Aspen Types

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1.Quaking Aspen (Populus tremuloides) grove— the tree growth form of "quakies" producing an obvious forest type with an understory that is almost exclusively forbs, including poisonous ones. Note the infamous false-hellebore or corn lily (Veratrum californicum) which causes the cyclops lamb tetrogenicity when eaten by ewes on the fourteenth day of gestation. The toxic western larkspur (Delphinum occidentale) is also common , but so are valuable forage forbs like Richardson's geranium (Geranium richardsonii).Routt National Forest, Jackson County, Colorado. July, peak estival aspect.There are no FRES or Kuchler Numbers for this cover type. FRES No. 19 (Aspen-Birch Ecosystem) would be a rough guide, but all the Kuchler equivalents therein are seral stages whereas quaking aspen does on some sites, as illustrated here, form populations that are not seral. On other sites quakies are clearly seral to spruce and fir climaxes such as those shown in the four preceeding slides. In cases of the latter, quaking aspen can exist as a fire-maintained type. The quaking aspen parkland as representedhere covers vast acreages in parts of Canada and the inland Northwest of the United States where it is scattered throughout or among grassland communities often as a boundary between grassland and the boreal coniferous forest or, at lower latitudes, Douglas-fir and pines like lodgepole and ponderosa. Quakies comprising most of these more northern aspen groves are shrubs. The stature and growth form of those quakies qualifies as a shrubland cover type and could as correctly be shown under the shrublands section. All quaking aspen types were placed here for convenience and to avoid confusion.

Approximate FRES No.19 (Aspen-Birch Ecosystem). SRM 411 (Aspen Woodland).SAF 217 (Aspen). Populus tremuloides subclimax Association in ecotone between Douglas Fir-White Fir (Mixed Conifer) Series and Yellow Pine Series of Brown et al. (1998, p. 37).

2. Interior of the quaking aspen grove shown in the preceding slide— Note abundance of false-hellebore and western larkspur. Note also bark-browsing by elk (Cervus elaphus= C. canadensis) as for example the scar and blackened bark on the largest trunk in center but not overbrowsing that prevents the visible regeneration of aspen. Routt National Forest (astraddle the Continental Divide), Jackson County, Colorado. July. No FRES or K- designations. Approximate FRES No.19 (Aspen-Birch Ecosystem). SRM 411 (Aspen Woodland); SAF 217 (Aspen). Populus tremuloides subclimax Association in ecotone between Douglas Fir-White Fir (Mixed Conifer) Forest Series and Yellow Pine Series of Brown et al. (1998, p.37).

3. Numerous plant communities comprising several range vegetation types—Beginning in foreground there is subalpine meadow of bluegrasses, hairgrasses, sedges, etc. Then a quaking aspen colony (far right) through to a conifer woodland of Douglas fir, lodgepole pine, and Englemann spruce.Next, slopes of talus (accumulated unstable rock fragments below steep slopes or cliffs; fragments accumulate and sort out by gravity with largest at the base) and scree (the same as talus except the accumulations are of smaller-sized fragments usually less than that of a tea cup). Finally on to alpine on top of distant peaks. The aspen and coniferous belt contains grassy patches among the scattered trees resulting in parkland, a form of savanna made up herbaceous communities interspersed among small colonies of shrubs and trees. Absence of fire has allowed increased cover of conifers, especially Douglas fir. These woody invasions constitute varying states of range retrogression. Glacier National Park, Montana. July.

4. A young colony of the clonal quaking aspen in competition with the graminoids of a subalpine mountain meadow— Browsing by elk has helped maintain a mixture of these shrubs and herbaceous plants that creates aspen parklands. Glacier National Park, Montana. July. Shrub variant (shrub growth form) of SRM 411 (Aspen Woodland)or SAF 217 (Aspen). No FRES or K- designations.

5. Interior of a quaking aspen grove- Many such local shrublands are scattered over rough fescue grassland to form aspen parklands, one of the largest and most widespread savannas in North America. Most of these groves or colonies are probably one tree, a single genetic individual, growing as a clonal organism.Waterton Lakes National Park, Alberta. July. This range vegetation type would likely be categorized most precisely as shrubland, a semiarid (not desert) scrub, and not as forest or woodland. For ease of location and consistency of species (consociation) placement all quaking aspen types were placed here. Scrub variant of SRM 411(Aspen Woodland) or SAF 217 (Aspen).

6. Quaking aspen grove- This is another example of a grove of quakies showing the physiogonomy and structure of a relatively young stand. It was growing just above a small stream at the base of a large hillside covered with a mountain big sagebrush (Artemisia tridentata subsp.or variety vaseyana) shrub steppe. Species in the aspen understorey were primarily those of the sagebrush shrub steppe including mountain big sagebrush several individuals of which were growing in the center foreground at the edge of the grove.

Grand County, Colorado. June. It was explained in the first caption of this series that there was no specific FRES or Kuchler Number for quaking aspen. FRES No.19 (Aspen-Birch Ecosystem) was as close as possible. SRM 411 (Aspen Woodland). SAF 217 (Aspen). Populus tremuloides subclimax Association in Douglas Fir-White Fir (Mixed Conifer) Forest Series of Brown et al. (1998, p. 37). Southern Rockies- Sedimentary Mid-Elevation Forests Ecosystem 21f (Chapman et al., 2006).

7. Interior of quaking aspen grove- Inside the grove of quaking aspen shown in the preceding slide. Species in the herbaceous understorey included timber oatgrass (Danthonia intermedia), Idaho fescue (Festuca idahoensis), cheatgrass (Bromus tectorum), Sandberg bluegrass (Poa secunda= P. sandbergii), and an unidentified species of lupine, all of which were at prebloom stage. Growing immediately adjacent to the boundary of the grove and adjoining mountainbig sagebrush steppe (ie. along the edge of the two range cover types) was squirreltail bottlebrush (Sitanion hystrix) and the prominent forb, false helleborne. The latter was introduced in the first slides of this series.

Grand County, Colorado. June. Approximate FRES No.19 (Aspen-Birch Ecosystem). SRM 411 (Aspen Woodland). SAF 217 (Aspen). Populus tremuloides subclimax Association in Douglas Fir-White Fir (Mixed Conifer) Forest Series of Brown et al.(1998, p. 37). Southern Rockies- Sedimentary Mid-Elevation Forests Ecosystem 21f (Chapman et al., 2006).

