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Designation of North American deserts has been, and remains, a difficult propositon. Some authorities avoided this problem by simply mapping and naming vegetation based on to large degree on physiogonmic dominants (eg. Kuchler, 1966). The Society for Range Management simply named and described rangeland cover types and ignored larger vegetation or community units like biomes or subdivisions thereof (eg. desert biome consisting of Sonoran, Mojave, Great Basin, and Chihuhuan Deserts). The current author followed the precedents set by giants like Shreve, Clements, Shelford, and Jaeger as well as more recent scholars like those in Bender (1982), Brown (1994), and Barbour and Major (1995) and recognized the merit and legitimacy of biomes and their major units. Thus the use of the traditional names and descriptions of North American deserts. Such use did not (yea, cannot) eliminate arbitariness of designations.
Given the inherently arbitrary distinction of deserts (especially the border between the Mojave and Sonoran) and the often confusing designation of a "Colorado Desert" (Jaeger, 1957, p. 85; Shelford, 1963, 378-383) some examples of vegetation were included under both Mojave and Colorado Deserts and Sonoran Desert in this publication. Readers are free to draw their own "property lines".
As a good beginning (and fairly comprehensive) reference on the Mojave Desert readers were referred to Shelford (1963, ps. 387-390), Rowlands et al, (Chapter 4 in Bender, 1982), and Brown (1994, ps. 157-179). The outstanding monograph of California vegetation by Barbour and Major (1995) was a classic when it was published and students are referred to chapter 24 on the Mojave Desert as well as chapter 25 on the adjacent Sonoran Desert. For easily read, unifying coverage of all North American deserts (Jaeger, 1957) would be hard to "best".
The Lower Colorado Valley is the largest and and most "desert-like" subdivision of the Sonoran Desert. Creosotebush is the dominant species over the vast desert "super-region" of North America from the Chihuhuan through the Mojave Deserts. Creosotebush is especially singularily dominant (and prominent) over the Lower Colorado portion of the Sonoran Desert.
1. Creosotebush flat (exterior view)- Example of the "Larrea plain" described by Clements (1920, p. 174) and the intermont plains of the Lower Colorado Valley subdivision of Shreve (Shreve in Shreve and Wiggins, 1964, ps. 49-50, 57-58). This is a creosotebush consociation with essentially no white bursage present (author did not find a single plant of bursage). Understorey was dominated by red brome (Bromus rubens) with fluffgrass (Tridens pulchellus= Erioneuron pulchellum) an associate or local do-cominant. There were periodic patches of Arabian or Mediterranea grass (Schismus arabicus). Fluffgrass is a native perennial, but it's stolons and their daughter plants are of such short life as to appear annual-like. Red brome is one of the least productive and -palatable Bromus species (although it will be eaten when young). Arabian grass was described by Hitchcock and Chase (1950) as "an excellent forage grass in winter".
The community shown here was obviously winter range, with the usefulness of that varying from year-to-year depending primarily on winter moisture. In describing creosotebush communities like the one shown here Humphrey (1960, p. 55) remarked that unless they "... may support a crop of winter or summer annuals in season, they could not even be classed as range".
This range community was part of the "Mojave Desert-Sonoran Desert transition", a segment of the Lower Colorado River Valley subdivision that was part of the "tenuous border with the Mojave Desert" (Brown, 1994, p. 190). It could logically be included with the Mojave Desert and, in point of fact, vegetation shown here made a case for the less common, more informal, and less accepted classification of this part of the southwestern desert region as the "Colorado Desert". Brown (1994, p. 157) remarked that the Colorado Desert was "Shreve's Lower Colorado subdivision of the Sonoran Desert". Kuchler (1966) designated this vegetation in lower California as unit #35, Creosote bush (Larrea), in contrast to unit #36, Creosote Bush- Bur Sage (Larrea-Franseria), farther east into Arizona.
Readers attention was directed to the large nest of California harvester ants (Pogonomyrmex claifornicus) in left center foreground. The other mounds were locations of former creosotebush plants (one shown closer in succeeding slide).
Vegetation in this photograph was in an intermont basin of the Sonoran Desert section of the Basin and Range physiographic province, specifically a bolson which is an undrained basin (Fenneman, 1931, ps. 357-377).
