upper red grama shoots with a comparatively high number of racemes (second slide) on a deteriorated (overgrazed among other disturbances) range in a year (warm-growing season) of abundant rainfall.

These examples of unusually large plants showed that these typically short (many times, very short) shortgrassses are capable of producing abundant herbage available as 1) moderately palatable, nutritious forage and 2) effective ground cover to reduce soil erosion as well as yielding 3) a copious quantity of seed (grain)-bearing flower clusters or inflorescences for sexual reproduction. The first of these two slides, along with the four slides in the immediately preceding slide/caption sets, demonstrated the high number of tillers (hence, the great capacity for asexual reproduction) inherent in red grama in a rare "good year" in the Rio Grande Plains.

Zavala County, Texas and Uvalde County, Texas (first and second slide, respectively). Early October; peak standing crop, grain-shatter phenological stage.

 

63. Color namesake- Inflorescences (inflloresecence type is raceme) of red grama showing the often-characteristic red coloration of these flower clusters. These racemes were at the seed-shattter stage and had largely turned to an amber color of maturity yet some of their immature red pigmentation remainded.

Zavala County, Texas. Early October; grain-shatter phenological stage.

 

64. Is it panicgrass or bristlegrass?- Reverchon's panicgrass (Panicum reverchonii) or Reverchon's bristlegrass (Setaria reverchonii) growing on a Clay Flat range site in the Rio Grande Plains. This is one--of many (too many in opinions of many rangemen)--of the grasses for which agrostologists cannot decide on its proper taxonomic placement, other than it is a panicoid species in tribe, Paniceae. Hitchcock and Chase (1950, ps. 627, 637) placed this species in Panicum under subgenus, Paurochaetium based on the axis ofa panicle branchlets extending as a bristle beyond the upper spikelet. In the first monograph of Texas grasses, Silveus (1933, ps.553-555) had done the same thing following Hitchcock and Chase [1910] in their The North American Species of Panicum. Silveus (1933, p. 553) did remark regarding Paurochaetium, "This group approaches Setaria in having branchlets produced into bristles ...". Correll and Johnston (1979, p. 182) followed this view, but Gould (1976, ps 542, 545-547) and Powell (2000. ps. 298-299) interpreted this panicoid grass a a bristlegrass (S. reverchonii).

By whichever closely related genus, Reverchon's bristlegrass/panicgrass is widely distributed in Texas occurring in all of Texas' vegetational areas except the Pineywoods and Blackland Prairies (Gould, 1975, p. 547), but it is not typically an important feed species except when it grows in fairly dense stands (which tends to be a local phenomenon). For example, in range site descriptions for Duval County, Texas (Natural Resources Conservice Service, 2011) where the two specimens presented here were growing, Reverchon's panicgrass was never listed as a major forage species. It was, however, a member of the climax plant community of most of the described range sites (Natural Resources Conservice Service, 2011).

Even as a minor member of the potential natural range vegetation, Reverchon's panicgrass is a distinctive grass species with a high incience of occurrence on the Rio Grande Plains (at least on this rangeman's reconnaissance of the region).

Duval County, Texas. Early October; peak standing crop, early grain phenological stage.

 

65. Representative panicoid species- Upper shoots of Reverchon's panicgrass or Reverchon's bristlegrass (first slide) and two inflorescences of another plant of this species (second slide) growing on two areas (Clay Flat range site) from which livestock were excluded in the Rio Grande Plains. Gould (1976, p. 547) described the inflorescence of this species "a narrow, contracted, spikelike panicle".

The species range of Reverchon's panicgrass is a restrictive one that barely extends into Oklahoma and south into Coahuila (Correll and Johnston, 1979, p. 182).

Duval County, Texas and Webb County, Texas (first and second slide, respectively). Early October; peak standing crop, early flowering phenoloogical stage.

 

66. Paniced or bristled?- Portions of two contracted panicle of Reverchon's panicgrass or Reverchon's bristlegrass produced on the western Rio Grande Plains.

Web County, Texas. Early October; peak-bloom phenological stage.

 

67. Invertebrate builders and grazers- Casing or tube constructed by the rangeland or desert termite (Gnathamitermes tubiformans) around shoots of some forb on a Gravelly Ridge range site in the northern Rio Grande Plains. Range Management students should always remember they are living in the Age of Insects (Ages of Reptiles, Mammals, and soo forth are past, part of geologic history). In addition to the larger insect orders like Coleoptera (beetles), Lepidoptera (moths and butterflies), Orthoptera (grasshoppers, katydids, crickets), and Hymenoptera (ants, bees, wasps), the Isoptera or oreder of termites is also important.

Rangeland (the adjective "desert" is much less accurate because G. tubiformans thrives in subhumid and semiarid zones as well as in arid eosystems) termites construct earthen tubes around their forage or browse and then proceed to feed inside their aboveground tunnel or casing.

There is a limited number of publications dealing with termites on range. For starters, students were referred to Bodine and Ueckert (1975), Ueckert et al. (1976), and Allen et al. (1980) for specifics on rangeland termites in the semiarid zone of greater southwestern North America. For summary treatment of rangeland termites see McDonald et al. 2010) and for general coverage on ecology of termites (as well as ants) see treatment by the International Biological Program (Brian, 1977).

Uvalde County, Texas. October.

 

68. Brush "as far as the eye can see"- Textbook example of Tamaulipan Thornscrub (Rio Grande Plains "brush country"). The expanse of this shrubland type extended from horizon to horizon. It would be hard to imagine a broader expanse of this range type which was dominated by guajillo or Berlandier's acacia. Other shrubs included granjeno (= spiny or desert hackberry), honey mesquite, border palo verde [or, as one word, paloverde] (Cercidium macrum), blackbrush, retama (Parkinsonia aculeata), Torrey's croton or vara blanca (Croton torreyanus= C. incanus), Texas wolfberry (Lycium texanu), Texas or Lindheimer pricklypear, lime prickly-ash (Zanthoxylum fagara), and cenizo. Grasses and forbs were almost nonexistent (ie. there was no herbaceous understorey), except along the edges on which herbaceous cover was dominated by the naturalized exotic, bufflegrass.

I was not known if this range plant commnity was an example where this mixed scrub (usually called "mixed brush") was, in fact, the ultimate in "brush" (noxious woody plants) and one that was in a steady state or dynamic equilibrium as a disturbance climax or, alternatively if it was the potential natural (=climax) vegetation for this range site. The latter alternative would be a climax form of Society for Range Management rangeland cover type designated Mesquite-Granjeno-Acacia (Shiflet, 1994). The describer of this range plant community was a classically educated range scientist (and primarily with a Clementsian perspective) such that it was hard for him to imagine this scrubland as any other than a disclimax.

The Soil Survey of Duval County Texas (Natural Resources Conservation Service, 2011, ps. 74-84) recognized 16 range sites for the Rio Grande Plains area and described all but one of these as "open grassland" or a savanna of widely speced woody lants. The one exception (sort of) was the Shalllow Ridge range site which was described as "semi-open chaparral or shrubland that has an understory of mid and short grasses". Even with this descriptive account the Shallow Ridge range site supported only 10% woody cover in 'the historic climax plant community" (Natural Resources Conservation Service, 2011, p. 83).

Duval County, Texas. October, autumnal aspect at peak standing crop. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Shallow Ridge range site (Natural Resources Conservation Service, 2011). Southern Texas Plains- Northern Nueces Alluvial Plains Ecoregion 31a (Griffith et al., 2004).

 

689. Brush big time- Interior of the classic example of Tamaulipan Thornscrub (Rio Grande Plains "brush country") introduced in the preceding slide. The dominant--and in "far and away" foliar cover proportions-- was guajillo with associate and othr major shrub species being desert or spiny hackberry, blackbush, honey mesquite, border palo verde retama, Torrey's croton or vara blanca, Texas wolfberry,Texas or Lindheimer pricklypear, lime prickly-ash, and cenizo. Herbaceous plants were essentially abseent except for a few large clumps of buffelgrass, an introduced and, now, naturalized panicoid grass.

This was a shallow, steep (by Rio Gande Plains standards), xeric habitat--a Shallow Ridge range site (Natural Resources Conservation Service, 2011) leading to the more spectacular visual portrayal of semiarid shrublandt in this region.

In this rangeman's judgment this range plant comunity was the ultimate expression or development of a disturbance climax, an anthropogenic steady state induced by improper range management and--without intensive human inputs in form of brush control--prmanent in human time scale. Some degree of restoration of the climax (pre-Coumbian) range vegetation was conceivably possible, but cost effectiveness would be problematic though not impossible.

This author did not "buy into" the statement made in the description for this rangeland cover type (Shiflet, 1994, p. 104) as: " Most [areas of the Mesquite-Granjeno-Acacia rangeland cover type SRM 728] are climax types. Failure to recognize this has point has led to many management roblems". In your author's view this statement is incorrect and it is what leads to misunderstanding and "management problems". Range plant communities like the one shown in this and the immediately preceding slide/caption set are disclimax shrublands induced and, in many instances, allowed to continue primarily by human disturbance.

It is brush, pure and simple; and the brush shown here is a Texas-sized patch of brush, an excessive cover of noxious woody plants.

For certain, such disclimax vegetation is now representative of much and, probably, most of the Rio Grande Plains, although the spatial scale and denseness of woody cover shown here was more pronounced than for most brush patches (even by texas standards).

Duval County, Texas. October, autumnal aspect at peak standing crop. FRES No., 32 (Texas Savanna Shrubland Ecosystem). K-54 (Mesquite-Acacia Savanna). SRM 728 (Mesquite-Granjeno-Acacia). Mixed Deciduous Series of Tamaulipan Thornscrub biotic community (Brown et al., 1998). Shallow Ridge range site (Natural Resources Conservation Service, 2011). Southern Texas Plains- Northern Nueces Alluvial Plains Ecoregion 31a (Griffith et al., 2004).

 

Synopsis on Rio Grande Plains "brush country"- There is near unanimous agreement that woody plant cover has increased--quite substantially and to management-important extents--in the Rio Grande or Tamaulipan Plains. Beyond this point, more specific estimates as to degrees of brush infestation remain undeterminable and somewhat controversial. Was the Pre-Columbian vegetation of the South Texas Plains primarily grassland with localized and/or site-specific woody plant communities? Or, was the range vegetation of the Indian Era more of a grass-shrub savanna? What roles did acknowledged overgrazing, reduced incidence of fire, increased commerce, introduction of exotic species, widespread tillage, climate change, etc. (all of which are took place as shown by incontrovertible evidence) play in the vegetational shift from primarily herbaceous to predominately woody vegetation during the White Man Era?

Modern man may never know the answers to such essential questions. Contemporary rangemen will, more frequently than not, have to manage range without benefit of a a baseline for the virgin vegetation and, hence, have less than complete knowldege as to the state of deterioration of current range vegetation.

One of the most interesting historical reconstructions of Rio Grande Plains vegetation at time of the first European explorations is that of Inglis (1964). His analysis was based on acconts of travelers throughout the region from earliest days of Spanish exploration to Anglo-American expeditions at end of the Nineteenth Century. Fascinating reading. In their ecosystem classification Garrison et al. (1977, ps. 39-40) ) interpreted this range vegetation --along with that of the Edwards Plateau--as the Texas Savanna Ecosystem. They described it as a "high shrub savanna" with woody cover ranging from "dense" to "very open".

The Society for Range Management recongized the Rio Grande Plains as being primarily of the Mesquite-Granjeno-Acacia rangeland cover type, SRM 728, (Shiflet, 1994, p. 104)."This cover type exist as open to dense shrubland with 3 to 4 strata". The description further stated that while these shrublands are sometimes vegetation resulting from human disturbances such as overgrazing and fire exclusion, most are "climax types". Traditionally, most range managers and scientists have not had such a benevolent attitude towards woody vegetation in the Rio Grande Plains which they regarded as "brush" and "brush invasions". At the same time, almost all range workers have acknowleeged that the potential natural (climax) vegetation of the Tamaulipan Plains Region is range site-specific. In something of the spirit of these shrub-dominated range plant communities being "climax types" (Shiflet, 1994, p. 104) they are--in this rangeman's view--textbook disturbance climaxes.

Plus, as is the case for most if not all disclimaxes the words of Hamilton et al. (2004, p. 6) quoted above bear repeating at this juncture: "Brush-dominated rangelands will not revert to productive grasslands or savannas if livestock grazing is reduced or even totally eliminated. The conversion of woodlands back to grasslands requires sustained human intervention, including brush removal (with reseeding in many cases), maintenance or follow-up control practices, and proper livestock grazing management".

The long section immediately below featured important, especially dominant and associate, plant species of the Rio Grande Plains grassland and grass-shrub savanna. Some range plant species were already presented along with the exact (or very similar) range plant communities and at the same locations. Other plants, including many of those presented below, were shown in a more generic venue.

 

70. Sward of understorey of guajillo ridge-mixed surub subtype- Detail of herbaceous layer of the general mixed bursh type of Tamaulipan Thornscrub (Rio Grande Plains "brush country") of the example shown above. Dominant grasses were silver bluestem and shortspike windmillgrass. Other grass species that were present in smaller propotions included little bluestem, sideoats grama, buffalograss, curly mesquite, plains bristlegrass, and reverchon bristlegrass.

Common bermudagrass (Cynodon dactylon) was also commonly present, but this species was limited to perimeters of ranges adjoining highway rights-of-way and it was not known if bermudagrass had naturalized or existed locally only as an adventive species. At some locations (but not the one from which these examples were taken) King Ranch bluestem (Andropogon ischaemum= Bothriochloa ischaemum) and buffelgrass (Pennisetum ciliare) were naturalized species in the sward of Tamaulipan Thornscrub range vegetation.

Live Oak County, Texas. October.

 

71. Plant of shortspike windmillgrass (Chloris subdolichostachya)- Shortspike windmillgrass is often a dominant grass on Rio Grande Plains shrub-grass savanna. Gould (1975, p. 327) concluded that this species was a natural hybrid derived from crosses between hooded windmillgrass (C. cucullata) and common windmillgrass (C. verticillata) and crosses between hooded windmillgrass and slimspike windmillgrass (C. andropogonoides).

Shortspike windmillgrass is one of the most strongly stoloniferous of Chloris species, many of which are strictly tufted (= cespitose) species (ie. all lateral shoots are tillers). Due in large part to its stoloniferous habit C. subdolichostachya is frequently a dominant grass species, especially at local scale, in the South Texas "brush country". A similar situation exists with regard to buffalograss (recall photographs presented above of the hardlands subtype of the deciduous mixed shrub savanna) and curly mesquite on South Texas Plains Savanna.

Shortspike windmillgrass is commonly a species of disturbed conditions (eg. situations of overgrazing or overmowing). No doubt this is largely due to the stoloniferous habit of this species. (Other stoloniferous grass species like buffalograss and curly mesquite are also frequent dominants of the Tamaulipan Thornscrub.

Live Oak County, Texas. October.

 

72. Inflorescences of shortspike windmillgrass- Two views of flower clusters of C. subdolichostachya. Interpretation and description of the inflorescences of Chloris species remains a confused affair. Traditionally the Chloris inflorescence was viewed either as 1) a group of spikelike racemes, a raceme being the Gramineae inflorescence type in which spikelets are pedicellate-- on a pedicel or short stalk-- on the rachis or central stalk of infloresecnce, or 2) an arrangement of one-sided spikes with or having sessile spikelets (Hitchcock and Chase, 1950, ps. 22, 519; Chase, 1964, ps. 54-57) consistent with the historic Chlorideae tribe .Gould and Shaw (1983, p. 120) described the Chlorideae inflorescence as "a unilaeral spike or of few to several unilateral spicate primary branches" while Gould (1975, p. 316) had previously characterized the Chloris inflorescence as ranging from "open to contracted panicles of few to several digitately to subdigitately arranged one-sided spicate branches".

Anyway, here is what the inflorescence looks like from both lateral and dorsal views. The inflorescence of C. subdolichostachya typically has only one whorl of "spicate branches" like C. cucullata rather than several such whorls as in C. verticillata.

Live Oak County, Texas. October.

ot show what it is supposed to show*, namely a extremely large specimen of red grama slimspike windmillgrass or, less commonly, bluestem windmillgrass (Chloris andropogonoides) growing on the Rio Grande Plains. Slimspike windmilgrass is one of the most abundant Chloris species in his region. It appears to do especially well on seedings of introduced grss species like King Ranch bluestem and bufflegrass. This plant was growing

 

73. Another one widespread in the Rio Grande Plains- Two examples (number of individual plants unknown) of slimspike windmillgrass (Chloris andropogonoides) growing on the Rio Grande Plains shown in two top-down (more-or-less), progressively closer camera-distance views. Plants of this widespread species could be described as having a "far-flung" appearance or, in more botanically correct terms, a sprawling habit. Along with that morphology, plants of this species can produce a "jillion" sexual shoots with a "gazillion" seeds (see details of flower clusters below).

Slimspike windmillgrass is primarily a cespitose species, but it does have short stolons (Gould, 1975, p. 324). The short stoloniferous habit was pronounced in the examples shown here, which helped to explain their robust size (that and fact that it was a "good rain year"). Everitt et al. (2011, p.79) remarked that slimspike windmillgrass becomes a conspicuous tumbleweed when the panicle infloresecences break off from the lower sexual shoots.

Successional status of slimspike windmillgrass is one of those finner points buried in old range site descriptions that have been lost (other than in archival storage or personal collections) and now supplanted by ecological site descriptions which, for most range sites, remain to be done. Natural Resources Conservation Service "pulled" (removed) the "out-dated" (in the agency's bureaucratic view) and long-used descriptions with nothing to replace them with. In your author's limited experience, slimspike windmillgrass is an increaser. It prefers clayey soils on which--as shown in these two images--can produce abundant herbage available for both forage and soil protective cover.

Zavala County, Texas. Mid-October; peak standing crop, grain shatter stage.

 

74. More views of a widespread Rio Grande Plains grass- Closer-in, top-down view (first slide) and side view (second slide) of inflorescences of slimspike windmillgrass produced on the Rio Grande Plains.

The morphology of slimspike windmillgrass appears quite avariable as one traverses the Rio Grande Plains Region. Perhaps that is because this species hybridizes with hooded windmillgrss (C. cuculata) and common or tumble windmillgrass (C. verticillata). Gould (1975, p. 324) explained that hybridization occurs where biological ranges of these species overlap and can esult in "rather large hypbrid populations, especially in disturbed areas". "Disturbed areas" describes most of current range conditions in the Rio Grande Plains.

As abundant as slimspike windmillgrass is, it is rather surprising that there has not been more treatment of it in the range literature. Everitt et al. (2011, p.79) provided the best coverage of this species that this author found. Everitt et al. (2011, p.79) described slimspike windmillgrass as weedy, especially along roadsides, and "... of poor livestock and widlife value".

Duval County, Texas. Mid-October; grain-shatter stage of phenology.

 

75. Not a exactly a slim inflorescence- Flower cluster of slimspike or, sometimes, bluestem windmillgrass produced on Rio Grande Plains mixed prairie range. The inflorescence of the Chloris species was described by Gould (1975, p. 316) as "open to contracted panicles of few to several digitately to subdigitately arranged one-sided spicate branches". Quite a mouthful for a genus of mostly weedy, rather low-vaue grassses. Flower clusters of the eragrostoid grasses are more complicated than those of most of the other Gramineae subfamilies (but eragrostoid spikelets/florets are less confusing than those of the panicoid grasses, at least to most beginning Agrostology students).

Obviosuly, panicles of slimspike windmillgrass are of the open habit or form.

Zavala County, Texas (first two slides) and Webb County, Texas (third slide). Mid-October; grain shatter phenological stage.

 

76. Drought-stressed and still standing- Local population of hooded windmillgrass (Chloris cuculata) on a hot, dry south slope in the West Cross Timbers at near end of a growing season in which less than two and a half inches of rain had fallen in the previous two-month period. This is another widespread Chloris species that is common in the Rio Grande Plains. Photographs of this species shown in this section were all from northcentral Texas, several hundred miles north of the South Texas or Tamaulipan Plains. In addition to the self-defining sameness of taxonomic features within a species, the droughted "look" of this plants was only all too typical of plants calling the plains of south Texas and Mexico their home.

This perennial (most Chloris species are perennials) is generally a weedy plant of disturbed habitats like waysides, refuse dumps, overgrazed pastures and overmowed lawns. On harsh sites, especially local areas (microsites) hooded windmillgrass should probably be interpreted as an increaser. On extremely abused ranges in the brushy Rio Grande Plains this species might be "about as good as we could expect". Obviously it--like any vegetative cover--offers some protection of soil from erosion and serves to slow rate of water runoff thereby enhancing infiltration even if ever so slightly.

Erath County, Texas. September; various stages of sexual reproduction.

 

77. Not a giant but a champion of its species- Two views of a relatively large (and probably comparatively old) plant of hooded windmillgrass. This individual was growing in the population shown immediately above. It was growing in an abandoned yard and had not been mowed during the entire current growing season thereby showing the size (height, shoot density, and biomass) to which this species is capale of attaining. This growth had occurred in a spring through late summer period that had gotten less than two and a half of rain in the last two months. This plant showed the extent of reproduction, both asexual (shoot, tiller, production) and sexual (grain yield), in a perennial eragrostoid grass under conditions of moderate to severe drought.

Examples of inflorescences of this species were presented in short order below so that viewers could gage the extent of plant effort (allocation of its resources) to sexual versus asexual reproduction. And, "that ain't the half of it": look at the next photograph.

Erath County, Texas. September.

 

78. Gnawed off and growed back- The large plant of hooded windmillgrass introduced in the two immediately preceding photographs was mowed "slick to the ground" and had produced this much regrowth in about 16 days on land that had received less than two and a half inches of precipitation in the previous two months of summer. This plant had not suffered any detectable defoliation throughout its entire growing season until the shoot was mowed to a stubble height of about one and a hald to two inches. a little more than two weeks before this photograph was taken. This and the previous two photographs showed the extent of regrowth in hooded windmillgrass that was possible under harsh conditions of moderate to severe drought following complete protection from grazing and mowing during the plant's current growing season.

Note that regrowth included sexual reproduction with the production of numerous inflorescences. This sexual reproduction was following an already heavy grain yield prior to mowing (two photographs above). Grass is a survivor: this plant (as a genetic individual, genotype, and as a representative of its species) provided a fine example of Darwin's Theory of Natural Selection and Survival of the Fittest. Could there be any doubt but what this genetically unique individual had produced propagules from a reshuffled genetic deck (recombination of genes)? Carry on, weedy grass.

Erath County, Texas. September.

 

79. Hood 'em up; put 'em out- Examples of hooded windmillgrass growing on a dry south slope in West Cross Timbers of northcentral Texas during a moderate to severe drought (less than two and a half inches of precipitation over the last two months). The two plants shown here were "pasture mates" of the large plant shown unclipped or not defoliated (first two photographs of hooded windmillgrass) and in regrowth following close mowing (photograph immediately above). These two specimens were considerably smaller and thus were better able to display to advantage the total aboveground portions of this species (ie. it is more likely that all parts of shorter plants can be kept in focus due to subject presenting less, meaning shallower, depth of field).

Viewers should observe that some two-thirds (probably more) of plant height is in sexual (flowering) shoots (ie. height to which leaves attain is a small fraction of total plant height). Low leaf height is one adaptation to heavy defoliation. These examples showed morphology of grasses adapted to defoliation and related disturbances. Hooded windmillgrass was interpreted by Hatch and Pluhar (1993, ps. 72-73) as a shortgrass having Fair feed value for livestock and wildlife.

Erath County, Texas. September; soft dough to grain-ripe stage.

 

80. A herd of hoods- Numerous inflorescences of hooded windmillgrass bearing grain in soft dough to ripe stages. These sexual shoots were produced on plants that had been completely protecting from grazing or mowing throughout the entire current growing season that was a moderate to severe drought (less than two and a half inches of rain fell in the two-month period prior to time of photographs). Later these plants were mowed to a height of two inches or shorter, but even under drought stress they regrew and produced a second crop of inflorescences that reached mature grain stage.

Erath County, Texas. September; soft dough to grain-ripe stage.

 

81. A closer look at hoods- Details of inflorescences of hooded windmillgrass with fully ripe caryopses (first photograph) and of one set of racemes with ripening caryopses (second photograph). Erath County, Texas. September; soft dough to grain-ripe stage.

 

82. Turnt dark and inward- Single inflorescence of hooded windmillgrass with fully ripened grains and the final upward and inward curl of inflroescence branches that are basis of the "hooded" characteristic that is basis of the common name.

Erath County, Texas. September.

 

83. Showy annual of disturbed sites- Showy or feather fingergrass (Chloris virgata) is one of the few annual Chloris species (one of only two in Texas; Gould [1975, p. 321). Showy chloris (as this species is also known) is typical of annual grasses in being generally a weedy (ruderal) species that does best on disturbed habitats. Hence this feathery little fellow is widespread throughout much of Texas (it occurs in every vegetational or land resource area) thriving on the infinite, locally abused environments such as barrow ditches and berms of roads, old fields, abandoned city lots, school yards, and, obviously, overgrazed ranges and pastures.

Feather fingergrass therby provides the indispensible functions of pioneer plant species as colonizers of denuded seres to begin the process of secondary plant succession. In the process, this species provides protection of exposed soil against ravages of accelerated erosion, furnished feed for livestock and wildlife, gives cover and nesting material for birds at the same time giving a striking presence to any landscape it graces.

Erath County, Texas. September; various phenological stages from grain-ripening to shatter.

 

84. Showy habit of showy fingergrass- A single plant (and part of another) of the annual Chloris species known by an assortment of common names such as feather fingergrass, showy fingergrass, and showy chloris. Shown here and in detailed photographs below is the prolific grain-producing feature of annual grasses. This is part of the ecological "strategy" of r-selected species and ruderals. For discussion of ruderal features, the ruderal strategy, see Grimes (1979, ps. 39-45, 48-49, 56-66). It was left it up to the reader to choose which of the various categories feather fingergrass fit best; an educational thought experiment as it were.

Feather fingergrass also provided an example of the cespitose growth form. As shown with the specimens presented here most shoots produced by this annual grass are tillers (vertical, intravaginated shoots). This species does, however, sometimes produce stolons (Gould, 1975, p.s 321).

Erath County, Texas. September; various phenological stages from grain-ripening to shatter.

 

85. Showy study of feathered fingers- Inflorescences of showy or feather fingergrass showing details of the features of this annual Chloris species. This is one grain-producing range grass. Gould (1975, p. 321) reported that there were approximately ten, one (sometimes two)-flowered spikelets per centimeter along each digitate branch of the panicle (and as many as 20 such branches).

Interpretation of Chloris inflorescences is, simply put, a muttled mess. Historically the Chloris inflorescence was viewed either as 1) a group of spikelike racemes, a raceme being the Gramineae inflorescence type in which spikelets are pedicellate-- on a pedicel or short stalk-- on the rachis or central stalk of infloresecnce, or 2) an arrangement of one-sided spikes with or having sessile spikelets (Hitchcock and Chase, 1950, ps. 22, 519; Chase, 1964, ps. 54-57). This was a tribal-wide (Chlorideae) description. Gould and Shaw (1983, p. 120) described the Chlorideae inflorescence as "a unilaeral spike or of few to several unilateral spicate primary branches" ; previously Gould (1975, p. 316) had characterized the Chloris inflorescence as ranging from "open to contracted panicles of few to several digitately to subdigitately arranged one-sided spicate branches".

The characteristic pubescence of this species is the combination of various sizes and patterns of hairs on margins, keels, and midnerves of lemmas (Gould, 1975, p. 321).

(Erath County, Texas. Phenology varied from grain-ripening (dough) to grain-shatter stages.

 

86. Fully ripe and still showy- Single infloresecence of showy fingergrass at grain-shatter stage. Erath County, Texas. September.

 

87. Sorta nifty- Bearded swallowwort (Cynanchum barbigerum) growing at the edge of a typical Rio Grande Plains brush. Well yes, the entire Rio Grande Plains was, in effect, converted by the whiteman into one big brush patch, but at margin of one of countless brush patches within the one big brush patch was this member of the milkweed family (Asclepediaceae). Some of the more recent taxonomic treatments put the Cynanchum species in family Apocynaceae, but this was probably based on some cladistic reinvention so this rangeman rejected it.

Your rangeman photographer/author thought bearded swallowwort was a nifty plant (and with a nifty common name) so it was included among Rio Grande Plains range plants. Of unknown economic value (if any), but at least it was a native range plant and was every bit as ornamental as most of the introduced botanical trash. Furthermore, there is probably a whole array of range symbiotic relations with this "vine milkeed". By the by, another (and very approprate) common name for this range plant is thicket threadvine.

Duval County, Texas. Mid-October; peak standing crop, peak-bloom phenological stage.

 

88. One sprawling shrub- A Texas-sized female plant of armed or tuberceled saltbush (Atriplex acanothocarpa) grrowing on sandy, disturbed area in the northern Rio Grande Plains. This gal covered an area roughly 15 feet by 10 feet. Tubercel refers to a projection or protuberance on the surface of organisms; tuberceled then means having tuberceles or surfact projections.

Tuberceled saltbush is an evergreen shrub according to Correll and Johnston (1979, p. 544), but Vines (1960, p.236) described armed saltbush as a subshrub that is woody at trunk and branch bases and herbaceous otherwise. The latter description was more correct in describing the specimen seen here. (Carter [2012, p. 350] "hedged his bets" and said armed saltbush was an evergreen shrub or subshrub.) Tuberceled saltbush has a species range as far west as Arizon and south into THE Mexican states of Chihuhua and Nuevo Leon.

The Atriplex genus is rich in species, many of which are major browse species, bu here are only four Atriplex species native to the Rio Grande Plains. The saltbush family (Chenopodaceae) is clearly a minor player in the Tamaulipan Plains compared to the legume family (Leguminosae).

Astute observers should have noticed that there were numerous other plants (with considerable crown cover) of armed saltbush behind the featured specimen in foreground of this wide-angle photograph.

Dimmit County, Texas. Early October; peak standing crop, immature fruit stage of phenology.

 

89. Armed but not dangerous- Views showing long leaders or branches (first slide) and shorter segments of these leaders (second slide) of the female plant of armed saltbush that was introduced in the immediately preceding slide.

Armed or tuberceled saltbush has not received "wide coverage" in the Rio Grande Plains range plants literature. The old stand-by of Vines (1960, ps. 235-236) and more recent treatments by Powell (1988, p. 134) and Carter (2012, p. 350) pretty much covered it (leaving much unsaid). Powell (1988, p. 134) remarked that tubrceled saltbush "is evidently not an important browse plant"

Dimmit County, Texas. Early October; peak standing crop, immature fruit stage of phenology.

 

90. Small arms compared to those of the legumes- Two closer-in views of a leader of a female armed or tuberceled saltbush. These views showed the tubercels around fruit units in the large, sprawling plant introducd above. Atriplex species are dioecious with there being male and female plants.

An old expression of the South Texas Brush Country holds that "everything on this range carries a weapon [or "is armed"]: brush, cattle, horses, reptiles, and men". A variant on this is the adage that "the only critters living in this God-forsaken country are varmits". Armed saltbush complies with these age-old observations, but the short arms of tuberceled saltbush do not begin to compare with those of the legumes (see below).

Dimmit County, Texas. Early October; peak standing crop, immature fruit stage of phenology.

 

Now is an opportune time for some DYCs (Damn Yellow Composites) at home on the Rio Grande Plains. The following composita species are all ecological invaders, "Plant species that were absent or present in very small amounts in undisturbed portions of the original vegetation of a specific range site and will invade following disturbance or continued overuse [ie. with overgrazing]" (Kothmann, 1974).

91. A golden composite- Common goldenbush (Isocoma coronopifolia) is a subshrub in tribe, Astereae The specimen presented here as whole plant (first slide) and flowering or saexual shoots (seond slide) was growing on a deadfully degraded range on a Clay Flat range site (Natural Resources Conservation Service, 2011). Goldenbush was described as a "bushy half-shrub" by Everitt and Drawe (1993, p. 57).

All of the Isocoma spcies are ecologicl invaders, but dense stands of goldenbush are largely--though not always--a local phenomenon. Correll and Johnsoton (1979, p.1579) summed up members of the Isocoma genus: "These plants that are nonpalatable to grazing animals increase in abundance because of the prevailing range-regime of ruthless and destructive overstocking in much of southern and western Texas".