In the author's observations (emperical not experimental) the understorey of quaking aspen groves varies greatly, even over remarkably short distances, depending on the species in adjacent or proximate plant communities where the surrounding vegetation is the dominant cover type of that general location. This observation obtains for scattered groves of quaking aspen in a matrix of other range type(s) and not where aspen is the general dominant range type for that location (not for instance where aspen parkland covers vast expanses and is the regional climax, the climatic climax at regional scale). Where aspen groves occur at elevations at or just above the ponderosa pine zone the aspen understorey tends to have the less mesic grasses and forbs of the pine forest whereas when aspen grows at higher elevations up into the Englemann spruce-subalpine fir forest the aspen grove understorey has the more mesic and shade-tolerant herbaceous species of the latter forest. (Or, as shown immediately below, quaking aspen is seral to the spruce-fir forest.). In the preceding example where the small aspen stand grew in a matrix of mountain big sagebrush steppe the dominant understorey species were those of the shrub steppe.

The successional status of quaking aspen for a given habitat (ie. on a specific sere) may be even more important in determining species composition and structure of the understorey. Aspen groves (or even the larger spatial scale of aspen woodland) might have a different understorey depending on whether aspen is a seral or the terminal stage of plant succession on a given range site or habitat type. An example was shown in the next slide which can be compared with those of other groves in this series.

An excellent source on maintenance of quaking aspen is the symposium proceedings compiled by Shepperd et al. (2001).

8. Yikes, we're being invaded!- A seral stand of young quaking aspen (Populus tremuloides) being invaded by Engelmann spruce and subalpine fir. This drama of Frederic Clements "dynamic vegetation" was on the boundary between upper montane and subalpine zones. Sucessional replacement of the "quakies" by spruce and spruce is the fate of seral aspen communities at elevations of subalpine forests Beidleman et al., 2000, ps. 14-15).

This process was probably accelerated by extremely heavy browsing by Rocky Mountain elk (Cervus canadensis subsp. nelsoni) which was obviously stressing some of the aspen shoots as was apparent in the second of these two photographs (this second slide was a closer-in version of foreground in the first slide).

Rocky Mountain National Park, Larimer County, Colorado. Mid-June (late vernal aspect). FRES No.19 (Aspen-Birch Ecosystem). SRM 411 (Aspen Woodland). SAF 217 (Aspen). Populus tremuloides subclimax Association in Douglas Fir-White Fir (Mixed Conifer) Forest Series of Brown et al.(1998, p. 37). Succession is taking this to: FRES No. 23 (Fir-Spruce Forest Ecosystem). K-14 (Western Spruce-Fir Forest). SAF 206 (Englemann Spruce-Subalpine Fir). Enlgemann Spruce-Alpine Fir Series of Brown et al. (1998). Southern Rockies- Crystalline Mid-Elevation Forests Ecoregion, 21c (Chapman et al., 2006).

Shown immediately below were several conspicuous understorey species in quaking aspen groves. Some of these were growing on mesic sites such as along streams where Douglas-fir was also found while others were on drier upslopes as in big sagebrush steppe. Relative soil moisture content was noted for the specific species.

9. Stand of quaking aspen being invaded by Englemann spruce and Colorado blue spruce- The successional status of quaking aspen is very much site-dependent, a fact that has often been overlooked when arguments have arisen where aspen was replaced by other species. Yes, indeed sometimes such replacement was due to improper management as when overbrowsing by livestock or big game resulted in loss of quakies and their replacement by herbaceous species or where underburning (or complete fire exclusion) allowed less fire-adapted shrubs and trees to invade stands and ultimately replace the aspen.

Ecologists may never understand completely the dynamics of such vegetational development. It is known that quaking aspen is the potential natural vegetation or climax where it forms extensive parklands in more northern regions. At the other end of plant succession aspen is sometimes a pioneer species that colonizes disturbed areas. This latter pehnomenon would apply to secondary not primary succession. It is also known that on some habitats quakies are seral to coniferous forests. One of the best known examples of this latter successional pattern is where (again, on some sites) quaking aspen is seral to the climax Englemann spruce-subalpine fir forest. That condition was shown in this photograph.

An old stand of quaking aspen was being invaded mostly by Englemann spruce and Colorado blue spruce with some limber pine (Pinus flexilis) also appearing to become established. (The pine saplings were too small to be relicts of the same age as the aspen.) Quaking aspen (along with cottonwoods) was ranked by the Society of American Foresters as Very Intolerant, the least tolerant of any western hardwood, whereas Englemann spruce was ranked as Tolerant and subalpine fir was Very Tolerant (Wenger, 1984, ps. 3-4). Where the site potential will support spruce-fir forest it is inevitable that these species will eventually replace the quakies, unless of course repeated disturbances like fire and avalanches prevent progression of plant succession.

The two young conifers in the far right foreground were Englemann spruce and the conifers in the background were the famed Colorado blue spruce. No subalpine fir were found and there were no adult subalpine fir trees present within the immediate vicinity. Blue spruce were more common downslope and Englemann spruce more abundant upslope from this forest stand, as was the limber pine which grew in association with the spruce-fir forest at higher elevations as the spruce and fir gave way to limber forests.

Readers can find a straightforward discussion of the natural history of quaking aspen groves in Mutel and Emerick (1992, ps. 141-151). These authors presented a very readable account of this community (both plant and animal) that will help students understand basic structure, composition, and dynamics of this forest or shrubland type.

Succesional sequel- The following four slide-caption set sequence was of the same stand of quaking aspen being invaded by Engelmann and Colorado blue spruce as shown immediately above-- except sixteen years later. This sequential set began with the same photopoint as shown in the preceding photograph.

10. Some of us grew; some of us only grew older- The same photgraphic point of a grove of quaking aspen being invaded by Engelmann and Colorado blue spruce as shown above-- sixteen years earlier. Oviously the conifers have grown (some of them considerably) while the existing aspen shoots have senesced (slowily dying following shoot maturity) and only a few new aspen shoots were produced (ie. senescence combined with lack of regeneration). This asexual reproduction of the "quakies" was limited to the perimeter of the grove so that there was some incremental expansion of aspen around outer edges while conifers were "banishing" (overwhelming) the senescing aspen shoots. With on-going plant succession conifers (primarily Colorado blue spruce) were in the process of "ousting" the quakies" and laying claim to the sere, specifically the interior of the aspen grove. Even previously existing lodgepole pine had grown and new seedlings and saplings of lodgepole pine had invaded (established).