Bureau of Land Management, San Bernardino County, California. June. FRES No. 30 (Desert Shrub Ecosystem). K-35 (Creosote bush). SRM 211 (Creosote Bush Scrub). Brown (1994, p. 162-163) included this as the Creosotebush series of Mohave Desertscrub while the scrub community co-dominated by creosotebush and white bursage was designated as the Creosotebush-White Bursage series of the Sonoran Desertscrub. The Kuchler (1966) vegetation map did not delinate deserts so the Mojave and Sonoran were not differentiated.
2. Interior of a creosotebush desert flat- Two views inside the creosotebush scrub range community presented in the immediately preceding slide. These slides showed the regular or uniform dispersion pattern typical of many arid shrublands-- the deserts or desert scrub-- (see Barbour and Major, 1995, ps. 840-841, 875). The understorey was a single herbaceous layer of annual red brome and perennial fluffgrass with periodic patches of the annual Arabian or Mediterranean grass. Both annual grasses were Eurasian natives of anthropogenic introduction. The grasses and a few other species of winter annuals or spring ephemerals had already disintegrated under action of dessicating winds and herbivory (recall harvester ant colony in first slide and note the deer trails in these two photographs: right midground in first slide and central midground of second slide).
The first slide included a mound with remaining woody stems where a creosotebush once grew. This showed the ring growth pattern or form of this sometimes clonal species. Some creosotebush clonal rings have been dated to be several thousand years of age with some rings having several satellite shrubs per clone making distinction of individual "plants" difficult. (Barbour and Major, 1995, p. 837-838). Creosotebush is obviously a xerophyte but it actually has many mesophytic-appearing features (eg. it has C3 metabolism; Barbour et al., 1999, ps. 426, 550 and Barbour and Major, 1995, ps. 881-882). The major adaptation of creosotebush to desert habitats appears to be ability of it's protoplasm to withstand desiccation (Barbour et al., 1999, p. 628).
Bureau of Land Management, San Bernardino County, California. June. FRES N0. 30 (Desert Shrub Ecosystem). K-35 (Creosotebush). SRM 211 (Creosote Bush Scrub). Brown (1994, p. 162-163) designated this as Creosotebush series of Mohave Desertscrub. Distinct from the dominance type with creosotebush and white bursage as co-dominats.
3. Ground-level of creosotebush scrub community- The grass-dominated herb layer (now largely disintegrated) was beneath a creosotebush shrub layer. Except for the sometimes-present cryptogamic layer this vegetation had a simple two-layer sructure. The creosotebush had a clonal ring growth pattern, but this was not as well-defined as in some cases (eg. mound in first slide above preceding caption).
This site was in the Sonoran Desert section of the Basin and Range physiographic province and could be interpreted as either part of the Lower Colorado subdivision of the Sonoran Desert (ie. "Colorado Desert") or as a part of the Mojave Desert. It was best described as the Creosotebush Section of the Mohave Desertscrub (Brown, 1994, ps. 162-163), but it was typical of much of the Sonoran Desert as well, delinations being as mentioned arbitrary.
Bureau of Land Management, San Bernardino County, California. June. FRES No. 30 (Desert Shrub Ecosystem). K-35 (Creosotebush). SRM 211 (Creosote Bush Scrub).
4. Desert saltbush (= allscale)-creosotebush range in Lower Colorado Valley- In what is probably the most comprehensive treatment of vegetation in southwestern North America, Brown and Turner (in Brown, 1994, ps. 194-197) recognized and described a Saltbush series of the Lower Colorado River Valley vegetational lsubdivision of the Sonoran Desert. This was consistent with early (and still outstanding) work by Humphrey (1960, p. 54) who placed both desert saltbush and creosotebush range types as well as "paloverde-triangleleaf bursage sites" (Humphrey's use of "site") and "desert wash" in the "southern desert shrub" (Humphrey, 1960, ps. 52-59)..