There you have it: a straightforward statement that applies to many of the range plants now growing in abundance on the Ro Grande Plains..

Duval County, Texas. Early October; peak standing crop, peak bloom phenological stage.

 

92. Golden crowns-Crown-resembling (supposedly) heads and deeply loved leaves of common goldenweed growing on a Clay Flat range site of deteriorated mixed prairie (formerly). Representative views of this species.

Duval County, Texas. Early October; peak standing crop, peak bloom phenological stage.

 

93. Golden eyes and green skeletons- Large specimen of skeletonleaf goldeneye or, lses commonly, rosinbush (Viguiera stenoloba) growing at edge of a brush patch in the Rio Grande Plains. Corell and Johnston (1979, p. 1647) described this invader secies (ecologicl invader) as a "much-branched shrub". This large shrub of the huge Heliantheae tribe has a spcies range in south and west Texas (Rio Grande Plains, Edwards Plateau, and Trans-Pecos Basin and Range vegetational areas) and westward to New Mexico and south into several Mexican states including Chihuhua and Durango (Powell, 1988, p. 471; Everitt and Drawe, 199, p. 62-63).

Treatment--brief though it was-- of skeletonleaf goldeneye was offered by the ever-reliable Vines (1960, p. 1011) as well as the previously cited Corell and Johnston (1979, p. 1647), Powell (1988, p. 471), and Everitt and Drawe (1993, p. 63).

Duval County, Texas. Early October; peak standing crop, peak bloom phenological stage.

 

94. Golden eyes and a green orthopteran- Various views of decreasing camera distance of skeletonleaf goldeneye. The capitulum (head) presented in the second slide provided a convenient perch for a male of the common short-winged katydid (Dichopetala brevihastata).

Duval County, Texas. Early October; peak standing crop, peak bloom phenological stage.

 

95. Gummed up the works- Gumhead or tatalencho (Gymnosperma glutinosum) or, based on the older scientific name, sticky selloa (Selloa glutinosa) at peak annual development (and in a "good"--meaning wet--"year"). Gymnosperma or Selloa is a monotypic genus within the aster tribe (Astereae). Plants of G. glutinosum were described by Correll and Johnston (1979, p. 1573) as a"straggly shrub". The fine examples presented here were growing on a degraded mixed prairie range on a Gravelly Ridge range site in the northwestern Rio Grande Plains.

Gumhead or sticky selloa is an ecological invader and is of such low palatability to most range animals that it thrives under conditions of overgrazing. In addition to the previously cited Correll and Johnston (1979, p. 1573), the always-ready Vines (1960, ps. 995-996) and, much more recently, Everitt and Drawe (1993, ps. 56-57) and Clendenin (2016, ps. 160-161). It was interesting that both the older and the newest sources both used the binomial, Selloa glutinosa.

Zavala County, Texas (first slide) and Uvalde County, Texas (second slide). Early October; peak standing crop and full- or peak-bloom phenological stage.

 

96. Still gummed up- Gumhead, tatalencho, or sticky selloa shown as one side of a large plant (first slide) and leaders or branches (seccond slide) growng on a Gravelly Ridge range site of a severely deteriorated mixed prairie range in the northern Rio Gande Plains.

Zavala County, Texas (first slide) and Uvalde County, Texas (second slide). Early October; peak standing crop and full- or peak-bloom phenological stage.

 

97. Even more gummed up- Many capitula (heads) of gumhead, sticky selloa, or tatalencho, a common invader on a degraded Rio Grande Plains range.

Zavala County, Texas Early October; at full- or peak-bloom phenological stage.

 

98. Bristles on the dog- Bristleleaf dogweeed (Dyssodia tenuiloba) on severely deteriorated range vegetation on a Gravelly Ridge range site (). This highly variable annual to short-lived perennial forb (Correll and Johnston [1979, ps. 1682-1683] described four taxonomic varieties in Texas) is definitely an invader of some of the worst rangeland from the Texas Coastal Prairies and Marshes westward to Arizona and south into northern states of Mexico. Decent summary treatent of bristleleaf dogweed was in Everitt et al. (1999, ps. 66-67).

Uvalde County, Texas. Early October; peak herbaceous development, full-bloom stage of phenology.

 

99. Is this really a dud?- Dudweed or dudweed paperflower (Psilostrophe gnaphalodes) growing on a Gravelly Ridge range stite (Soil Conservation Service, 1985) of a severely depleted range in the western Rio Grande Plains. This range forb is a biennial (rarely a short-lived perennial) found from south and west Texas down nto northern states of Mexico (Correll and Johnston, 1979, ps. 1700-1701).

Dudweed paperflower is a toxic range plant, but mostly for sheep which usually recover on their own afer removal from paperflower-infected range. A quick, handy reference is this ragard is Hart et al. (2003, ps. 160-161). Much more detailed information is available in the two editions of the encyclopedic Toxic Plants of North America (Burrows and Tyrl, 2001, 2013). Everitt et al. (1999, ps. 56-57) noted that while this forb is poisonous to sheep and catle, its leaves and flowers are consumed by white-tailed deer.

Zavala County, Texas. Early October; peak- to late-bloom phenological stage.

Time for an installment of one of the quintessential Rio Grande Plains shrubs: Texas or Lindheimer pricklypear (Opuntia engelmannii var. lindheimeri= O. engelmannii var. engelmannii = O. engelmannii var. texana= O. lindheimeri var. lindheimeri= O. phaeacantha, at least in part). Nomenclature and taxonomy of this taxon (including as many as three or four varieties) has been controversial and confusing for decades. Powell et al. (2008, ps. 104-109) stated that the varieties were distinguishable based on color (white or yellow) of spines and features of glochids. Nevertheless, confusion "reigns supreme" in regards to the proper scientific name of good ole, every place, every day Texas pricklypear.

This iconic succulent is so much a part of the Rio Grande Plains"brush county" that your instructor inserted examples in two "episodes" (photographic parts) of this chapter. Immediately below was the first or introductory installment.

100. One example (and there must be a billion others about like it)- Large specimen of Texas pricklypear of the "common garden variety". This plant was growing in the dense, fine-textured soil of a Clay Flat range site. It was bearing a heavy fruit crop in a "wet year". Coverage of Texas prickly pear can be foun in Correll and Johnston (1979, ps. 1091-1092), Weniger (1984, ps. 244-258), Everitt and Drawe (1993, ps. 36-37), and Powell et al. (2008, ps. 104-109).

Webb County, Texas. Early Ocober; fruit-ripe phenological stage.

 

101. Bearing much fruit- Berries (the fruit type of the Cactaceae) along the "ridgeline" of cladodes or cladophylls, the fleshy or succulent shootsections or segments of the large specimen introduced in the preceding slide. The large genus, Opuntia has some species which have flattened or plate-shaped cladophylls known gererally as "pricklypear" and other species that have cylinderical or rod-shaped cladophylls generically called "cholla". These are in subgenus Platyopuntia and subgenus Cylindropuntia, respectively. Some authorities have elevated these two subgenera to the level of two genera, but more commonly Opuntia is the genus for both groups. Students should note in this regard that the scientific name or binomial consist of genus and specific epithet not subgenus as in Opuntia engelmannii not Platyopuntia engelmannii unless,of course, Platyopuntia is regarded as the proper genus (subgenus elevated to genus).

The fruit of priccklypear can be viewed as either "bad" from the perspective of spreading seed of an ecological invader and worsening an already horrible brush problem. Alternatively, pricklypear berries can ber seen as "good" from the standpoint of providing a concentrate feed for range animals (especially some wildlife species) and food for humans (as in "larrupin' good" pricklypear jelly).

Webb County, Texas. Early Ocober; fruit-ripe phenological stage.

 

102. Along the top- "Ridgeline" of a cladophyll of Texas pricklypear. Top-down view of a flattened or plate-like shoot of Texas pricklypear showing spines, glochids, and berries on one shoot segment of the large plant introduced above. Glochids and berries were discussed in the immediaely following caption.

Webb County, Texas. Early Ocober; fruit-ripe phenological stage.

 

103. Berries with glochids- View of ripe berries on the "ridge row" of a cladophyll (first slide) and sliced open berry (second slide) of the big specimen of Texas pricklypear presented above. Glochids, the tiny (and barbed) hairs usually arranged circularly, can be seen on the intact still-attached berries in the first slide. All experienced ragemen know that it is the small, short glochids (not the the big, hard, thorn-like spines) that are the most troublesome. Spines pierce the skin and then readily come out of their puncture wound as the careless traveler moves away. Glochids, on the other hand, break off and stay attached to the skin where they are difficult to grasp and remove. If the tiny, bristly glochids remain attached long enough, they can cause skin iritation.

In the Rio Grande Plains all the varmits--from plants to insects to reptiles to men--carry "weepons". This included the "long-armed" Texas Longhorn cattle before they were replaced by the likes of non-discript, muhly, black cattle. The other Rio Grande denizens remain fully armed.

"The cactus plants are hard on pants deep in the heart of Texas. That's why, perhaps, they all wear chaps deep in the heart of Texas." Song, "Deep in the Heart of Texas".

At any rate the Texas pricklypar berries are a concentrated source of nourishment for insects, birds, reptiles, and mammals (including man). The prickly pear fruit was an expecially valuable food for the Indians.

Webb County, Texas. Early Ocober; fruit-ripe phenological stage.

* As a classroom teacher for upwards of 40 years your instructor learned some of the "tricks of the trade". One such technique is to have important points in several locations (at least more than one) in the lecture, textbook, notes, web publication, etc. This is a variant form of repeating important points. Students learn better if the teacher says the same thing several times at normal or even fast "speaking speed" rather than saying it once very slowly. The chanting auctioneer is a master of this technique saying the same times numerous times in rapid succcession. Any way, students will encounter Texas pricklypear later on in this chapter.

 

104. Interesting, introduced exotic- Specimen of cow's-tongue pricklypear (O. engelmannii var. linguiformis) growing by an apparent home site in the Lampasas Cut Plain in northcentral Texas. This taxonomic varity of Texas pricklypear is a commonly planted (at least in in parts of Texas) introduced form of "ye ole standard" Texas pricklypear. Correll and Johnston (1979, p. 1094) commented that it was "widely cultivated and sporadically introduced in Texas". Weniger (1984, ps. 258-259) explained that reproduction in this frequently planted variety wa almost always asexual. Perhaps presence of berries on the specimen featured here was unusual.

This example of cow's-tongue pricklypear was included because its unique lingulate (tongue-shaped) cladophylls are commonly seen and commented on by viewers who "naturally" assume that it is a naturally-occurring cactus. This exotic (introduced) taxonomic variety does not appear to be naturalized, but instead persist as an ornamental (that is, as a relict surviving after someone planted it for ornamental purposes).

Mills County, Texas.

 

105. Mid-size shrub named little coyote- Humboldt's coyotillo (Karwinskia humboldtiana) at edge of a local brush patch in the central Rio Grande Plains. Coyotillo is defined as the diminutive of coyote. It is a member of the buckthorn family or Rhamnaceae which is one of the more important shrub families across the vast Western Range Region of North America. In this instance, however, this member can be toxic to most range animals. Everitt and Drawe (1993, p. 143) noted that the fruit is eate by El Coyote, which is not so surprising given the highly varied and adaptable diet of Canis latrans.

Duval County, Texas. Early October; fruit-ripe phenological stage.

 

106. Little coyote, but larger leaves- View of crown (first slide) and leaders with leaves and green fruit (seond slide) of Humboldt's coyotillo. Leaf shape and texture are typical of members of the buckthorn family.

Standard treatment for Humboldt's coyotillo is the old stndby Vines (1960, p. 700) and the newer treatment by Powell (1988, ps 276-277), plus briefer treatments but with color plates, by Everitt and Drawe (1993, ps. 142-143) and Taylor et al. (1997, ps. 74-75).

Webb County, Texas (first slide) and Duval County, Texas (Second slide). Early October; immature-fruit phenological stage.

 

107. Now for a little wolf- Berlandier's woldberry, cilindrillo, or tomatillo (Lycium berlandier). Single plant of Berlandier's wolfberry. This species is an example of the typical custom of knowing many shrubs in the Rio Grande Plainsby more widely by their Spanish common names. This woody member of the nightshade family (Solonaceae) has two widely used Spanish common names. Tomatillo refers to small (and, usually, green) tomatoes which, of course, are also members of the nightshade family.

Duval County, Texas. Early October; fruit-ripe phenological stage.

 

108. Lots of little wolves or tiny tomatoes- Berlandier's woldberry, cilindrillo, or tomatillo fruit-laden leaders (first slide) and part of this high fruit yield (second slide). The fruit type of Lycium species is a berry. At least in this instance the common name of the fruit and the actual fruit type are the same, and, by the say the fruit of a domestic tomato, is also a berry.

Good source for abbreviatd treatment of Berlandier's wolfberry is the standard Vines (1960, ps. 911-912) as well as Powell (1988, ps. 380-381), Everitt and Drawe (1993, ps. 164- 165), and Taylor et al. (1997, ps. 38-39).

Duval County, Texas. Early October; fruit-ripe phenological stage.

 

109. Now for a liana- Shooots of the woody vine, Drummond's or Texas virgin's bower (Clematis drummondii). Most Clematis species in North America are forbs being herbaceous. The woody Drummond's virgin's bower is widespread in the Lone Star State being found in all of Texas' vegetational or land resource areas except the Piney Woods.

Duval County, Texas. Early October; peak annual development, late-flowering phenological stage.

 

110. One with flowers less showy than its fruit- Inflorescences of Drummond's virgin's bower. These organs were on the specimen introduced in the preceding two slides. Texas virgin's bower is not an important range plant species in the Rio Grande Plains, but it is one more of many native species that make this range region so botanically rich in plant species and vegetational structure. References for this liana were Vines (1960, ps. 265-266) and Everitt and Drawe (1993, ps. 148-149).

Duval County, Texas. Early October; peak annual development, late-flowering phenological stage.

 

112. Allthorn, spiny allthorn, or junco (Koeberlinia spinosa)- This shrub to small tree is in the small family Koeberlinaceae. This interesting, unique range plant is interpreted by some taxonomists as the only species of a monotypic genus with some authorities regarding Koeberlinia as monotypic for Koeberlinaceae. Plants of this species are typicall leafless but with numerous interlocking branches armed with spines all of which photosynthesis for the highly adapted desert-dweller.

Spiny allthorn has a biological range extending from the Rio Grande Plains westward through the Chihuhuan and Sonoran Deserts though barely reaching southeastern California. It is an interesting and distinctive range plant and while it "adds character" (biodiversity) to the range plant community and earns respect of botanists and "desert tats" like this author it is of no obvious browse value. Birds and small rodents undoubtedly eat its fruit.

Chaparrosa Ranch, Zavala County, Texas. May.

 

113. Allthorn, spiny allthorn, crown-of-thorns (Koeberlinia spinosa)- Another specimen of this unique xeric shrub. Spiny allthorn is commonly regarded as a noxious range plant. It is a frequent though not usually abundant (other than locally) component of scrub communities, especially in the Rio Grande Plains of Mexico and south Texas westward and northward into the Edwards Plateau, Rolling Red Plains, and Trans Pecos Basin and Range areas.

In fact, the next three slide/caption units were of spiny allthorn growing in the Trans Pecos Basin and Range area of Texas.

114. Spiney all around- Plant of spiny allthorn or, simply, allthorn or junco (Koeberlinia spinosa var. spinosa). growing on ecotonal grassland that was part of a broad transition zone between semiarid Staked Plains mixed prairie and arid Trans-Pecos semidesert grassland. This was in the Marfa Basin at eastern margin (Trans-Pecos) Basin and Range physiographic province. This plant seen here was part of banded vegetation in a swale habitat on which blue and black grama were co-dominant climax grasses.

Allthorn is in its own monotypic allthorn family (Koeberliniaceae) (Correll and Johnston, 1979, 1074) and is regarded as ideal cover and feed habitat certain wildlife species, especially quail (Powell, 1988, p. 297). It certainly is a classic example of evolutionary adaptation to xeric environments, and an attention-grabbing plant.

According to Vines (1960, ps. 299) allthorn (in one of its varieties or the other) has a species range extending from the Gulf of Mexico across to Arizona and deep into the Republic of Mexico (Tamaulipas, Sonora, Hildago). In Texas, allthorn is found in the Coastal Prairies and Marshes, Rio Grande Plains, Edwards Plateau, Rolling Red Plains (Redlands), and Trans-Pecos Basin and Range vegetational (= land resource) areas (Gould, 1962, p. 63). hence, this species is not strictly a desert plant by any stretch of imagination. Nonetheless, spiny allthorn is a characteristic plant of the Chihuahuan Desert and adjoining semidesert grasslands (as well as transitional grasslands such as examples featured here). Shreve and Wiggins (1964, ps. 936-937) described both K. spinosa var. spinosa and K. spinosa var. tenuispina for the Sonoran Desert with the latter variety limited to the Lower Sonoran Zone (ie. K. spinosa var. spinosa is much more widely distributed).

Presidio County, Texas. Mid-October; ripe-fruit phenological stage.

 

115. Thorny customer on an ecotone- Fruit (berry)-bearing branches of allthorn that was part of a climax plant community that developed in the form of banded vegetation (explained below) in the Marfa Basin of Trans-Pecos Texas in an ecotonal grassland in this eastern edge of the Basin and Range physiographic province. Leaders (branches) in these two photographs were on the same plant that was introduced in the immediately preceding slide.

This highly branched shrub to, occasionally, small tree with its green-barked, photosynthesizing (and spine-tipped) branches is largely leafless with ephemeral leaves typically reduced to small scales (Vines, 1960, p. 299; Shreve and Wiggins, 1964, ps. 936-937; Correll and Johnston, 1979, p. 1073-1074). Shreve and Wiggins (1964, ps. 936-937) described allthorn as having "rigid, often interlocking, spinose branches". This branching pattern forms an intricate, interlocing, spine-tipped "botanical barricade" that is nearly impenetrable to all but invertebrates and smaller vertebrate species such as reptiles, birds, and mammals which are safely tucked inside a natural breastwork from most predators. The abundant berries are a feed source for animals as well. All in all a very hospitable habitat for those who can enjoy it.

Presidio County, Texas. Mid-October; ripe-fruit phenological stage.

 

116. Spines and berries in banded vegetation- Leafless, spine-tipped, green-barked leaders with ripening berries (first slide) and berries in various stages of maturity with spine (second slide) of spiny allthorn growing in banded vegetation in a swale environment in the Marfa Basin of the eastern (Trans-Pecos portion) Basin and Range physiographic province. Coulter (1891-1894, p. 55) described K. spinosa (no variety given) as a "curious shrub or, sometimes arborescent, apparently destitute of leaves with green stiff very intricate branches tapering into thorns". He went on to describe " minute scale-like caducous leaves" and the fruit as "a small subglobose berry" (Coulter, 1891-1894, p. 55).

According to Allred and Ivey (2012, p. 371) there are three other taxonomic varieties of K. spinosa besides variety spinosa with K. spinosa var. wivaggii the variety in New Mexico. Given close proximity of this Trans-pecos Texas specimen to New Mexico, the specific variety of this plant might be subject to interpretation, but Powell (1988, p. 297) clearly placed all Trans-Pecos spiny allthorn plants in variety spinosa.

Neat plant species to share with fledging students in Range Management, Wildlife management, Conservation Biology, etc. and folks with interests in the amazing natural world.

Presidio County, Texas. Mid-October; ripe-fruit phenological stage.

 

117. Goatbush or amargosa (Castela texana= C. erecta ssp. texana )- This is another spiny shrub of the "brush country". Besides being armed as many, if not most, woody plants of xeric habitats are this is another species in a limited and unique family, Simaroubaceae.

Goatbush furnishes useful browse and mast for native browsers such as white-tailed deer, but it has a much smallere species range than many other woody range plants. Texas goatbush is also found in drier parts of the Edwards Plateau.

Chaparrosa Ranch, Zavala County, Texas. May.

 

118. Desert yaupon, capul, or panalero (Schoefferia cuneifolia)- This is another evergreen shrub in a small family, the Celastraceae (bittersweet or staff-tree family). Interestingly, desert yaupon has a species range remarkably similar to that of goatbush. Likewise, it provides some browse and mast for wildlife. The fruit, which can be important mast at times, is a drupe.

Chaparrosa Ranch, Zavala County, Texas. May.

 

119. Guayacan with naturalized buffelgrass to it's right- Guayacan (Porlieria angustifolia= Guaiacum angustifolium) is one of the more distinctive yet uncommon shrubs (as compared to the myraid species of legumes, cactus, and composites) in the South Texas Plains. Guayacan is one of only two important woody members of the caltrop family (Zygophyllaceae). So students, "who" is the other (and much more important woody member of the Zygophyllaceae? Hint: it is not as important in the Rio Grande Plains as it is in the Chihuhuan, Sonoran, and Mohave Deserts where it is the dominant woody range plant? If you cannot get this one you are a beginning range student. Answer: creosotebush (Larrea tridentata).

Even in second place, guayacan is an important and characteristic (yet, distinctive) shrub of the Tamaulipan Plains, especially the Mixed Brush cover type, the classic Rio Grande Plains Brushlands.

This author could not find a single publicaton devoted exclusively to guayacan. Instead, the following treatments were recommended: Vines (1960, p.575), Powell (1988, p.224), Everitt and Drawe (1993, ps. 190-191), and Taylor et al., (1997, 90-91).

Live Oak County, Texas, October.

 

120. Apex of leader of guayacan showing fruit and leaves- Guayacan is a locally valuable browse, especially for smaller browsers such as sheep, goats, and white-tailed deer.

Live Oak County, Texas, October.

 

121. Crown of a caltrop- View of part of the canopy of a plant of guayacan on a range in the central Rio Grande Plains.

Duval County, Texa. Early October; ripening-fruit stage of phenology.

 

122. Sorta ornate- Leaves and fruit of guayacan on the plant whose crown was presentd in the immediately preceding slide.

Duval County, Texa. Early October; ripening-fruit stage of phenology.

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123. Desert hackberry, spiny hackberry, or granjeno (Celtis pallida)- This is one of three or four species (depending on treatment to subspecies or varietal level) of Celtis species growing in the Rrio Grande Plains, but it is the only that has the evergreen feature. Granjeno is thus one that is more valuable for game browse. In fact, spiny hackberry is one of the more valuable browse plants for wildlife in the Tamaulipan Plains or the southern "brush country"; however, it is seldom used by livestock. Stubbendieck et al. (1992, p. 429) declared granjeno as "worthless for livetock", but it did make the famous "200 [species] list" for the International Range Plant Contest of the Society for Range Management.

Granjeno grows as a shrub rather than as a small tree. Its species range extends deep into and throughout Mexico westward through both the Chihuhuan and Sonoran Deserts to southern California and Baja California.

Chaparrosa Ranch, Zavala County, Texas. May.

 

124. Netleaf hackberry or palo blanco (Celtis reticulata= C. laevigata var. reticulata= C. dorglasii)- Interpretation of the specific standing of netleaf hackberry is varied and, thus, not precisely known. Some workers interpreted it as a distinct species while others viewed it as but one of several varieties of C. laevigata. Plants interpreted as reticulata (regardless of taxonomic level) grow from northern Mexico to the Interior Northwest of Washington and Idaho. In Texas netleaf hackberry occurs in all vegetational areas except the Pineywoods, Blackland Prairie, and Post Oak Savanna. It is often a locally dominant woody plant in the brush country of the Rio Grande Plains where its abundance beyond trace levels (other than locally, on specific range sites, or at microsite scale) is indicative of range degradation due to post-Columbian disturbances ranging from commercial developments like oil fields to a long human history of underburning, overgrazing, tillage, etc.

The small tree presented here was growing in the Coastal Prairies and Marshes land resource area adjacent to the Rio Grande Plains (Nueces County, Texas). October.

 

125. Leader of netleaf hackberry- Terminal part of major branch of netleaf hackberry. Taxonomy--especially the correct specific epithet of this species remains in question. Is it a separate species ((Celtis reticulata) or merely a taxonomic variety of sugarberry (C. laevigata var. reticulata)?

Nueces County, Texas. October.

 

126. Still yet another hackberry and a spiney customer- Desert or spiney hackberry or, more commonl, granjeno (Celtis pallida). This shrubby member of the hackberry subfamily (Celtoideae) of the elm family (Ulmaceae) is one of the characteristic shrubs of the Rio Grande Plains grass-shrub savanna; and, in typical fashion, it carries a weapon.

By the way, observant readers of recent taxonomic treatments may have observed that some of the more modern taxonomists (probably *^#! cladists) have put the Celtoideae in another family. This rangeman so abhored that imaginative mistreatment that he refused to give the plant family name to which Celtis was transferred. (Your author was never one to miss an opportunity to disparage Cladistics so he put down this much. Otherwise, this author is something of a thorny customerwhen it comes to non-traditional Plant Taxonomy.)

Standard authorities for this distinctive shrub included Vines (1960, p. 207), Powell (1988, ps. 116-117), Everitt and Drawe (1993, ps. 176-177), and Taylor et al. (1997, ps. 12-13).

Uvaalde County, Texas. Early October; ripening-fruit stage.

 

127. With its share of fruit- Leaders of spiney or desert hackberry with fruit. The second (lower) slide presented the namesake spines of C. pallida. Fruit type of Celtis species is a drupe.

Zavala County, Texas. Early Octover; both immature- and mature-fruit stage.

 

128. Not so spiney as some, still...- Side view of the outer leaders or branches of a plant of la coma (Bumelia celastrina) on a Shallow range site in the Rio Grande or Tamaulipan Plains grass-shrub savanna. The "about medium" (relatively mid-length) spines or thorns of this shrub species do not compare in size to those of most legume shrubs that dominate so much of the South Teas Plains mixed brush type, but these shorter, smaller spines help to distinguish this shrub to small tree of the Sapotaceae or sapodilla family.

Everitt and Drawe (1993, p. 161) observed that the relatively high protein content (Crude Protein of 12-14 percent) are an imortant browse plant for white-tailed deer while the fruit (drupe fruit type) is an important concentrate for smaller wildlife species including birds and fur-bearers.

This example of an important browse plant was growing as a minor species on a blackbrush-dominated mixed thornscrub range.

Atascosa County, Texas. Early October.

 

 

129. An important nonlegume legume- Local stand of blackbrush, blackbrush acacia, or chaparro prieto (Acacia rigidula) as part of a mixed thornscrub shrubland on a Shallow range site (Soil Conservation Service, 1980) in the central Rio Grande Plains. As a member of tribe, Acacieae blackbrush is in the Mimosoideae subfamily of the Leguminoseae or, according to some authorities, the family Mimosaceae in contrast to the family of "true legumes, Papilionaceae (or, alternativeely, subfamily Papioionoideae). The infloresecneces or flower clusters of the Mimosoideae (or Mimosaceae) are not comprised of papilionaceous flowers which have five petals (two keels, two wings, and the single banner). The only feature that the standard three Leguminosae subfamilies have in common is their fruit which, of course, is the legume fruit type.

In most instances, the only nitogen-fixing nitrifying bacteri-hosting) legumes (dicotyledons whose fruit type is the legume) are the papilionaceous legumes (member species of Papilionoideae= Papilionaceae). Hence, the papilionaceous legumes are also known as the nodulated legumes. Infrequent nitrogen-fixing in the non-papilionacceous legumes is generally minor and more "for the record" than of much ecological significance.

Instead, blackbrush is one of many major noxious woody range plant (meaning brush) speciesthroughout the Rio Grande Plains. In this regard (although dated) see Scifres (1980, ps. 46-47). Standard references for blackbrush acacia included Vines (1960, ps. 492-493), Powell (1988, ps. 184-185), Everitt and Drawe (1993, ps. 94-95), Hatch and Pluhar (1993, ps. 180-181), and Taylor et al. (1997, ps. 8-9).

Atascosa County, Texas. Early October.

130. Lot 'a shootin' goin' on- Multi-trunked specimen of blackbrush acacia growing on mixed thornscrub cover type in the central Rio Grande Plains. There were at least ten individual woody stems to this happily shooted custoer that was growing on a Gravelly Ridge range site. Aboveground parts of this specimen were presented asan upright or vertical view of most shoots (first slide) and as a basal view of the numerous lower trunks.

Movement through dense stands of such blackbrsh plants is neigh on to impossible.

Duval County, Texas. Early October.

 

131. Another specimen and more shoots- Two views of the base of a single blackbrush acacia plant growing on a Gravelly Ridge range site in northwestern Rio Grande Plains. One of the characteristics that usually or typically distinguishes a shrub from a tree is presence of more than one trunk or single base of shoot in a shrub (Helms, 1998). Blackbrush acacia conforms "religiously" to this distinction. Blackbruh is one multi-(often, many) stemed scrubby species. Makes for a quite attractive plant actually; more pertinent to a rangeman is the added difficulty in mechanical (including manual) control of this brush species.

Rangemen can see the multiple facets (faces)--Clint Eastwood's "the good, the bad, and the ugly"--of things such as this range plant species, on the range. We have to take our pleasures where we find them, especially on the mixd brush, thornscrub cover type of the Tamaulipan Savanna Region.

Zavala county, Texas. Early October.

 

132. Not so black as the name implies- Portions of branches of blackbrush acacia growing in the northern Rio Grande or Tamaulipan Plains grass-shrub savanna.

Zavala county, Texas. Early October.

 

133. Blackbrush or chaparro prieto- A young blackbrush was in full bloom in late winter. Looked like a high yield of seed-bearing legumes (wait 'til you see heavy harvest three slides later), but nothing is certain botanically (except more brush) in the uncertain weather of south Texas. This showy specimen was growing on the Gulf coastal prairie that neighbored to the east of the Rio Grande Plains.

Santa Gertrudis Division, King Ranch, Jim Wells County, Texas. February.

 

134. Inflorescences of blackbrush- Details of flower clusters on leaders (branches) of blackbrush. Acacia species are in the mimosa subfamily (Mimosoideae) of the Leguminosae (= Fabaceae). Some authors have placed members of this subfamily (including other major shrub genera like Mimosa and Prosopis of the Rio Grande Plains) in a separate mimosa family (Mimosaceae) and restricting Leguminosae to those taxa that bear the characteristic papilionaceous corolla of banner or standard, keels, and wings.

This latter interpretation has generally been rejected because, as presented below, all these species bear the classic "bean" fruit (= legume).

Santa Gertrudis Division, King Ranch, Jim Wells, County, Texas. February.

 

135. Chaparro prieto or black brush- Heavy fruit yield helped assure continued invasion of this weapon-carrying dominant shrub in the Rio Grande Plains. Chaparrosa Ranch, Zavala County, Texas, May.

 

136. Just what theRio 'grande Plains needed- Huisachillo or twisted acacia (A. tortuosa) is still yet another genus Acacia. Huisachillo was covered in all the standard sources, but this rangeman also referred readers to the classic Sargent (1933, p.593).

Lyle Ranch, Uvalde County, Texas, May.

 

 

137. Guajillo or Berlandier acacia (Acacia berlandieri) on Rio Grande Plains- Specimen of guajillo at fruit-ripe/seed-shatter stage growing on a stoney, sandy ridge in the guajillo ridge-mixed shrub subtype of Rio Grande Plains Chaparral (the example vegetation that was shown above). Guajillo and cenizo were the dominant range species on this example of Tamaulipian Thornscrub Savanna.

Guajillo is one of the major brush species in the Rio Grande Plains. Although his work is dated, Scifres (1980, ps. 67-68) remains good beginning coverage of guajillo as a noxious woody species. General discussion of guajillo was provided by Vines (1960, ps. 497-498), Powell (1988, ps. 187-188), Everitt and Drawe (1993, ps. 90-91), Hatch and Pluhar (1993, ps. 178-179),and Taylor et al. (1997, ps. 12-13).

Live Oak County, Texas. October.

 

138. Guajillo at closer distance- Leaders of guajillo shown at shorter camera distance to feature both compound leaves and legumes of this oft-dominant native shrub in the Rio Grande Plains. This specimen was growing on a Gravelly Ridge range site.