Growth rate of all these trees had been relatively slow in the continental climate of the Southern Rocky Mountains with long, cold winters and short, cool summers. This slow growth of all tree species can be easily ascertained by comparison of this photograph with the one of sixteen years earlier seen immediately above. Nonetheless, increase in size of trees (height, diameter breast height, canopy cover) was visibly greater in conifers, especially blue spruce, than in quaking aspen. Furthermore (and ultimately more important) was the greater rate of regeneration of conifers relative to aspen, the latter of which was nearly nil. It was obvious what the successional outcome would be over time, the time period of forest development. That is, of course, unless some other factor(s) changed the trajectory of forest community change (see below).

Quaking aspen, as was detailed above, is a clonal organism. This aspen grove was mostly--if not exclusively-- one tree (one clone= one genetic individual, one genotype) of numerous shoots. The "trunk" of the tree is a rhizomatous system with "trees" in the grove being shoots ("limbs" or "branches") off of the underground "trunk". In absence of a regenerating "disturbance" such as fire or avalanche the aging aspen clone became a maturing (and slowly dying) grove of old "trunks" (shoots).

Meanwhile, individuals of the two coniferous species (single trees of a genotype, a unique genetic individual conifer) continued to grow and increase in size and crown cover (trees got taller with larger crowns of bigger and more branches with more needles), plus with some sexual reproduction (seed production). In the sixteen year interim between time of forest vegetation shown in the preceding photograaph and that seen in this (and subsequent) photographs Colorado blue spruce had "outdistanced" Engelmann spruce and had come to dominant the developing forest. More lodgepole pines had established (invaded) in the perimeter of the advancing aspen grove.

As new shoots of "quakies" grow and mature around the perimeter of the grove, Colorado blue spruce and Engelmann spruce along with loegepole pine will invade that land and displace (replace) aspen through plant succession.That is, this successional sequence, this profression of plant succession and conifer forest development, would continue if some other factor or phenomenon did not interfere. More on that phenomenon below ...

Rocky Mountain National Park, Larimer County, Colorado. Early July (earrly estival aspect). Formerly this forest vegetation fit the following approximate units: FRES No.19 (Aspen-Brich Ecosystem), SRM 411 (Aspen Woodland), SAF 217 (Aspen),. Populus tremuloides subclimax Association in Douglas Fir-White Fir (Mixed Conifer) Series of Brown et al. (1998). Sixteen years later the forest had undergone progression (plant succession) on the sere to the extent that the range vegetation now more closely fit the following units: FRES No. 23 (Fir-Spruce Ecosystem). K-19 (Spruce-Fir-Douglas-fir Forest). SAF 216 (Blue Spruce) locally at elevation just below the zone of SAF 206 (Englemann Spruce-Subalpine Fir). Englemann Spruce-Alpine Fir Series of Brown et al. (1998). Southern Rockies- Sedimentary Subalpine Forests Ecoregion, 21e (Chapman et al., 2006).

11. Coming on strong and slowing going out- Exterior (general) and interior views--first and second photographs, respectively--of a grove of quaking aspen, the adult shoots of which were senescing faster than reproduction (which would have mostly asexual) of new shoots necessary to replace mature ones and maintain the population. Concurrently, Colorado blue spruce was on tract to become dominant (with some Engelmann spruce and lodgepole pine as associate species) as existing trees of these species advanced in age, size and relative canopy cover as well as having sexual regeneration so as to expand their presence and cover into parts of the grove previously unoccupied by them.

This upper montane, east-slope forest was moving via plant succession from an aspen grove to a conifer forest dominated by blue spruce. There had been some regeneration of aspen--as seen in foreground of first photograph--on the outer margin of the grove, but there had been essentially no (certainly very litttle net) regeneration of aspen in the interior of the grove. Meanwhile, the conifers (again, mostly Colorado blue spruce) were continuing to grown, reproduce, and increase their relative canopy cover throughout this forest community including at the margin or outer extremity of the forest as seen clearly in the second photograph. Conifers at the exterior of this forest (second photograph) where it was advancing into (invading) a wet meadow ranged from larger seedlings to saplings and included both blue spruce and lodgepole pine. New aspens (clonal shoots or sexual seedlings/saplings) were absent from the leading edge. The "quakies" have had it--unless something changes.

Rocky Mountain National Park, Larimer County, Colorado. Early July (earrly estival aspect). FRES No. 23 (Fir-Spruce Ecosystem). K-19 (Spruce-Fir-Douglas-fir Forest). SAF 216 (Blue Spruce) locally at elevation just below the zone of SAF 206 (Englemann Spruce-Subalpine Fir). Englemann Spruce-Alpine Fir Series of Brown et al. (1998). Southern Rockies- Sedimentary Subalpine Forests Ecoregion, 21e (Chapman et al., 2006).

12. Overwhelmed- Adult Colorado blue spruce grrew up through quaking aspen which senesced and died out (perhaps partially reduced due to competition with the conifers) so that the previus aspen grove (SAF cover type 217 SRM cover type 411) was converted through plant succession to blue spruce fores (SAF cover type 216).

This was a local stand in the larger aspen grove shown above. It was the part of tht grove that had moved farthest on this sere (forest site) toward coniferous forest and away from the previous advanced seral stage of the quaking aspen cover type. A spring or water seepage characterized and distinguished this local habitat of the sere (most precisely it was a wet hill slope microsite) so that it was the wettest part of the (former) aspen grove.

Eyre (1980, ps. 95-96) interpreted the blue spruce forest cover type as "subclimax" that typically was replaced (succeeded) by the Engelmann spruce-subalpine fir cover type.It was further explained that the blue spruce type (SAF 216) was a relatively restricted type that was present as climax only along streams, where forest edges met meadows, on "low moist soils", or "subirrigated slopes", The latter three of these conditions existed on the land on which this stand of maturing blue spruce had developed. Furthermore, this forest vegetation was on an east slope so as to be more mesic to begin with.

It was predictable that successional advance from quaking aspen to blue spruce-dominated coniferous forest would be most rapid on this wet hillside. Wet edaphic conditions probably also explained why blue spruce was dominant instead of Engelmann spruce (or even subalpine fir) which dominated higher elevation forests immediately above this developing forest.