Note: It was explained above that recent workers in Brown (1994) added details and subunits to the traditionally recognized deserts (and other biomes in southwestern North America). The subunits were designated as "series". Series was a hierarchial level within a digitized classification syustem for biotic communities (Brown, 1994, ps. 303-315 passim). The series unit (Brown, 1994, p. 306) was taken from several sources including the Daubenmire "climax series" based on "major dominants in climax communities" and also the "series' or "cover types" going back to the Society of American Foresters (1954) as well as the natural vegetation approach of Franklin and Dryness (1973). Obviously series is either the traditional or slightly modified dominance type and therefore corresponds closely to forest and rangeland cover types. Application of the "climax series" (and along with biotic communities [= biomes]) to vegetation of the Sonoran Desert was yet another irony to the Clements-Shreve argument discussed in the introduction to the Sonoran Desert. And again, as was more often the case than not, Shreve lost out. By using climax dominance types in a system built on the "biome approach" (Brown, 1994, p. 8-12) the individualistic concept of communities introduced by Shreve and Gleason was, once again, either ignored or made to "suck hind tit" to the organismic concept of Clements. "The biome as a complex organism" (Clements, 1939, ps. 21-25) and biome, formation, and climax were synonyms "when used in the biotic sense" (Clements, 1939, p. 20) vs. "It is not possible to use the term 'climax' with reference to desert vegetation" (Shreve in Shreve and Wiggins, 1964, p. 29).
In their treatment of the Sonoran Desert, Turner and Brown (in Brown, 1994, ps. 193-200) included five series within the Lower Colorado Valley vegetational subdivision of Forrest Shreve. The only one of these series that received much recognition by those who previously mapped and described Sonoran Desert vegetation was the creosotebush-bursage type. The saltbush series refers to desert saltbush that is also known as allscale, cow lettuce, and cattle spinach (Atriplex polycarpa). Desert saltbush was described as "highly palatable" for livestock and big-game and "excellent cover and nesting habitat for quail" by Sampson and Jespersen (1963, p. 66). Humphrey (1960, p. 54) described desert saltbush range and concluded that desert saltbush was "the most palatable and valuable forage plant in most of the area where it grows" (Humphrey, 1960, p. 114). Given the value of this dominant range plant and it's dominance as a "climax series" the saltbush series should be accorded a separate SRM rangeland cover type designation in future publications (ie. Desert Saltbush-Creosotebush).
In the range community shown in this and in several of the next photographs creosotebush was the associate species overall and co-dominant locally (in patches). Western honey mesquite (Prosopis glandulosa var. torreyana= P. juliflora var. torreyana) was also present (eg. left center of the slide for this caption).
Relict area except as understorey modified by annual exotics. Maricopa County, Arizona. Early estival aspect, June. FRES No. 30 (Desert Shrub Ecosystem). K-35 (Creosotebush) is closest thing but not the same. Likewise closest rangeland cover type was variant of SRM 211 (Creosote Bush Serub) or perhaps of SRM 506 (Creosotebush-Bursage); neither one was descriptive or precise enough. Desert Saltbush (allscale) series of Lower Colorado River Valley subdivision of Sonoran Desertscrub (Brown, 1994).
5.Colorado Desert— Another hot desert but a much smaller one is named after the river draining into it. Here is the creosote bush-bursage (mostly Ambrosia dumosa) section of a scrub composed of both arborescent and succulent shrubs. The herbaceous understory is an intermingled stand of the naturalized Mediterranean red brome (Bromus rubra) and the native perennial big galleta (Hilaria rigida). Note the immense alluvial fan at foot of the mountain range. San Bernardino County, California. June. FRES No. 30 (Desert Shrub Ecosystem). K-36 (Creosotebush-Bursage). SRM 506 (Creosotebush-Bursage). Creosotebush-White Bursage Series of Brown et al. (1998).
6.Colorado Desert scene with basin and range topography and desert pavement— Creosotebush and teddy bear or jumping cholla (Opuntia bigelovii). Joshua Tree National Monument, Pinto Basin, California. June. FRES No. 30 (Desert Shrub Ecosystem). K-36 (Creosotebush-Bursage). SRM 506 (Creosotebush-Bursage) variant. Also variant of Creosotebush-White Bursage Series of Brown et al. (1998).
7. Creosotebush-white bursage (= burroweed) flats in Colorado Desert- This desert basin was co-dominated by two of the most common scrub species of the Colorado Desert. These were featured in the immediate foreground: creosotebush (left) and bursage or burrow bush (right). This landscape was a good example of the physiography characteristic of the Basin and Range province (a basin in foreground; a mountain range in background). Herbaceous species were largely absent from this browse range. The dried herbage was red bromegrass.
The palatability of creosotebush to larger herbivores like ruminant livestock and wildlife and horses is zero "for all intents and purposes", but white bursage is often a valuable browse plant. Dayton, 1931, p. 154) cited observations that reported white burrow bush to be the most palatable shrub in the region for horses plus being nutritious to cattle and sheep. Stubbendieck et al. (1992) also stated that burrow bush was "preferred by horses and donkeys".