 

139. Guajillo- Rather sparse leader foliage-wise yet plentiful fruit (legume)-wise shoot of guajillo (A. belandieri) growing on a largely degraded range in the northwestern Rio Grande Plains. Guajillo honey (honey made largely from nectar of guajillo) is regarded by many honey connessiours as one of the finest, if not the finest, honey on Earth. Uvalde County, Texas has been at the commonity "epicenter" of guajillo honey for decades.

Lyle Ranch, Uvalde County, Texas, May.

 

140. It will reach out and grab ya- Typical plant of catclaw or catclaw acacia (Acacia greggii var. greggii). This acacia species is widely distributed growing from northern Mexico to the Pacific Ocean (coastal northern California) and in three North Amcerican deserts (Mojave, Sonoran, and Chihuhuan). It also calls the Rolling Red Plains of Texas home which is where the following examples were photographed.

Runnels County, Texas. Mid-October; ripe-fruit stage.

 

141. Little enough but present- Small catkin and compound leaf of catclaw acacia produced on the Rolling Red Plains of Texas. It was expolained in the immdediately preceding caption that catclaw is a widespred--and thus morphologically vriable--woody legume. Catclaw acacia sometimes blooms profusely with large, fully filled inflorescences. The example seen here was produced in the single worst one-year drought in texas weather records.So this plant did well to produce even this much.

Runnels County, Texas. Mid-October; early stage of flowering in this catkin.

 

142. Legume and leaves- Examples of legumes and small compound leaves of catclaw acacia produced on the Rolling Red Plains of Texas in the worst single-year droughton record. Catclaw is more abundant on a regional basis in the Rio Grande Plains than in the Rolling Plains portion of the Great Plains. This species is also widespread in the Chihuhuan, Sonoran, and Mojave Deserts.

Catclaw acacia is treated in most of the standard references. Your author noted especially Sargent (1933, ps. 594-594) to remind students that the timeless sources, although often difficult to find, are still some of the best. (They were there before Cladistics and its abortive efforts at reinventing Plant Taxonomy, and they will be around long after this research-motivated fad passes.)

Runnels County, Texas. Mid-October; ripe-fruit stage.

 

143. Ready to grow- Ripe, dehisced legume with seeds of catclaw acacia. Runnels County, Texas. Mid-October; following an Exceptional Drought.

 

144. Ebano, ape's earring (and where did they come up with that one?), or Texas ebony (Pithcellobium flexicaule= Ebenopsis flexicaulis= Siderocarpus flexicaulis)- This native legume is also in the Mimosoideae subfamily of the Leguminosae. Texas ebony is a small tree or shrub, often the major source of shade where the same is a valued "commodity" (especially when combined with a breeze). Alone in shrub form or as a small tree growing in association with other woody species, ebano often forms dense thickets (as if there is a legume in the "brush country" that does form thickets).

The dense, dark heartwood of ebano is used for decorative items (eg. belt buckles).

San Patricio County, Texas. June.

 

145. Branch of Texas ebony- Compound leaves, fruit, and inflorescence of ebano (or ape's earring for the imaginative or refined readers of Tarzan novels). San Patricio County, Texas. June.

 

146. Flower clusters of ebano- The inflorences of Texas ebony mark it immediately as a member of the Mimosoideae. San Patricio County, Texas. June.

 

147. Legume (= pulse) of Texas ebony- The opened, ripe fruit of ebano showing the individually encased seeds. Note absence of constricted spaces between seeds in legumes of this species (also obvious in photograph of immature fruit above). San Patricio County, Texas. June.

 

148. Overall, second only to mesquite- Leader (first slide) and compound leaves (second slide) of huisache (Acacia farnesiana= A. smallii) Standard references for huisache are Vines (1960, ps. 496-497), Powell (1988, ps. 182-183), Everitt and Drawe (1993, ps. 92-93), Hatch and Puhar (1993, ps.182-183), and Taylor et al. (1997, ps. 16-17). From a taxonomic perspective see Sargent (1933, ps. 592-593).

Although huisache can be a valuable browse for both livestock (even cattle) and wildlife as well as an important honey bee plant (see about any of the above-cited sources), it is probably the second most invasive brush species in the Rio Grande Plains (behind honey mesuite obviously). For coverage of huisache as a brush species see Scifres (1980, ps. 72-74) who remarked succcinctly: "Huisache is a formidable management problem...".

Bank, Frio River; Uvalde County, Texas. Mid-October.

149. Huisache (A. farnesiana)- Lampasas County, Texas, April.Acacia species are members of the Acacieae tribe of the Mimosoideae subfamily of the Leguminosae (= Fabaceae). It has often been assumed that the leaves and, especially, the fruit of the Mimosoideae legumes are relatively nutritious because animals are commonly observed eating them and the browse test high in crude protein. Recently it has been discovered that these crude protein determinations were substantially over-estimated because the correct coefficient for conversion of Kjeldahl nitrogen to crude protein is closer to 3.0 than to the commonly used "standard" value of 6.25.

Specifically, much of the nitrogen in the legumes is nonprotein nitrogen rather than amino nitrogen so that to accurately determine legume nitrogen contents Kjeldahl values should have been multiplied by 3 and not 6.25. In other words the crude protein values estimated and reported for legumes are twice as high as they really are. (T.D.A. Forbes, Texas Agricultural Experiment Station, Uvalde, Texas, personal communication).

For example, Subcommittee on Feed Composition and Committee on Feed composition (1971) listed the protein (N X 6.25) content of fresh common mesquite pods at 14.4% whereas this feedstuff was actually closer to 6.9%
( 3.0 = 48% then 6.25 0.48 X 14.4% = 6.9%).

Furthermore, members of the Mimosoideae have several secondary plant compounds (eg. tannins) which are detrimental, perhaps at subclinical levels, to ruminants, even to goats and deer. In final analysis, overgrazed ranges in the Rio Grande Plains are "sub-optimal" even for browsers like goats. This country was overstocked with livestock for several centuries and if the leguminous shrubs were palatable to domestic animals those shrubs would not be there now. They would have been grazed out as happened with the grasses. Instead, Acacia and Prosopis species are there because they were eaten less than the grasses and when fires were stopped fire cessation selectively benefited these woody legumes more than it did the grasses.

Most of these native woody shrubs have increased in cover, density, etc. due to mismanagement and retrogression of the rangeland is the result. At the levels at which these species now occur they are noxious range plants. Nor are high levels of such shrubs as are found on many south Texas plains ranges beneficial as habitat for white-tail deer or bob-white quail. Rangemen should do everything economically feasible and biologically possible to destroy these ecological woody invaders. After establishment of proper stocking rates, brush control is the first step in restoration of these once productive savannas.

 

150. Fruit-bearing leaders of huisache- Legumes and compound leaves on branches of huisache. Huisache is often called "sweet acacia" after it's use in the perfume industry. At the densities and crown cover at which huisache often grows on deteriorated ranges in the Tamaulipas savanna rangemen think of it as anything but "sweet".

Pima County, Arizona. June.

 

151. Mature huisache fruits- Ripened legmues of huisache showing some insect predation. Herbivory of range plants takes many forms. Students should never entertain the erroneous assumption that vertebrates like livestock and wildlife are the only range herbivores. Unfortunately, insects have not eaten enough huisache seeds to curtain the excessive invasion of this native plant at unnatural rates since man "progressed" from Noelithic burner of the range to a more technologically advanced range manager.

Pima County, Arizona. June.

DEATH TO MESQUITE, HUISACHE AND ALL THEIR BRUSHY KIN!

152. Honey mesquite (Prosopis glandulosa= P. juliflora var. glandulosa)- Fruit and leaves of the number one noxious range plant in Texas. Mesquite (Adenanthereae tribe of Mimosoideae) does not make a fruit crop every year, but this shot of one cluster of fruit on one branch of one tree (in which each legume or pulse contains roughly 12-15 seeds) demonstrates why this species readily reproduces a new generation of seedlings without a seed crop every year. The fruit is food for a number of seed parasites and predators as well as vertebrates that consume the entire fruit— for what difference, if any, that makes.

Honey mesquite is so widely recognized throughout parts of southcentral and southwest North America as being in a "league by itself" in regards to a brush species that your author was content to refer his readers to "any and all" of the standard sources such as Vines (1960, ps. 515-516) as well as the classic dendrological encyclopedia (Sargent, 1933, ps. 599-603 passim). In addition to coverage by Scifres (1980, ps.) of honey mesquite as generally the number one brush problem in Texas, the Texas Agricultural Experiment Station research monograph edited by Scifres (1973) and the marvelous comprehensive publication by Bovey (2016) were uplifted to serious students of the Brush Problem.

Erath County, Texas, September.

 

153. A new mesquite (read brush) crop- Mature fruits (and the next generation) of honey mesquite shed on Texas range.

Erath County, Texas, October.

 

154. Two mesquite seedlings that germinated in cattle dung- Apparently all ruminants will eat mesquite "pods" with domestic cattle appearing especially fond of them. Many rangemen have observed cattle which were so attracted to mesquite fruit that they forsook almost all other forage and browse as long as the "bean pods" were abundant. It has been long reported in the literature that consumption of mesquite fruit results in scarification and distribution of the seed in their own fertile "seedbed". This is one factor that contributes to spread of this native invader. Buffalo (Bison bison)— among other native ruminants— undoubtedly were native dispersal agents long before the "white man's buffalo" arrived on the scene. This fact continues to raise the unanswered question as to why there was not the mesquite "epidemic" on the virgin range. This is obviously a complex interaction of several factors, but presence of fire on the pre-white man range had to have been one of these (which is not to ignore overgrazing and all other anthropogenic influences including wholesale extermination of prairie dogs, a favorite hypothesis among pioneer Texas cattlemen). Kelton (1993, p. 79) reported accounts of early day farmers who told of their plows frequently hitting old burnt mesquite stumps as they broke virgin Texas sod.

 

155. A young mesquite sapling only 3 ½ feet tall producing a healthy crop of new mesquites amid western ragweed on "go-back land"- "Girls by the mill pond about half-growed; jump on a man like a dog on a bone." (Bob Wills and The Texas Playboys)

Early sexual maturity is one adaptation (natural selection to insure survival of the most fit genes) of shrubs to harsh environments that include frequent burning and other forms of defoliation. This mesquite was approximately five years old. "Mesquite is usually fully mature after 3 years" (Scifres et al, 1973, p. 15).

 

156. Nurse plant phenomenon- Mesquite causes indirect injury and contributes to range deterioration (retrogression) through the process of serving as a nurse plant to numerous species. This has an especially insidious impact in the "brush country" of the Rio Grande-Tamaulipan Plains, but is an important part of the "mesquite problem" even on the Rolling Red Plains where as here mesquite serves to host seedlings of hackberry, pricklypear, and lotebush.

 

157. Torrey croton (Croton torreyanus= C. incanus)- This specimen of Torrey croton was grwong on the example of guajillo ridge-mixed shrub subtype of South Texas Chaparral presented above in four photographs. Gould (1962, p. 56) listed 19 Croton species (several of which consisted of different varieties) growing in Texas. These included shrubs and forbs with both annual and perennial forb species. Torrey croton is a shrub, but its stems (shoots) are typically suffretescent or suffruticose such that upper parts of shoots frequently die back sometime each year (ie. upper portions of stems are annual organs). That condition was clearly visible in this photograph (it appeared that there were more dead than live annual shoots).

Live Oak County, Texas. October.

 

158. Torrey croton in bloom- Shoot tips of Torrey croton at full-bloom. Live Oak County, Texas. October.

 

Second installment of Texas pricklypear- It was remarked above that Texas pricklypear is such an important woody range plant in the Rio Grande Plains that the 'tried and true method" of repeating a subject variously in the lecture was employed in regards this alll-too-often dominant range plant. Here is part 2.

159. Texas pricklypear and, though often causing confusion (and perhaps erroneous to boot) Englemann or Lindheimer pricklypear (Opuntia engelmannia var. lindheimeri= O. lindheimeri)- Shown here and in details of the next three slides is one of the most widely distributed cactus species. It's range extends from the Gulf Coast to the Pacific and from southern Mexico to central Oklahoma. The specific epithet lindeimeri has been proven conclusively to be in error, but it is still commonly used. To add further confusion (to be expected with any species as wide-ranging as this one) some authorities have included varieties of other species (eg. O. phaeacantha var. discarta) in their interpretation of O. engelmannia.

Powell and Weedin (2004, ps. 172-181) may have cut the Gordonian knot and resolved the matter once and for all (but don't bet the ranch on it) by distinguishing Texas pricklypear (O. englemannii var. lindheimeri) from Englemann pricklypear (O. englemannii var. englemannii) synonyms of which include O. englemannii var. discata, O. phaecantha var. discata, O. discata, and O. englemannii).

Whichever author(s) one follows this taxon remains one of the farthest-ranging cacti in North America. It is extremely common in the Rio Grande Plains and Trans Pecos Texas and throughout much of Mexico.

The neighbor to this specimen was the shrubby composite commonly known as mariola. Mariola was shown in full-bloom in several slides below under which it was discussed in greater detail.

Elephant Mountain Wildlife Management Area, Brewster County, Texas. July.

 

160. Texas prickly pear (O. englemannii var. lindheimeri= O. lindheimeri)- According to some authorities this species was incorrectly named and described as Lindheimer prickly pear (O. lindheimeri) based on a mistaken description that was actually a combination of two species, pads of one and fruit of another (Weniger, 1984, p. 245). The probability of such an error was increased by the wide distribution-- and thus much ecotypic variation and phenotypic plasticity-- of this "often misunderstood" species (Weniger, 1984, p. 245). Hopefully Powell and Weedin (2004, ps. 177-181) straightened out the confusion.

The large individual shown here (about five feet tall) had produced a number of large but still immature fruits (along the top ridge of the pads). The "pads" (a common layman's term) are actually the broad, circular-shaped stems (shoot segments) that have two different forms of appendages or sharp outgrowths (ie. "stickers" to employ another lay term) and small, ephemeral leaves (see below). The more technically precise term for these highly modified shoots or stems is variously (depending on reference) that of cladophyll, phylloclade, phyllode, or cladode (a modified, often flattened, photosynthetic stem or branch). Different botanists use these terms in slightly different detailed meanings. (It would appear that almost everything of a scientific nature about these amazing plants is interpreted in various ways by various taxonomists.) By whatever name they are known these highly modified shoots or branches bear either no leaves or short-lived ones such that photosynthesis (the water-conserving Crassulacean-acid metabolism, CAM, pathway) takes place in the stem. This stem is a trunk or bole in some of the larger cacti. This feature is an obvious evolutionary adaptation to water shortage. One of the most spectacular examples of convergent evolution is development of this leafless and succulent stem feature or trait in the spurge family (Euphorbiaceae) and the milkweed family (Asclepiadaceae) as well as in Cactaceae. This is standard textbook fare (see for eg. Raven et al. 1992, p. 518).

The mature fruit of prickly pear is a many-seeded berry often known as a "tuna" (Spanish). These tunas are the source of some of the finest jellies imaginable. They are also used for making candy. The "pads" have sometimes been used for human food as well, first learned by American Indians of course and later passed on to Mexicans and gringos.

The main concern with this species of prickly pear is as a brush (= a noxious plant) species resulting from all of the standard causes ranging from overgrazing, underburning, oil and gas development to climatic shifts. Englemann (and numerous of the other Opuntia species) are major feed plants for wildlife. They provide both browse as in case of the javelina or collared peccary (Tayassu tajacu) and mast (the fruits) for birds, coyotes, coons, etc. as well as for javelina. Under emergency feeding conditions, especially drought, Lindheimer or Englemann prickly pear is one of the major species of "pear" from which the spines are scourced for use as a major survival feed source for cattle and sheep. "Burning pear" (by use of propane burners) has been a principal duty of otherwise proud vaqueros or cowhands during drought that is so recurrent in the Southwest. O. englemannia is a "mixed blessing" on southwestern and southcentral ranges.

The Englemann prickly pear in this photograph was growing on a Sandy Loam range site dominated by blackbrush (Acacia rigidula) in the Rio Grande Plains. Chaparrosa Ranch, Zavala County, Texas. May.

 

161. Fleshy or succulent shoots (cladodes or cladophylls) of Texas pricklypear- In the first of these two slides new "pads" (the succulent stems) of O. englemannia var. lindheimeri) had begun growth from the apical portion (meristem) of parent "pads". The new daughter cladophylls still had their ephemeral leaves (the slightly curved or bent nail-appearing appendages) present along their apices. These rudimentary organs are characteristic of Opuntia species.

Also visible in both of these slides are the epidermal appendages that are modified protective organs. These sharp outgrowths of the members of Cactaceae are of two major forms: 1) spines which are the long, sharp, usually woody, thorn-like "jaspers" and 2) glochids or spicules which are much smaller, hair- or bristle-like "stickers" usually having many tiny (almost microscopic) barbs. These appendages are usually interpreted as modified leaves or leaves reduced to spines as an obvious adaptation to reduce transpiration and increase survival in arid environments as well as adaptative defensive organs to protect these water-storing xerophytes from herbivores. Some cactus specialists and ecophysiologists interpreted spines, especially those resembling hairs (often even white in color), as adaptative structures to shade and insulate the fleshy shoots in order to prevent heat and/or wind injury as well as to reduce water loss by transpiration. Conversely, the insulation feature of these structures prevents heat loss and cold injury at night and in winter. Fluted trunks of cactus serve these same functions (Vankat, 1979, ps. 195-198).

One of the key characteristics of the Cactaceae is the presence of areoles, the area or location on the "pad" around which the spines and glochids (and ephemeral leaves) arise. Areoles are either raised areas (like a pimple) or depressions (ie. pits) which are openings in the epidermis. The areole is unique to the Cactaceae. Areoles are interpreted as buds because they are the source of leaves and the protective outgrowths of spine and glochid. Incidentially it is numbers of the latter organ which cause the most aggravation and irritation to animals (including man) which carelessly stray too close to these succulent species.The spines can obviously cause more injury, but the pesky glochids typically break off in the animal epidermis and are extremely difficult to remove due to the many tiny barbs arranged along the individual glochid.

Areoles, complete with conspicuous glochids and spines, were clearly visible on the pad shown in the second slide. Newly emerging ephemeral leaves were also visible around areoles below the apex of this shoot. Also clearly visible in this second photograph was a developing cactus flower in the center of the "ridge line" (apex) of the cladophyll.

Erath County, Texas. April.

 

162. Ephemeral leaves on a perennial shoot- A cladode or cladophyll of Texas or Englemann's pricklypear with characteristically small, ephemeral leaves called cylindroids. Such tiny, tubular (oblong and slightly pointed) leaves are shed soon after appearing prompting one to wonder for what purpose these short-lived organs evolved.

Ephemeral leaves (the only leaves of Opuntia species) grow near the aeroles or areolas, circular areas out of which grow the long, hard spines and the shorter, flexible (and much more troublesome to remove) appendages known as glochids.

"Pads" (cladodes) of the pricklypear species are flat and thinly circular (somewhat plate- or platter-like) so these Opuntia species are in subgenus Platyopuntia (in contrast to the cylindrical cholla species which comprise the Opuntia subgenus, Cylindropuntia).

Erath County, Texas. Late April.

 

163. Short-lived organs- Ephemeral leaves known as cylindroids of Englemann's or Texas pricklypear on the dorsal surface "spine" or "ridgeline" of a cladode (or cladophyll).

Erath County, Texas. Late April.

 

164. Blooming on the ridge- Inflorescences of Texas or Englemann's pricklypear atop immature fruits aligned along the dorsal edge ("ridgeline") of jointed units of shoots, each of which is a cladode or cladophyll.

In the first photograph there are three blooms each of which is a different stage of flowering: 1) immediate pre-bloom (will bloom tomorrow morning), 2) initiation of flowering (opening bloom) , and 3) flower fully open (peak bloom), right to left, respectively. The second photograph showed a large bloom with a reddish-colored corolla atop a fruit which was a fourth flowering stage: 4) immediate post-bloom (bloom in porcess of closeing; petals senescing/dying). Also in second photograph and to immediate left of post-bloom flower was an unopened flower that was about two days away from opening (ie. this floral unit was one day behind the rightmost floral unit in the first slide or just before 1) in first image).

Each of these inflorescences sat on an immature fruit. The cactus fruit is a many seeded berry (Smith, 1977, p. 104) or in common usage, a "fig",or (in Spanish), a tuna.

Erath County, Texas. Late April.

 

165. Flower of Texas prickly pear- An example of the beautiful inflorescence so characteristic of the Cactaceae. The circular arangement of numerous stamen is an obvious and attractive feature of the cactus flower. Unfortunately (from a human perspective) the blooms of most of the cactus species are notably short-lived, often persisting for only a few hours. Some of the most beautiful cactus inflorescences open solely at night when they are pollinated by nocturnal animals including insects, reptiles, birds, and mammals like bats. Even those that bloom at mid-day are opportunistic and infrequent as to their schedule, erratic precipitation events often dictating when sexual reproduction occurs. The more common and widely adapted species like many of those of Opuntia are less extreme in this regard. This example of O. englemannia var. lindheimeri was right "on schedule" by blooming in May in northcentral Texas (Erath County).

As is true for many perennial range plants, much (probably most) reproduction in Cactaceae is asexual by means of profuse production of cladophylls and their feature of rapid rooting upon physical separation of these fleshy shoots from the parent plant. Cactaceae members are yet other examples of clonal organisms in which individual segments of their fleshy stems ("pads") are modules or ramets of the genetic individual, the genet. A striking example of this was shown two slides below for the next species.

 

166. Beetles in the blooms- Two blooms (inflorescences) of Engelmann's or Texas pricklypear on the dorsal edge of a cladophyll (cladode). The inflorescence at left was a current (today's) bloom while flower at right was a "spent" (yesterday's) blossom. The currently open (today's) flower was shown at closer range (though from a different angle or direction) in the second slide.

Both of these flowers was occupied by a number of scarab beetles known as the common flower scarab or bumble flower beetle (Euphoria kernii), the topic of the next slide and its caption.

Erath County, Texas. Late April.

 

167. Scrounging scarabs- A "herd" of common flower or bumble flower scarab beetles (Euphoria kernii) in a flower of Lindheimer or Texas prickly pear. This ornate scavenger feeds on a wide array of spring flowers throughout southcentral and southwestern North America. It is a pollenivore. Grant et al. (1979) reported that E. kerni was "virtually ubiquitous" in flowers of O. lindheimeri in central Texas and that they "... do carry out some pollination, but not very much". Conversely, these scarab beetles were "highly destructive in some flowers" mainly through consumption of stamens (beetles cannot reach ovules of the inferior ovary so this much is safe from their voracious apetites). McFarland et al. (1987) reported that E. kerni was regarded as being of no more importance than as an accidental pollinator of cholla (Opuntia imbricata) in southern Colorado.

In other words, the flower scarab beetle is a showy, sort-of-cute little "bug" that gets one's attention but is of undetermined ecological importance. Sort of reminded the author of a lot of students he was plagued with over the decades; the difference being that the insects knew and (cared about) what they were doing, died cute, and were less of a burden on their environment.

E. kernii is in subfamily, Cetoniinae family, Scarabaeidae of tribe, Cetoniini.

Erath County, Texas. Mid-May.

 

168. Cactus Jack would be proud- Before leaving the cactus blossum the author included one last pair of nested photographs of Texas or Englemann's pricklypear inflorescences.

The beautiful cactus flower entered the folklore of American and Texas history via the personality of a Texas original, John Nance Garner, IV. Garner ultimately settled in or near Uvalde, Texas from which he was elected to the Texas House of Representatives. During the time that John Garner was a member of the Texas house the state legislature set out to select the Texas State Flower. The flower of the pricklypear cactus was one of several nominees for this honor, and it was the one that John Garner promoted with much colorful enthusiasm. As every Texan knows the cactus flower lost to the bluebonnet, but for the rest of his long life the pricklypear promoter was known as "Cactus Jack". "Cactus Jack" won election to the US House of Representatives and eventually became Speaker of the US House. After being re-elected for 14 consecutive terms Garner decided to run for the US Presidency. When "Cactus Jack" realized that he was going to lose this political contest (like the state flower battle) he cut a deal with the nominee-to-be and settled for position as Franklin Delano Roosevelt's running mate. "Cactus Jack" served two terms as vice-president of the United States, but concluded the vice-presidency was "not worth a bucket of warm piss". (Garner was a traditional--though progressive-- southern Democrat who became progressively at odds with New Deal welfare liberalism.) FDR chose Iowa corn-breeder Henry A. Wallace as his third-term running mate. Garner returned to private life in Uvalde County, Texas where he remained as "Cactus Jack" until he died shortly before reaching his 99th birthday.

Texans and southern conservatives like "Cactus Jack" could interpret these colorful inflorescences as paying tribute to a "yellow dog Democrat" and "cactophil" (or "cactophile"). Otherwise, these provided images of the corolla encircling numerous stamen that surrounded the single, columnar style with its several stigma (appearing as lobes of the style), a key charactistic of the Cactaceae.

Erath County, Texas. Late April.

 

169. Large Texas or Englemann pricklypear in fruit- This old "pear" plant was bearing fruit, but the most obvious mode of reproduction in this clonal plant had been by vegetative (= asexual) reproduction: simply growing more cladophylls. The versality of both asexual and sexual reproduction was illustrated. A county road cut provided a favorable microsite for this representative of it's species.

Texas West Cross Timbers. Erath County, Texas. Late August.

 

170. Texas pricklypear bearing a "bumper crop" of fruit- This large specimen of Texas or Englemann pricklypear (it is still O. englemannii var. linheimeri) bore a fantastically high yield of nearly ripe fruit. It was growing in an area of disturbance in the Texas West Cross Timbers. Erath County, Texas. Late August.

 

171. Fruit of Texas pricklypear- The "ridgeline" of cladophylls (= cladodes) is location on which pear fruit is borne. The concave (dished) upper surface (dorsal or "top") of fruit is the umbilicus. It is the site where inflorescence had been attached. The fruit of the cactus family is a many seeded berry. A berry is a multiseeded, indehiscent, fleshy fruit in which the pericarp (fruit wall) is fleshy throughout; other examples of berries are grape and tomato. The cactus berry of many species, including Englemann pricklypear, is used for making of jellies and candy.

Texas West Cross Timbers. Erath County, Texas. Late August.

Technical Note: The partially out-dated reference, Brush Management - Principles and Practices for Texas and the Southwest (Scifres, 1980), is still the definitive bound source for descriptions, ecology, and key biological aspects of the major brush species in Texas and adjoining parts of neighboring states. Many of the specific brush control practices given by Scifres (1980) are obsolete (eg. 2,4,5-T, arguably the most economically effective broad-spectrum herbicide ever, has been off the market for nearly two decdes).

Brush Management- Past, Present, Future (Hamilton et al., 2004) was the fitting "sequel" to Scifres (1980). Both of these fine works were highly recommended by this author.

For the current best brush control practices one should consult the various Cooperative Agricultural Extension Services, Natural Resources (= previously, Soil) Conservation Service, and/or field representatives of the various companies offering products and services for brush and weed control.

 

172. Cute baby but don't be fooled- Seedling of Texas or Engelmann's pricklypear (O. englemannia var. lindheimeri). Even the little guys of this succulent species are natural-born survivors. Note the swollen-appearing bulb that is the rootcrown (union of shoot and root) of this cactus. Even at this small size and young age this rascal is adapted to survival following defoliation. If a range fire topkilled this tiny plant it could quickly and effectively resprout from the meristem of this organ which is a form of lignotuber. Likewise, even at this "tender young age" the infantile root system consist of a long, shallow lateral root (wrappeed or doubled around for purposes of the photograph) and an already enlarging tap root growing down from the lignotuber.

Hunewell Ranch, Erath County, Texas. Mid-April.

Advanced source: outstanding reference on morphology, anatomy, and physiology of major woody plant species of Rio Grande Plains, the Tamaulipan Tornscrub is Maiti (2016).

 

173. Naturalized Rio Grande Plains grassland (or, more precisely, grassland-shrub savanna)- On more fertile sites in the South Texas Plains (and where the war against brush has not been lost) introduced perennial forage grasses have naturalized and together with the more grazing-tolerant native (typically seral) grass form a kind of naturalized range. As in the better known (and recognized) cases in California, these man-made grasslands are disturbance or anthr.opogenic climaxes. They are the "new" vegetation types to be managed as if native and for which "proper use" range management practices are appropriate (ie. they are naturalized range and are capable of being managed for sustained yield). The grassland seen here (in the middle of one of the most severe droughts in Texas history) is, though locally variable, about an equal population of the introduced perennials buffelgrass, bermudagrass, and King Ranch bluestem (Andropogon ischaemum= Bothriochloa ischaemum) with the increaser species multi-(four-) flower trichloris as the dominant native. Silver bluestem is also a common native. Capitana or frostweed (Verbesina microptera) is a common forb (visible here). The dominant species of the original or natural climax grassland was typically little bluestem but seacoast bluestem and gulf cordgrass were the climax dominants on coastal sands and flats. Little bluestem is a decreaser on these sites and is a minor component of the South Texas naturalized grasslands. Mesquite and/or huisache are essentially always present as the major shrubs and trees. Various species of pricklypear, especially Engelmann pricklypear or nopal or cacanapo (Opuntia engelmannii= O. lindheimeri), are usually also present depending on fire history. Thus the Rio Grande-Tamaulipan Plains savanna, and the physiogonomy of it, persist on these now-permanent anthropogenic grasslands. Motas Negras pasture on Santa Gertrudis unit of the King Ranch. Kleberg County, Texas. October. Naturalized varient of FRES No. 32 (Texas Savanna Ecosystem), K-54 (Mesquite-Acacia Savanna), SRM 728.

Naturalized variant of FRES No. 32, K-32 (Texas Savanna Ecosystem), SRM 728 (Mesquite-Granjeno-Acacia). Variant of Mesquite Disclimax Series of Brown et al. (1998). Southern Texas Plains-Texas-Tamaulipan Thornscrub Ecoregion, 31c (Griffith et al., 2004).

 

174. Burnt pricklypear flat- Engelmann or Lindheimer prickly pear along with mesquite, huisache, and brasil on a cactus flat three months following a prescribed burn (and in a severe drought). Routine use of prescribed fire is an essential tool in management of naturalized grasslands with species like King Ranch bluestem, bermudagrass, and buffelgrass in association with natives like multi-flowered trichloris and silver bluestem. Cactus is very effectively controlled, but the leguminous shrubs are at best top-killed and usually just "flagged" resulting in fewer lower branches and less shading (and transpiring leaves). Patricio pasture on Santa Gertrudis unit of King Ranch. Kleberg County, Texas. October.

 

175. South Texas Plains naturalized grassland- A disclimax grassland that is permanent— at least in human time-scale— and is an anthropogenic range type. This is range on which original (climax) vegetation was a Prosopis-Acacia-little bluestem savanna with such associates as sideoats grama and pink pappusgrass but which has stabilized as a disturbance climax at a seral stage of increasers and naturalized tame pasture grasses. Four-flower trichloris is the major, often sole, dominant native grass while silver bluestem and windmillgrasses are native associates with introduced grasses like KR bluestem, buffelgrass, and bermudgrass being co-dominant with the trichloris. San Patricio pasture, Santa Gertrudis unit of King Ranch. Kleberg County, Texas. October.

Naturalized variant of FRES No. 32, K-32 (Texas Savanna Ecosystem), SRM 728 (Mesquite-Granjeno-Acacia). Variant of Mesquite Disclimax Series of Brown et al. (1998). Southern Texas Plains, Texas-Tamaulipan Thornscrub Ecoregion, 31c (Griffith et al., 2004).

 

176. Four-(multi-) flower trichloris (Trichloris pluriflora)- Rangemen in the Rio Grande Plains recount that this is the native grass most commonly occurring and most apt to end up as the dominant species on grasslands and savannas that have recovered from range deterioration. In many instances the original (climax) dominated by little bluestem will not return and instead the man-altered ranges stabilize at a sub-climax stage where the native dominant, the new potential dominant decreaser, is four-flower trichloris. Motas Negras pasture, Santa Gertrudis unit, King Ranch, Kleberg County, Texas. October.

 

177. Inflorescence of four-flower trichloris- Chlorideae tribe of Eragrostoideae subfamily, Gramineae. Motas Negras, Santa Gertrudis, King Ranch.