13. Come and go, give and take- Another view of the advancing margin of a mesic, high montane forest on which conifers (namely Colorado blue and Engelmann spruce with some lodgepole pine) were replacing quaking aspen with the progression of plant succession (ie. aspen is seral to a blue spruce climax or subclimax on this forest site). This forest was on an east slope and invading a wet meadow.

Immediately obvious was the absence of any quaking aspen reproduction (neither asexual or clonal shoots nor new trees as seedlings or saplings) accompanied by abundant reproduction of both Colorado blue and lodgepole pine (foreground). Higher up on this east slope Engelmann spruce of sapling and small pole sizes were abundant.

Engelmann spruce and lodgepole pine were also in trouble. In spite of regeneration of these two conifers a widespread catastrophic outbreak of spruce (or spruce bark) and pine (pine bark) beetles (Dendroctonus species) had decimated populations of Engelmann spruce and lodgepole pine throughout this region. Plus, bark beetles were continuing to kill many and, in local areas, most of the few remaining trees. Some beetle-killed, pole-size Engelmann spruce were visible in this photograph (midground). These Dendroctonus species are native insects. For millenia bark beetles have functioned as natural disturbances that displaced climax conifers and set secondary plant succession into motion. Impact of the Dendroctonus decimation on Engelmann spruce-subalpine fir, lodgepole pine, and ponderosa pine climax forests in this area were described earlier in this chapter.

Bark beetle herbivory--again, a natural disturbance--was a phenomenon that was favorable to the seral quaking aspen. Examples of this were shown above. Aspen were still "not out of the woods", however, because excessive defoliation, overbrowsing by elk had been a major factor in preventing reproduction (sexual and asexual) of quaking aspen along the advancing edge of this forest. The result was that woody invasion of the wet meadow downslope from the established forest had been limited to that by conifers. The natural pattern of forest succession was interrupted by elk overbrowsing so that blue spruce, Engelmann spruce, and lodgepole pine were establishing without having to replace aspen (and perhaps without facilitation by this seral species).

Another sure sign of heavy browsing by elk were the many glaring scars on aspen trunks resulting from "barking" (bark feeding) by this generally grass-preferring cervid. This showed up well on this photograph. Close-up photographs of bark scars were presented in the immediately two succeeding slides.

Herbivory by bark beetles had slowed the advance (and were still in process of slowing) invasion of the wet meadow except Colorado blue spruce had yet to be impacted by Dendroctonus species. Smaller trees (seedlings and saplings) of affected conifer species typically are not fed on by bark beetles. Hence, conifers of these age/size classes were still alive at advancing (invading) edge of this forest (foregroung of photograph). Would bark beetle populations subside to normal level so that these young trees would reach adulthood? Would the wet meadow ecosystem survive or would it become a coniferous forest (or maybe woodland or savanna)? Only God knows and time alone will tell.

14. Elk-carved totem pole- Bark scars on trunks of adult quaking aspen at the edge of a senescing aspen grove that had expanded down an east slope and invaded a wet meadow. Elk prefer herbaceous plants, especially grasses and grasslike plants, but they are opportunistic and diverse feeders that readily consume browse. Quaking aspen are a preferred elk browse plant. Leaves, buds, and young shoots appear to be the more preferred parts of aspen, but elk readily feed on aspen bark. Bark-feeding has appeared to be more widespread under conditions of high stocking rates of elk, especially at levels regarded as overbrowsing.

Feeding on new clonal shoots by elk had unquestionably retarded--in fact, at this location elk overbrowsing had completely precluded--aspen regeneration. In combination with ample reproduction of blue spruce, lodgepole pine, and, at lower rates, Engelmann spruce this grove of quaking aspen was moving rapidly via plant succession to a blue spruce forest. (This was explained immediately above.)

The small shrubs in these two photographs (especially the first slide) were alder (Alnus incana), a riparian species that was locally abundant in the wet meadow at the edge of and immediately below this aspen grove that was becoming a forest dominated by Colorado blue spruce. The yellow-flowered forb on ground layer was heartleaf arnica.

Commonly, quaking aspen quickly replaces bark removed by browsing elk. That was evident from these two photographs. Extremely "deep browsing" by elk below bark and into cambium results in much slower healing wounds. Two such wounds were visible in the shoot shown in the first of these slides. Also noteworthy in this slide was the small snag of a sprout (offshoot, clonal shoot) produced by this adult, parent shoot and promptly killed by elk overbrowsing. Again, an overpopulation of elk and consequent overbrowsing had virtually stopped aspen regeneration.

The disgrace of this unacceptable management was on a national park! Rocky Mountain National Park should be opened to sport hunting or else culling by government employees such as personnel of Animal Damage Control in the United States Department of Agriculture. Establishment of native predators, especially the grey wolf (Canis lupus), might eventually result in reduction of elk numbers in Rocky Mountain National Park. If and until such natural population control occurs human intervention by hunting (culling) is absolutely essential for proper use of range resource and the general Southern Rocky Mountain ecosystem.

Degradation of quaking aspen range by elk-overbrowsing has received--quite justifiably--much attention, by range and wildlife researchers. Range investigators found that heavy utilization and, especially, overbrowsing of quaking aspen is compounded by (and conclusions confounded with) invasion of aspen groves by conifers. One thorough study of this dual threat to "quakies" in the Southern Rocky Mountains was conducted in Rocky Mountain National Park and Roosevelt and Arapahoe National Forests, two large neighboring parcels of public elk range (Kaye et al., 2005). In addition to its original research (which demonstrated what any observant and impartial observer already knew), this paper by Kaye et al. (2005) provided a thorough bibliography of this on-going threat to and, on all-too many ranges, loss of natural vegetation and wildlife habitat.

15. Heartleaf arnica (Arnica cordifolia)- This low-growing composite is one of the more common forbs in the understorey of quaking aspen groves and woodlands in the Southern Rocky Mountains. These specimens grew on a relatively moist lowland site within 50 yards or so of a stream. Their neighbor was the next forb shown. Roosevelt National Forest, Jackson County, Colorado. June.

16. Colorado or blue columbine (Aquilegia caerulea)- The State Flower of the Centennial State is one of the forbs growing most consistently in quaking aspen groves though not usually in large numbers (but like women it does not take many when you're this good-a-lookin'). Beginning students should take note of the leaf shape of this member of the Ranunculaceae (the buttercup or crowfoot family). This same general pattern of palmately compound leaves, usually with a partly enclosing sheath-like basal leaf, is a consistent characteristic of this family. Roosevelt National Forest, Jackson County, Colorado. June.