Pinto Basin, Joshua Tree National Monument, Riverside County, California. June. FRES No. 30 (Desert Shrub Ecosystem). K-36 (Creosotebush-Bursage). SRM 506 (Creosotebush-Bursage). Creosotebush-White Bursage Series of Brown et al. (1998).
8. Creosotebush (Larrea tridentata= L. divaricata)- If there was one overall dominant species of the Sonoran Desert it would unquestionably be creosotebush. It is the defining dominant of the Lower Colorado Valley (= "Colorado Desert") and Arizona Upland vegetational subdivisions of the Sonoran Desert (Shreve in Shreve and Wiggins, 1964, ps. 49-50). "Larrea is one of the most abundant and widespread shrubs of the Sonoran Desert, and it is equally prominent in the vegetation of the Chihuhuan Desert, the Mojave Desert, and a small part of the Great Basin Desert" (Shreve in Shreve and Wiggins, 1964. p. 165). Creosotebush is the quientessential range plant of the North American deserts.
Creosotebush is also called "greasewood" (especially in west Texas), but this is very confusing and as close to an "incorrect" common name as is possible because greasewood is the preferred common name for Sarcobatus vermiculatus.
The individual plant displayed here was of the Sonoran Desert ecotype (Brown, 1994, ps. 172-173). It was growing as an associate on the Desert Saltbush series of the Lower Colorado Valley vegetational subdivision. Maricopa County, Arizona. June
9. Leader of Sonoran Desert (Lower Colorado Valley subdivision) creosotebush- Leaves, fruit, and bark of the Sonoran Desert ecotypic form of creosotebush. Maricopa County, Arizona. June.
10 White bursage, burroweed, or burro bush (Ambrosia dumosa= Franseria dumosa= F. albicaulis)- A view of an individual plant of white bursage from the basin shown immediately above. Pinto Basin, Joshua Tree National Monument, Riverside County, California. June.
11. Leaves and the small fruits of white bursage- Dayton (1931, p. 154) reported that these small fruits were quite valuable for fattening range livestock. White bursage is a member of one of the largest tribes of the Compositae. There are many shrubby as well as hearbaceous composites on the ranges of North America, including all the deserts.
12. White brittlebush or incienso (Encelia farinosa)- This is another woody composite (and of the same tribe as the preceding species). The alternate, ash-gray leaves of this much-branched low shrub make identification of this desert denizen an easy matter. Colorado Desert. San Bernardino County, California. June.
13. Incienso or white brittlebush in bloom- The farmer "makes hay while the sun shines", but desert plants bloom "if and when it rains". Brittlebush was shown here blooming in the Sonoran Desert in winter (January). The general precipitation pattern of the Sonoran Desert is biseasonal with the major moist periods being winter and summer. (The Sonoran Desert is located between the Chihuhuan Desert which gets most of it's moisture in summer and the Great Basin Desert which gets most of it's precipitation in winter. The Sonoran Desert receives some moisture from the storm tracks and precipitation patterns of each of the neighboring deserts.)
Pinal County, Arizona. January.
14. Inflorescences of white brittlebush or incienso- White and yellow are the two predominant colors of the huge composite family. Brittlebush is readily identified (though not readily by it's flowers), but that is not generally the case for many of the composite forbs. It is common practice among rangemen and foresters when asked the identity of a blooming composite that they do not know to reply with the tongue-in-cheek answer, "Some DYC (or DWC)" (codifying Damned Yellow Composite or Damned White Composite). Viewers see a bright DYC blooming in winter in the Sonoran Desert.
Pinal County, Arizona. January.
15. Desert wash vegetation- The Colorado Desert has the physiography of the general Basin and Range province of which it is one part. This landscape has pronounced dendritic drainages and such smaller land forms as alluvian fans, benches, arroyos (desert gullies), and stream beds. Many of the latter are ephemeral water courses that are dry much or most of the year. They have often been described as desert washes. Increased quantity of available water, even for brief periods, in these washes supports vegetation that differs from that of adjoining plant communities in species composition, structure, etc. These desert wash communities could be interpreted as riparian vegetation though some might argue that such a perspective is more imagination than interpretation. The general dominant of wash vegetation in the Colorado Desert is the leguminous shrub or small tree commonly known as smoketree (Dalea spinosa= Parosela spinosa). Common associate species include palo verde or green tree (Cerdicium floridum= Parkinsonia floridum), desert ironwood (Olneya tesota), and Fremont cottonwood (Populus fremontii).