 

178. Just so's not to miss it- Overall and detail views of four-(multi-) flower trichloris. These specimens were from the Lmpassas Cut Plain to the north of the Rio Grande Plains at the margin of their biological range. Lampassas County, Texas. October, grain ripening stage of phenology.

Following is the second portion devoted vine mesquite in this chapter of the Rio Grande Plains.

 

179. Curly mesquite (Hilaria belangeri)- Sward of curly mesquite. This is one of seven Hilaria species in North America, four of which are important range grasses. According to Gould (1951, p. 159) H. belangeri is the most palatable of these species, all of which are sod-forming (rhizomatous and/or stoloniferous). Curly mesquite has been the Hilaria species typically regarded by rangemen as a dominant of the "shortgrass country" (both shortgrass plains and overgrazed mixed prairie) and a species associated with such other shortgrass species as buffalograss and blue grama. Other vegetation specialists, particularly vegetation classifiers and mappers, in more recent works interpreted galleta (H. jamesii) as the dominant Hilaria on the Great Plains grasslands. For example, the Kuchler (1964, 1966) unit K-58 (Gramagrass-Buffalograss) did not list curly mesquite (Kuchler, 1964, p. 65). The Society for Range Management (Shiflet, 1994) did not even mention curly mesquite in descriptions of rangeland cover types SRM 705 (Blue Grama-Galleta) and SRM 715 (Grama-Buffalograss) of the Southern Great Plains Region. Dick-Peddie (1993, p. 104) gave galleta and not curly mesquite as the associate of the codominants, blue grama and buffalograss, of plains-mesa grassland. Curly mesquite does not grow in the central and northern Great Plains, but galleta occurs as far north as Wyoming so it is the Hilaria species sometimes found in rangeland cover type SRM 611 (Blue Grama-Buffalograss) of the Northern Great Plains Region.

In the experience of the current author omission of curly mesquite was somewhat erroneous, misleading to say the least. From his observations this author felt that Thomas (in Correll and Johnston, 1979, p. 11) was much "closer to the mark" when he listed curly mesquite immediately following buffalograss as a major increaser species on the Texas Rolling Red Plains portion of the Great Plains. Perhaps this was the reason why other (and more recent) authors did not list curly mesquite: it is an increaser and not a decreaser on most range sites (ie. it is not a climax species or a major species of the potential natural vegetation).

[By the way, this was still more evidence that SRM rangeland cover types typically resemble quite closely the climax or potential natural vegetation in spite of statements that explained SRM cover type "classification is based on existing vegetation" such that of these types "...most do not..." coincide with those of Kuchler (Shiflet, 1994, p. xi-xii). In fact the SRM rangeland cover types of the Great Plains province included essentiallly all of the Kuchler units of potential natural vegetation, and most of the other Great Plains rangeland cover types that did not correspond exactly with Kuchler units were smaller spatial subunits of these. One thing was certain: if qualifying statements given in Shiflet (1994, ps. xi-xii) were taken literally there would definitely have been far more reference to curly mesquite as well as a curly mesquite rangeland cover type. There are thousands of acres in the Texas Great Plains on which the dominant herbaceous species is curly mesquite, typically with honey mesquite as a scattered overstorey. This plains vegetation is a widespread form of depleted range: a seral stage on rangeland damaged by various combinations of former cultivation or "go-back land", severe overgrazing, oil and gas activity, and perhaps unique meteorological sequences of events or even climatic changes.]

The indespensible Pasture and Range Plants (Phillips Petroleum, 1963, p. 43) explained that curly mesquite had "increased and invaded ranges where better grasses were killed out by abusive grazing". Furthermore, curly mesquite is less palatable than buffalograss and blue grama and goes dormant earlier in drought all of which enable curly mesquite to survive "when better grasses die or thin out". While curly mesquite forms a dense sward such as the one shown here it's "forage production is very low when compared to the better grasses it replaced." (Phillips Petroleum Company, 1963, p. 43).

Regardless of successional status, forage value, soil cover, or usefulness as an indicator species, curly mesquite is-- for better or worse-- a nonclimax dominant on many ranges throughout much of southern Great Plains, a vast range region. In something of an overstatement when applied to the Rolling and High Plains Hitchcock and Chase (1950, p. 485) got the essence of the situation in regards curly mesquite: "Curly mesquite is the dominant 'short grass' of the Texas plains". (When the Rio Grande Plains are included this statement was "right on target".) Silveus (1933, p. 361) wrote that curly mesquite "is one of the most important grazing grasses on the Great Plains of Texas and New Mexico, extending into Mexico". Curly mesquite is commonly about the only perennial grass providing forage and soil protection over a large portion of Great Plains grasslands.

The examples in this section were from the Texas West Cross Timbers (Shally Hills range site) which is about the eastern limit of this species that is more typical of the semiarid zone. Erath County, Texas. Estival aspect in moderate drought,Late August.

 

180. Growth habit of curly mesquite- Typical appearance of curly mesquite plants. Parts of three stolons of curly mesquite (diagonally aligned from lower left to upper right). Erath County, Texas. Late August.

 

181. Typical curly mesquite plant- This unit of a curly mesquite clone showed the usual habit and leaf features of this shortgrass species. Erath County, Texas. Estival aspect, late August.

 

182. Crawling across the rocks- Asexual (= vegetative) reproduction and the clonal structure of curly mesquite was obvious in this specimen as it sent out stolons and daughter plants over this sandstone. Note also however sexual reproduction by production of grain: "seed stalk" (culm with the fascicle arrangement of spikelets) in right foreground.

Erath County, Texas. Estival aspect in moderate drought, late August.

 

183. Curly mesquite runner- This stolon of curly mesquite had four daughter plants developing at nodes of the shoot. Curly mesquite is a clonal organism in which the genetic individual (the plant of an individual genotype) is the genet (= ortet) and the new daughter or sister plants are ramets (= modules) of the genet. Essentially all perennial plants are clonal organisms, but the new clones (modules or rametas) are very obvious-- hence the concept of clonal organization readily understood-- in sod-forming shortgrass species like curly mesquite and buffalograss.

Stolons are extravaginal shoots. They are secondary shoots arising out of the parent shoot (itself a secondary shoot-- as distinguished from the primary shoot that originated from the embryo asexual generations previously). In extravaginal shoots (which also include rhizomes) the new secondary shoots pierce or come up through the sheath, an organ of invaginated tissue (hence these piercing shoots are extravaginated). Intravaginated shoots are those which grow upward inside of (rather than piercing) the sheath. Intravaginal shoots are labeled tillers. Grasses whose secondary shoots are intravaginated (ie. tillers) have a tufted or cespitose growth form and are called "bunchgrasses". This is in contrast to "sod-forming grasses" like curly mesquite. (Some grasses like Indiangrass and many of the bluestems have both tillers and extravaginal shoots, especially rhizomes.)

Stolons and rhizomes are more effective than tillers in invasion of new ground by the genet (genetic mother plant). Said another way, extravaginal shoots are more efficient propagules for populating a plant's "resource frontier".

Erath County, Texas (Western Cross Timbers), Texas. Late August.

 

184. Curly mesquite module- "Close-up" view of a daughter plant (ramet or module) developing along a runner (stolon) which is an offshoot of the oretet or genet (the "original" plant of the individual genotype).

 

185. Curly mesquite spikes- Various portions of curly mesquite inflorescences were displayed for today's lecture. The infloresecence of curly mesquite (all Hilaria species for that matter) is a spike, an unbranched flower cluster-- the inflorescence-- in which the spikelets are sessile--without a pedicel or not pedicellate-- on the rachis. The rachis of curly mesquite is one of the most distinctive of any species of North American grass. It forms a right angle zig-zag pattern known to rangemen as the "crankshaft rachis".

Hilaria spikelets are arranged in fascicles, clusters or bunches, each of which (and each spikelet within which) is sessile. There are characteristically three spikelets per fascicle (two lateral spikelets, both of which have several florets that are each staminate, and a single central spikelet which is one-flowered and perfect).

Inflorescences in the second photograph were in various stages of maturity, including one that was immature (green).

Erath County, Texas. Late August, and after recent rains.

 

186. Pink pappusgrass (Pappophorum bicolor)- A shoot of one of the most distinctive and defining grasses of the Rio Grande and Tamaulipas Plains region, the infamous brush country. Pink pappusgrass is not one of the most palatable native grasses of this range type, the various range sites of which have as their natural potential (= climax), major Gramineae species as diverse as sideoats grama, buffalograss, curly mesquite, tanglehead (Heteropogon contortus), crinkleawn (Trachypogon secundus), longspike silver bluestem (Andropogon saccharoides var. longipaniculatus= Bothriochloa saccharoides var. longipaniculata), and Arizona or California cottontop (Triachne californica) . The intermediate (= fair) palatability of pappusgrass may be a major factor why it is locally abundant and generally fairly common on less depleted ranges in the Tamaulipas brushlands that were (many continue to be ) subjected to overgrazing and fire cessation for several centuries beginning with development of livestock ranching by the Catholic Church out of Spain.

Pink pappusgrass is a cespitose (= tufted) mid-grass-- a grass species of medium height relative to tallgrass and shortgrass species-- that attains a stature of two to three feet on more favorable habitats (sandy to gravelly soils). It's size and habit mirrors the general physiogonomy of the herbaceous understorey of the climax shrub-grass savanna. The biological range of pink pappusgrass extends from the Coastal Prairies and Marshes on the east, northward through the Edwards Plateau into the Rolling Red Plains and westward into the Basin and Range Province.

Bexar County, Texas. April.

 

187. Shoot apex of pink pappusgrass- The panicle inflorescence and characteristic flag leaf, the leaf subtending (the one immediately below) the inflorescence, of pink pappusgrass. The blunt tips of blades of upper leaves (eg. flag leaf) is a readily observatable identification aid of this grass. Bexar County, Texas. April.

 

188. Spikelets of pink pappusgrass- This portion of a panicle of Pappophorum bicolor presented the spikelets of this range grass. Pappophorum species are members of the small tribe Pappophoreaepae in the Eragrostoideae, the Gramineae subfamily that tends to predominate in warm or hot, arid and semiarid climates. The spikelets of this genus consists of several (usually four to six) florets, the lower one to three being fertile. The lemmas subdivide into numerous awns of varying lengths, and as the spikelet is shed (with florets remaining together as a unit) these awns appear as a pappuslike crown (Hitchcock and Chase, 1951, p. 225).

Bexar County, Texas. April.

 

189. Autumn coloration- Pronounced fall blazonry is not limited to woody plants as evidenced by onset (early stage) of the brilliantly blazing autumnal coloration in shoots of tanglehead (Heteropogon contortus). Plants in this example of tanglehead, one of the more widely distributed grasses on Earth (see below), were growing in Trans-Pecos Texas. Powell (1988, ps. 336-337) explained that in autumn in Trans-Pecos Texas "dense stands of tanglehead can be recognized on hillsides from far away because of the clumps of rusty herbage". In reference to Powell's "fall coloration", Hatch and Pluhar (1993, p. 44-45) described the herbage of tanglehead as "a reddish-brown color at maturity".

This member of the bluestem tribe (Andropogoneae) is not only notable for the beauty but also the nutritive value and palatability of its herbage. Hatch and Pluhar (1993, p. 44-45) regarded forage value of tanglehead as being good for livestock and poor for wildlife. Of course, wildlife covers a multitude of species that, just within vertebrates, includes amphibians to ungulates. It is hard to imagine tangelhead as being good for livestock (eg. cattle, goats, sheep, horses) and poor for such wildlife species as bison, elk, desert bighorn sheep, mule deer, and pronghorn. Yes, that is an apt comparison. Tanglehead is abundant in the Gulf Coastal marshes and prairies, the Rio Grande Plains, and parts of the Edwards Plateau (Hatch and Pluhar (1993, p. 45). Ungulates ranging from bison to deer were native to all of these Texas vegetational areas. American buffalo (= bison) where apparently not plentiful in the Trans-Pecos/Chihuhuan and Sororan Desert Regions where tanglehead was abundant, but smaller native ruminants were (are).

Tanglehead is one of the most widely distributed grasses on Earth with a species (biological) range that "has a world-wide distribution" (Hitchcock and Chase, 1950, p. 779) encompassing parts of South America, Africa, southern Asia, Australia, and Oceania. Across this vast biological range tanglehead can be mechanically injurious, especially to thinner skinneda animals like sheep, when the spikelets become ripe. This situation was discussed below in captions accompanying slides of these unique spikelets.

Tanglehead can be a major grass species--and as a decreaser--on numerous range sites throughout the greater Southwest Region including the western Rio Grande Plains. The individuals shown in this slide were growing on a Chihuhuan Desert habitat, but they could just as easily have been from the Rio Grande Plains where the species has been increasing over the last quarter to third of a century (see below).

Tanglehead is one of the 200 plant species included in the International Range Plant Identification Contest conducted and sponsored by the Society for Range Management (Stubbendieck et al. 1992, p. 38-39).

Big Bend National Park, Brewster County, Texas. Early October; peak standing crop, anthesis.

 

190. Even inflorescences show fall color- Flower clusters (raemes) with ripening spikelets of tanglehead in the Chihuhuan Desert in the Big Bend area of Trans-Pecos Texas. The reddish-brown to burnt-orange autumn coloration of tanglehead herbage was beginning to show in these racemes.

Big Bend National Park, Brewster County, Texas. Early October, anthesis.

 

191. Yes, it is in the bluestem tribe- Racemes of tanglehead at anthesis in the upper Chihuhuan Desert in the Big Bend area of Trans-pecos Texas. Although initial and superficial examination can be misleading, tanglehead is a member of tribe, Andropogoneae. Tanglehead has paired spikelets, the fertile being sessile and the staminate or neuter (sterile) spikelet being pedicellate (Chase, 1959, 1964). Chase (1964, ps. 86-87) interpreted the inflorescence of tanglehead as a raceme and described it as "a more complicated arrangement" in which the sessile fertile spikelet and the pediceled sterile spikelet (paired spikelets) form a "joint of the raceme"; however, "a further modification" is that the "lower two or three pairs of spikelets are all sterile". This entire graminaceous contraption is confusing even to veteran rangemen. (It took Agnes Chase to sort it out.). After all this, the fertile lemma developes "into a strong, bent and twisted brown awn" ( Hitchcock and Chase, 1951. p. 779), "a stout geniculate and twisted awn" (Shaw, 2012, p. 559).

An interesting (some might say, intriguing) aspect of tanglehead is that it is obligate apomict (Gupta, 2007, p. 302). Carino and Daehler (1999) reported on genotypic variation of tanglehead in the Hawaiian Islands and within-population variation go "more typical f sexually reproducing". Apomixis is common in several grass species (Pullaiaih eta al. 2002). Production of pollen is essential in almost all apomictic species because fertilization of polar nuclei (double fertilization) is necessary for production of endosperm (Horandl, 2010). Hence, pollen produced by anthers seen in these two images was not for naught.

In addition to these sources, Gould (1951, p. 302), Gould (1975, ps. 614, 618), Powell (1988, ps. 336-337), Reilly and Maher (2005), and Everitt et al. (2011, ps. 158-159) were suggested.

Big Bend National Park, Brewster County, Texas. Early October, anthesis.

192. Hard, sharp, and sometimes troublesome- Spikelets (fertile ones were the ones in evidence) of tanglehead (first slide) and spikelets along with racemes of tanglehead (second and third slides) that had been produced on an upper part of the Chihuhuan Desert in the Big Bend area of Trans-Pecos Texas. The floral arrrangement or pattern of the inflorescence of tanglehead is "complicated" (Chase, 1964, ps. 86-87) with some details of this confusing inflorescence arrangement elaborated in the immediately preceding caption. Most standard treatments of the Heteropogon inflorescence did not elaborate to the detail provided by Chase (1964, ps. 86-87). Description, diagrams, and photographs given by Shaw (2012, p. 558-560) made up the closest (though still a "fur piece" away from that the immortal Agnes Chase). Shaw (2912, p. 558) did provide this bit of "comfort" for those of us initially bamboozled by the tanglehead "spear": "Mature fertile spikelet superficially similar to the floret of stipoid grasses in appearance". Similarity ends there.

The most distinctive features of tanglehead (other common names include black speargrass, steekgras, and pili, this latter being Hawaiian) are the long, bent, twisted awn combined with the sharp callus at the other end of the lemma of the fertile spikelet. As in the case of florets of the Stipa species, this structure or organ can be mechanically injurious to thin-skinned animals including sheep. Hitchcock and Chase (1951. p. 779) stated that "mature fruits are injurious to sheep", but if tanglehead is "grazed constantly the troublesome awns do not develop". Of course, some grain production is usually advantageous even in perennial grasses where most reproduction is asexual (vegetative). Shaw (2012, p. 559) stated: "Sharp callus can be damaging to livestock". Injury is not limited to puncture wounds by the callus. In instances where the callus-initiated puncture wound permits entry of the entire (or more of) the spikelet, the cable-like awn compounds the damage. The spikelet, including awn, will sometimes work its way beyond skin into muscle or even into internal animal organs.

Notwithstanding possible mechanical injury, herbage of tanglehead has good forage value for ungulates. From an ecological (successional) standpoint tanglehead is a climax decreaser grass that is often a local dominant. Tanglehead is a damn fine range plant. Axiomatically, tanglehead has less value for bird species, but even here the cespitose (bunchgrass) habit would likely be of similar value as other cespitose species, such as little bluestem (Andropogon scoparius), to, say, nesting bobwhite quail. This condition was noted by Everitt et al. (2011, p. 159) who specified that tanglehead "provides good nesting cover" for bobwhite quail and wild turkey "and fawning cover for white-tailed deer".

By the way, these grass organs were laid on granite which is one of the major soil parent materials in the Big Bend area of the Chihuhuan Desert and adjoining range cover types, but tanglehead also thrives on various other edaphic and topographic habitats including the Texas Coastal Sand Sheet or the Rio Grande Plains (Glass et al, 2016).

Big Bend National Park, Brewster County, Texas. Early October; grain-ripe (first slide), anthesis (second and third slides).

 

193. Parting summary shots- These two views made a synopsis of tanglehead. The first slide showed five cespitose plants (genetic individuals; genotypes) showing both 1) the bunchgrass habit of this panicoid (tribe, Andropogoneae) grass and 2) the frequent occurrence of several plants growing in very close proximity to each other. The second slide showed the inflorescence-- interpreted as a raceme by Chase (1964, ps. 86-87)--of tanglehead at anthesis.

Tanglehead grows in both the northern and southern hemispheres and is an important range grass in the western Rio Grande Plains on westward into the Chihuhuan Desert and Sonoran Desert (Kearney and Peebles, 1960, p. 144; Shreve and Wiggins, 1964, p. 300-301; Leithead et al., 1976, p. 98-99; Correll and Johnston, 1979, p. 201).

The plants seen here were growing in an ecotone of Chihuhuan Desert scrub and sotol grasslands in the Trans Pecos Region, but where included in this chapter because tanglehead is an important climax (decreaser) grass in the Rio Grande Plains.

Recommended summary treatments of tanglehead included Gould (1951, p. 302), Gould (1975, ps. 614, 618), Powell (1988, ps. 336-337), Hatch and Pluhar (1993, p. 44-45), and Shaw (2012, p. 558-560).

Tanglehead is one of the 200 plant species on the International Range Plant Identification Contest sponsored by the Society for Range Management (Stubbendieck et al. 1992, p. 38-39).

Big Bend National Park, Brewster County, Texas. Early October; peak standing crop, anthesis.

194. Tangled mess is what it was- Sexual shoots of tanglehead with one grain-shatter stage inflorescence of hairy seed paspalum (Paspalum pubiflorum) on high condition class range in the Rio Grande Plains of south Texas.

Jim Hogg County, Texas. Mid-October. Grain shatter stage of phenology.

Ecological note: Over the last two to three decades tanglehead has increased in general abundance (especially noticeable as greater foliar cover) in certain areas. Perhaps most notable mong these is the Rio Grande Plains. This increase has generated considerable interest (and speculation) along with some investigations as to cause(s) of this increase. The increase in tanglehead has also caused controversy with some observers seeing this increase as undesirable invasion while others have taken a "longer look" at this increase of a native climax grass.

This rangeman author interpreted the increase in tanglehead has an indication that range condition was improving. Increased cover (or, simply, greater general abundance) of this decreaser grass species in vegetational areas and ecological regions such as the Rio Grande Plains and Chihuhuan Desert Region is simply improvement in range condition (movement of range plant communities closer toward potential natural, the climax, vegetation). Range deterioration has been well documented for such (for that matter, most) areas. Range retrogression was due to a number of factors including overgrazed, fossil fuel development, cessation of natural fire, road-building, and introduction of exotic plants (and animals) coupled with drought and, even, gereral change in climate.

From the criterion of plant sucession (progression of range vegetation toward higher community developmental states) increases in tanglehead are simply the dynamics of vegetation as it progresses toward its potential. Obviously, composition and structure of potential vegetation will vary from range site to range site. Tanglehead will vary in its successional status by range site potential: tanglehead may not be (in fact, would ot be expected to be) a climax species on every habitat on which it grows. Nonetheless, the general increase in tanglehead in regions like Rio Grande Plains or Sonoran Desert is "a good thing" from the standpoint of natural vegetation. Such vegetational development is an indication (tanglehead is an indicator species) that range is improving from the standpoint of successional advance. In other words, in range plant communities in which tanglehead is increasing, there is continuing range improvement or progressive development toward higher successional state or higher range condition class.

Furthermore--and of more immediate economical importance--such increases in tanglehead result in improved range feed conditions and improved wildlife habitat. Grace et al. (2016) summarized and cited standard published observations and conclusions regarding tanglehead. They concluded that tanglehead had fair to good nutritive value for cattle and low forage value for sheep while furnishing excellent nesting and fawning cover for wildlife (Grace et al., 2016). Bielfelt and Litt (2016) felt that impacts of increases in tanglehead amounted to a "tangled issue" for a range plant that they described as a "native invasive species". This was most evident in instances where tanglehead grew in more-or-less homogenous stands with fewer plant species present (ie. less or lower species diversity).

Ecological (vegetational) dynamics like this become "tangled issues" to large extent due to different or conflicting value judgments, management goals (eg. profit maximization in commercial cattle production, aesthetic perspectives, species of wildlife desired), past experiences, and scientific interpretations of natural phenomena. For instance, the adjective "invasive" has several interpretations in agricultural, ecological, and even human cultural contexts. In the classic view of the discipline of Plant Ecology invasion is the culmination of a species establishing (or re-establishing) itself in a new (or returning) home. Invasion is the terminal stage going from migration through aggregation and competition resulting in displacement of existing species by the invader (Weaver and Clements, 1938, ps. 166-168 ). If little bluestem is invading an old field or overgrazed range that had once been a little bluestem-dominated grassland in the Rio Grande Plains (Johnston, 1963) little bluestem is re-establishing itself in its former "natural home". Little bluestem is re-populating "go-back land" as part of on-going re-development of the climax plant community via secondary plant succession. This is invasion in the classic sense.

In this context, plant invasion and, by extension, invasive plant species does not imply or suggest the same negative connotation as brush invasion by natives like honey mesquite or huisache at cover or density greater than that of the natural plant community. Even more to the point, invasive climax species such as tanglehead (or little bluestem) are certainly not invasive species in the same context or ecological category as are rapidly establishing, invading exotics (exotic invaders) such as salt cedar (Tamarix spp.) or, among grasses, buffelgrass ((Pennisetum ciliare), Lehmann's lovegrass (Eragrostis lehmanniana), or King Ranch bluestem (Andropogon ischaemum= Bothriochloa ischaemum).

Note here that in cases of invasive, exotic (agronomic or introduced) forage grasses, the agricultural desirability or, alteratively, the weediness (eg. detriment to upland bird production) of the plant is irrelevant to the ecological feature of invasiveness. Weed or crop, trash or treasure is in the eye of the beholder, but the feature of invasion or invasiveness whereby an alien or exotic displaces/replaces a native is a scientific fact not a perception. Such invasion by an exotic is not the same as invasion by a native back into its new home--especially when the native invader was formerly a climax species.

Invasion (hence, invader) is a process (and an invading species). Whether the outcome of invasion-- by natives or aliens--is "good" or "bad" depends upon human values and management goals along with ecological criteria, but invasion of a native back to its pre-disturbance status is always "good" in regards to--from perspective or criterion of--vegetation development. Invasion is an essential part of plant succession. It part of the means by which Nature heals its range plant community. Hence, invasion by tanglehead is one thing; invasion by bufflegrass is quite another.

The process of secondary plant succession largely explains--in this author's judgment--much of the recent increase in tanglehead, a climax grass species (again, potential relative cover varies with range site potential). Range deterioration (retrogression of the range plant community) due to the various factors listed above has occurred throughout most regions of Earth and certainly on ranges historically subjected to these disturbance factors over decades or even centuries as in the case of, say, the Rio Grande Plains. In fact, the degradation of ranges in such areas as become as much a part of "lore and legend" as it is of scientifically documented ecological change. An example of such joint literature was the classic paper on changes in the grasslands and savannas of the Rio Grande Plains by Johnston (1963), a study that cited much previous work which described the same pattern of deterioration. By the way, in this study of Rio Grande Plains vegetation Johnston (1963) did not find tanglehead to be one of the major grass species on undisturbed grassland and savanna.

It is your author's suspicion that the relatively recent increases in tanglehead are to a large extent the result of lighter grazing (= lower stocking rates) and, thus, less degree of use of grasses by livestock. For instance, throughout much of the Rio Grande Plains of south Texas there has been generally lower stocking rates of cattle as landowners (many of them absentee) emphasized production of the more lucrative white-tailed deer and bobwhite quail (fee hunting) rather than (in preference to) traditional livestock ranching. Enclosure of private land with high game fences attests to this shift in range animal production.

Prior to this more recent (last quarter or third of a century) chage in range animal management and production, the ranges of the South Texs Plains had been heavily grazed. Leithead et al., 1976, p. 99) stated that tanglehead could not persist on ranges with continuous heavy grazing. Of course, animal grazing would be only one of several possible factors involved in dynamics of range vegetation. On the Hawaiian Islands, where tanglehead is native, Goergen and Daehler (2001) concluded that the introduced, agronomic, panicoid species, fountain grass (Pennisetum setaceum) had increased and to large degree, displaced tanglehead. Goergen and Daehler (2001) surmized that this development was due to the superior invading capacity (competitive ability) of fountain grass largely due to greater grain production capability relative to that of tanglehead. On more marginal habitats for both species, tanglehead was able to out-compete fountaingrass and, as a consequence, the native, andropoid tanglehead had become limited to drier, less fertile environments.

At the present time it is not known how tanglehead was been able to increase in areas where bufflegrass, Lehmann's lovegrass, and King Ranch bluestem have naturalized and become major "new" range grasses. There has certainly been criticism of the extreme "take-over" of the range by these exotic or introduced species by those who prefer high-quality habitat for bobwhite quail over outstanding pasture for beef cattle (see for example the perspective by Smith [2010]). Again, value judgments and management preferences have major influence on how humans perceive an invasive species--native or introduced. By contrast, invasion and re-establishment of a climax species is the end result of plant succcession with the only ecological criterion as to desirability of this development being the relative potential proportion of the plant community that the re-established native should constitute. This is the successional equivalent to the truism that the dose determines the poison.

The indisputable fact is that tanglehead is a native, climax grass that--under proper management (always a stipulation)--is a valuable species for range uses ranging from cattle forage to wildlife cover to erosion control to revegetation of deteriorated land. Value of tanglehead was shown by releases of "naturally occurring tanglehead germplasm" from Soil Conservation Service [now, Natural Resources Conservation Service] plant materials centers in Arizona ("Rocker") and Hawaii ("Kahoolawe Germplasm Piligrass") as reported by Alderson and Sharp (1994) and Reilly et al. (2002). In the instance of Hawaii, an implement named the "Pili Comb" was developed to efficiently harvest tanglehead grain or, more specifically, spikelets (Reilly et al., 2002).

A thorough and detailed (though prelimentary) report on tanglehead in the Rio Grande Plains--and also as related to this species globally--was that of Tjelmeland (2011).

 

195. Tangled base- Root crown and basal shoots of tanglehead that grew on a grass-shrub savanna in the lower Rio Grande (Tamaulipan) Plains of south Texas. These shoots--other than grains in the panicles--were dead having completed their life cycle. These shoots and portions of root crown (the union of shoot and root) were just a part of a large plant of tanglehead. Tanglehead is a cespitose or tufted species having only tillers and no stolons or rhizomes (Hitchcock and Chase, 1950, p. 778; Gould, 1975, p.614).

Jim Hogg County, Texas. Mid-October. Grain shatter stage of phenology.

 

196. Tangled "seed heads"- Panicle (left) and part of shoot (right) of tanglehead in the first slide and "fully ripe" caryopses in spikelets of tanglehead in the second slide that were produced on a grass-shrub savanna in the lower Rio Grande (Tamaulipan) Plains. All these organs were on dead (senesced; completed their annual life cycle) shoots of dormant tanglehead. The grains (caryopses) with their embryo-bearing seeds and endosperm (stored carbohydrate reserves) were still alive (viable).

At this final stage of maturity, the nutritive value of tangelehead shoots is very low (poor forage quality) and palatability of the herbage is even lower. Range animals will select it as a last resort. Furthermore--and, sometimes, more importantly--awns of the now-dry florets can be mechanically injurious. At this phenological (and maturity) stage, tanglehead herbage does not make for good animal feed. Probably even more difficult for microbes to decompose this high-cellulose content organic matter.

Given that tanglehead is strictly cespitose with vegetative or asexual reproduction limited to tillers, recent observations and documentations of the great increase in tanglehead cover in many areas, especially the Rio Grande Plains, attest to the heavy yields of caryopses (high seed output) and strongly suggests that a high proportions of tanglehead seed are viable. This means that establishment of tanglehead--and perhaps much of this has been re-establishment of a previous dominant native grass--has been sexual rather than asexual (establishment of new genotypes rather than clonal offshoots or modular units).

If this was so, it means that invasion (the result of successional processes beginning with dispersal and migration through to aggregation and, finally, competition [Weaver and Clements, 1938, ps.148, 166]) was dependent primarily on propagules (= germules) that were diaspores (caryopses; the combined fruit and its seed) produced by genetic recombination such there was the potential for on-going evolution and improved fitness or increased adaptation to more recent selection factors such as grazing livestock, exotic (non-native) grazers. The potential final outcome is that tanglehead could become re-established as a dominant range grass (regain its climax status throughout some of its biological or species range) through better adapted germ plasm via natural selection. Return to home: welcome or otherwise.

Jim Hogg County, Texas. Mid-October. Grain shatter stage of phenology.

 

197. Tangled phytomer- Two examples of a phytomer--a node-internode unit of a grass shoot--in dormant tanglehead (= dead shoots) that grew on a grass-shrub savanna in the deep Rio Grande Plains. The first example (upper slide) also had part of the panicle inflorescence (along the left margin of the slide image).

Jim Hogg County, Texas. Mid-October. Grain shatter stage of phenology.

 

198. Spanish dagger, Torrey yucca, or palma pita (Yucca treculeana= Y. torreyi)- This is the major (most widespread) arborescent lily on the Rio Grande Plains. Most contemporary authorities place Yucca species in the Agavoideae (agave subfamily) of the lily family (Liliaceae), but other authors put the yuccas in the Agavaceae (agave family).

Spanish dagger is also commonly found in other vegetational areas especially the Trans Pecos Basin and Range and Coastal Prariies and Marshes. This specimen was proudly growing the Wild Horse Desert portion of the Kenedy loose sand prairie that is part of the western Guld Coast prairie vegetation. Kenedy County, Texas. February, full-bloom phenological stage.

 

199. Tasty treat- Inflorescence of Torrey yucca, Spanish dagger, or palma pita, the large treelike Yucca species most common on parts of the Rio Grande Plains, Coastal Prairies and Marshes, and eastern Trans Pecos Basin and Range vegetational or land resource areas of Texas. Supposedly the flower cluster is used as a starchy food in Mexico. Many species of insects, birds, and quadraped mammals are extremely fond of the sweet taste of these flowers. This inflorescence was growing on the plant presented in the preceding photograph.