17. Shoot apex and detail of inflorescence of blue or Colorado columbine- Students should also pay attention to the basic structure and arrangement of parts of the inflorescence of the columbine. There are numerous range and forest forbs that are members of the buttercup family including larkspur (Delphinium spp), marsh marigold (Caltha spp.), wind flower (Anemone spp.), and Clematis spp. Some of these genera are especially common in the Rocky Mountains, both in various forest zones and the alpine. Other of these genera commonly occur on grasslands including the eastern prairies and the deciduous forests like the oak-hickory type. Roosevelt National Forest, Jackson County, Colorado. June.

18. Rocky Mountain locoweed, white loco, or silky crazyweed (or other combinations of these descriptive words)- Oxytropis sericea is another showy forb found in aspen groves and, in particular, along edges of groves. This robust example was growing where an aspen grove adjoined a subalpine mountain meadow. The pigmented spot on the keel of this papilinaceous legume allowed positive identification to this rather varied species.

Oxytropis is one of the more intriguing genera of poisonous range plants, and O. sericea has figured prominently in the saga. Some Oxytropis species and some of the Astragalus species are classic locoweeds, those that induce locoism or loco poisoning. This condition has been the subject of scientific study for over a century. The poisonous principle was identified as a group of indolizidine alkaloids. Summary coverage was provided by Cheeke and Shull (1985, ps.142-146). Recently O. sericea has been implicated in big brisket, high mountain disease, or congestive right hear failure. For detailed recent treatment see Burrows and Tyrl (2001, ps. 594-599). And never forget Kingsbury (1964, ps. 306-311). Investigations with Oxytropis, including O. sericea, have been reported consistently in the peer-reviewed proceedings of the International Symposium on Poisonous Plants. Readers with a joint enjoyment of Chemistry, Botany, and Range Management can get a full-course feast there. The subject of poisonous range plants has long fascinated those who study and report on "things range". The current writer was no exception.

Rocky Mountain National Park, Larimer County, Colorado. June.

19. Inflorescence of elephant head or little red elephant (Pedicularis groenlandica= Elephantella groenlandica)- This is another showy member of the aspen community (and adjoining forest cover types such as interior Douglas fir). Elephant head was described in both Notes on Western Range Forbs (Hermann, 1966, ps. 264-266) and Range Plant Handbook (Forest Service, 1941, p. W143) where it was described as usually no higher than Fair forage for small ruminants. It is very distinctive and adds species diversity to range plant communities. Elephant head is an easy one to learn (and to impress others with one's knowledge of native plants). This one grew along the edge of an aspen grove in association with cowparsnip (Heracleum lanatum).

Rocky Mountain National Park, Grand County, Colorado. Early August.

20. Cow parsnip (Heracleum lanatum)- This rank-growing rascal is common along mountain streams throughout the Rockies. Where aspen groves are associated with springs, seeps, streams, etc. cow parsnip is a large conspicuous forb of the aspen cover type. Rocky Mountain National Park, Grand County, Colorado. July.

21. Inflorescence of cow parsnip- Cow parsnip is one of many members of the Umbelliferae (=Apiaceae). This traditional name of this family comes from the distinguishing feature of the umbel type inflorescence. An umbel is a more-or-less flat-topped or umberella-shaped indeterminate inflorescence having all the flowers borne on pedicels of approximately equal length and arising from a common point. This arrangement results in the characteristic "umberella" of flowers as seen here. Rocky Mountain National Park, Grand County, Colorado. July.

22. Fruit of cow parsnip- This portion or section of a cow parsnip inflorescence was bearing fruit. This fruit type is a schizocarp, a dry indehiscent fruit from a syncarpous (having two or more fused carpels, the ovule-bearing structures of the flower) gynoecium, in which the carpels separate from each other into one-seeded segments. Montplier Canyon, Caribou National Forest. Cache County, Utah. July.

23. False helleborne or cornhusk lily (Veratrum tenuipetalum)- According to some of the more recent treatments (eg. Weber and Wittmann, 2001) this is the only species of Veratrum found in the Southern Rocky Mountains in Colorado, but previous work (eg. Dayton, 1960) reported that western false hellebore (V. californicum) occurred in Colorado and, in fact, in all of the 11 Western States. From the current author's observation V. californicum has broadly ovate leaves that are clearly distinct from the lanceolate leaves of the individuals shown here which were therefore designated as V. tenuipetalum. More importantly from this authors perspective was presence of the numerous conspicuous lanceolate leaves on the flower stalk of these plants in contrast to the leafless rachis of the ovate-leaved plants displayed immediately below.

The plants presented in this slide were representative of many growing prolificly at the edge of a the last grove of quaking aspen shown above (Grand County, Colorado). The toxicological property of Veratrum species and the resultant phenomenon of the cyclops lamb was noted in the first caption of this quaking aspen series. The most recent comprehensive reference tretment was that of Burrows and Tyrl (2001, ps. 782-787). These authors did not list V. tenuipetalum but discussed all Veratrum species as toxic. They too showed V. californicum as native to Colorado, western Colorado.

Grand County, Colorado, Colorado. June.

24. Western false helleborne or corn lily (V. californicum)- The broadly ovate leaves of these plants appeared to to this author to be distinctly different from those examples shown immediately above. Even more definitive was the presence of the lanceolate leaves all along the flowering stalk of the plants your author labeled V. tenuipetalum immediately above and the leafless rachis of the plants shown here and labeled V. californicum. Yes, indeed these species-- as interpreted by your author-- both grew in northern Colorado and in adjoining large counties, but the two were on opposite sides of the Continental Divide. The species shown here was on the West Slope and the one shown above on the East Slope. Numerous plant species have been distinguished and separated out on the basis of morphological features much less distinctive and obvious that these, and with less geographic separation than that of the Great Divide. In the first comprehensive maunal of Colorado plant life, the classic Flora of Colorado, Rydberg (1906, p. 76) showed both of these species (V. speciosum was used as the synonym for V. Californicum). Rydberg separated them on oval versus oblong-lanceolate petals. This might be a good research project for some budding plant taxonomist.

One last lesson from this example, the author bought a copy of Rydberg's Flora of Colorado that had been discarded from, first, the University of Montana and, next, Montana State University (discarded stamps from both institutions). Do these two universities, both of which have programs in Forestry and Range Management, have another copy? Just because a book is a century old does not mean it is no longer valid or of use. The currently commonplace practice of discarding texts and references by university libraries based on nothing but copyright dates and how many times the book was checked out is as stupid and short-sighted as it is sinful to knowledge. Oh yes, of course there is inter-library loan. This author can tell you about that too.