Vegetation shown in this slide was a smoketree consociation, but jojoba (Simmondsia californica) as the associate species was also plentiful (by desert standards). Two jojoba plants can be seen here (the dark green, tall shrub in left center and the spreading shrub in far right background). Jojoba as a range browse plant was discussed in two time-honored USDA publications (Dayton, 1931, ps. 94-95; Forest Service, 1940, B148). The current author can personally attest to the value of jojoba as cover for California quail (Callipepla californicus). He "bird-dogged" a nice covey from one of the pictured jojoba plants back to the other. As seen in the photograph herbaceous species were absent from this wash.
Joshua Tree National Monument, Riverside County, California. June. FRES No. 30 (Desert Shrub Ecosystem).Subunit of K-36 (Creosotebush-Bursage). The water course variant or subdivision of SRM 211 (Creosote Bush Scrub).
16. Smoketree (Dalea spinosa= Parosela spinosa) growing in a desert wash. Joshua Tree National Monument, Riverside County California. June.
17. Inflorescences of smoketree- Smoketree is a papilionaceous legume, a member of the Papilionoideae subfamily. The species of this subfamily are often thought of as the "true" legumes because they are the ones with the papilionaceous flowers that are characterized by five petals: the largest and unpaired petal known as the banner or standard, two keels (partially fused), and two wings. Some taxonomists have concluded that this subfamily is the "real" bean or legume family (Leguminosae= Fabaceae) and that the other subfamilies (Mimosoideae) and Caesalpinioideae) should be elevated to the distinct and separate mimosa family (Mimosaceae) and senna or caesalpinia family (Caesalpiniaceae). There is general agreement that it is only members of the papilionaceous group that host nitrogen-fixing bacteria in sufficient populations to add much nitrogen to the soil. Thus papilionaceous legumes are more or less synonymous with nodulated legumes.
Both of these two slides were of the same tree. Joshua Tree National Monument, Riverside County, California. June.
18. Catclaw or catclaw acacia (Acacia greggii)- Catclaw has one of the largest biological or species ranges of any Acacia species in North America. It grows from the Coastal Prairies & Marshes and Rolling Red Plains vegetational areas of Texas west to California and south into Baja California and as far north as southern Nevada. It occurs in the Mojave, Colorado, Sonoran, and Chihuhuan Deserts yet is also found in the mixed and western part of the tallgrass prairies. Ecotypic variation in this species has to be nothing short of amazing.
The individual shown here was in the Mojave Desert of California. Riverside County, Califolirnia. June.s
19. Inflorescences of catclaw- The profusion of flower clusters of this prosperous plant provided one of the elements of beauty so often characteristic of the unforgiving harshness of the desert. Mojave Desert, Riverside County California. June.
20. Details of catclaw acacia- Leaves, inflorescences, and fruits of A. greggii were presented in this example from the Mojave Desert (Riverside County, California). June.
There are several woody legumes (shrubs or, sometimes, small trees) in the deserts of southwestern North America that are members of the senna subfamily (Caesalpinoideae) or, according to some authors, the senna family (Caesalpiniaceae). Three of these species that grow in the Mojave and Colorado Deserts were presented below. The first two are very similar with distinctions being made on basis of leaves with petioles and glabrous branches (the first species) or leaves without petioles or sessile and pubescent branches (the second species) according to Hickman (1993). These three species have green bark that is capable of carrying out some photosynthesis (undoubtedly an adaptation to aridity through evolution of reduced transpiring leaf surface area).
21. Border or blue palo verde (Cercidium floridum)- This is generally the larger of two Cerdicium species found in the Mojave Desert and the Colorado Desert section or portion of the Sonoran Desert. Riverside County, California. June.
22. Inflorescence and legume of border or blue palo verde- Close-up of fruit and flower of the tree shown immediately above. Riverside County, California. June.
23. Palo verde (Cercidium microphyllum)- This and the preceding species resemble each other closely, but they are distinguished as described when they introduced above. This individual was growing at the edge of a desert wash by an ephemeral seep where persistently moist soil and/or ground water of a surface aquifer were highly probable.
Joshua Tree National Monument, Riverside County, California. June.
