Moutain Scrub

[ Home ]

Shrublands (= scrubland or, just, scrub) in mountain and coastal regions and habitats are generally semiarid or even subhumid in contrast to the arid shrublands which are deserts. Traditionally non-arid scrub in North America was designated by the Spanish term of chaparral. In the early Clementsian treatment of North American native vegetation the Chaparral Climax was divided into the Coastal or Pacific Chaparral and the Petran Chaparral associations (Clements, 1920, ps. 177-193; Weaver and Clements, 1938, ps. 531-533). Although Coastal Chaparral extended into parts of the Baja California Peninsula and as fragments or "islands" north through parts of British Columbia the Pacific Chaparral was historically interpreded as the California Chaparral which more or less coincided with Mediterranean Climate (or, in adjaceant locales, as a variation thereof). In contrast, the Petran or "soft" Chaparral was primarily mountain (including foothills) shrubland. Representatives of Quearcus and Ceanothus genera are common to both major categories (Clementsian associations). In addition, Clements (1920, ps. 187-190) recognized the Subclimax Chaparral (Rhus-Quercus Associes).

Keeley (in Barbour and Billings, 2000, p. 204) indicated that the term "chaparral" was used in reference "to the sclerophyllous shrub vegetation of southwestern North America". Keeley (in Barbour and Billings, 2000, ps. 234-237) designated and dsecribed the general sclerophyllous range community eastward of the California Chaparral as Interior Chaparral. Keeley differentiated Interior Chaparral into 1) Arizona chaparral (with Quercus turbinella a major defining dominant) and (using the Clementsian title) 2) Petran chaparral (Q. gambellii being the defining dominant). Keely specifyied that this latter community was "largely winter-deciduous shrub vegetation at 2000-3000 m in the central Rocky Mountains". This latter scrub vegetation corresponded to the Mountain Mahogany-Oak Scrub (Cercocarpus-Quercus) potential natural vegetation of Kuchler (1964, 1966, 1976) which included as component species bigtooth maple (Acer grandidentatum), serviceberry (Amelanchier spp.), bitterbrush and cliffrose (Purshia and/or Cowania spp.), and tobaccobush (Ceanothus velutinus) among others. The Society for Range Management (Shiflet, 1994) recognized several separate range types within the Petran Chaparral based on dominance by various of these shrub species. Some of these range (= dominance or cover) types were presented below.

 
Mixed Mountain Scrub
 
1. Rocky Mountain shrub (= mixed mountain scrub = petran chaparral) type- Western serviceberry (Amelanchier alnifolia), mountain showberry (Symphoricarpos albus), rabbitbursh, bitterbrush, mountain mahogany, Indian ricegrass, Letterman needlegrass (Stipa lettermani), slender wheatgrass, elk sedge (Carex geyeri), bluebunch wheatgrass, big sagebrush, Thurber fescue (Festuca thurberi). Diverse community. Routt County, Colorado. Late July. Major omission form SRM Cover Type descriptions: montane scrub of central Rocky Mountains was left out.Would be the Front Range equivalent of SRM 209 (Montane Shrubland), 413 ((Gambel Oak), 415 - 417 (Mountain Mahogany Types), or possibly 503 (Arizona Chaparral). The Rocky Mountain scrub type was described in standard texts like Range Management by Stoddart et al. (all three editions) and Range Management – Principles and Practices by Holechek (all three editions). FRES No. 34 (Chaparral-Mountain Shrub Ecosystem). K-31 (Mountain Mahogany-Oak Scrub). Mixture of Mountain-Mahogany Series and Oak-Scrub Series of Brown et al. (1998). Southern Rockies- Foothill Shrublands Ecoregion, 21d (Chapman et al., 2006).
 
Mountain mahogany (Cercocarpus spp.) Scrub
 
In various western mountain ranges, especially those of the Intermountain West, various species of mountain mahogany are major, often dominant, shrubs. Mountain mahogany species occupy niches as important browse species on grasslands, savannas, and forests. For instance, true mountain mahogany (Cercocarpus montanus) often comprises a shrub layer in ponderosa, western yellow, pine (Pinus ponderosa). This range type was treated under the Woodlands and Forests biome in the chapter entitled Northern and Central Rocky Mountain Forests. On drier mountain slopes such as on ranges in the Great Basin a unique scrubland dominated by curl-leaf mountain mahogany develops at elevations just above the pinyon pine-juniper woodland zone. The relatively restricted curlleaf mountain mahogany shrubland, SRM 415 (Curlleaf Mountain Mahogany), was regarded by the current author as being of such patchy and limited spatial occurrence that it was included as a miscellaneous scrub type. SRM 415 was also included in the Intermountain Forest chapter wherein it can be studied with conterminous zones of forest range communities.
 