Kenedy County, Texas. February, full-bloom stage of phenology.

 

200. Rain lily or, sometimes, Cooper's rain lily, giant rain lily, white rain lily; also eveningstar (Cooperia pedunculata= Zephyranthes drummondi)- This member of the amaryllis group can be interpeted as being in either the Amarylloidideae (subfamily) of the Liliaceae or the Amarylldcaceae (amaryllis family). Its biological range is rather restricted extending from northcentral Texas into northern Mexico. In Texas this species occurs in the Blackland Prairie, Cross Timbers and Prairies, Edwards Plateau, and Rio Grande Plains vegetational areas. In a restricted area of Texas this particular species causes primary photosensitization (Hart et al., 2003, p. 74). It was included here because it is one of the more conspicuous forbs in the Rio Grande Plains, especially on deeper sands.

Diggs et al. (1999, p. 1200) distinguished between C. drummondii the habitat of which is shallow, calcareous soils and C. pedunculata that grows on a greater diversity of habitats, including sandy soils. According to these authors the former species blooms in late afternoon or evening whereas the latter species blooms from late night to early morning. The "morning bloomers" shown here played by the rules. As was characteristic of their species these plants emerged and flowered "almost immediately" after a good, soaking rain that broke a summer-long drought. These specimens were growing on sandy land of the West Cross Timbers.

Erath County, Texas. Late August.

 

201. It rained lilies- Detailed views of some of the flowers of the rain lilies introduced in the preceding slide. Erath County, Texas. Late August.

 

202. When it really rains- An unusually large and dense local stand of Cooper's or white rain lily (first photograph) and a dense clump or, perhaps, one clonal unit of rain lily (second photograph). These plants like those pictured above were growing naturally in the West Cross Timbers rather than in the Rio Grande Plains. Cooper's rain lily can be found in the following vegetational areas of Texas: coastal prairies and marshes. post oak savanna, Cross Timbers, Edwards Plateau and Rio Grande plains. This species is, however, more frequently associated with the Rio Grande or Tamaulipan Plains. This perhaps due to the impression created by the sudden appearance of any plant in this harsh, drought-prone area.

The plants seen in these two photographs were blooming in the morning so, as was noted above, they would be interpreted as Cooperis pedunculata (Diggs et al., 1999, p.1200).

Erath Copunty, Texas. Mid-October (and just a week or so after exceptionally heavy rains).

 

203. Ready for more lilies?- Ready or not more plants of Cooper's or Drummond's rain lily are on the way. The fruit of these members of the lily family is a trilocular capsule. The three locks were shown prominently here. Cooperia genus is in the Amarylloideae (Amaryllis subfamily of Liliaceae). Erath County, Texas. Early September.

 

204. Adios, argenta- Female silver garden spider or silver argiope (Argiope argentata) poised on her orb web spun across an opening in the Mixed Brush disclimax cover type in the central Rio Grande Plains. This orb weaver is one of the more common (and certainly more showy) invertebrates of the south Texas brush country. This ornate lady said, "Adios, amingo and come back to visit my arthropod offspring next year". There may be better reasons to revisit the brush country, but that one will do for starters.

Duvall County, Texas. Early October.

 

Live Oak-Mesquite-Tallgrass Savanna

205. Live oak-mixed prairie savanna- A savannah of old-growth live oak (with a disturbingly limited regeneration) and a grass understory dominated by sideoats grama followed closely by four-flower trichloris, silver bluestem, little bluestem, and panicgrasses (including some upland switchgrass) but with very limited shortgrass component of buffalograss, hairy grama, and Texas grama. The dominant (and conspicuous) forb which is growing adjacent to oak trunks is Turk's cap (Malvaviscus drummomdii). A sandy loam range site in Good range condition class due to the limited cover of little bluestem, the dominant decreaser. Live Oak County, Texas. October. Defies precise FRES and Kuchler classification. Most closely resembles Florida live oak hammock in physiogonomy and dominant tree species: FRES No. 16, (Live Oak-Gum-Cypress Forest Ecosystem) or No. 15 (Oak-Hickory Forest Ecosystem), specifically K-72 (Oak Savanna) thereof. On basis of understory grass community it is a deteriorated form of bluestem prairie (K-66) or a bluestem-grama prairie (K-62). Yet neither is correct because this is clearly part of FRES 32 (Texas Savanna Ecosystem) either K-55 (Mesquite-Live Oak Savanna) or K-78 (Mesquite-Oak savanna). East Central Texas Plains- Southern Post Oak Savanna Ecoregion, 33b (Griffith et al., 2004).

 

206. Little bluestem-live oak savanna- This is the Texas live oak-tallgrass savanna at climax stage. As a single-species understory to old-growth live oaks, little bluestem forms a consociation almost to complete exclusion of any other herbaceous species. The only contender (and it is barely that) for an associate species is, interestingly, the annual colonizer of old-fields known variously as marestail, horse-weed, or old-field fleabane (Conyza canadensis= Erigerion canadensis). There is good regeneration of the live oak. (Note young trees at far left margin of slide and the clump of young trees with gray trunks immediately behind and to the right of the the right front mature live oak.) A bromeliad known as ball moss (Tillandsia recurvata) is growing on branches of the live oaks. This is as beautiful and pristine a savanna as the author ever encountered.

Atascosa County, Texas. Autumnal aspect, October. As was the case of the live oak-mixed prairie savannah this vegetation defies precise FRES and Kuchler designations, primarily perhaps because these classifications did not involve mapping at this fine a scale. This community could be interpreted as a cover type variant or form of K-72 (Oak Savanna) though in physiogonomy it clearly resenmbles the Florida live oak hammock which seemed to be most closely K-81 (Live Oak-Sea Oats). Yet, it is not the coastal live oak- sea oats understory. Neither is there an SRM designation. East Central Texas Plains- Southern Post Oak Savanna Ecoregion, 33b (Griffith et al., 2004).

 

207. Ball moss or gallitos (Tillandsia recurvata)- This close relative of Spanish moss is obviously not a true moss . It is an advanced vascular plant, a monocotyledon. Ball moss a member of the Spanish moss subfamily of the Bromeliaceae. It is a range plant rarely enjoyed by ground-limited ungulates, but when ball moss-festooned, rotten branches fall it is literally a "wind fall" for livestock and wildlife which readily eat the ill-fated bromeliated. Ball moss was included in this publication to show students of Range Management the diversity of range plant feeds available to range animals.

 

208. Ball moss on a limb on the ground- Dead limb of a live oak fell to the ground carrying with it its arboreal hitchhiker, ball moss. Throughout parts of the Balcones Escarpment this commensal epiphyte is a common member of Edwards Plateau range vegetation even though it is often--perhaps, usually--overlooked or ignored. What, if any, contribution this monocot makes to diets of range animals was unknown to this author. The species merited inclusion in any detailed treatment on range plant communities of the southern extremity of the Edwards Plateau-- and, it was emphasized, southeastern terminus of the Great Plains.

Kerr County, Texas. October.

 

209. Out of its nest- Another plant of ball moss that was blown by high winds from its moorings (this one from post oak limb) fell to the leaf-littered ground. While this plant had met its untimely end with dislodgment from its host tree the accident victim was put to the service of educating the next generation of rangemen with inclusion of these and the next two photographs.

Bexar County, Texas. February. Post- fruitripe stage and perhaps a stage of semi-dormancy (prior to its recent death).

 

210. Dried flowers, mature fruit- Closeup views of the inflorescence and mature fruit of the plant of dislodged ball moss introduced immediately above. The fruit of Tillandsia species is a septicidal capsule containing cylinderical or fusiform seeds with an attached plumose appendage. Generally there are only one or two inflorescences per plant.(Correll and Johnston, 1979, ps. 355-356), but this particular specimen had four flowers which undoubtedly maked it as a fecund individual.

Bexar County, Texas. February. Post- fruitripe stage.

Historic pointers: For those interested in the rich ranching history of the Rio Grande Plains, which were commonly known as the Wild Horse Desert in frontier days, begin with the classic A Vaquero of the Brush Country by Dobbie (1929, 1957). Then move on to the classic work on sheep ranching in the south Texas brushlands, Forgotten Legions, by Lehmann (1969). Chapter 4 of Texas Woolybacks is outstanding, and of course any serious stdent should read the scattered pertinent parts of the The Great Plains by the immortal Webb (1931).

 

211. A woodland on the coastal sand prairie- A live oak woodland had developed on the Kenedy sand prairie (Johnston, 1963, p. 460), one form or subtype of Gulf coastal tallgrass prairie inland from the coast but within the Texas Coastal Prairies and Marshes Area. Seen from perspective of Landscape Ecology this range vegetation (these units of hardwood evergreen woodland), ecosystems, and/or landscape elements could be interpreted as patches of live oak woodland in a matrix of seacoast bluestem (Andropogon littoralis= Schizachyrium scoparium var. littorale)- sacahuiste or Gulf cordgrass (Spartina spartae) coastal prairie. From the classical viewpoint of savanna as put forth by Dyksterhuis (1957) this overall grassland-woodland landscape could be seen as a savanna in which units or assemblies of woody vegetation ranging from smaller mottes (Texan for "groves") to extensive "woods" of several hundred acres are the physiogonomic equivalent of vegetation consisting of individual to "a few" trees and/or shrubs isolated on grassland. In other words, this would be a savannah in which the woody elements are larger and include more woody plants (eg. groves) rather than the typical situation of scattered individual trees and/or shrubs. This would not necessarily imply that such a structural or physiogonomic savannah was a successional or genetic (as to origin) savanna, this latter of which is the usual definition or, at least, connotation of an ecotone (a transition) from herbaceous to woody vegetation.

Interpretation of the woody vegetational units perhaps would hinge on whether mottes or woodlands were actually one up to "just a few" genetic plants whose individual stems (trunks or boles) were repeating clonal units or, alternatively, if these groves or woodlands were composed of many genetic individuals (each or most trees as denoted by a single tree trunks were derived from one embryo, that is, one acorn).

Range vegetation shown here was part of what has long been known as the Wild Horse Desert part of the Rio Grande Plains. This native grazing land is a slightly rolling or hummock aeolian plain of sand entitled the "Kenedy loose sand prairie" that consist of different range plant communities as "a tight mosaic of vegetation types..." (Johnston, 1963, p. 460). The uncertain successional status of large live oak mottes like the one shown here that develop on loose sand uplands was mentioned briefly in the caption of the immediately succeeding slide. The present photograph illustrated the spatial arrangement of sandy sachuiste prairie and mottes dominated by live oak that attest to the "very complex mosaic of vegetation types" (Johnston, 1963, p. 460) of the Wild Horse Desert on the Rio Grande Plains.

Norias Division, King Ranch, Kenedy County, Texas. February, late hibernal or early vernal aspect.

 

212. Live oak motte turned woodland- Exterior view of a live oak woodland or forest (larger than typical live oak motte) situated within seacoast-sacahuista tallgrass coastal prairie. The dominant herbaceous plant growing at perimeter of live oak woodland was Gulf cordgrass or sacahuista. Other tree species present--at rare to trace amounts of canopy cover--werehoney mesquite (Prosopis glandulosa) and common hackberry or sugarberry (Celtis laevigata). Even though crowns of trees produced a fairly closed canopy with considerable interlocking of branches there was a well-developed (e) herbaceous understorey (often consisting of two to three layers) as well as a second (lower) woody layer or understorey of shrubs and small (immature) trees.

Areal extent (acreage) of this live oak-dominated range community was considerably larger than typical live oak mottes and therefore was viewed more as a live oak woodland or forest rather than as a grove of trees within or on a prairie. Perhaps this distinction was arbitrary or even incorrect but, as in the case for fire behavior, at some point size (spatial scale) becomes an ecologically critical feature. Impacts and role of fire would be a case in point. Prairie fires could easily burn under or scorch crowns of small mottes whereas with expansive woodland areas there would places where fire could not reach (ie. as size of live oak-dominated stands increase in area there is increased probability that larger proportions of stands will be unaffected by fire). The situation would be similar for dispersal of plant propagules from outside live oak-dominated stands as well as for penetration of light from edges (vs. through canopy) of live oak stands.

Successional status of mottes on coastal (and sone iinterior tallgrass and mixed) prairies apparently has not been completely established. Johnston (1963) described, quantified, and discussed changes in range vegetation in the much of the area of the Rio Grande Plains, including that part known as the Wild Horse Desert. Based on personal accounts, including that of a longtime ranchman on the Norias Division of King Ranch, Johnston (1963, p. 464) concluded that live oak had so increased on the sandy seacoast bluestem-sacahuiste coastal prairie that previously separate live oak mottes had coalesced and become interconnected. Causes of the shift from more herbaceous to woody vegetation included the "usual suspects" of overgrazing, seed dispersion by livestock, and reduction or cessation of fire were proposed for the increased in woody vegetation, including that of live oak mottes. Notwithstanding brush invasion due to influences of white man, live oak mottes (of much smaller acreage) are native, potential natural, or climax range vegetation.

The range vegetation of both live oak mottes and surrounding Gulf cordgrass or sacahuista sand prairie were samples of two climax (= potential natural) plant communities. Live oak mottes had expanded into range that was formerly "Kenedy loose sand prairie" (Johnston, 1963, p. 460) so that the overall vegetation of this natural grazing ground had departed from climax conditions of the virgin range. Yet species composition, structure, etc. of the two range communities was representative of that of each climax community. A description and discussion of the general or overall range vegetation over much of the Rio Grande Plains was provided by Fulbright in Shiflet (1994) as SRM 719 (Mesquite-Live Oak-Seacoast Bluestem). The Society for Range Management did not offer a separate designation or treatment of live oak motte as a distinct range type. Likewise, the Live Oak forest cover type of the Society of American Foresters (Eyre, 1980) did not include the live oak motte form of the Gulf Coast prairies.

Norias Division, King Ranch, Kenedy County, Texas. February, later hibernal or early vernal aspect. FRES No. 16 (Oak-Gum-Cypress Forest and Woodland Ecosystem). Variant of K- 81 (Live Oak-Sea Oats), Variant of SAF 89 (Live Oak). Alternatively and based on geographic location: FRES No. 32 (Texas Savanna), K-55 (Mesquite-Live Oak Savanna). Live Oak variant of SRM 719 (Mesquite-Live Oak-Seacoast Bluestem). Western Gulf Coastal Plain- Coastal Sand Plain Ecoregion 34d (Griffith et al, 2004).

 

213. Into the woods we go- Inside a live oak motte with a well-developed (and heavily utilized) herbaceous understorey and a shrub/immature tree layer. Almost all tree trunks where those of live oak (clonal trunks or those of individual genotypes was not determined), but there were a few honey mesquite and sugarberry trees (at least nine out of ten trunks were live oak). There were immature trees of three of these species. Most common (abundant) shrubs were Hercules club that also "goes by" tickle-tongue, pricklyash, pepperbark, and toothache tree (Zanthoxylum clava-herculis), lime pricklyash or colima (Z. fagara), and mustang grape (Vitis mustangensis). The herbaceous layer was made up almost exclusively of numerous grasses including: Gulf cordgrass or sacahuista, seacoast bluestem, tumble windmill grass (Chloris verticillata), and hooded windmillgrass (C. cucullata), red lovegrass (Eragrostis secundiflora ssp. oxylepis),Gulf dune paspalum (Paspalum monostachyum), Canada wildrye (Elymus canadensis), white tridens (Tridens albescens), Texas tridens (T. texanus), redtop panicgrass or thatchgrass (Panicum rigidulum), and Ghiesbreght panicgrass (P. ghiesbreghtii) as well as naturalized King Ranch bluestem (Andropogon ischaemum= Bothriochlor ischaemum) and Guineagrass (Panicum maximum). There were no obvious or conspicuous forbs other than an Aster sp ("go figure").

Norias Division, King Ranch, Kenedy County, Texas. February, late hibernal or early vernal aspect. FRES No. 16 (Oak-Gum-Cypress Woodland and Forest Ecosystem). Variant of K-81 (Live Oak-Sea Oats). Variant of SAF 89 (Live Oak). Alternatively and based on geographic location: FRES No. 32 (Texas Savanna), K-55 (Mesquite-Live Oak Savanna). Live Oak variant of SRM 719 (Mesquite-Live Oak-Seacoast Bluestem). Western Gulf Coastal Plain-Coastal Sand Plain Ecoregion 34d (Griffith et al., 2004).

 

214. Inside the live oaks- Another view of the interior of an upland (loose sand) live oak woodland or an extensive motte dominated by live oak. Tree cover and density was almost exclusively live oak (of both mature and immature tree trunks), but there were occasional honey mesquite, sugarberry or common hackberry, and least abuncant huisache (Acacia farnesiana= A. smallii). These three species were also of both mature and immature ages. Most abundant shrubs were Hercules-club or tickle-tongue (all leafless short shrubs in foreground), lime pricklyash, and mustang grape. Grasses included the dominants, Gulf cordgrass or sacahuiste and seacoast bluestem plus tumble windmillgrass, hooded windmillgrass, red lovegrass, Gulf dune paspalum, white tridens, Texas tridens, Canada wildrye, redtop pancigrass or thatchgrass, and Ghiesbreght panicgrass plus the naturalized King Ranch bluestem and Guineagrass. Strangely, no forbs other than a species of Aster were obvious.

Norias Division, King Ranch, Kenedy County, Texas. February, late hibernal or early venal aspect. FRES No. 16 (Oak-Gum-Cypress Forest and Woodland Ecosytem). Variant of K-81 (Live Oak-Sea Oats). Variant of SAF 89 (Live Oak). Alternatively and based on geographic location: FRES No. 32 (Texas Savanna), K-55 (Mesquite-Live Oak Savanna). Live Oak variant of SRM 719 (Mesquite- Live Oak-Seacoast Bluestem). Western Gulf Coastal Plain- Coastal Sand Plain Ecorgeion 34d (Griffith et al., 2004).

 

215. King Ranch? Ya gotta be kiddin'!- Interior of live oak woodland that developed on a surrounding Western Gulf Coast tallgrass prairie. Morphology of trees, including features of branches and crowns, and general architecture (structure and arrangement of vegetation) of a live oak motte of such area (relative spatial scale) and development as to be a woodland. Trees were exclusively live oak except for occasional (rare) mesquite, Texas hackberry or sugarberry, and, least of all, huisache. There was a prominent herbaceous layer composed of coastal prairie grasses and a woody understorey of shrubs like Hercules club, lime pricklyash, and mustang grape. Grass species included isolated individuals of the dominants, Gulf cordgrass and seacoast bluestem, as well as common and hooded windmillgrasses, Gulf dune paspalum, red lovegrass, white and Texas tridens, Canada wildrye, redtop panicgrass or thatchgrass, and Ghiesbreght panicgrass, plus naturalized King Ranch bluestem and Guineagrass. A quick search for forbs was fruitless.

The woodland range shown here does not purport with images of ranches in the popular imagination or perception or as shown in Hollywood Westerns, but there are numerous such live oak mottes and woodlands on large ranches in south Texas,especially those along the Gulf Coast. This scene was on the Norias Division of King Ranch. Live oak woodland range like this furnishes outstanding habitat for the Rio Grande turkey (Meleagris gallopavo intermedia) as well as providing shade for cattle and horses like the renowed Santa Gertrudis and sorrel Quarter Horses of the famous King Ranch.

Kenedy County, Texas. February, later hibernal or early vernal aspect. FRES No. (Oak-Gum-Cypress Woodland and Forest Ecosystem). Variant of K-89 (Live Oak). Variant of SAF 89 (Live Oak). Alternatively and based on geographic location: FRES No. 32 (Texas Savanna), K-55 (Mesquite-Live Oak Savanna). Live Oak variant of SRM 719 (Mesquite-Live Oak-Seacoast Bluestem). Western Gulf Coastal Plain-Coastal Sand Plain Ecoregion 34d (Griffith et al, 2004).

 

216. Crowding an ole patriarch- An old-growth speciment live oak with a unnaturally high (man-caused increase in) cover of understorey trees and shrubs. The well-developed lower tree and shrub layer was clearly a recent (hence almost assuredly anthropogenic) woody invasion. Great spreading limbs of the "big momma" or "gran'paw" live oak were undeniable proof that this ancient tree developed in the open (ie. in absence of crowding). The small-sized (relatively young) understorey trees and shrubs attested to recent establishment of these individuals suggesting absence of fire (at least low fire frequency), perhaps combined with overgrazing or periodic overuse that reduced grass cover. Most of the leafed-out shrubs were honey mesquite (eg. larger shrubs at far-right foreground with trunks inclined to the right) but there were also some huisache. Texas sugarberry or common hackberry was also present though largely dormant.

The multi-stemmed shrub with smooth, light-grey bark was lime pricklyash with an accompaning and readily identified mustang grape with its serpentine single-stem covered by dark, deeply furrowed bark. These shrubs were the subject of the next photograph.

Norias Division, King Ranch, Kenedy County, Texas. February, later hibernal or early vernal aspect. FRES No.16 (Oak-Gum-Cypress). K-89 (Live Oak). Alternatively and based on geographic location: FRES No. 32 (Texas Savanna), K-55 (Mesquite-Live Oak Savanna). Variant of SAF 89 (Live Oak). Live Oak variant of SRM 719 (Mesquite-Live Oak-Seacoast Bluestem). Western Gulf Coastal Plain-Coastal Sand Plain Ecoregion 34d (Griffith et al., 2004).

 

217. Prickly and twisted invaders- Close-up of lime pricklyash and mustang grape that had invaded the undersrtorey of a live oak motte on the sandy plains of the Wild Horse Desert in Rio Grande Plains. Age of these shrubs was not determined, but they were relatively young having not yet grown to height of first horizonal limb of an old live oak under the canopy of which these plants were growing. (This was presented clearly in the immediately preceding photograph.)

Successional status of these invading shrubs was unclear, but their relative youth in comparison to the obvious age of the large live oak indicated that lime pricklyash, mustang grape (as well as mesquite and huisache) had established after the live oak had reached adult size. The terms invasion, invaders, and invading shrubs could have one or two meanings in this usage, only one of which was certain. The certain meaning or usage of invasion referred to movement of plants from one area into another and subsequent successful establishment of these new plants in their environment. This is the classic original meaning of invasion in the Clementsian usage (Weaver and Clements, 1938, ps. 131-132144, 148, 166) and, hence, as used by most foresters and rangemen (at least those of the Anglo-American school of "dynamic plant ecology"). From this original meaning a star student of Weaver, E.J. Dyksterhuis adapted invasion and, especially, invader to a second meaning (an extension or outgrowth of the original meaning of Clements). This second usage was applied to plant species that continued to invade (Clementsian meaning) on habitats that had been disturbed (denuded was Clements' term) or that were continuing to be disturbed, especially by overgrazing (Dyksterhuis, 1949).

As applied to this live oak woodland Gulf cordgrass has to re-establish itself on (ie. to invade) a previously denuded (as by overgrazing, plowing, drought) range. Gulf cordgrass has to invade (ie. complete or effect an invasion) but because this species declines with disturbances (specifically abusive or improper grazing) it is a decreaser not an invader in usage as applied to plant succession and range condition/trend (Dyksterhuis, 1949). Decreaser corresponds to member of the climax plant community. On the live oak-dominated range type/site featured here lime pricklyash, mesquite, and huisache also invaded when they successfully established. Up to this point invasion has the same meaning as successful establishment of a decreaser such as Gulf cordgrass, but because these particular woody range plants have continuing or on-going invasion under disturbances such as overgrazing or, as is also likely, underburning these shrub species are invaders in contrast to decreasers like Gulf cordgrass.

The prevailing judgment of rangemen with regard to such abundant establishment (invasion) of these woody species on the live oak woodland and sacahuista sand prairie range types is that this unnatural excessive invasion is symptomatic of disturbance (perhaps cessation of fire, improper grazing management, or drought) so that these shrubs are invaders in the meaning of Dyksterhuis, 1949). This is an invasion of brush, of woody invaders as per the Dykstehuis (1949) model and therefore noxious range plants. This brush invasion is different from the general (the Clementsian) invasion. Invasion by Dyksterhuis (1949) invaders is range deterioration through the process of retrogression (retrograde movement from climax vegetation).

Continuing invasion by species like lime pricklyash, honey mesquite, huisache, and, probably, mustang grape resulting in development of a lower woody understorey constituted brush invasion (changes in the plant community by retrogression) and commensurate loss of economically valuable and ecologically natural forage.

The real question is, "How much of the cover of live oak is brush invasion"? Or same thing with reversed emphasis, "How much of the uniting (the coalescing) of live oak mottes into extensive live oak woodland is climax (potential natural) vegetation"?

Norias Division, King Ranch, Kenedy County, Texas. February.

 

218. Ranchman's touch- Naturalized Guineagrass (Panicum maximum) formed the complete understorey of a motte of mature live oak. On this large live oak motte or woodland on the King Ranch, the understorey was such an exclusive single species- stand of Guineagrass that woody species as well as other grasses were absent. This isolated tract was subject only to infrequent defoliation.

There are various "versions" of how the introduced Gunieagrass (native of Central and South America) naturalized and spread throughout the Coastal Prairies and Marshes and eastern parts of the Rio Grande Plains. One of the more popular explanations is that Guineagrass was spread by Hurricane Beluah from seed nurseries and experimental plantings at branch stations of the Texas Agricultural Experiment Station. Others insist that Gunieagrass spread from some of the larger ranches in the region, especially King Ranch, that had planted it as the latest "miracle grass". Cypher (1995, ps. 77, 92, 94, 107, 183) described planting of Guineagrass on King Ranch under direction of Bob Kleberg. However most of these plantings and established pasturess of Guineagrass described by Cypher (1995) were King Ranch holdings in Cuba and South America.

As late as the early 1970s Guineagrass was probably not established in any part of Texas (Gould, 1975, p. 469). This introduced forage grass is a "new comer" compared to Johnsongrass, bermudagrass, King Ranch bluestem, and buffelgrass.

Norias Division, King Ranch, Kenedy County, Texas. February, later hibernal or early vernal aspect. Understorey so modified that FRES, Kuchler, SAF, and SRM designations would be meaningless. Western Gulf Coastal Plain-Coastal Sand Plain Ecoregion 34d (Griffith et al., 2004).

 

219 A. Leader of the western taxon of eastern or southern live oak (Quercus virginiana var. fusiformis= Q. fusiformis)- Catkins and new leaves have emerged on this live oak on the Grand Prairie of northcentral Texas. Shedding of last year's leaves and emergence of this year's leaves typically occurs synchronously causing some lay observers to state that "the new leaves are phushing off the old leaves". "Leaving out" usually also occurs with flowering. It's a busy (and critical) time in the life of a live oak.

Erath County, Texas. March, immediate pre-anthesis to anthesis stage.

 

219 B. Flushing in eastern or southern live oak- The synchronous emergence of new leaves (from preformed buds of previous season) and shedding of old or current year's leaves in trees (such as the plateau form of southern live oak shown here) is known as flushing. These two views of a leader of southern live oak illustrated this phenological phenomenon.

Erath County, Texas. March.

 

219 C. Off with the old on with the new- Tip of branch in plateau form of southern live oak on which current season's or old leaves (large leaves of dark green color) persisted even as new leaves emerge accompanied by catkins. This phenomenon is designated as flushing.

Erath County, Texas. March, early catkin (pre-anthesis) stage of phenology.

 

220. A live oak's life in the fall- Summer-hardened leaves provided a backdrop for this southern live oak acorn. Southern (eastern) live oak is a white oak (Leucobalanus subgenus), the species of which produce an annual (vs. a biennial) acorn crop. Acorns are a rich and major carbonaceous (energy) concentrate on numerous ranges and range types. Acorns are often extremely important components of the diets of many species of range animals ranging from insects through birds and mammals, the latter often including man (American Indians especially relied heavily on various kinds of acorns.). Excessive intake of acorns (as well as buds, catkins, and leaders) can result in toxicity. Older leaves are not toxic. The poisonous principle is a group of tannins known as gallotannins. Energy stores of acorns generally offset adverse impacts of poisoning for wildlife such as upland game birds, especially wild turkey and white-tailed deer (Odocoileus virginianus).

Grand Prairie, Erath County, Texas. October, fruit-ripe.

 

221. Doubleheader or twins- Two cotyledons emerging from a single acorn while still on the tree exemplified the phenomenon of vivipary in plants. Vivipary is the condition in which seeds germinate and emerge from fruit or seed while they are still attached to the parent plant. Under certain conditions live oak has viviparous germination as shown here. "Plant species in which the embryo grows sufficiently to emerge visibly from within the seed tissues before dispersal are termed
viviparous" (Farnsworth, 2000). Bonner and Vozzo (1987) reported that vivipary was common in southern live oak (as well as white oak [Q. alba]) when wet weather occurred during acorn maturation. That was exactly growing conditions that existed when this acorn (and those in a pile shown in the succeeding photograph) had two cotyledons emergent from one acorn in the Grand Prairie of northcentral Texas.

Emergence of two embryos (and hence potentially two trunks) of southern live oak complicated the understanding of distinct shoots (trunks) of this species in live oak mottes. Not only is there the question as to whether trunks are asexual shoots from roots of existing trees (= shoots or trunks) or derived from acorns (such sexual shoots would be unique genotypes), but also as to if more than one trunk arose from a single fruit and a single fertilized ovule. In other words, are most of the "trees" (trunks or shoots) in a motte of southern live oak clones (= such offshoots are ramets) or are they distinct (genetic) plants that are genets?

Erath County, Texas. Late October.

 

222. Ready to grow- Numerous viviparous acorns off of the same young southern oak presented in the preceding slide. All these acorns had germinated while still attached to this tree. Theses viviparous acorns subsequently fell to ground from which they were gathered and arranged by the author for viewing purposes. All of these viviparous acorns had a single embryo (cotyledon) emerging from the nut. Almost all acorns of southern live oak are shed from a cup that persist much longer on the tree. An ecception to this pattern was included in this pile. Predation on nutrient-rich acorns is universal and by many species.

The acorn at lower left had been bored into and fed upon by some larval insect. The rest had been spared (so far) and were ready to grow in soil beneath the parent live oak. This situation illustrated how sexual reproduction contributed to formation of mottes.

Erath County, Texas. Late October.

 

223. A big ole good 'un or a good ole big 'un- Trunk and inner crown of an immense and, by extrapolation, very old southern live oak. This magnificant specimen of Q. virginiana var. fusiformis or Q. fusiformis. specimen was growing at the outer edge of the floodplain of Bosque River. It epitomized the size and shape of which this taxon is capable of achieving under ideal habitat. The pattern of huge trunk ( frequently with forks) from which arise tremendous limbs explains much of the beauty and adoration attributed to southern live oak.

This tree had just shed last year's leaves and grown the current year's foliage to adult size. Hence the bright, light-green color.

Erath County, Texas. April.

Ceniza Scrubland

Ceniza Shrub (Lecophyllum, Larrea, Prosopis), unit #45 (Kuchler, 1964) and unit #38 (map in Garrison et al., 1977) is one of the most unique and restricted (in spatial area) types of potential natural vegetation mapped for the North American United States. In fact, the ceniza scrub is the second smallest unit of natural vegetation in Texas and one of the smallest designated/delineated for the entire republic except for the islands of Hawaii and Puerto Rico (Kuchler map in Garrison et al., 1977).

Ceniza shrubland lies in a narrow band along the banks and low bluffs of the Rio Grande (= Rio Bravo) where this slow-moving, shallow stream descends from the Chihuhuan Desert-Stockton Plateau Region to the south southeast nearing its floodplain and mouth at the Gulf of Mexico. Ceniza shrub vegetation joins the mixed grass-woody legume (mesquite-acacia) savanna of the Rio Grande Plains (Tamaulipan) plains which, with the tallgrass-live oak-mesquite savanna, makes up almost all the rest of this large range region except for riverine gallary and floodplain forests.

 

224. Where the silvery ceniza reigns supreme- Rio Grande range dominated by silver or gray-leaved ceniza (Leucophyllum frutescens) with guajillo (Acacia belangerii), the associate species, which along with some Texas persimmon (Diospyros texana)formed a woody layer above two herbaceous layers, one on which was composed of midgrasses with Wright's threeawn (A. wrightii) the dominant and sideoats grama the assocciate species and the other herbaceous layer made up of shortgrasses of which red grama (Bouteloua trifida) was most common.Widely scattered pricklypear (Opuntia spp.) and catclaw mimosa (Mimosa biuncifera= M. lindheimeri)were lower-growing shrubs that contributed to vegetation struction and formed a discontinuous lower woody layer (though barely) in this range plant community. These minor shrub species were more plentiful in examples presented below of this range type.