The specimens presented here grew inside of and all around the quaking aspen grove shown in the first two slides of this series (Routt National Forest, Jackson County, Colorado, July).

25. Aspen grove in the park- Woodland or open forest of quaking aspen with an herbaceous understorey dominated by Arizona fescue along exterior of the grove and by mountain muhly in the interior of the grove. Letterman's needlegrass and Thurber's fescue were important associate and indicator species, respectively, that varied in abundance and relative cover at local scale. Forbs were non-existant for all practical purposes.

The first of these two photographs was taken from the edges of this quaking aspen grove and a montane, bunchgrass prairie dominated by Arizona fescue which was climax vegetation and contiguous with the aspen grove. This was the outer margin of the mountain prairie or steppe (a subalpine "park" in local and traditional parlance) so that the photograph included both range plant communities. Montane grassland at this location was a relict of the Arizona fescue-mountain muhly-Letterman's needlegrass-galucous or timberline bluegrass steppe (bunchgrass, cespitose grasses, prairie). Immediately across a state highway the rest of this montane steppe ("park") was a livestock range that was degraded with evidence of previous and severe spot grazing. On this side of the highway this relict tract of Arizona fescue-mountain muhly grassland and quaking aspen woodland did not have obvious impacts of past livestock grazing although use by livestock had almost assuredly taken place in the not-too-distant history of this range vegetation. There was a narrow though pronounced clearing through the aspen grove (left side of this first slide) where a power or utility line formerly ran through the stand of "quakies". The electricity transmission lines had been removed within the last few years and "quakies" had not yet repopulated the narrow corridor previously kept clear of woody growth. The herbaceous component in the power line clearing was of the same composition and physiogonomy as that of the pristine tract of steppe. It would soon share the land with offshoots (new asexual shoots) of aspen.

Small shoots of quaking aspen in the foreground of the two slides were invaders into the relict pristine grassland. These shoots could have been separate trees (genetic individuals) produced from wind-dispersed seed rather than "suckers" or vegetative shoots from the existing tree(s) of the grove. [Discussion of asexual reproduction or the clonal feature of quaking aspen was discussed in the caption for the last slide covering this example of quaking aspen-dominated vegetation.]

The second of these two photographs was of range vegetation farther inside the aspen grove (away from exterior of aspen stand). Mountain muhly was the dominant herbaceous species at most local spots inside the grove (beneath aspen cover) with Letterman's needlegrass and Arizona fescue generally vying for associate status. There were some plants that appeared to be Thurber's fescue. All grasses were still in early to mid-stages of development so identification had to be based on vegetative features which, incidentally, this author was not familar with having not worked closely with these species.

This example of quaking aspen range was in South Park in contrast to an aspen grove shown above that had an understorey of timber oatgrass and Idaho fescue at lower elevation in foothills of a mountain range.

FRES No.19 (Aspen-Brich Ecosystem). SRM 411 (Aspen Woodland). SAF 217 (Aspen). In Brown et al. (1998, p. 37): Rocky Mountain Montane Conifer Forest (122.6), Yellow Pine Series (122.62), Populus tremuloides subclimax Association (122.628). Mountain Outwash range site. Aspen ecological series (10), with Arizona Fescue ecological series (19) and Thurber Fescue ecological series (20), in part (Johnson et al., 2001). Southern Rockies-Grassland Parks Ecoregion 22j (Chapman et al., 2006).

26. In the grove's interior- View of the innermost portion of a grove of quaking aspen with a well-developed herbaceous layer composed almost entirely of perennial bunchgrasses. The grass species that comprised the herbaceous layer of this range plant community included Arizona fescue which was the dominant grass on the perimeter of the grove (visible as the tall, straw-colored, sexual shoots from last year), mountain muhly which was the dominant to co-dominant grass (with Arizona fescue) in the interior of the grove, Letterman's needlegrass which was mostly in the interior of this community (sometimes as associate species), and, least of all, Thurber's fescue. Parentage of tree trunks (shoots) could not be determined on the range, but probably all of these were offshoots or "suckers" from the huge network of rhizomes beneath this grove.

A valuable treatment of the clonal concept of Populus species, including an actual map of a root system of P. tremuloides, was that of Barnes (1966). Other sources were cited in the last caption (below) devoted to this particular aspen grove.

27. At the groves exterior- On the outer margin of a grove or small woodland of quaking aspen where it abutted a climax bunchgrass prairie dominated by Arizona fescue with montain muhly, Letterman's needlegrass, and Thurber fescue (in that relative order) as other decreaser (climax) grasses. Arizona fescue was conspicuous as the tall, leaning, bleached shoots from last year some of which still retained the rachis of the panicle (foreground). Forbs were not present--at least at a mentionable cover or proportion--in either the aspen grove or the montane bunchgrass prairie.

This portion of subalpine grassland or "park" was the perimeter of a much larger area of bunchgrass prairie (complete with mima mound microtopography) that was part of a deteriorated range that was on the opposite side of a state highway. The montane or subalpine grassland that was degraded (severe spot grazing throughout) had several species of forbs as well as glaucous or timberline bluegrass (Poa glauca var. rupicola) all of which were absent from both the relict tract of climax steppe (bunchgrass prairie) and the herbaceous component of the quaking aspen woodland.

A note on organization and location: The example of Arizona fescue-dominated montane or subalpine grassland that was conterminous with this quaking aspen grove was covered in the Mixed Prairie chapter of Grasslands. While this arrangement might cause some initial confusion it was the most logical or rational organization because it allowed the grouping of range plant communities by biome, the largest, most general hierarchial level of natural plant community. Aspen-dominated range types (SRM 411; SAF 217) were grouped in a separate chapter within Woodlands and Forests, the forest biome, while mountain grasslands--even when they touched (spatially joined) forest vegetation--were grouped under Grasslands, the grassland biome.

28. Reproduction on the edge- Young shoots (sapling size) beside three adult ("full-grown size") shoots or trunks of quaking aspen at the outer edge of a grove that developed beside an Arizona fescue-dominated bunchgrass prairie in South Park Colorado.It was not known what proportion of these smaller shoots were new trees (saplings of other genotypes produced from seed) or asexual offshoots or clonal shoots of the mature trees. Quaking aspen is dioecious so shoots in the interior of a vegetative unit like the one presented here are almost assuredly asexual shoots or suckers of the one genetic individual, the single tree. Shoots on the perimeter of this stand could be other trees (separate genetic individuals) arising from the readily wind-blown seed.