24. Mexican palo verde, California retama, or Jeruselum thorn (Parkinsonia aculeata)- This woody legume is scarce in the California deserts, but it has distinctive flowers and legumes The individual shown here was accompanied by California sagebrush (Artemisia californica), the silver grey shrub at far right foreground, which is another fairly uncommon shrub to these parts. Most of the dead grass was red brome (Bromus rubens), a naturalized Eurasian annual grass.
Riverside County, California. June.
25. Detail view of the foliage of California retama or Jeruselum thorn- Leaves, inflorescences and a legume on the small tree presented in the preceding photograph. Riverside County, California. June.
26. Jojoba or goatnut (Simmondsia chinensis)- This rather unique species has been placed in either of two families (Simmondsiaceae or Buxaceae) by different taxonomists. Judd (1962, p. 93) stated that "California jojoba is one of the most important browse plants in the Southwest". The Forest Service (1940, p. B148) rated jojoba as good to very good winter browse and fair summer browse for all livestock classes. Jojoba is monecious.
Sonoran Desert, Cochise County, Arizona. December.
27. Leaves of jojoba- Mojave Desert, Riverside County, California. June.
28. Big galleta (Hilaria rigida)- This robust specimen of a robust desert grass was one of many growing in a transition zone between a plant community of the creosote bush cover type of the Colorado Desert and a range community of the Joshua tree form of the Mojave Desert. The Society for Range Management (Shiflet, 1994) description of the Creosote Bush Scrub (SRM 211) specified that big galleta was frequently co-dominant with jumping cholla, burrow brush, and brittle bush.
This is the largest of five Hilaria species in North America. The inflorescences in the second slide can be compared with those of tobosabrass (H. mutica) shown under the Semidesert Grasslands series of the Grassland sets.
29.Whereas the previous hot deserts and the one cold desert in North America are "high deserts" elevation-wise, the Colorado Desert is a low elevation desert, and hence has an occasional and beautiful oasis like this one. California fan palm (Washingtonia filifera) pose a striking appearance against a desert sky as young cottonwoods (Populus fremontii), creosotebush, honey mesquite (Prosopis glandulosa var. torreyana), and the palatable cattle-spinach saltbush (Atriplex polycarpa) grow below to from a lush plant community. Twenty Nine Palms Oasis, Joshua Tree National Monument, California. June. This unique and distinctive but locally limited vegetation type was not described by SRM. Local variant of SRM 506 (Creosotebush-Bursage). Precisely identified by Brown et al. (1998) as Palm Series in Sonoran Riparian and Oasis Forest biotic community.
30.Palms at the oasis- California fan palms at the Twenty Nine Palms Oasis shown above. The immediately preceding slide showed the entire oasis community whereas these two slides featured the palms with part of the understorey dominated by honey mesquite and cattle-spinach saltbush. These mature palms their skirts due to a combination of shedding and human burning. Note mountain range behind the oasis in background of first slide.
Joshua Tree National Monument, California. June. Local variant of SRM 506 (Creosotebush-Bursage). Precisely identified by Brown et al. (1998) as Palm Series in Sonoran Riparian and Oasis Forest biotic community.
31.Fan crown- A crown of a large California fan palm planted outside its species range in the Phoenix Valley of Sonoran Desert. This native of oases in western parts of the Sonoran Desert, especially the Coloroado portion or section, has been widely planted as a horticultural ornamental eastward of its biological range. This individual and parts of fan palm crowns shown immediately below provided examples of inflorescences of this native desert palm. Maricopa County, Arizonia. July.
32.Inflorescences of California fan palm.- A fan palm planted eastward of its natural (species) range in the Phoenix Valley provided details of the large inflorescence of this member of the Palmae. Maricopa County, Arizonia. July.
33.Baby fans- Sexual reproduction of California fan palm in the Phoenix Valley. These seedlings demonstrated that this species can persist outside its natural species range. Cute little fellers to boot.. Maricopa County, Arizonia. July.
34. Blooming youngster- A young California fan palm (compare to mature fan palms shown above) was losing it skirt and showing off its inflorescences. This individual had grown from seed like those seedlings shown in the preceding photograph. Maricopa County, Arizonia. July.