This photo-plot was an example of a local range plant community of relatively low biodiversity, but it represented typical range that was dominated by ceniza.

Upland at northern limit of the Rio Grande Valley. Val Verde County, Texas. October, autumnal aspect at peak standing crop. FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-38 (Ceniza Shrub). No SRM for this range type. Mixed Deciduous Series 134.31 of Tamaulipan Thornscrub (Brown et al., 1998, p. 42; also, Figure 53, p. 103 of Brown, 1994). Range site: Shallow Ridge (South). Rio Grande Floodplain and Terraces Ecoregion 31d (Griffith et al., 2004).

 

225. Uplands above the Rio Grande- Ceniza-guajillo scrubland or, more specifically as to potential natural or climax vegetation, ceniza-guajillo-mixed grass savanna on uplands of the Valley of the Rio Grande. Here ceniza and guajillo as codominants formed an upper shrub layer above a discontinuous lower shrub layer composed of catclaw mimosa and pricklypear and two herbaceous layers: 1) midgrass layer dominated by sideoats grama with Wright's threeawn as associate species and 2) shortgrass layer dominated by red grama. Incidental grass species included cane bluestem (Andropogon barbinodis= Bothriochloa barbinodis var. barbinodis) and slim tridens (Tridens mutica). Other shrubs having general abundance varying from that of associate species to trace portions included lotebush, knifeleaf condalia, and tasajillo. There were occasional, even rare, plants of Texas persimmon which varied in heights from those similar to that of ceniza and guajillo to a few having sizes suggestive of small trees. In the examples of range vegetation presented here these low-growing shrubs were nowhere abundant enough to constitute a separate woody layer, at least not other than an extremely discontinuous stratum of plants (see seven and eight slides below).

Successional status of the herbaceous component was not known. It flollowed that range condition class could not be determined. It seemed likely that the herbaceous cover had been reduced by grazing animals with species composition shifted from sideoats grama toward greater proportions of red grama and arrowfeather threeawn. Such was not determined by grazing trials, but some circumstantial evidence was preented in the next photograph.

Val Verde County, Texas. October, autumnal aspect at peak standing crop. FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-38 (Ceniza Shrub). No SRM for this range type. Mixed Deciduous Series 134.31 of Tamaulipan Thornscrub (Brown et al., 1998, p. 42; also, Figure 53, p. 103 of Brown, 1994). Range site: Shallow Ridge (South). Rio Grande Floodplain and Terraces Ecoregion 31d (Griffith et al., 2004).

 

226. Details of cenizo-guajillo-mixed grass savanna or, if described by woody dominants, cenizo-guajillo scrubland- Ceniza, the gray-colored shrub, and guajillo, the bright and light-green legume with compound leaves, clearly dominated the ridge top above the Rio Grande Valley. There was an herbaceous, bi-layered understorey comprised of the generally co-dominant midgrasses, sideoats grama and Wright's threeawn, and the shortgrass species of red grama. There were trace amonunts of slim tridens and Texas grama.

Close observation--even of this photograph--revealed that sideoats grama and, though less pronounced, Wright's threeawn were more common and with greater cover when adjacent or at least in close proximity to the shrubs. This suggested to knowledgable rangemen that perhaps longterm grazing had reduced grasses in spaces among shrubs. Experienced animals learn to avoid grazing too closely to woody plants with branches, thorns, prickles, spines, etc. that could possibly cause injury to eyes or sensitive muzzles. This is more the case with cattle or even sheep than browsing species like goats and deer.

There were other variables that could account--in part or solely--for sparcity of grasses and forbs besides or in addition to grazing. Aspect as between north versus south slopes, local edaphic differences, and microtopographic features were some examples of abiotic factors that could have influenced cover and density of grass species on this range. An illustration was presented in the next two sets of two slides.

Val Verde County, Texas. October, autumnal aspect at peak standing crop. FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-38 (Ceniza Shrub). No SRM for this range type. Mixed Deciduous Series 134.31 of Tamaulipan Thornscrub (Brown et al., 1998, p. 42; also, Figure 53, p. 103 of Brown, 1994). Range site: Shallow Ridge (South). Rio Grande Floodplain and Terraces Ecoregion 31d (Griffith et al., 2004).

 

227. Grass to go along with shrubs- Ceniza-guajillo-mixed grass savanna on a north-facing slope. These two slides and the set of two slides immediately below were of vegetation on the same range as that of the vegetation presented in the preceding slide. The range vegetation in these slides and the succeeding set of two slides was on a predominately north slope whereas vegetation in the preceding photograph was on more of a south-facing slope. All photographs were taken within an approximately 30 yard radius or less.

In addition to a much greater relative abundance and foliar cover of grass (primarily sideoats grama and Wright's threeawn) the other immediately observable difference in range vegetation was less cover of guajillo on the north slope. Students should compare again the difference in guajillo on the range between these two photographs and the preceding photograph. Other shrubs present in much lower proportions included pricklypear, tasajillo, knifeleaf condalia, lotebush, and catclaw mimosa. These woody species were generally more abundant (greater frequency, more cover, higher density) on microhabitats where there were fewer grasses (in particluar, lower foliar cover).

Relations--if any--among general grass and shrub cover and among specific grass and shrub species was an example of the sorts of studies range scientists have conducted on range. Often, however, such studies have been more observational and than experimental (done when opportunistic or fortutious events permit rather than by carefully planned ecological field experiments) so that actual cause-effect relations could be not be determined.

Val Verde County, Texas. October, autumnal aspect at peak standing crop. FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-38 (Ceniza Shrub). No SRM for this range type. Mixed Deciduous Series 134.31 of Tamaulipan Thornscrub (Brown et al., 1998, p. 42; also, Figure 53, p. 103 of Brown, 1994). Range site: Shallow Ridge (South). Rio Grande Floodplain and Terraces Ecoregion 31d (Griffith et al., 2004).

 

228. Composition and structure of ceniza-mixed grass savanna- Two photographs that showed plant species composition and plant layers of climax (potential natural) vegetation of Rio Grande ceniza-associated shrubs-midgrass-shortgrass savanna. These two samples served as photo-transects extending from a draw up to a ridge top in the low bluffs above the greater floodplain of the Rio Grande. Texas persimmon grew along the less xeric draw (than ridge sides and ridge tops). In the first photograph shrubs and/or small trees of Texas persimmon were distinct as the tallest and greenest plants beginning with the green crown in left-hand corner (left margin) with more persimmons behind extending to background. The gray-colored shrubs were ceniza. A local grass community was in the foreground of the first photograph. This small graminaceous community was composed of sideoats grama, Wright's threeawn, and red grama plus a trace of slim tridens.

The second photograph was taken farther up the draw and at closer range to feature a population or colony of sideoats grama in foreground. Also shown in foreground was the partial crown of Texas persimmon (left-hand corner) and several ceniza. This photographer/author speculated that the second photo-transect was a fairly represntative example of the pre-Columbian (= climax or potential natural) vegetation of the ceniza-dominated mixed grass savanna for this range site.

Taller and more treelike Texas persimmon resulted in a different structure and, consequently, different physiogonomy of the example of this range type, but these were not seen by this author as comprising a separate or distinct vegetational layer. Similarly, widely scattered individuals of lower shrub species (pricklypear, catclaw mimosa, knifeleaf condalia) formed a second stratum of woody plants only in very localized microenvironments so as to constitute at most a discontinuous layer in the plant community.

Val Verde County, Texas. October, autumnal aspect at peak standing crop. FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-38 (Ceniza Shrub). No SRM for this range type. Mixed Deciduous Series 134.31 of Tamaulipan Thornscrub (Brown et al., 1998, p. 42; also, Figure 53, p. 103 of Brown, 1994). Range site: Shallow Ridge (South). Rio Grande Floodplain and Terraces Ecoregion 31d (Griffith et al., 2004).

 

229. Grass and snake in the grass- Photo-quadrant of a local community of three grass species red grama, sideoats grama, and Wright's threeawn (in that approximate order of foliar cover). These grasses constituted either one or two herbaceous layers (depending on individual interpretations as to how distinctive a layer of vegetation would be in the sparse cover and low density characteristic of this range). This sample of the herbaceous component of a ceniza-associated shrubs-midgrass-shortgrass savanna was growing on the same range shown in preceding slides.

The snake was a western coachwhip (Masticophis flagellum testaceus). This specimen was "movin' on", but a dependable Nikon FM and Kodachrome 64 captured the encounter. Western coachwhip is a general predator and not selective about the flesh it eats. Grasshoppers are just fine, thank you, even if small mammals and birds might be preferred. Would any other other outlook permit survival on this "slim pickin's" range?

Val Verde County, Texas. October, autumnal aspect at peak standing crop. FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-38 (Ceniza Shrub). No SRM for this range type. Mixed Deciduous Series 134.31 of Tamaulipan Thornscrub (Brown et al., 1998, p. 42; also, Figure 53, p. 103 of Brown, 1994). Range site: Shallow Ridge (South). Rio Grande Floodplain and Terraces Ecoregion 31d (Griffith et al., 2004).

Photographic comment: The preceding nine photographs of the ceniza-associated shrubs-midgrass-shortgrass Rio Grande Valley savanna were taken in full sun at mid-day (about 1300 hours). The next six photographs were of the same vegetation taken on the same range late in the evening (1730 hours) of the preceding day. Differences in light shining on vegetation due to declination of the sun was interesting and provided a lesson to photographers of range plants and plant communities. Frequently (probably usually) range photographers have limited choice of light conditions. Unless one lives in an area and can choose when to photograph, the photographer can only do the best that he can with light conditions Nature saw fit to provide when the phtographer happened upon the photographic subject. The western coachwhip portrayed above will not wait until "the light is right".

As a general rule, full-sun exposure is usually best when using slow film (eg. Kodachrome) for purposes of reducing graininess, most accurately capturing color as seen by the human eye, and extending archival longevity (Kodachrome is still the "gold standard" for color-fastness under dark storage) and, at the same time, maximizing depth of field (a key feature for photographing vegetation, plants, and related range subjects). There are exceptions. Two such in Range Management photography include capturing pale, pastel colors of petals and getting diagonal rays of light in order to highlight slender objects like grass shoots. Full, bright, light at early morning or late evening works typically best for such purposes. Alternatively, cloudy skies may permit photographs that have more detail and use dim light to advantage than can be obtained under dazzling full-sun (eg. portrayal of pale plant parts that might otherwise be washed out.

The following six photographs taken near sundown and long shadows presented a lighting effect and an illumination that resulted in greater detail of grass in the understorey of the ceniza-dominated Tamaulipan thornscrub.

 

230. Sundown on the ceniza-guajillo-mixed grass savanna- Two photographs of the subtype of Tamaulipan thornscrub characterized by ceniza above floodplain of the Rio Grande taken with the long shadows of early evening. Light and direction (orientation) of the ridge on which this range plant community grew provided detailed views of plants in the vegetation. Light was especially useful in illuminating the various grasses which included sideoats grama, Wright's threeawn, red grama, and slim tridens in that approximate rank (sideoats grama and arrowfeather threeawn swapped places back-and-forth as the herbaceous dominant on different microenvironments).

Gray-leafed shrub was ceniza, the overall dominant species of this range plant community; bright-green shrub was guajillo, the associate species on the range. Other, though minor, shrubs included pricklypear, tasajillo, catclaw mimosa, lotebush, and knifeleaf condalia. A specimen of catclaw mimosa appeared in the far-right foreground of second photograph (in right front corner). Texas persimmon, a woody associate species, on some microsites of this range (see photograph immediately below and set of two slides above the preceding "snake slide") was not visible in these "group portraits".

Val Verde County, Texas. October, autumnal aspect at peak standing crop. FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-38 (Ceniza Shrub). No SRM for this range type. Mixed Deciduous Series 134.31 of Tamaulipan Thornscrub (Brown et al., 1998, p. 42; also, Figure 53, p. 103 of Brown, 1994). Range site: Shallow Ridge (South). Rio Grande Floodplain and Terraces Ecoregion 31d (Griffith et al., 2004).

 

231. Shrubs in the spotlight- An example of ceniza-guajillo-mixed grass savanna in Rio Grande Plains that emphasized woody species. Overall dominant plant,as well as dominant shrub, of this range plant community was ceniza which was readily distinguished by silvery or grayish leaves. The two tallest plants (and both of treelike-form) were Texas persimmon. Lower woody plants with bright green canopies were ceniza, the associate shrub of this vegetation. Bunchgrasses visible in foreground were sideoats grama and arrowfeather threeawn.

General size (height and canopy size) of Texas persimmon was that of large shrubs or small trees which, depending of interpretation, could be seen as adding a woody stratum above that of ceniza and guajillo and of lower-growing shrubs like catclaw mimosa, lotebush, knifeleaf condalia, pricklypear, and tasajillo. If the arboreous Texas persimmon were seen as being or forming a discontinuous (extremely so) layer of vegetation there were three woody layers of this range plant community. There were also two herbaceous layers made up by 1) !midgrasses and 2) shortgrasses.

Val Verde County, Texas. October, autumnal aspect at peak standing crop. FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-38 (Ceniza Shrub). No SRM for this range type. Mixed Deciduous Series 134.31 of Tamaulipan Thornscrub (Brown et al., 1998, p. 42; also, Figure 53, p. 103 of Brown, 1994). Range site: Shallow Ridge (South). Rio Grande Floodplain and Terraces Ecoregion 31d (Griffith et al., 2004).

 

232. Delighting in shrubs in the light- Oblique shafts of evening (sundown) light highlighted foliage of both shrubs (and some grasses) in a ceniza-guajillo-mixed grass savanna on a ridge above the Rio Grande floodplain. Ceniza was dominant plant as well as dominant shrub of this range plant community, but in scattered local spots ceniza and guajillo were con-dominants. Similarly, sideoats grama and Wright's threeawn were often co-dominant, though sideoats grama tended to have greater density and foliar cover sometimes forming homogenous colonies (continuous, exclusive populations). Red grama also formed local single-species stands or exclusive populations. Other shrubs present (though not visible here) were Texas persimmon, lotebush, knifeleaf condalia, pricklypear, and tasajillo.

Val Verde County, Texas. October, autumnal aspect at peak standing crop. FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-38 (Ceniza Shrub). No SRM for this range type. Mixed Deciduous Series 134.31 of Tamaulipan Thornscrub (Brown et al., 1998, p. 42; also, Figure 53, p. 103 of Brown, 1994). Range site: Shallow Ridge (South). Rio Grande Floodplain and Terraces Ecoregion 31d (Griffith et al., 2004).

 

233. "... Lambs among wolves" (Luke 10:3 KJV)- On a ceniza-guajillo dominated savanna in the Rio Grande Plains Wright's threeawn and red grama (to side and behind the threeawn) managed to persist and even sexually reproduce their species. Species composition of pre-Columbian (= climax or potential natural vegetation) of this range type and, even, more of this range site is a matter of "best guess" scientific speculation and experienced judgment. It has generally agreeded and/or assumed that this range vegetation at climax is a shrub-grass savanna with cover and density of shrubs having increased and of grasses having decreased with impact of European man (overgrazing-browsing, underburning, pest introduction, commercial activities ranging from transportation to petroleum exploration/development, etc.) along with climatic change (including, but not limited to, planetary warming).

Wright's threeawn was frequently co-dominant with sideoats grama. The threeawns have traditionally been classified as invaders on most range sites. On the shallower, more xeric range sites in arid and semiarid zones such as those in the western Rio Grande Plains and associated Trans-Pecos Region it seemed more realistic (at least to this author) to regard some of the perennial threeawns as increasers.

Val Verde County, Texas. October, autumnal aspect at peak standing crop. FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-38 (Ceniza Shrub). No SRM for this range type. Mixed Deciduous Series 134.31 of Tamaulipan Thornscrub (Brown et al., 1998, p. 42; also, Figure 53, p. 103 of Brown, 1994). Range site: Shallow Ridge (South). Rio Grande Floodplain and Terraces Ecoregion 31d (Griffith et al., 2004).

 

234. Arrowfeather threeawn (Aristida Wrightii)- Two specimens of Wright's or arrowfeather threeawn which, depending on microsite, was either the associate or co-dominant grass on a ceniza-guajillo-mixed grass savanna in the western edge of the Tamaulipan thornscrub.

Specimen in the first of these slides was growing in front of a guajillo. Specimen in the second slide had for neighbors other plants of Wright's threeawn and red grama (low-growing, small bunchgrass to left of the threeawn). All photographs of Wright's threeawn presented in this segment were growing on the ceniza-guajillo-mixed grass savanna range shown immediately above.

Almost all threeawns have low palatability. Under heavy use and, particularly, overgrazing almost all other grass species disappear or decline before the Aristida species. Even perennial threeawns are almost invariably classified as invaders. However, various Aristida species are well-adapted to xeric environments and are grazed in earlier phenological stages (prior to apperance of awn-armed panicles). As such, some threeawns are treated as increasers or, depending on range site, even decreasers (though at relatively low levels of species composition of range plant communities).

Taxonomy of numerous of the Aristida species remains a matter of some debate, personal interpretation, and on-going controversy. In fact, it seemed likely that the "most likely correct" or "nearly corrrect" nomenclature and identification of the Aristida taxa that form complexes will never be resolved-- genomes mapped or otherwise. This appeared to be the situation with A. wrightii.which intergrades with the A. purpurea complex as well as A. fendleriana, A. longiseta, and who knows which other species.

Val Verde County, Texas. October, autumnal aspect. Peak standing crop; grain-ripe phenological stage. Range site: Shallow Ridge (South).

 

235. Inflorescence of Wright's threeawn- Inflorescence of A. Wrightii shining in the sundown light on a ridge of a Shallow Ridge (South) range site of the ceniza-guajillo-mixed grass savanna range type. Inflorescences of Aristida species are interpreted as panicles of one-flowered spikelets (a rather narrow panicle in A. Wrightii). The lemma of the threeawn spikelet has a sharp-pointed callus at one end and a trifid (three-pronged) awn at the other end.

Val Verde County, Texas. October. Peak standing crop; grain-ripe stage of phenology.

 

236. Red grama on a gray ceniza range- Local "parcel" of herbaceous understorey consisting almost exclusively of red grama. Red grama is an invader under various forms of disturbance so that high proportions of this species on a range indicates range retrogression, for whatever cause(s).

Bouteloua trifida is a small, tufted perennial, but it is not strictly cespitose as it sometimes produces rhizomes. Occurrence of several tufts in close proximity (as in right foreground) is commonly due to production of new ramets or clones ("daughter plants") from rhizomes.

This and following examples of red grama were on the same ceniza-guajillo-mixed grass savanna range presented and described in detail above. Val Verde County, Texas. October.

 

237. Red grama grabbed aholt- On the same range of ceniza-guajillo-mixed grass savanna presented above (a ridge above Rio Grande floodplain) there were microenvironments populated primarily up to exclusively by red grama. These local stands or mini-populations were situated among colonies of sideoats grama or Wright's threeawn. Such a red grama stand was shown here. At other microlocations on this (and similar ranges) these three grass species grew together forming simple herbaceous communities.

This ecological invader is typically a grass of short stature and regarded as a shortgrass species like numerous of the species with which it is associated (eg. buffalograss, curly mesquite, Texas grama, hairy grama). Red grama is an opportunistic species and it demonstrates considerable phenotypic plasticity. Under extremely favorable growing conditions red grama grows to heights of almost a foot. That was the situation with the specimens presented here. A period of unusually heavy rainfall during late summer-early autumn (shortly before time of photographs presented herein) was responsible for the atypically tall plants viewed here.

Val Verde County, Texas. October. Peak standing crop and hard-dough to grain-ripe phenology.

 

238. Tall and sexually prolific shoots of a shortgrass- Red grama is an opportunistic and invader species that flowers prolifically under good growing conditions (especially after "good rains"). Shoots of red grama also extend to greater heights under such favorable--though short--periods of plenty. An example of that phenomenon was shown here at hard-dough to grain-ripe stage at period of peak biomass that was close on the heels of a wet late summer-early autumn.

Val Verde County, Texas. October.

 

239. Red stripes in the range air- Racemes of red grama on shoots that were shown in the two immediately preceding photographs. These plants were flowering on the ceniza-guajillo-mixed grass svanna range that was featured throughout this portion of the publication.

Val Verde County, Texas. October, maximum biomass and hard-grain stage.

Location note: the Ceniza Scrub developed as a narrow band of potential natural vegetation along the formerly impressive river known as the Rio Grande (Rio Bravo in Mexico). Today, this international border between the United States of America and the Republic of Mexico has been nearly dried up by man's misuse of it. The climax vegetation that bears the name Ceniza is still largely intact (minus a grazed out herbaceous, largely grassy, understorey in many areas) along the Rio Grande (inland from riparian vegetation zones). Part of this narrow strip of climax range vegetation is in the Rio Grande (= Tamaulipan= South Texas) Plains while other sections of this range plant community (at scale of a range cover type) are in the Chihuhuan Desert.

While most coverage of Ceniza Scrub in Range Types of North America was that of the Tamaulipan Savanna form treated in this Rio Grande Plains chapter, the part of the Ceniza Scrubland that developed in the even more arid Chihuhuan Desert was covered in the chapter under that title.

Tamaulipan Thornscrub-Chihuhuan Desert Scrub Ecotone

Ecotone is the term for a transition (= transition zone) between two, sometimes more, natural communities. These communities are used defined or described primarily on basis of vegetation (ie. plant communities) although designations of ecotonal communities frequently include names of dominant animals as well as dominant, defining plants. Ecotone has most commonly been used in reference to large plant (again, sometimes plant and animal) communities such as the biome (biotic community) or association, and hence, "vegetation types" such as rangeland and forest cover (= dominance) types.

Ecotones or transition zones are "edges" of adjoining native communities. This is a natural form of the "edge effect" spoken of by wildlifers as between cropland and forest or fence rows, hedgerows, transmission line clearings (ie. corridors in context of Landscape Ecology). The difference is that ecotones are 1) "edges" writ large and 2) naturally occurring. Ecotones vary greatly in size and shape with some being small and others very large, some narrow and often serpentine-shaped (winding) while others are broad and blockly in shaped, and some ecotones are continuous with others being discontinuous or interrupted.

Most of the major ecotones in North America are transition zones between major communities (biomes, associations, dominance types) of herbaceous vegetation, especially grassland(s) and sometimes marshes, and communities dominated by woody plants (forests, deserts, chaparral). Ecotones formed by "overlapping" of "mixing of" grassland and woody communities (shrubland or forest) are designated as savanna(h)s. Savannas are the most widespread of North American ecotones. Tamaulipan thornscrub of the Rio Grande Plains is a grassland-shrubland (= scrub or scrubland) econtone. The Cross Timbers, post oak savanna, and Edwards Plateau are also savannas though these transition zones are more between forest (rather than shrubland) and grassland. Incidentally, these latter three adjoin at some locations to the Rio Grande Plains.

The four ecotones just listed are major transition zones. Other ecotones (again, these are natural transition communities not edges among cropland, fields, and other manmade communities) are smaller and/or more of a continuum of neighboring natural communities. Frequently there are gradual transitions or "blends" of native (or anturalized) vegetation between major ecotones These occur when natural plant communities exist as continua (plural of continuum) with indistinct graduations among adjoining natural vegetation, including savannas. For example, there are gradual changes in range vegetation between the Cross Timbers and Edwards Plateau or between post oak savanna and pineywoods.

There is an ecotone--mostly a rather narrow one--between the ceniza-mixed grass savanna of the Rio Grande Plains and the Chihuhuan Desert of the Trans-Pecos Basin and Range with a "touch" of a floristic element from the semiarid Edwards Plateau.. This transition between the western edge of the Tamaulipan thornscrub and eastern parts of the Chihuhuan Desertscrub with a minor part of Edwards Plateau is also an ecotone though one of smaller spatial scale and less well-known than major ecotones like Tamaulipan thornscrub or Edwards Plateau. In short, this is an ecotone formed by merging of parts of three major ecotones (an ecotone among ecotones).

Disagreement as to precise boundaries of Edwards Plateau, Rio Grande Plains, and Trans-Pecos Chihuhuan Desert among authorities (Gould, 1962, ps. 1, 11; Correll and Johnston, 1979, map 1, ps. 9-10, 12; Kuchler, 1964; Kuchler map in Garrison et al., 1977; Griffith et al., 2004) complicated description of range plant communities that are transitional among these conterminuous units. Differences in interpretation of natural vegetation among these units was discussed in introduction to Edwards Plateau in this publication.

The ecotone or tansition between ceniza-dominated savanna of Tamaulipan thornscrub and Chihuhuan Desert was dealt with in the portion below, including a disturbance climax of the same.

 

240. Mixture of two range types- Transition of ceniza-dominated savanna of Rio Grande Plains Tamaulipan thornscrub and eastern margin of mesquite-dominated form of Chihuhuan Desert, and with some floristic features of semiarid Edwards Plateau savanna. A unique range plant community with remarkable biodiversity of woody species including (in addition to dominant ceniza and honey mesquite): Texas persimmon, Texas (= Lindheirer or Englemann) pricklypear, tasajillo, guajillo (much less abundant that on range where it was co-dominant), lotebush, Berlandier wolfberry or cilindrillo (Lycium berlandieri), Spanish dagger or Torrey yucca, catclaw mimosa, knifeleaf condalia, agarito, coyotillo (Karwinskia humboldtiana), desert-yaupon (Schaefferia cuneifolia), dog or devil cholla (Opuntia schattii), guayacan (Porlieria angustifolia), huisache (Acacia farnesiana), leatherstem which is also known as dragon's blood or sangre de drago (Jatropha dioica var. dioica), hog-plum (Colubrina texensis), and broom snakeweed (Gutierrezia sarothrae).

Herbaceous species present in autumn were limited to grasses of which Wright's threeawn, red grama, slim tridens, and sideoats grama (in that general relative order based on estimated foliar cover) were the major species. No forbs were present at any meaningful cover of density. Major composite was the shrub, broom snakeweed.

Rather dense herbaceous layer comprised of slim tridens and Wright's threeawn was featured in midground of second slide. Foreground of this photograph included catclaw mimosa, coyotillo, and leatherstem.

This range vegetation was clearly in some state of retrogression, but degree of range depletion was not determined and, frankly, this author was not convinced that there is enough knowledge available to evaluate range plant communities in this range type and for these range sites (elaborate, authoriative-sounding site descriptions notwithstanding). On these arid range types there does not appear to be enough basic scientific information to write actual succession-based descriptions of climax and seral vegetation. State-and-transition models are less dogmatic and give the appearance of being more flexible than traditional Clementsian models, but the fact remains that there have been next-to-none long-term ecological observations--not to mention actual experiments (eg. grazing trials)-- on which to ground range site descriptions.Furthermore there are few relict areas that can serve as references for baseline range plant communities.

Even at greater and more general scale of rangeland cover types this transitional Rio Grande Plains-Chihuhuan Desert scrubland has not been described to any meaningful degree that would be adequate to describe potential natural vegetation. For instance, Kuchler (1964; in map adapted and included in Garrison et. al, 1977) mapped and described potential natural vegetation of this area as Ceniza Shrub (Leucophyllum-Larrea-Prosopis),but after extensive search of several ceniza-dominated ranges in this area this author was unable to find even a single plant of Larrea tridentata! Most of the other woody species and many of the herbaceous ones listed for this unit of vegetation (Kuchler, 1964, p. 45) were handily located, including dominant grasses. It appeared that even the relatively small and restricted Ceniza Shrub unit had various minor forms (subtypes) that were partial exceptions to the general description of the physiogonomic unit and, therefore, that were not adequately descriped even at mapping scale greater than that of range sites.

Val Verde County; Texas. October, autumnal aspect and peak standing crop for most warm season species (eg. perennial eragrostoid grasses). FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-38 (Ceniza Shrub). No SRM for this range type. Mixed Deciduous Series 134.31 of Tamaulipan Thornscrub (Brown et al., 1998, p. 42; also, Figure 53, p. 103 of Brown, 1994), but in transition to Chihuhuan Desertscrub. Range site: Flagstone. Rio Grande Floodplain and Terraces Ecoregion 31d (Griffith et al., 2004).

 

241. Rich floristic diversity in a dry land- Multi-storied range vegetation on a three-way (more like two and a half) ecotone between western part of ceniza-dominated savanna of Tamaulipan thornscrub of Rio Grande Plains and extreme eastern edge of Chihuhuan Desertscrub with a "sprinkling" of floristic features of the semiarid Edwards Plateau. Tremendous biodiversity of plant species in this range vegetation resulted from "overlap" of desertscrub with semiarid thornscrub plus "parts" of an adjoining second savanna that "jist sorta wandered in".

Biodiversity is an old but expanded concept with a new name. The Society of American Foresters (Helms, 1998) defined biodiversity as: " "The variety and abundance of life forms, processes, functions, and structures of plants, animals, and other living organisms, including the relative complexity of species, communities, gene pools, and ecosystems at spatial scales that range from local through regional to global-- synomym biological diversity...". With emphasis herein on native (or naturalized) vegetation it was the variety and relative abundance (composition) of life forms and plant species component of biodiversity that was of primary interest. Major concentration was placed on species richness: "A measure of the number of species present in a community, ecosystem, landscape, region, etc." (Helms, 1998).

In plant communities shown on the ranges representing the ecotone ceniza-dominated savanna of Rio Grande Plains Tamaulipan thornscrub and Chihuhuan Desert with minor features of semiarid Edwards Plateau pshown here vegetation

Woody species present in the range plant community viewed here included the ceniza, honey mesquite, Texas persimmon, huisache, Texas (= Lindheirer or Englemann) pricklypear, dog or devil's cholla, tasajillo, guajillo, lotebush, Spanish dagger or Torrey yucca, desert-yaupon, Berlandier wolfberry, catclaw mimosa, knifeleaf condalia, coyotillo, guayacan, agarito, leatherstem or sangre de drago, and broom snakeweed. Grasses included Wright's threeawn, slim tridens, red grama, and sideoats grama. Forbs were effectively absent from this autumn array of species.

This was an amazing biodiversity for arid savanna. The transitional nature of this range vegetation (in this instance an ecotone formed by "confluence" of desert shrubland and two semiarid savannahs) accounted for this biodiversity.

Most of the shrub species in above were visible. For instance, the rounded shrub with gray-blue tone in right foreground (lower right corner of photograph) was Berlandier wolfberry (missing most leaves, for whatever reason). Texas pricklypear easily distinguished in left foreground. Center cluster of shrubs included Spanish dagger, Texas persimmon, agarito, knifeleaf condalia, and lotebush. Shorter shrubs with bright green leaves were coyotillo.

Wright's threeawn was readily seen by its panicles.

Val Verde County; Texas. October, autumnal aspect and peak standing crop for most warm season species (eg. perennial eragrostoid grasses). FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-38 (Ceniza Shrub). No SRM for this range type. Mixed Deciduous Series 134.31 of Tamaulipan Thornscrub (Brown et al., 1998, p. 42; also, Figure 53, p. 103 of Brown, 1994), but in transition to Chihuhuan Desertscrub. Range site: Flagstone. Rio Grande Floodplain and Terraces Ecoregion 31d (Griffith et al., 2004).

 

242. Witch's brew of range vegetation- Example of the species-rich, multi-storied savanna that developed at vegetational confluence of Tamaulipan thornscrub of Rio Grande Plains and Chihuhuan Desert scrub of Trans-Pecos Basin and Range (with minor tributary of semiarid Edwards Plateau). Shrub species tallied on this brushland (and it was almost assuredly was brush by having woody plant cover in excess of climax range vegetation) included the apparent local dominant, Texas persimmon, lotebush, mesquite, lotebush, desert-yaupon, catclaw mimosa, Berlandier wolfberry or cilindrillo, huisache, Texas (= Lindheimer's or Engelmann's) pricklypear, dog cholla, tasajillo, knifeleaf condalia, Spanish dagger or Torrey yucca, common broomweed, leatherstem or sangre de drago, and hog-plum.