Quaking aspen is renowned for its clonal reproduction often referred to as "suckering". Each individualclonal shoot is a "sucker" that arises from a common and immense underground "trunk". Colonies of "quakies" are one tree (= one genotype= one genetic individual) with many shoots (each of which superficially appears to be a separate tree) of various sizes and ages arising from a single massive system of roots and "rootstocks" (woody rhizomes). Some of these asexual colonies cover considerable acreage. For instance, the largest--to date--of these (nicknamed Pando, Latin for "I spread") covers over a hundred acres, has about 47,000 shoots, and is thought to be one of the largest organisms on Earth (Kemperman and Barnes, 1976). Each "sucker" or shoot is a ramet of the genet, the genetic organism. Populus deltoides is dioecious so each of these "quaky thickets" is either male or female. Quaking aspen is likely the ultimate clonal organism among vascular plants. Each shoot that survives to maturity completes its own life cycle (just like a limb or branch on a typical tree) and dies, but the tree lives on into almost immortality unless killed out. One of the easier ways by which this death of the colony (clonal organism) happens is through overbrowsing by wildlife or livestock, many species of which relish its leaves, buds, and/or bark. Judicious range management is required to maintain healthy populations of quaking aspen (shoots as well as trees).

There are a remarkable number of quality studies into biology of Populus species including clonal aspects (Barnes, 1966; Kemperman and Barnes, 1976), genetics and populations (Jelinski and Cheliak, 1992; Mitton and Grant, 1996), and comprehensive treatment (Stettler et al., 1996). From these few sources the most serious student can tack down all he ever wanted to known about quaking aspen, a most remarkable range plant.

The herbaceous layer was comprised almost entirely of grasses the dominant species of which along the outer margin of the grove was Arizona fescue. It was readily distinguished by the tall, straw-colored, sexual shoots that still bore the central axis of last year's panicles. Farthr inside the grove mountain muhly tended to dominate though there was considerable cover of Letterman's needlegrass. Lastly (and least of all) was Thurber's fescue.

29. Bad quaking- Local colony of quaking aspen on higher reaches of the Little Missouri River Badlands. The surrounding range vegetation varied from true prairie co-dominated by western wheatgrass (Agropyron smithii) and needle-and-thread (Stipa comata) to a form of juniper woodland dominated by Rocky Mountain juniper (Juniperus scoparium). Somehow this nice little stand of quakies snuck in. Nor was this the only such colony in the Little Missouri Badlands, but they were probably the least common ranged type dominated by woody vegetation in this unique landscape.

This provided yet another example of the variation in habitats to which this salicaceous species is adapted. Populus tremuloides is one of the most widely distributed plant species on Earth.

Theodore Roosevelt National Park (North Unit), McKenzie County, North Dakota. Late June.FRES No. 19 (Aspen-Birch Forest and Woodland Ecosystem). K-97 (Northern Hardwoods, Seral Stages). SAF 217 (Aspen). Northwestern Great Plains- Little Missouri Badlands Ecoregion Ecoregion 43b (Byce et al., Undated).

Organization note: An Arizona fescue-dominated montane grassland (subalpine park) conterminous to this aspen grove was treated under the Mixed Prairie chapter in the Grasslands biome section of Range Types of North America. This arrangement was done for purpose of consistency so as to include all range cover types under sectional organization based on biome. From this perspective the montane fescues-muhly steppes were included with adjacent zonal grasslands (ie. grasslands of the Great Plains, Southwestern Tablelands, and Front Range) while quaking aspen-dominated range types were "housed" within the forest biome section even though the herbaceous layer of aspen groves along their contact with montane grassland was nearly identical to that of the subalpine parks that existed as bunchgrass prairie.

Likewise, ponderosa pine forests and Engelmann spruce-ponderosa pine ecotonal forests with the same (or nearly so) fescues-mountain muhly herbaceous understorey were included in the Southern and Central Rocky Mountain Forests chapter under the forest biome section. Again, range types in this publication were placed as to organizational hierarchy based on and beginning with the biome, the broadest and most general level of range plant community.

30. Quakies in the Canadian zone- In the famous--and still useful--scheme of C. Hart Merriam the Canadian Life Zone was the next highest in elevation and the one above the Transition Zone. Classically, in the mountains of southwestern North America the Canadian Life Zone was characterized by forest communit(ies) consisting of several species of conifers such that it was often regarded as a mixied conifer type. Douglas-fir and white fir tend to dominate with Engelmann spruce and limber pine from forest communities of still higher elevation being associate or subordinate species. Quaking aspen (Populus tremuloides) of the Salicaceae (willow or poplar family) is the only angiosperm tree that achieves dominance among the tall gymnosperm representatives.

Alpine range on the far mountain (Wheeler Peak) was obvious in this Great Basin panorama.

This landscape-scale view of a quaking aspen forest community was at the upper elevtional limits of quakies in the Snake Range of the Great Basin. The forest cover type above (next one up and higher in elevation) the quaking aspen forest was the forest community dominated by Engelmann spruce (Picea engelmannii). Several individual trees of Engelmann spruce were clearly visible in this stand or colony of quakies.

Snake Range, Great Basin National Park, White Pine County, Nevada. June. Elevation of aspen groves ranged from roughly 9,000 to 9,500 feet. Two different communities of quaking aspen were presented in the following photographs so units for ecosystems, Kuchler "vegetation types" forest and rangeland cover types, and other designations were cited in those captions.

31. Grove with a woody carpet- In the Canadian Life Zone of the Snake Range quaking aspen formed a grove with greenleaf manzanita as a shrub or lower woody layer and with much recruitment of young quakies. Most of these are undoubtedly clonal shoots from the creeping woody rootstocks of this colony forming species (ie. most of the "trees" are actually limbs arising from a spreading underground shoot which is the trunk of one genetic individual; the grove is one or a few trees). Quaking aspen recruitment has been primarily by asexual means ("tillering" by trees so to speak) rather than establishment from seed. This method of vegetative regeneration allowed aspen to emerge and co-exist with greenleaf manzanita. Young quakies came up in the middle of dense mats of manzanita so that this range plant community consisted of two species and two layers of vegetation.