35. Joshua Tree (Yucca brevifolia) series of the Mojave Desert forming a woodland appearance with a diverse understory of winterfat (Eurotia lanata), Nevada joint-fir (Ephedra nevadensis) and desert blackbrush (Coleogyne ramosissima). The Mojave is often interpreted as an ‘intermediate” desert, neither a hot scrub like previous deserts nor a cold desert like the Great Basin Desert soon to be seen. A higher elevation in parts of the Mojave retards domination of the range communities by the otherwise ubiquitous creosotebush. The magnificent Yucca specimens seen here are as old as 600 to 800 years. Joshua Tree National Monument, California. June. FRES No. 30 (Desert Shrub Ecosystem). One form of the extremely variable unit, K-35 (Creosotebush). SRM 211 (Creosote Bush Scrub) and 212 (Blackbrush), variation thereof. Mixture of Blackbrush Series and Joshuatree Series of Brown et al. (1998).
36. Leaves and fruits of Joshua tree (Yucca brevifolia)- This species has been interpreted as a tree (an arborescent woody plant) because it does have cambium and secondary growth (ie. increase in stem diameter). McMinn (1939, p. 51) included Y. braevifolia in his manual of Calfiornia shrubs but he described it as "commonly a tree". Yucca species are in the agave subfamily of the lily (Liliaceae).
Joshua Tree National Monument, Riverside County, California. June.
37. Mojave yucca or Spanish dagger (Yucca schidigera)- This is another Yucca species that has a trunk with secondary growth. The trunk of Yucca species (those species that have trunks) is a caudex, a short trunk or, more specifically, the stem root axis of a plant and commonly applied to trunks of monocotyledons. There are a number of Yucca species in southwesterrn North America that are referred to as Spanish dagger.
Joshua Tree National Monument, Riverside County, California. June.
38. The blackbrush series of the Mojave Desert— This is excellent range furnishing quality browse in blackbrush and tough but nutritious forage in big galleta, galleta, and desert needlegrass (Stipa speciosa). The smaller yuccas are Yucca schidigera. FRES No. 30 (Desert Shrub Ecosystem). K-33 (Blackbrush). SRM 212 (Blackbrush). Blackbrush Series of Brown et al. (1998).
39. Blackbrush (Coleogyne ramosissima)- Blackbrush is the dominant shrub over some range sites in the greater Great Basin region especially in the Mojave Desert. While blackbrush protects its branches and buds with spines and has small leaves it is often a valuable browse species. The Range Plant Handbook (Forest Service, 1940, B61) characterized blackbrush as having fair browse value and Dayton (1931, p. 55) noted that it provided some browse. Yeah, sure. Afterall the critters have to eat something, right? Joshua Tree National Monument, Riverside County, California. June.
40. Desert needlegrass (Stipa speciosa)- This robust cespitose species is a dominant grass in climax vegetation (ie. well-managed range in this case) of the Great Basin and Mojave Deserts, including the blackbrush cover type. Multiple-"guess" question: most species of ungulates prefer 1) blackbrush or 2) desert needlegrass. Rangeland cover type SRM 212.
Josha Tree National Monument, Riverside County, California. June.
41. Princes Plume (Stanlea pinnata)- This is an obligate selenium accumulator, a species of plant that requires selenium as a mineral nutrient for some physiological or metabolic role (or as an indicator of some unknown other factor that is required for survival and is closely associated with selenium). Prince's plume is thus an indicator plant. It indicates seleniferous soils. There are also facultative species or secondary selenium absorbers which do not require senenium (or some factor associated with selenium) but which do absorb selenium when they grow on seleniferous soils. Facultative species are not indicator species because they will grow on non-seleniferous soils also.
Selenium toxicity is one of the well-studied kinds of animal (and, possibly, human) poisoning. Viewers are referred to the classic text, Poisonous Plants of the United States and Canada (Kingsbury, 1964, ps. 44-50). Fortunately, this beautiful plant does not cause livestock poisoning on range or pasture because animals will not eat it if they are starving (Kingsbury, 1964, p. 169). It is just another interesting and attractive range plant. Incidentially, every serious student in Range Management should have a copy of Kingsbury (1964) on his shelf. Dinosaur National Monument, Unita County, Utah. June.
42. Inflorescence and fruits (siliques) of prince's plume, an obligate selenium accumulating-crucifer- Joshua Tree National Monument, Riverside California. July.
43.A large playa— Soda Lake surrounded by creosotebush-dominated communities. As there is little or no drainage from most of the basin and range province, large and salty playa lakes frequently form. This one supports a healthy population of the endangered or rare fish, Mojave tui chub (Gila bicolor mohavnsin). San Bernardino County, California. FRES No. 30 (Desert Shrub Ecosystem). K-35 (Creosotebush). SRM 211 (Creosote Bush Scrub).
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