Grasses included the overall dominant herbaceous species, Wright's threeawn, along with slim tridens, sideoats grama, red grama, cane bluestem (Andropogon barbinodis= Bothriochloa barbinodis var. barbinodis), and naturalized Lehmann's lovergrass (Eragrostis Lehmanniani). At time of this photograph (early autumn) there were no forbs of consequence.

Val Verde County; Texas. October, autumnal aspect and peak standing crop for most warm season species (eg. perennial eragrostoid grasses). FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-38 (Ceniza Shrub). No SRM for this range type. Mixed Deciduous Series 134.31 of Tamaulipan Thornscrub (Brown et al., 1998, p. 42; also, Figure 53, p. 103 of Brown, 1994), but in transition to Chihuhuan Desertscrub. Range site: Flagstone. Rio Grande Floodplain and Terraces Ecoregion 31d (Griffith et al., 2004).

 

243. Deep in the heart of an ectone- Interior of an mixed shrub-mixed grass savanna that is an ecotone or transition zone of Rio Grande Plains Tamaulipan thornscrub and Chihuhuan Desertscrub with a "dash" of semiarid Edwards Plateau mixed in. Woody plants included Texas persimmon (largest shrub, white bark on radically twisted limbs), lotebush, Berlandier wolfberry or cilindrillo, knifeleaf condalia, mesquite, catclas mimosa, Texas (= Lindheimer's or Engelmann's) pricklypear, tasajillo, dog cholla, huisache, desert-yaupon, coyotillo, leatherstem or dragon's blood, Spanish dagger or Torrey yucca, common broomweed, and guayacan (undoubtedly among others).

Dominant grass overall was Wright's threeawn, but with slim tridens, sideoats grama, red grama, cane bluestem and naturalized Lehmann's lovergrass locally common to dominant species. Wright's threeawn, sideoats grama, cane bluestem, and Lehmann's lovegrass were all visible in both of these photographs. Presence of cane bluestem and sideoats grama under protection--including some protection from grazing--of shrubs was evidence strongly suggesting that past overgrazing had reduced cover of grasses that would have dominant understorey herbaceous species on this transitional savannah.

Second photograph was a close-in view of lower woody layer and herbaceous layer beneath crown of the larger Texas persimmon at left margin of first photograph. The shrub with large thorns and oblong leaves in lower left foreground was lotebush.

Val Verde County; Texas. October, autumnal aspect and peak standing crop for most warm season species (eg. perennial eragrostoid grasses). FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-38 (Ceniza Shrub). No SRM for this range type. Mixed Deciduous Series 134.31 of Tamaulipan Thornscrub (Brown et al., 1998, p. 42; also, Figure 53, p. 103 of Brown, 1994), but in transition to Chihuhuan Desertscrub. Range site: Flagstone. Rio Grande Floodplain and Terraces Ecoregion 31d (Griffith et al., 2004).

 

244. Sticky understorey- Even the herbaceous and lowest growing shrubs carry weapons on this "hard-fought" range as evidenced by the coarse-stemmed Wright's threeawn with its panicle of three-awned spikelets and the universally detested dog cholla on the stony, shallow soil of a Flagstone range site in western Rio Grande Plains.

Val Verde County; Texas. October, autumnal aspect and peak standing crop for most warm season species (eg. perennial eragrostoid grasses). FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-38 (Ceniza Shrub). No SRM for this range type. Mixed Deciduous Series 134.31 of Tamaulipan Thornscrub (Brown et al., 1998, p. 42; also, Figure 53, p. 103 of Brown, 1994), but in transition to Chihuhuan Desertscrub. Range site: Flagstone. Rio Grande Floodplain and Terraces Ecoregion 31d (Griffith et al., 2004).

 

245. Dog or devil's cholla (Oputia schottii)- Two views of dog or devil's cholla showing 1) whole plant above ground (first photograph) and 2) individual clonal units or ramets made up of individual succulent or fleshy shoots known as cladodes or cladophylls. This species is more apt to inflict mechanical injury to pedestrians (man or beast) than most other cactuses. The individual shoots (shoot units or cladophylls) of dog cholla readily separate from the rest of the plant (ie. break off) and handily attach to feet and legs of any unwary passerbys who carelessly come into contact with this particularily obnoxious succulent. When attached cladophylls are quickly and carefully dislodged by the transporting agent these vegetative diaspores (= propagules or disseminules) usually take root and propagate another plant of the same genotype (ie. a clone) It does not take long before dogs, livestock, and humans learn to watch every step when traveling on ranges sporting devil's cholla.

This is mean stuff and a pesky, often painful, example of zoochory, dispersal of plant progagules by animals.

Val Verde County; Texas. Understorey of the same range as shown in seven immediately preceding photographs. October.

 

246. So colorful for being so mean- Dog or devil's cholla in bloom. This specimen was in the herbaceous layer of a Chihuhuan Desert range where its spines protected two plants of black grama (Bouteloua eriopoda).

Big Bend National Park, Brewster County, Texas. May. Full-bloom stage of cholla; dormancy in black grama.

 

247. Flagstone formation- Flagstone is the parent material of soils over much of the ceniza-dominated mixed grass savanna of the western Rio Grande Plains. There is both a Flagstone Hill and Flagstone range site, the latter of which included herein.

Val Verde County, Texas. October, late afternoon-evening (about sundown) light.

 

248. Ceniza Shrub disclimax- Ceniza-dominated shrub savanna degraded to state of disturbance climax with amazing biodiversity of woody species. Except for rare local populations of Wright's threeawn and, more rare still, red grama there were no herbaceous species on this woefully depleted range. This example was presented as typical of semiarid Rio Grande Plains shrub-mixed grass savanna range at advanced stages of retrogression (successional states [seral stages] substantially below climax).

Interestingly, biodiversity of woody plants was remarkable (much more so than on less degraded range). The following species of shrubs and small trees grew on this disclimax range vegetation: ceniza, the overall dominant species, Texas persimmon, guajillo, Texas palo verde (Cercedium texanum= Parkinsonia texana), lotebush, Berlandier wolfberry, knifeleaf condalia, mesquite, catclaw mimosa, Texas (= Lindheimer's or Engelmann's) pricklypear, tasajillo, dog cholla, huisache, desert-yaupon, whitebrush, blue sage (Salvia ballotaeflora), tatalencho (Gymnosperma glutinosum), coyotillo, leatherstem or dragon's blood, Spanish dagger or Torrey yucca, common broomweed, guayacan, willow baccharis (Baccharis salicina= B. neglecta= B. angustifolia), and there were undoubtedly other species common in this locale that were overlooked in what was a brief reconnaissance (eg. probably huisache).

There was evidence of relatively severe sheet erosion although soil was currently stable with all the brush (woody species present at excessive cover and/or density compared to climax vegetation) to break flows of wind and water. This range produced very little browse or herbage that could be used as feed by animals larger than rodents and lagomorphs. Range vegetation at this severe stage of degradation is of little value other than to prevent further erosion of soil and put oxygen in the air. The land would not be worth taking for free. It would not pay even minimal property taxes unless the sucker who took it could find a bigger sucker who was willing to pay for a deer lease hoping to find a disoriented deer who wandered onto the place by mistake.Of course, there is always hope for a housing development which would be a good use for otherwise good-for-nothing-land.

Val Verde County; Texas. October, autumnal aspect with blooming in several shrub species (shown below). FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-38 (Ceniza Shrub). No SRM for this range type. Mixed Deciduous Series 134.31 of Tamaulipan Thornscrub (Brown et al., 1998, p. 42; also, Figure 53, p. 103 of Brown, 1994), but in transition to Chihuhuan Desertscrub. Range site: Flagstone. Rio Grande Floodplain and Terraces Ecoregion 31d (Griffith et al., 2004).

 

249. Ceniza shrub transition savanna- Ceniza-dominated savanna that was similar to the ceniza-guajillo-mixed grass savanna that was detailed previously except that in the vegetation of this range there was much greater biodiversity in woody plants and the herbaceous component was less xeric overall. Also there was a lot more variation in kind of range sites over much smaller spatial scale (and much more varied than shown at the large mapping scale of the published soil survey).

In the first of these two photographs the shrub in right foreground (right front corner) was Berlandier wolfberry or cilindrillo. Adjacent and immediately to left of the condalia was the dioecious shrub, grassland croton or New Mexico croton (Croton dioicus= C. neomexicanus). Cane bluestem was the green grass in center foreground (immediately to right of Berlandier wolfberry). On this grazed range cane bluestem growing in the Berlandier wolfberry had not been grazed and it's panicle-bearing shoots were conspicuous against backdrop of the protecting shrub.

Range vegetation presented in the second photograph included a large saccahuista (Nolina texana) along margin of right foreground. Ceniza and Wright's threeawn were the two most common plants which were dominants of the shrub and herbaceous components. Other shrubs present from view of second slide included Texas persimmon, honey mesquite, and huisache which were visible as the larger, green crowns in the background.

Just beyond perimeters in both photographs this Gravelly Ridge range site sloped over into several clay bottomland range sites that supported stands or colonies of tobosagrass (Hilaria mutica) that were surrounded along their perimeters by mesquite and huisache of tree size and shape. An example of one of these small tobosa flats, which is one of the major range types of semidesert grassland, was presented in the next slide.

Val Verde County; Texas. October, autumnal aspect. Peak standing crop for most warm season species (eg. perennial eragrostoid and panicoid grasses); fruit ripe stage in knifeleaf condalia. FRES No. 32 (Texas Savanna Shrubland Ecosystem). K-38 (Ceniza Shrub). No SRM for this range type. Mixed Deciduous Series 134.31 of Tamaulipan Thornscrub (Brown et al., 1998, p. 42; also, Figure 53, p. 103 of Brown, 1994), but in transition to Chihuhuan Desertscrub. Range site: Gravelly Ridge. Rio Grande Floodplain and Terraces Ecoregion 31d (Griffith et al., 2004).

 

250. Tobosagrass flat, tobosagrass swale, or tobosa basin- Small clay flat (= bottomland) populated exclusively by tobosagrass that was situated among several different range sites in extreme northwestern edge of the Rio Grande Plains. Range vegetation in this area was mapped by Kuchler (1964; in map in Garrison et al., 1977) as part of the Trans-Pecos Shrub Savanna (ie. the Chihuhuan Desert) at very edge of (or so close as to be part of) the Ceniza Shrub. The plant community could be interpreted as a stand (Clementsian consociation) of tobosagrass or, alternatively, as an interior population of tobosa comprising the herbaceous layer with honey mesquite, huisache, and a few Texas persimmon that ringed the tobosa flat as constituting the woody layer(s) of a semidesert savanna. The author left this choice to his readers and fellow viewers

This sample of Rio Grande Plains range was included in both the Rio Grande Plains and semidesert grassland chapters of this publication for continuity and to show spatial patterns of range vegetation. From perspective of Landscape Ecology the tobosa swale was a patch of semidesert grassland in a matrix of vegetation that was a transition between ceniza-dominated mixed grass savanna of the Rio Grande Plains Tamaulipan thornscrub and the Chihuhuan Desertscrub of the Trans-Pecos Basin and Range Region.

Val Verde County, Texas. October; full-bloom to hard-dough phenological stage of tobosagrass.FRES No. 40 (Desert Grasslands Ecosystem). K-48 (Gramagrass-Tobosagrass Prairie). SRM 505 (Grama-Tobosa Shrub) variant. Chihuhuan Deserts- Chihuhuan Desert Grasslands Ecoregion, 24b (Griffith et al., 2004).

Technical note: the next three sets of slides are paired comparisons of slide-scanning by an Epson Perfection V700 (left) and Hewlett Packard Scanjet 7400c (right) equipment. Neither brand of scanner reproduced colors accurately. Color reproduction was somewhat closer to that of Kodachrome (the most accurate color as perceived by human eyes of any realistically available film), but Epson Perfection V700 created a "sparkle-like" effect anytime photographs were copied ("copied-at" is a more precise description). HP Scanjet 7400c does not create "sparkles" (a pixelized effect), but it adds a bluish-green cast to yellows, reds, and oranges. Neither Epson Perfection V700 (left) nor Hewlett Packard Scanjet 7400c was satisfactory for scanning Kodavhrome, but they are about the "only games in town". "Beats nothing" is the best assesssment this author/photographer could grant.

 

251. "And the green grass grew all around, all around; and the green grass grew all around" (American folk song)- Characteristic sward of tobosagrass on a swale showing the semi-cespitose habit of this rhizomatous perennial eragrostoid grass. Individual plants of tobosagrass typically grow in close proximity to each other so as to form an open sod or turf, especially on more mesic habitats (eg. swales and larger bottomland sites), so that stands of tobosa have a bunchgrass-like appearance. This is in contrast to the "kissin' cousin", curly mesquite (H. belangeri), which is stoloniferous and forms a more nearly closed turf or complete sod.

This small stand or consociation had been lightly grazed by cattle such that individual plants and the open sod or turf were more obvious. These photographs were "picture perfect" examples of proper degree of use, which in the semiaridity or aridity of this range environment was on the light side of moderate. This range professor reminded his student readers that moderate grazing (= defoliation) is not automatically synonymous with proper grazing any more than is light or heavy degree of grazing defoliation proper or improper. Proper use factors are not only species-specific, but even site-specific for species-specific standards or guidelines. A key diagnostic guide to proper degree of use (the first and usually the most important of the Four Cardinal Principles of Range Management) is presence of individual shoots that were ungrazed and, usually, matured to flowering and grain production. Reproduction of perennial grasses like tobosa is usually asexual (by tillers and rhizomes in H. mutica) so seed production is not necessary nor usually important for regeneration of this valuable climax species (decreaser on swale sites). Rather, presence of sexually reproductive shoots is a very good sign to graziers that the tobosagrass range was properly managed as to degree of use. Plus, this degree of grazing defoliation with subsequent seed-set best provided for the option of establishment of seedlings that can fill in interspaces among existing tufts of older plants. Seedling establishment permitted presence of new genotypes (the opportunity for on-going genetic adaptation) of this remarkable and valuable semidesert species.

Val Verde County, Texas. October, phenological stage of tobosa varied from anthesis through grain-ripe to grain-shatter. FRES No. 40 (Desert Grasslands Ecosystem). K-48 (Gramagrass-Tobosagrass Prairie). Not specifically described by SRM cover type; variant of SRM 505 (Grama-Tobosa Shrub) variant. Tobosa Grass-Scrub Series of Brown et al. (1998). Level III ecoregion of Texas was transition between Chihuhuan Deserts and Playas Ecoregion 24a of Chihuhuan Deserts and Semiarid Edwards Bajada Ecoregion 31b of South Texas Plains (Griffith et al., 2004).

 

252. Beautiful, and outstanding example to boot- Individual plant of tobosagrass that was grazed during current growing season to proper degree of use as determined by general qualitative appearance, but not on specific quantitative guidelines (assuming that such even exist). Key features of proper grazing included: 1) adequate photosynthetic tissue (both leaves and culms) remaining following grazing, 2) some shoots that were permitted to mature to sexually reproductive (= flowering) stage, 3) irregular, domed shape of grazed plant rather than a heavily cropped one having a flat, highly hedged appearance, and 4) overall degree of utilization (composite of defoliation for whole plant) that was somewhat on light (conservative) side of the total or maximum utilization that would enable the plant to survive. In regards feature #4, management of this tobosagrass range was such that some "surplus" feed was left for an emergency, risk, etc. that might befall plant, animal, or ranching firm. The conservative or cautious grazing use would come closer to permitting higher levels of herbage production under environment stress, especially drought. The rangeman responsible for husbandry of this range had hedged his bets and left "a little extra" grass just in case "things get tight". Such wise stewartship is good ranch as well as good range management.

The rest of the explanation for the bountiful flowering of tobosa on this range as shown in these photographs was an extremely wet late summer and early autumn. Numerous, well-spaced showers and cool temperatures resulted in near ideal soil moisture conditions. Students take note: even abundant rainfall and other features of a fabulous plant-growing environment would not have permitted the profuse flowering and lush foliage of this tobosagrass had it been grubbed to the ground by overuse. Vice versa, even if growing conditions had been adverse for tobosa on this swale there would still have been some sexual reproduction in the stand given the wise use management--especially proper degree of utilization--it received.

Val Verde County, Texas. October, phenology ranged from anthesis to grain-shatter stages.

 

253. Nothing much purtier to a desert grassman- A large speciment of tobosagrass at peak bloom on a swale in Rio Grande Plains savanna-Chihuhuan Desert ecotone. This plant had been properly grazed (defoliation of outer edge of grass still evident in foreground) and, with blessings of late-growing season rain showers, a high number of shoots had developed to sexual maturity.

Val Verde County, Texas. October. On this one plant phenological stage varied from anthesis through grain-ripe to grain-shatter (with more soil water from each new shower ever more shoots advanced to flowering stage).

 

254. Anthesis in tobosagrass- The inflorescence type in this eragrostoid grass is interperted as a spike because spikelets are sessile on the rachis (Hitchcock and Chase, 1950, p.485). Gould (1975, p. 366) described the Hilaria inflorescence as a bilateral spike. Of these three spikelets only the center one is fertile (usually one-flowered) with two outer (lateral ) spikelets being staminate. The bifid anthers were visible in this "sexy" portrait of one of the dominant decreaser grasses on more mesic range sites in the semidesert grassland, Chihuhuan Desert, semiarid Edwards Plateau, and Rio Grande Tamulipan thornscrub savanna.Val Verde County, Texas. October.

 

255. Grain ripe and shattering in tobosagrass- Spikelets on spikes of Hilaria spceies are in units of three with the entire three -spikelet structure or unit being designated a fascicle which falls entire (together) from the spike (as if the fascicle was one spikelet). Numerous fascicles were present and readily seen on both of the spikes shown in these slides. Val Verde County, Texas. On a swale situated among converging ridges. October.

 

256. Tatalencho or nakedseed (Gymnosperma glutinosum= Selloa glutinosa= Xanthocephalum glutinosum)- A suffriticose or suffrutescent composite that exudes a glutinous substance from its leaves and flowers that is often prominent in the lower woody layer(s) of shrub communities on ranges from the Rio Grande Plains to parts of the Edwards Plateau through to the Chichuhan Desert. Short discussions of tatalencho were presented in Vines (1960, p. 995-996), Powell (1988, ps. 437, 438), and Everitt and Drawe (1993, p. 57).

Val Verde County, Texas. October, full-bloom stage of phenology. Growing on Flagstone range site.

 

257. Inflorescence of tatalencho or nakedseed- Two views of a semi-woody range composite named for its feature of secreting an exudate from leaves and head inflorescence. Val Verde County, Texas. October, full-bloom stage.

 

258. Texas paloverde (Cercidium texanum= Parkinsonia texana)- One of numerous leguminous shrubs frequently common throughout much of the Rio Grande Plains, southern Edwards Plateau and parts of Chihuhuan Desert. Characteristic of many woody members of the Tamaulipan thornscrub range type, this shrub is armed with sharp porturbances from stems that are described variously as spines, thorns, or short and sharp branches. This species usually flowers sparingly rather than blooming profusely in the manner of most other Tamaulipan woody legumes.

Val Verde County, Texas. October, full-bloom stage (such as it was).

 

259. Shoot and inflorescence of Texas paloverde- Texas paloverde is in the Caesalpinioideae, bird-of-paradise or redbud subfamily of the Leguminosae. Flowers are not papilionioidaceous, but the fruit is a legume which is the key feature that unifies members of this large and diverse family of dicotyledons. Vines (1960, p.534-535), Powell (1988, p. 202-203), and Everitt and Drawe (1993, p. 113) provided brief treatments of this range shrub.

Verde County, Texas. October, full-bloom stage.

 

260. Texas paloverde in fruit- Portion of crown (trunk and limbs) with abundant legumes of a small specimen of Texas paloverde. Val Verde County, Texas. October, fruit-ripe phenological stage. Flagstone range site.

 

261. Coyotillo (Karwinskia humboldtiana)- The Rhamnaceae or buckthorn family furnishes several member species across the Rio Grande Plains into the Chihuhuan Desert. One such species--and a poisonous one-- is coyotillo, an evergreen the biological range of which extends west through the Sonoran Desert to California. On the ecotonal Tamaulipan thornscrub-Chihuhuan Desert range featured above plants of coyotillo were low-growing shrubs that were often associated with leatherstem.

Val Verde County, Texas. October. On a Flagstone range site.

 

262. Shoot of coyotillo-Details of leaves and branches of coyotillo growing on a Flagstone range site that was a transition between Rio Grande Plaind Tamaulipan thornscrub and Chihuhuan Desertscrub. Summary treatment of this shrub was presented in Vines (1960, p. 700), Scifres (1980, p. 58-59), Powell (1988, p. 277, 279), and Everitt and Drawe (1993, p. 143).

Coyotillo is one of the notariously toxic range plants that frequently poisons--often fatally--all kinds of livestock. It is also poisonous to humans when they eat the seeds, one of the toxic parts of the plant, are eaten along with the tasty fruit. Leaf tissue is also toxic. Coyotillo consistently received extensive coverage in the poisonous plant literature (Kingsbury, 1964, ps. 220-221; Sperry et al., 1964, ps. 29-30; Burrows and Tyrl, 2001, ps. 1034-1038, Hart et al., 2003, ps. 116-117).

Val Verde County, Texas. October. Growing on a Flagstone range site.

 

263. Knifeleaf condalia, squawbush, or costilla (Condalia spathulata)- A usually low-growing member of the Rhamnaceae found on rocky, especially limestone, habitats. Vines (1960, p. 696), Scifres (1980, p. 76), and Everitt and Drawe (1993, p. 143) provided brief treatments of this range shrub..

Val Verde County, Texas. October. Growing on a Flagstone range site.

 

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264. Hog-plum or Texas colubrina (Colubrina texensis)- This is one of many interesting species growing on ranges across Rio Grande Plains into the Chihuhuan Desertscrub. Short coverages of this member of the Rhamnaceae were given by Vines (1960, p. 693-694), Scifres (1980, p. 107-108), Powell (1988, ps. 268-269), and Everitt and Drawe (1993, p. 141).

Val Verde County, Texas. October. Growing on a Gravelly Ridge range site.

 

265. Shoots and small inflorescence of hog-plum- This shrub was not one of the more widespread range species on the ecotonal shrub-mixed grass savanna where Rio Grande Plains, Chihuhuan Desert and "touch" of semiarid Edwards Plateau came together, but it was one of the more distinctive ones.

Val Verde County, Texas. October. Gravelly Ridge range site.

 

266. Guayacan (Porlieria angustifolia= Guaiacum angustifolium)- Guayacan is one of the most distinctive shrubs of the Tamaulipan thornscrub and eastern portions of the Chihuhuan Desert. Like creosotebush, a far more common shrub (the dominant shrub of Chihuhuan, Sonoran, and Mojave Deserts), guayacan is a member of the Zygophyllacceae, caltrop family. Brief but interesting treatment of guayacan was given by Vines (1960, 575), Scifres (1980, ps. 69, 70), Powell (1988, p. 224-225), and Everitt and Drawe (1993, p. 191).

Val Verde County, Texas. October. Growing on a degraded Flagstone range site.

 

267. Shoots of guayacan- Details of shoot morphology, bark, and fruit of guayacan. Val Verde County, Texas. October, fruit-ripening to fruit-ripe stage. Photographed on a depleted Flagstone range site.

 

268. Blue sage, mejorana, or ballo (Salvia ballotaeflora)- The Labiatae, mint family, was represented on the deteriorated on the ceniza-dominated shrub-mixed grass savanna, especially the woody disclimax (brush-dominated seral stage) form thereof, by blue sage. This specimen consisted of a large proportion of dead material in the crown. Herbaceous members of the mint family are generally more common than shrubs on most range types and range sites. On the disturbance climax state of the ecotonal Rio Grande Plains savanna (= Tamaulipan thornscrub)-Chihuhuan Desert blue sage was commonly associated with whitebrush, Texas persimmon, guajillo, and Texas paloverde.

S. ballotaeflora is not the flavoring sage of commerce (S. offiicinalis), but the former serves the purpose more economically and about as well (like a lot of things, use enough and can't tell the difference). Vines (1960, p. 911), Powell (1988, p. 371), and Everitt and Drawe (1993, p. 89) provided descriptions and either a line drawing or photograph of blue sage.

Val Verde County, Texas. October, full-bloom phenological stage. On severely degraded Flagstone range site.

 

269. Berlandier wolfberry or cilindrillo (Lycium berlandieri)- The nightshade family, Solanaceae, is another family of range plants in which herbaceous species are generally more common and better known than are woody species. Lycium is a genus that is an exception to this general situation. There are seven Lycium species in Texas, all shrubs and all of which furnish some browse and bitter berries that are readily consumed by a range of animals (Correll and Johnston, 1979, ps. 1400-=1402). Berlandier wolfberry is the most common Lycium species over much of the western Rio Grande Plains, semiarid Edwards Plateau, and eastern contacts of Trans-Pecos Basin and Range Region.

L. berlandieri was covered briefly by Vines (1960, p. 911), Scifres (1980, ps. 44-46), Powell (1988, ps. 380-381), and Everitt and Drawe (1993, p. 165).

Val Verde County, Texas. October, fruit-ripe phenological stage. On severely depleted Flagstone range site.

 

270. Desert-yaupon, capula panalero, or capul (Schaefferia cuneifolia)- The bitter-sweet staff-tree family, Celastraceae, is a minor family as rangeland and forest plants go. There ae, however, some notable taaxa in the Rio Grande Plains thornscrub savanna across to the Chihuhuan Desertscrub including three important genera. Capul is the only species of it genus in that vast region.

Desert-yaupon was dealt with by Vines (1960, p. 666), Powell (1988, ps. 260-261), Scifres (1980, ps. 61-63), and Everitt and Drawe (1993, p. 43).

Val Verde County, Texas. October. Associated with guayacan, Texas paloverde, lotebush, and Berlandier wolfberry. On Flagstone range site at stage of extreme retrogression.

Palm Forest

One of the most unique and restricted types of native vegetation in southeastern North America and in the important range state of Texas is the jungle-like forest dominated by the native palm that grows to tree size and habit and is known variously as sabal palm, Texas or Rio Grande palmetto, palma de micharos (Sebal texana= S. mexicana). This native woodland is a flatwoods or floodplain forest (more commonly than it is a riparian or gallery forest which is a narrower zone of wetland vegetation) that develops over the greater or general floodplain or the Rio Grande (= Rio Bravo) in the states of Texas and Tamaulipas. The other major woody plant species that defines this woodland community is Texas ebony or ebano (Pithcellobium flexicaule= P. ebano). Thus this natural plant community has been described as the sabal palm-Texas ebony jungle forest. A common associate (when interpreting sabal palm and ebony as co-dominants) is anacua or knock-away (Ehretia anacua), a small tree (and often with multiple trunks like a large shrub) in the Boraginaceae (borage family). The successional relation of Texas ebony and anaqua was described later in this introduction.)

Other frequent large shrubs or small trees in this forest community include tpeguaje (Leucaena palverulenta) and tenaza (Pithecellobium pallens). The most common-- and, in fact, often dominant --understorey shrub is David milkberry or cahinca (Chinococca alba). Milkberry or cahinca frequently forms the entire understorey in groves of mature palms (shown below). Other common understorey shrubs include chile piquin, chillipiquin, or bird pepper (Capsicum annuum var. minus) and Drummond's turk's cap or Drummond wax-mallow or Texas mallow (Malvaviscus drummondii= M. arboreus). Bloodberry, rouge plant, pigeonberry or coralito (Rivina humilis= R. laevis= R. portulaccoides) is one of the most common forbs in the understorey of this floodplain forest vegetation.

There is typically little or no understorey beneath larger adult palms as the older mature fronds (leaves) are shed complete with their immense petioles that can be as much as four or more inches wide at the abscission zone. These shed fronds form a mulch of multi-layers in various stages of decomposition so that the forest floor is devoid (or nearly so) of understorey plants. The hard woody petioles sometimes extend as much as two feet above the blade parts of fronds making travel through fallen palm leaves very difficult. These shed fronds are ready fuel and many of the trunks of older palms are blackened from past fires. Sabal palm appears to regenerate beneath adult palms, sometimes even in the dim-lite, frond-mulched interior of the palm forest (see photographs below).

There has been comparatively little material written describing this extremely restricted vegetation. The most readily available discriptions may be Texas Natural History, the original Biological Survey of Texas by Vernon Bailey with introduction and updates by Schmidly (2002, ps. 65, 75, 145, 319, 320, 326, 390, and 426) and the mostly faunal description in Saving the Best of Texas (Bartlett, 1995, ps. 132, 134-136). Vines (1962, p. 46) listed trees and shrubs in the sabal palm forest based on his previous visit to the Frank Rabb Ranch in Cameron County, Texas (this became the Sabal Palm Audubon Center and Sanctuary). Woody species included on Vines' list (and using his names) were Texas ebony or ebony apes-earring (Pithecellobium flexicaule= P. ebano), apes-earring (P. pallens), granjeno (Celtis pallida), Rio Grande or Mexican or Berlandier ash (Fraxinus berlandieri), Berlandier mimosa (Mimosa berlandieri), tepeguaje or great lead-tree or tpeguaje (Leucaena pulverulenta), white popinac lead-tree (L. glauca), Barbados-cherry (Malpighia glabra), lime pricky-ash (Zanthoxylum fagara), lotebush (Condalia obtusifolia= Ziziphus obtusifolia), saffron-plum bumelia (Bumelia angustifolia), Texas persimmon (Diospyros texana), and autumn salvia or autumn sage (Salvia greggii). Strangely, Vines (1962, p. 46) did not list anacua, one of the major trees, nor drummond's turk's cap and chile piquin, which are some of the major shrubs, for the sabal palm forest.

The sabal palm forest was apparently not a large community even in pre-European North America. Officials associated with various organizations like the Sabal Palm Audubon Center and Sancttuary and World Wildlife Fund have reported in worldwide web publications (eg. www.tx.audubon.org/centers/ sabal) that in North America sabal palm-dominated forest was limited primarily to the floodplains of such rivers as the Rio Grande and San Bernard and, except for isolated relict vegetation, extending northward primarily through the Lower Rio Grande Valley and up the Rio Grande for about 80 miles (Bartlet, 1995. p. 135). According to reports from the LaSalle Expedition sabal palm grew much farther west including along the Guadalupe River. There is no evidence, however, that the sabal palm-Texas ebony (ebano) jungle forest developed north or west of the Lower Rio Grande Valley.

Bartlett (1995, p. 135) reported that the pre-white man sabal palm forest totaled about 40,000 acres in the Lower Rio Grande Valley. It was not clear if this included acreage in both the United States and Mexico. Almost all of the sabal palm forest on the USA side of the Rio Grande (= Rio Bravo) was cleared for irrigated agriculture and, later, for urban sprawl, beginning in the early Twentieth Century. Prior to clearing, or simultaneously with clearing, sabal palms were felled so that logs from the limb-less, easily bucked boles could be used for warf-pilings. According to Landon Lockett (www.audubon.org/ local/sanctuary/sabal/nativepalms.html) the wood of sabal palm is resistant to consumption by shipworms. Demand for shipworm-resistant wood in ports along the Gulf Coast was great enough that sabal palm populations were devastated by the "cut-and-run" logging practices of the time.

Interesting sidebar note: There are several species of bivalve marine mollusks that are known as shipworms because they are capable of destroying submerged wood by eating burrows or tunnels throughout the wood, a dire condition that can ultimately destroy submerged (or partly submerged) wood that is then said to be "wormshot". Burrowing begins with the larval stagae. The most common of these marine bivalves is the tropical species, Teredo navalis, an elongated two-shelled clam that reaches lengths up to two feet. This species is especially active in the warm waters of the Gulf of Mexico.

As of this writing the only remaining sabal palm-ebano forest remaining in anything resembling natural vegetation is that preserved on the Sabal Palm Audubon Center and Sanctuary in Cameron County, Texas. Of the 527 acres in this sanctuary (www.audubon.org/local/sanctuary/sabal) only 32 acres is virgin palm-Texas ebony jungle forest (Bartlett, 1995. p. 135). Most of the vegetation remaining on the Audubon Sanctuary is second-growth, recovering (= secondary successional) forest.