This understorey contrsted sharply with that of the more common quaking aspen-dominated herbaceous vegetation that grew adjacent to this aspen-manzanita woody plant community.

Successional status of quaking aspen remains a matter of interpretation. In absence of periodic fire coniferous species (eg. Englemann spruce on the range considered here) successfully invades aspen groves prompting numerous workers to declare the quakies as seral vegetation. Other workers have insisted that fire is a natural part of climate such that when "normal" climate (ie. that which "spawns" fire) is not overridden by fire suppression quaking aspen does fine, thank you. Grazing/browsing of aspen-dominated range vegetation constitutes another natural component of forest and woodland ecosystems in Great Basin, Rocky Mountain, Cascade, etc. ranges that must be included in any analysis of plant succession.

To rangemen, foresters, and wildlifers quaking aspen is a native or natural plant community that is forest and rangeland. This range type provides browse, cover, general habitat, watershed vegetation, aesthetics and recreational value so it merits recognition as both a forest cover type by the Society of American Foresters (Eyre, 1980. ps. 96-97) and a rangeland cover type by the Society for Range Management (Shiflet, 1994, ps. 50-51). Incidentially, both of the authorities just cited stated clearly that quaking aspen was either climax or seral depending on habitat (range or forest site).

Snake Range, Great Basin National Park, White Pine County, Nevada. June, early estival aspect. Elevation was about 9,000 to 9,500 feet. FRES No. 19 (Aspen-Birch Forest and Woodland Ecosystem). There was no meaningful Kuchler unit for western quaking aspen. Many workers, including Kuchler (1964, 1966), interpreted quaking aspen as seral to other "vegetation types" such as Englemann spruce in this case so that quakies did not get a designation/description which, for example, in terminology of Kuchler (1964, 1966) was potential natural vegetation. SAF 217 (Aspen); SRM 411 (Aspen Woodland). Would have to be lumped with Rocky Mountain Montane Conifer Forest 122.6, Douglas Fir-White Fir (Mixed Conifer) Series 122.61, Populus tremuloides subclimax Association 122.614 of Brown et al. (1998, p. 37). Populus tremuloides / Arctostaphylos patula woodland which was not shown either Bougeron et al. (29 August, 1994) or Nevada Natural Heritage Program (26 September, 2003) even when both gave other Populus tremuloides associations "by the droves". Central Basin and Range- High Elevation Carbonate Mountains Ecoregion 13e (Bryce et al., 2003).

32. Invaded but out-distancing the invasion (maybe)- Quaking aspen grove in the Snake Range of Great Basin that was being invaded by Engelmann spruce from the Engelmann spruce forest of the Hudsonian Life Zone just "up the hill". There was recruitment of both Engelmann spruce and quaking aspen with both tree species represented by several age classes. Both species were also represented by dead and downed timber indicating that both had co-existed for several generations. Attention was drawn to the log of Engelmann spruce in right background of second photograph (we will stumble across this log in the next immediately succeeding photograph).

The understorey appeared bare, especially on the predominately east slope presented in the first slide. These photographs were of early summer vegetation from which the last snow had melted only recently and on which there had been grazing by native ruminats. Young plants of the following grasses were present: Cusic bluegrass (Poa cusickii ssp. epilis), Letterman needlegrass (Sipa lettermanii), fringed brome (Bromus ciliatus= B. richardsonii), and California or mountain brome (B. carinatus= B. marginatus). Blackroot or kobresia sedge (Carex elynoides) and, in smaller amounts, dark or blackened sedge (C. atrata= C. heteroneura) were also present in herbaceous understorey

Snake Range, Great Basin National Park, White Pine County, Nevada. June. FRES No. 19 (Aspen-Birch Forest and Woodland Ecosystem). No K- units for what Kuchler (1964, 1966) apparently interpreted as seral and not potential natural vegetation or else could not map at his mapping scale. SAF 217 (Aspen);SRM 411 (Aspen Woodland). For Brown et al. (1998, p. 37) units would have to lump Great Basin with Rocky Mountain (as was done for Subalpine Conifer Forest) which gave Populus tremuloides subclimax Association 122.614 of Douglas Fir- White Fir (Mixed Conifer) Series 122.61 under Rocky Mountain Conifer Forest 122.6. Populus tremuloides / Bromus carinatus Forest (Nevada Natural Heritage Program, 26 September, 2003). Central Basin and Range- High Elevation Carbonate Mountains Ecoregion, 13e (Bryce et al., 2003).

33. Aspen grove with a story but not much understory- Up-to-the-log, close-up view of range vegetation in the quaking aspen woodland shown in the immediately preceding slide. This fallen log (not all logs in such forests and woodlands fall intact) of Engelmann spruce was evidence that this species and quaking aspen had lived together on this forest range site for "many snows". Here in the Canadian Life Zone aspen was replacing itself aminst a corpse of the tree species that is the dominant of the climax Engelmann spruce-limber pine forest of the next vegetation and life zone. Engelmann spruce was also reproducing (sexually in contrast to asexual reproduction of aspen) on this site as was shown in the two preceding photographs.

Grasses and grasslike plants on this range site (more obvious in the second of these two slides) included Cusick's bluegrass, fringed brome, Calirornia or mountain brome, Letterman's needlegrass, blackroot sedge, and dark or blackened sedge. A few miscellaneous forbs were not identified.

Snake Range, Great Basin National Park, White Pine,County, Nevada. June, early estival aspect. Elevatrion was about 9,000 to 9,5000. Ecosystem, forest and rangeland cover types, biotic community, associations, ecoregion, etc. of this range vegetation were cited in the immediately preceding caption.

34. Don't tremble 'til the shutter clicks- Details of quaking aspen presented at the scale of a limb in crown of mature tree (first photograph) and leaves on twig (second photograph). Arrangement and shape of leaves (including curved petiole) of quaking aspen causes these relatively small leaves to twist in the slightest breeze giving the appearance of trembling or quaking. Hence origin of both common and scientific names of this valuable forest and range plant. From a range perspective quakies are valuable as browse plants for just about any animal that can reach leaves, buds, twigs, or even bark.

For general introduction and natural history to quaking aspen Lanner (1984, p. ps. 132-137) was recommended. Old "stand-bys" for treatment of quaking aspen as a range browse plant included Day (1931, p. 17), Forest Service (1940, B111 ), and Sampson and Jespersen (1963, p. 51).

Snake Range, Great Basin National Park, White Pine County, Nevada. June.

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