Diamond (1998, p.1) described southwestern subtropical forest types in the Lower Rio Grande Valley. These included: 1) southwestern subtropical upland forest composed of broad-leaved, mostly evergreen species and that developed on moist uplands and resaca terraces (an evergreen low forest type), 2) floodplain hardwood forest composed mostly of (ie. dominated by) sugarberry (Celtis laevigata), cedar elm (Ulmus crassifolia) and Berlandier as (Fraxinus berlandieri), and 3) the Texas palmetto or sabal palm-dominated floodplain forest. Diamond (1998, ps.4-5) divided the upland subtropical evergreen forest type into two series: 1) Texas ebony-anaqua series that was described as a "well-developed forest and 2) Texas ebony-snake eyes (Phaulothamnus spinescens) series described as a "low forest grading into shrubland" but these series formed a continuum of vegetation on the uplands of the Lower Rio Grande Valley. Texas ebony was the defining dominant species on the more favorable sites of both of these upland forest series. Stands of old-growth upland subtropical evergreen forest also contain large trees of anaqua as well as Texas ebony. Shrub species in (and indicative of ) understorey of these old-growth forest include brasil, snake-eyes, and Texas persimmon. Sugarberry, cedar elm, soapberry (Sapindus drummondii), and tepeguaje are generally successional woody species. Neither mesquite nor huisache are dominants of these forest types. In fact, mesquite was usually found to be almost absent in interior of old-growth stands while Texas ebony or Texas ebony and anaqua comprise almost all of the canopy of climax forests. There is little or no understorey in such forests resulting in a see-through feature below the canopy.

Apparently this Texas ebony or Texas ebony-anaqua upland forest type intergrades with the sabal palm-dominated floodplain forest. Furthermore the description that the Texas ebony or Texas ebony-anaqua forest type occupied ox-bow (resaca) terraces (Diamond, 1998, p. 1) seemed to the present author to argue for it also being a bottomland forest type under such conditions (ie. when it occurs on ox-bows of floodplains). In such locations ebano- or ebano-anaqua-dominated forests would likely "blend" into sabal palm-dominated forests.

It was the sabal palm-dominated and, often, sabal palm-ebano- or, even, sabal palm-ebano-anaqua-dominated floodplain or gallery forests that the following section was devoted to. On some local habitats there were palm groves whereas on others there was a mix of palm, ebano, and anaqua. Mostly sabal palm and ebano were co-dominant. All photographs were of forest vegetation from Sabal Palm Audubon Center and Sanctuary, (written in abbreviated form as "Audubon Sanctuary").

This natural community was not designated specifically by any of the standard authorities like Kuchler (1964), Garrison et al., 1977), Brown et al. (1998), Society of American Foresters (Eyre, 1980), or Society for Range Management (Shiflet, 1994). Diamond (1998, p. 4) also emphasized that there was no Society of American Foresters cover type. Vegetation was probably too small a unit to merit inclusion in treatments devoted to general units of vegetation or in hierarchial vegetation classification systems. Anyway, there were not published vegetation units for this range vegetation so none were shown. While this forest range vegetation was not named or described as a cover type or specific biotic community or series it was in Western Gulf Coastal Plains- Lower Rio Grande Alluvial Floodplain 34f (Griffith et al., 2004).

271. Exterior view of sabal palm-ebano or Texas ebony forest- Physiogonomy of a virgin palm-ebano Rio Grande Valley forest. Local small palm grove (= stand) with Texas ebony in background. Understorey consisted of David milkberry or cahinca (Chinococca alba), bloodberry or rogue plant (Rivina humilis), chilipiquin or bush pepper (Capsicum annuum var. glabriusculum), and Drummond wax-mallow or Texas mallow (Malvaviscus arboreus). Bloodberry was the only major forb.

Audubon Sanctuary, Cameron County, Texas. October.

 

272. Stand of sabal palm forest- Species composition and structure of a virgin grove of Sabal mexicana (= S. texana) with understorey dominated-- almost exclusively --by David milkberry or cahinca. Mature and immature individuals of Texas ebony or ebano (Pithecellobium flexicaule= P. ebano) were visible in midground of both photographs.

The smooth bark on trunks of palms indicated mature trees. Abscission scars and residue of frond petioles were "long-gone" in contrast to younger trees (see photographs below).

Audubon Sanctuary. Cameron County, Texas. October.

 

273. Species diversity of a sabal palm-ebano jungle forest- Co-dominants of this floodplain forest were in close association on this "photo- sample" of one of the most rare of North American range types. Ebano or Texas ebony was growing alongside sabla palm with David milkberry or cahinca dominated the shrubby understorey. Rouge plant or bloodberry was most abundant forb.

Note abscission scars and "trash" (residue) of shed fronds on trunk of the young palm. These leaf bases are commonly known as "boots".

Audubon Sanctuary, Cameron County, Texas. October.

 

274. "Outskirts" of a sabal palm-Texas ebony floodplain jungle forest- On the edge of this Lower Rio Grande Valley floodplain palm-ebano forest both of these dominant tree species were accompanied by lime prickly ash and young plants of anaqua and tpeguaje (Leucaena pulverulenta). In the lower understorey the most common species were bloodberry and chilipiquin.

Dead fronds of sabal palm are shed and fall to the forest floor to form a relatively deep litter layer. "Boots", the bases of shed fronds, typically remain for a period of time (perhaps several years) following shedding of the leaves.This relative early shedding of dead leaves is in contrast to some other palm species in which dead fronds remain on trees to form a "skirt".

Audubon Sanctuary, Cameron County, Texas. October.

 

275. Jungle on the Rio Grande- Vegetation layers of sabal palm-ebano jungle forest were conspicuous in this photograph of the interior of the virgin vergetation that got sunlight for only a relatively short period (at least long enough for this composed shot).

Regeneration of sabal palm beneath its own shade was obvious in this and the next three succceeding slides as well as others below. Sabal mexicana (= S. texana) was not included in the Forest Service Silvics of North America (Burns and Honkala, 1990), but the similar S. palmetto was classed as shade- tolerant and probably both climatic climax and fire climax (Burns and Honkala, 1990, p. 765).

Audubon Sanctuary, Cameron County, Texas. October.

 

276. Palm and ebony along a resaca- The sabal palm-Texas ebony virgin forest shown in this series of photographs developed around a resaca (Spanish for ox-bow or ox-bow lake) that formed on the previous bed of the meandering Rio Grande. In 1895 the Rio Grande flooded to such extent that it changed course-- formed a new meander as such rivers are wont to do --and formed a new river bed. After being cut off from the main channel of the Rio Grande the old riverbed developed into a lake (or several small lakes) along the old meander. Ox-bow takes its name from the bows of an ox yoke. A bow is one of the two curved, slender wooden pieces that fits around the ox's neck. Later a saddle stirrup in which the boot is less likely to hang up was patterned after this piece so as to become known as ox-bow stirrup. Pioneer geologist adopted the name of the then-common piece of teamster (bull-wacker) equipment and applied it to stream meanders, especially when backwater lakes formed behind river meanders that became cut off from the main stream channel as when floods changed the river or its major tributaries.

Sabal palm-ebano jungle forests developed along the floodplain of the Rio Grande in the Lower Rio Grande Valley, especially around an ox-bow (or, again the Spanish, resaca). That phenomenon was "caught on Kodachrome" in the scene shown here and in the next photograph. Both ebano or Texas ebony and sabal palms were growing in standing surface water and with tree crowns of both species outlined against the humid Gulf Coast sky. Furthermore, the tolerant palm had regenerated such that young palms were growing in open water of the resaca.

Audubon Sanctuary, Cameron County, Texas. October.

 

277. Crowns along the El Rio de las Palmas- One of the numerous names of the river now know as Rio Grande and Rio Bravo alluded to the palm-lined terminus of the river that has its source in the Rocky Mountains of Colorado. Spanish explorers were forced to skirt the dense palm jungle forest that grew in the floodplain of the Rio de Palmas. Deep mud and perhaps quicksand may have "teamed-up" with the multi-storied floodplain forest in causing diversion of horseback Spanish exploration parties.

That combination of treacherous river and formitable forest vegetation was presented in this photograph. Crowns of sabal palm and ebano, co-dominants of this range type, clearly showed botanical composition of this riparian corridor or what could be viewed as a gallery forest at this location. In addition to reproduction of sabal palm, other plant species growing along the resaca included anaqua, tpeguaje, tenaza, David milkberry, bloodberry, chilipiquin, lime prickly ash, Texas mallow or Drummond wax-mallow, and, the large native wetland grass, common reed or carrizo (Phragimites communis= P. australis).

Audubon Sanctuary, Cameron County, Texas. October.

278. The "drier end" of sabal palm-ebano jungle forest- The series of three photographs presented immediately below showed range vegetation that developed on parts of the floodplain palm forest above (higher in elevation) and farther from the resaca (ox-bow lake) and its vegetation that were shown in the two immediately precdeding photographs. On these "higher and drier" localized habitats plant species composition shifted from that of palm groves with less dense understories to dense, impenterable thickets of thornscrub that lived up to the billing of a "jungle".

 

278 A. Regeneration of palm and ebano in the "jungle"- Young sabal palm and Texas ebony or ebano were growing along with lime prickly ash, anaqua, and common reed on a location within 25-30 steps of the backwater of the Rio Grande in a resaca. Audubon Sanctuary, Cameron County, Texas. October.

 

278 B. No wonder the explorers detoured- Lime prickly ash, night-blooming cereus (Acanthocereus pentagonus), ebano, tpeguaje, and anaqua along with a few sabal palm presented this formitable fortress of vegetation "uphill" (maybe a yard increase in elevation) from an ox-bow along the former channel of the Rio Grande.This would seem to be the "jungle"-like expression of sabal palm-ebano floodplain forest that forced Spanish explorers to divert from the Rio Grande then known as El Rio de las Palmas. Cameron County, Texas. October.

 

278 C. "There's gotta be a better way than this" (or "Ah, but what interesting vegetation")- Spanish dagger (Yucca treculeana) and some species of pricklypear (Opuntia sp.) joined ebano, tpeguaje, lime prickly ash , chilipiquin, and Berlandier fiddlewood to form this vegetational arrangement often described as a "jungle". It was readily apparent why such a barrier of thornscrub forest caused mounted explorers to find another route. Audubon Sanctuary, Cameron County, Texas. October.

 

279. Past fire and present undergrowth- Boles (trunks) of sabal palm and ebano or Texas ebony along with tenaza, tpeguaje, Berlandier fiddlewood, lime prickly ash, chilipiquin, and bloodberry or rouge plant produced this "jungle"-like sample of floodplain palm-ebano virgin forest. This range vegetation was close to the edge of a resaca (ox-bow lake) that formed when a flood 110 years ago changed the course of the Rio Grande. The resaca formed along the former channel meander that was cut off from the new riverbed.

Viewers atttention was drawn to the fire-burnished trunks of sabal palm. Readers were reminded of the dense, often multi-layered litter or debris composed largely of shed fronds that covered the forest floor. This constitutes a readily available fuel for fire which, as evidenced by fire-charred palm trunks, has occurred in this vegetation. It was cited above that in Silvics of North America Burns and Honkala (1990, p.765) regarded the cabbage palm (Sabal palmetto) of Florida as a fire-climax species. S. mexicana (= S. texana) was not treated in Silvics but it seemed likely that sabal palm was similar to S. palmetto in response to fire (and shade).

Ages of trees and shrubs was not determined. Indeed, the monocotyledonous palm does not produce annual growth rings so ages of individuals of this species could not be accurately determined. It seemed obvious, however, that Texas ebony or ebano trees (pole-size trunks) were younger than the larger palms because there was no evidence of fire on bark of ebano poles. It followed from this that ebano had grown after the fire that charred palm trunks. From this self-evident fact it was obvious that ebano had grown under shade of the pre-existing sabla palms. Ergo, ebano or Texas ebony is also relative shade-tolerant, which is consistent with its ecological niche and role in this forest range type as a climax (and co-dominant) species.

Audubon Sanctuary, Cameron County, Texas. October.

 

280. Intriguing view of virgin forest- A composite scene of old-growth sabal palm-ebano Rio Grande floodplain forest revealing regeneration of both co-dominant climax tree species. Other woody species in this forest tract were lime prickly ash, anaqua, tenaza, tpeguaje, Spanish dagger, and David milkberry or cahinca (the overall dominant understorey shrub). Other low-growing shrubs that were common in the understorey included chilipiquin and Texas mallow or Drummond wax-mallow. Bloodberry or rogue plant was the major forb. Common reed or carrizon, the large arundinoid grass, was locally dominant and frequently present as a major herbaceous species (in latter case, as in foreground of this photograph).

Abscission scars from shed fronds were distinctive on trunk of palm (right foreground).

Audubon Sanctuary, Cameron County, Texas. October.

 

281. Not an island paradise but Texas' Lower Rio Grande Valley- No, this was not a tropical island in the Caribbean Sea, but sabal palms, an anaqua, Texas persimmon, and common reed welcomed guests to a floodplain forest near the mouth of the Rio Grande emptying into the Gulf of Mexico. Young palms and ebano saplings attested to regeneration of these climax co-dominants of this forest range type.

(And, yes for some folks this always warm-- and, usually, hot -- and humid, mesquite-infested, closed-in, backwater "jungle" is paradise. "To each his own".)

Audubon Sanctuary, Cameron County, Texas. October.

 

282. Next crop of co-dominants- Regeneration of sabal palm (foreground) and ebano or Texas ebony (background) was shown distinctly in this view of the understorey of a palm-ebano floodplain forest.

Litter from shed palm fronds covered much of the forest floor, but some plant species grew through this debris (and perhaps benefitted from it). It was remarked previously that based on tolerance of cabbage palm it was logical to assume that sabal palm is probably a shade- tolerant species. .

Audubon Sanctuary, Cameron County, Texas. October.

 

283. Inside a sabal palm-ebano forest- Deep interior of a Rio Grande floodplain forest with young sabal palms and older and larger ebano (largest tree trunk but with uncharcteristic lower bark) and anaqua (two trees with dark trunks in right background and one tree at extreme right margin). It was mentioned above that Sabal mexicana is likely shade-tolerant so that palm regeneration occurs in climax forests.

Low-growing plants on forest floor included David milkberrry or cahinca, chilipiquin, bloodberry, and common reed. Almost all individuals of these species were stunted and were not flowering or bearing fruit in sharp contrast to individual plants of these same species. (Sexually reproductive specimens of these species that were photographed at this same time and in this forest were presented below.)

Climax forest vegetation seen here was a representative sample of the Texas ebony-anacua series of upland subtropical evergreen forest described by Diamond (1998, p.4). The author of the present publication explained in the introduction to this section on Palm Forest the likelihood that floodplain sabal palm groves (the Texas palmetto [S. mexicana]-dominated forest of Diamond [1998. p.1]) intergraded (ie. "blended") into the ebano-anaqua series. Diamonde (1998, p. 4) described a vegetational continuum of similar and floristically related plant communities in the Lower Rio Grande Valley.

The absence of a well-developed understorey that was described by Diamond (1998, p. 4) as "... essentially no middle story or ground cover" was evident in this photo-quadrant.

Audubon Sanctuary, Cameron County, Texas. October.

 

284. Forest smorgasbord- Within this dense sabal palm-ebano forest community several strata (layers) of vegetation were visible illustrating the structure of this floodplain range type. David milkberry was the conspicuous twining, leafy shrub ascending trunks and into the more open canopy. Bloodberry or rouge plant (also pigeonberry), the most common forb, and Texas wax-mallow or shrubby turk's cap and Berlandier fiddlewood were other common shrubs. Also present (and very conspicuous in right foreground) was common reed or carrizo. The forked-limb tree with the "dead giveaway" mottled bark was Texas persimmon. Recall from the introduction of this section that Texas persimmon was interpreted by Diamond (1998, p. 4) was a member of the climax Texas ebony-anaqua forest type. Dead fronds and "boots" (remaining bases of dead leaves) were visible on almost the entire trunks of sabal palms in foreground indicating that these were relatively young trees and that regeneration of sabal palm was on-going..

Audubon Sanctuary, Cameron County, Texas. October.

 

285 A. New forest on an old-field- Old-field is an "old" term in American ecological circles where it is still used in reference to abandoned farm land, most of which consisted of fields (referring to land that had been devoted to field crops). Historically before involvement of the Federal (United States) government, abandoned farm ground was left without much, if any, attempt at revegetation. What natural revegetation took place on such abandoned land did so by secondary succession. Land so abandoned was left to "go back on its own" and hence also became known as "go-back land" (a synonym for old-field and used in more more western-- subhumid to arid --regions). With advent and wide acceptance of government cost-sharing (ie, subsidized) programs for soil conservation and revegetation like the Soil Bank and, later (and more successful), Conservation Reserve Program most abandoned fields (and mined lands) in the United States are now artificially revegetated by seeding or tree planting.

The range presented in this slide was an old-field or go-back land undergoing secondary succession. Forest range vegetation was in an advanced seral stage that was approaching plant species composition of climax sabal palm-ebano forest. The complete chronology of agricultural use (livestock grazing, field crop farming, horticultural cropping) on this land was, of course, not known. Likewise, the record of human inputs-- direct and/or indirect --on this stand of Texas ebony or ebano was incompletely known. Diamond (1998, p. 5) pointed out that while there had been considerable effort directed toward reforestation of abandoned cropland in the Lower Rio Grande Valley (more than 5000 acres) "only dubious records" had been kept on materials and methods or successes and failures of this restoration effort. Even on property of proverbial "crack-conservation outfits" like The Nature Conservancy details of restoration projects are far from complete.

On the Audubon Society forestland shown here it was not known how much or what proportion--if any-- of Texas ebony forest regeneration was due to artificial revegetation (including tree planting) and what was atrtributable to the natural processes of secondary plant succession. Furthermore, "little is known about processes in old-growth Texas ebony forests, nor about presettlement disturbances". "Gap-phase succession is not clearly apparent in old-growth upland forests of the Rio Grande Valley" (Diamond, 1998, p. 5). Consistent with the latter statement, it appeared that on go-back land adjacent to sabal palm-ebano forest (such as the old-field shown here) climax plant species reestablished rapidly on the forest sere via old-field (= secondary) succession.

A possible important factor in reforestation-- natural and/or artificial revegetation --of subtropical evergreen forests, including the various cover types and series of both floodplain and upland forests, was role played by invasive and naturalized plant species. The introduced guinea grass (Panicum maximum) recently and with unbelieveable rapidity naturalized throughout much of southern portions of the Rio Grande Plains vegetational area (and extending north of the Lower Rio Grande Valley). Naturalization (Clementsian invasion) of (by) guinea grass was complete within the time frame of approximately 30 or 40 years. This phenomenonal rate of spread rivaled that of annual grasses in California and King Ranch bluestem throughout much of Texas. Guinea grass comprised almost all of the herbaceous cover in the vegetation seen in this and the next succeding slide. Role, if any, of guinea grass in re-establishment of Texas ebony, anaqua, sabal palm, Texas prsimmon, etc. has apparently not been established or, perhaps, not even investigated. Would presence of dense cover by perennial grass have any impact on invasion by native species-- climax and/or seral -- on the forest sere? Would any such impact be different with an exotic like guinea grass than with native species?

Audubon Sanctuary, Cameron County, Texas. October.

 

285 B. Forest come-back on go-back land- Young Texas ebony or ebano and sabal palm re-established on an old-field adjacent to old-growth floodplain forest co-dominated by these climax tree species. This was another view of the same land and range vegetation introduced in the preceding photograph. The forest community was obviously dominated by Texas ebony and sabal palm which are climax dominants of this forest cover type, subtropical evergreen upland forest. Anaqua was also established but at much less cover and density than the other two tree species. The herbaceous layer of this range plant community was composed almost exclusively of the introduced and naturalized guinea grass. There were trace amounts of bufflegrass (Pennisetum ciliare), another introduced (exotic or alien) and widely naturalized grass, present in the otherwise single-species herbaceous layer. Other woody species present as widely scattered individual plants included mesquite, huisache, lime prickly ash, and the subshrub ivy treebine (Cissus incisa). These species did not comprise a shrub layer.

Audubon Sanctuary, Cameron County, Texas. October.

 

285 C. Species line-up of come-back forest- Botanical make-up of the young forest that was developing on the go-back land introduced in the two immediately preceding photographs was shown here in greater detail. Re-establishment of climax tree species of Texas ebony, sabal palm, and anaqua along with shrubs like Texas persimmon and lime pricklyash resulted in on-going reforestation of a subtropical, evergreen upland palm-ebano-anaqua forest, the climax vegetation for this forest range site.

Attention was drawn to the smaller (younger) individual plants of the climax tree species that had regenerated in close proximity to larger (more mature) and, apparently, parent plants. A closed-canopy, climax palm-ebano forest was developing on this old-field. Secondary plant succession had advanced on this forest sere to advanced stage(s) such that botanical composition of this forest community was very similar to species make-up of what is interpreted as climax (= potential natural) vegetation.

Almost all of the herbaceous layer was the introduced and naturalized guinea grass.

Other local aggregations of vegetation on this go-back land had not advanced to this successional stage and instead were in various brush stages composed largely of mesquite and huisace (along with guinea grass, lime prickly ash, tpeguaje, tenaza, Texas fiddlewood, etc.).

Audubon Sanctuary, Cameron County, Texas. October.

 

285 D. Botanical sampler- Detailed sample of second-growth sabal palm-ebano forest. This photo-plot showed the plant species composition of a young but climax forest. It may not have all the outer trappings of an old-growth sabal palm-Texas ebony forest like scenes from the virgin tract shown above but this "little bit" of vegetation had the species composition of climax palm jungle forest.

Tallest, sparsely foliated trees were ebano or Texas ebony. Foremost tree (shorter than ebano and with dense foliage and ripening fruit) was anaqua or knock-a-away. A young sabal palm was at extreme left foreground (margin of photograph). Grass in front of young palm was common reed or carrizo. All of these speceis were present in an adjacent old-growth floodplain forest that had developed along a resaca (ox-bow) of the Rio Grande. Thus species composition of this local aggregation of vegetation consisted of the same climax tree species as the virgin forest vegetation. However, species make-up was not as rich or diverse as that of the relict old-growth in that there was an absence of many of the understorey shrub and forb species (eg. chilipiquin, shrubby turk's cap or Drummond wax-mallow, Texas fiddlewood, and bloodberry or rouge plant) and twining or liana-like shrubs (eg. typical understorey dominant, David milkberry or cahinca).As such, structure and function of the smaller, botanically incomplete stands of vegetation was not the same as in larger and pristine palm-ebano forest communities.

Audubon Sanctuary, Cameron County, Texas. October.

Shown below were examples of major plant species of climax subtropical evergreen sabal palm-Texas ebony forest. Photographs of twigs, inflorescences, and legumes of Texas ebony or ebano or ape's earring were presented above with the other species of woody legumes.

 

286. Fruit of sabal palm (Sabal mexicana= S. texana)- Fruit cluster (panicle inflorescence type) in sabal palm. Fruit type in the Palmae (palm family) is a drupe or berry. Fruit of sabal palm has been described as "berrylike" or "fruitlike" (Correll and Johnston, 1979).

The common name for sabal palm in Spanish is palma de micheros. Micheros is Spanish for the palm fruits which are resemble grapes but are have more of a datelike flavor and are relished by numerous species of animals including humans (at least under the right conditions).

Cameron County, Texas. October (both ripe and unripe fruits).

 

287. Texas ebony or ebano- Trunk and major limbs of a mature tree with characteristic bark. Smaller tree or shrub to immediate right of ebano with its "can't miss this one" bark was Texas persimmon. It was explained previously in this section that Texas persimmon is a climax (and indicator) species associated with ebano-anaqua forest (see again Diamond, 1998, p. 4).

Audubon Sanctuary, Cameron County, Texas. October.

 

288. Anaqua (Ehretia anacua)- This medium-sized tree of the Boraginaceae (borage family) is a climax co-dominant with Texas ebony on forest sites of the Texas ebony-anacua series of subtropical evergreen upland forest in the Lower Rio Grande Valley (Diamond, 1998, p. 4). In the present publication anaqua was interpreted as the major associate of co-dominant species, sabal palm and Texas ebony, on climax floodplain forests near mouth of the Rio Grande. This was based on empherical observations by this author in the relict vegetation of Sabal Palm Audubon Center and Sactuary, Cameron County, Texas.

The example of leaves and fruit shown here was of the large anaqua specimen in the last photograph of forest range vegetation on the old-field of the Audubon Sanctuary. October.

 

289. Leaves and fruit of anaqua or knock-away- Fruit type in anacua (anaqua is spelled with either a "c" or a "q") is a drupe. Each drupe has two stones or pits each of which has two seeds. The fruit is juicy and eaten by numerous wildlife species. Viewers should scroll back to the preceding slide and observe again the heavy fruit crop. Multiply that by four and get an idea of the number of seeds dispersed from a single tree. Anacua trees deep inside sabal palm-ebano forest do not produce high fruit yields like the specimen in the go-back land above. More realistic examples of fruit yield in forest interiors were presented in the present two photographs. Still, a "heap of seeds" are produced by one tree.

Trunk of sabal palm in background of first of these photographs depicted close association of these two climax tree species.

Audubon Sanctuary, Cameron County, Texas. October.

 

290. David milkberry or cahinca (Chincocca alba)- This woody vine has been interpreted as the most common dominant species of the understorey of climax sabal palm-Texas ebony floodplain forest. Cahinca is expecially common-- sometimes the exclusive or nearly sole --dominant shrub of palm groves.

 

291. David milkberry or cahinca- Leader and shoot apex with some fruit of the dominant shrub (woody vine) of sabal palm groves. Audubon sanctuary, Cameron County, Texas. October.

 

292. Shrubby or woody turk's cap, Drummond wax-mallow or Texas mallow (Malvaviscus drummondii= M. arboreus var. drummondii)- One of the more common and, certainly, conspicuous understorey shrubs in climax sabal palm-Texas ebony forests is this member of the mallow family (Malvaceae). Audubon Sanctuary, Cameron County, Texas. October.

 

293. Drummond wax-mallow- Shoot apex with inflorescence. The telltale staminal column of the mallow family was displayed prominently by this proud member of the lower woody layer of the climax sabal palm-ebano floodplain forest. Audubon Sanctuary, Cameron County, Texas. October.

 

294. Chilepiquin or chilitepin (Capsicum annuum var. glabriusculum)-The official native pepper of the Lone Star State. Yep, that's right. Passed the Texas House of Representatives in 1997 as some sort of House Resolution. Ain't it fine to have statesmen with such leadership, vision, and botanical insights! Would you believe a sense of political savy and a taste of subtle seasonings?. Anyway this little annual chili is widespread in various habitats and range regions in the Southwest. The individual shown here was growing in the understorey of a stand of sugarberry (Celtis laevigata) in the Western Cross Timbers, but it is also common in the Rio Grande Plains including the sabal palm forest. This individual (including the details of its leaves and inflorescences shown in the succeeding slides) seemed to be an unusually intact and unbattered specimen so it was included here.

Erath County, Texas. September; full-bloom and immature fruit stages.

 

295. Details of a seasoned native- Leaves and inflorescence chilepiquin. This individual (introduced in the preceding photograph) was growing in the West Cross Timbers of northcentral Texas, but the species is so widespread that the same taxonomic variety is even more common in south Texas and Mexico.

Erath County, Texas. September.

 

296. Chilipiquin, bird-pepper, or bush pepper (Capiscum annuum var glabriusculum= C. annuum var. minus)- This member of the nightshade family (Solonaceae) is regarded as subshrub or undershrub (suffrutescent or suffrticose), at least in the more southern portions of its range (a forb elsewhere). Whichever term is most appropriate, this is one of the more widely distributed species along the Rio Grande(= Rio Bravo) growing from the Gulf of Mexico through the Chihuhuan Desert portions of the Trans-Pecos Region.

Chilipiquin was a common associate of David milkberry, Drummond wax-mallow, and bloodberry as a member of the understorey of sabal palm-Texas ebony forests. This one was happy in the Audubon Sanctuary, Cameron County, Texas. October.

 

297. Leaves and fruit of chilipiquin- Close-up photograph showing detail of shoot apex with unripe (immature) and ripening fruit. Fruit type is a berry. Capsicum is the genus of various chilis and peppers. C. annuum is the species commonly known as cayenne pepper. Fruit of chilipiquin is commonly used as a sesoning, in various "hot sauces", and as an all-around good tonic. This little fruit is adored as a wild spice by rangemen and foresters, cowhands and loggers, and other outdoorsmen who take life's litle pleasures where we find them. Have some on the woods.

Audubon Sanctuary, Cameron County, Texas. October.

 

298. Berlandier fiddlewood or negrito (Citharexylum berlandieri)- This member of the verbena or vervain family (Verbenaceae) is a not-so-common species in climax sabal palm-ebano forest. Negrito is most commonly found growing in well-lite forest microsites (eg. outer edges of floodplain forests). Fiddlewood can grow to size of a small tree. It bears considerable fruit which is undoubtedly feed for animals, especially birds.

Audubon Sanctuary, Cameron County, Texas. October (fruit-ripe stage).

 

299. Barbed-wire cactus or triangle cactus, or (Acanthocereus pentagonus= Cereus pentagonus)- This sprawling specimen was growing in the most dense, most jungle-like thicket of a sabal palm-Texas ebony floodplain forest just upslope from a resaca (ox-bow) along an old riverbed of the Rio Grande. This species blooms at night and ever so briefly such that it is sometimes referred to as night-blooming cereus, but most authorities reserve that title as a preferred common name for another species (one which does call palm jungles home).

This specimen's dancing pardner was a a lime prickly ash (single-stemmed shrub with gray-colored trunk immediately to right of the cactus). Both were safe at home in Audubon Sanctuary, Cameron County, Texas. October.

 

300. Shoot apex and fruit of triangle cactus- The cactus plant shown in the preceding photograph was at fruit-ripe phenological stage and the happy occasion was a "Kodak moment" for the reader's fortunate author/photographer. Fruit of triangle or barbed-wire (the origin of second common name was obvious in first photograph) is extremely sweet and a bon apetite bonanza for animals including the hymenopteran (ous) guests shown here. All were happy on the Audubon Sanctuary, Cameron County, Texas. October.

 

301. Leaves of lime prickly ash or colima (Zanthoxylum fagara)- In recent times the Lower Rio Grande Valley became famous for its production of fine citrus fruit. This species is not one of those horticultural fruit crops, but it is in the citrus family (Rutaceae). Z. fagara is widely distributed in the Rio Grande Plains and Coastal Prairies and Marshes vegetational areas of Texas across the Gulf Coastal Plain to Florida and south into Central America. Lime prickly ash is a common member of climax sabal palm-texas ebony forest as well as of the "brush country" in general. Colima superficially resenbles legumes including possessing catclaw-like prickles.

The example shown here was growing at the edge of a resaca in association with (and within wind-blown touching distance of) sabal palm, anaqua, and ebano on the Audubon Sanctuary, Cameron County, Texas. October.

 

302. Bloodberry, pigeonberry, coralito, or rouge plant (Rivina humilis)- This is one of the few forb species that grows in the usually deeply shaded interiors of climax sabal palm-Texas ebony forest, but it is a common herbaceous plant in that range plant community. Bloodberry is in the small family Phytolaccaceae although some taxonomists have included teh genus in the Petiveriaceae. Audubon Sanctuary, Cameron County,Texas. October.

 

303. Shoots of bloodberry or coralito- Leaves, flowers, and fruit of one of the most common (and one of the few) forbs in climax palm-ebano floodplain forest. Audubon Sanctuary, Cameron County, Texas. October.

 

304. Cow-itch, ivy treeebine, or hierba del buey (Cissus incisa)- This woody vine or liana was growing on the old-field land featured in photographs above that was undergoing natural reforestation back to a sabal palm-Texas ebony forest. Cow-itch was not common in an adjoining old-growth palm-ebano forest where it was observed (in very scrawny form) on more open local sites (microsites). Audubon Sanctuary, Cameron County, Texas. October.

 

305. Shoot tip of ivy treebine- Details of leaves and flower cluster of cow-itch growing on go-back land on floodplain of Rio Grande where it was growing in association with sabal palm, Texas ebony, anaqua, and common reed. Audubon Sanctuary, Cameron County, Texas. October, full-bloom stage.

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