2. True mountain maohgany scrub- Cercocarpus montanus scrubland on a north slope in Laramie Mountains. Almost all shrubs were true mountain mahognay except for some fringed sagewort (Artemisia fridida), the low, gray clumps in center foreground in first of these two slides. These two shrub species by themselves were enough to constitute two woody layers. There was an almost continuous herbaceous layer made up of grasses that dominated adjoining foothill mixed prairie. These major grasses were needle-and thread (Stipa comata), blue grama (Bouteloua gracilis), and western wheatgrass (Agropyron smithii). Secondary grass species included Junegrass (Koeleria cristata= K. pyramidata), Great Basin wildrye (Elymus cinerus), slender wheatgrass (Agropyron trachycaulum), bluebunch wheatgrass (A. spicatum), Sandberg's bluegrass (Poa secunda), big bluegrass (P. ampla), Canby's bluegrass (P. canby), squirreltail (Sitanion hystrix), local stands of cheatgrass (Bromus tectorum), and scattered plants of the naturalized, Eurasian crested wheatgrass (Agropyron cristatum).

At slightly higher elevations (distant background on and near ridgetop) scattered saplings and seedlings of ponderosa pine (Pinus ponderosa) and Douglas-fir (Pseudotsuga douglasii) were conspicuously present.

This was excellent wildlife range. True mountain mahogany as well as the festucoid, C3 grasses and blue grama furnished feed par excellence (at least by natural pasture standards).

Laramie County, Wyoming. Late June (estival aspect) FRES No. 34 (Chaparral-Mountain Scrub Shrubland Ecosystem). K-31 (Mountain Mahogany-Oak Scrub). SRM 416 (True Mountain Mahogany). Closest unit in Brown et al. (1998. p. 39) was Cold Temperate Scrubland 132, Great Basin Montane Scrub 132.1, Mountain Mahogany Series 132.12 (the only mountain mahogany unit given; there should be a Rocky Mountain Montane Scrub but none was shown).Southern Rockies- Mid-Elevation Forests and Shrublands Ecosystem, 21c (Chapman et al., 2003).

 

3. Shrubland-grassland mosaic- In foothills of Laramie Mountains there was an endless vegetational "tug-of-war" between true mountain mahogany scrubland and foothill mixed prairie of needle-and-thread, blue grama, western wheatgrass and many other grasses many of which were listed in the immediately preceding slide. This variant differed somewhat from the true monutain mahogany shrubland presented in the above pair of photographs that was higher up in the Laramie Mountains rather than this form which was more of a Great Plains-Rocky Mountain foothills transition (note differences in Level III Ecosystems).

Emphasis here was on the true mountain mahogany scrub. The foothill mixed prairie was treated in the grassland chapter, Mixed Prairie. Cercocarpus montanus was almost the exclusive woody species except for plains pricklyper (Opuntia polycantha) and widely scattered individuals of fringed sagewort or fringed sagebrush. Even though the fringed sagewort was scattered, this architectural structure consisted of three shrub layers. True mountain mahogany was in the late-bloom phenological stge.

Laramie County, Wyoming. Late June (estival aspect) FRES No. 34 (Chaparral-Mountain Scrub Shrubland Ecosystem). K-31 (Mountain Mahogany-Oak Scrub). SRM 416 (True Mountain Mahogany). Closest unit in Brown et al. (1998. p. 39) was Cold Temperate Scrubland 132, Great Basin Montane Scrub 132.1, Mountain Mahogany Series 132.12 (the only mountain mahogany unit given; there should be a Rocky Mountain Montane Scrub but none was shown). Southern Rockies- Foothill Shrublands Ecosystem, 21d (Chapman et al., 2003).

 

4. Leader of true mountain mahogany- Shoot of true mountain mahogany with flowers at late bloom stage (first photograph) and recently spent flowers on this same plant (second photograph) on the foothill scrubland shown in the immediately preceding pair of photographs. Laramie County, Wyoming. Late June.
 
5. Details of a twig of true mountain mahogany (Cercocarpus montanus)- Inflorescences and leaves on twig of mountain mahogany. Dayton (1931, p. 43) noted that this was the most widely distributed of the Cercocarpus species and "one of the most important species of western browse" with palatability rated as good or higher. Kimble County, Texas. September.n
 
6. Mountain mahogany- Characteristic leaves and fruit of a major browse plant. The Cercocarpus genus has several species that furnish extremely valuable browse especially in foothill and mountain scrub (petran chaparral) communities.     
 

7. Upper elevation of Upper Sonoran Life Zone- Curl-leaf mountain-mahogany (Cercocarpus ledifolius) shrubland was the range vegetation at the highest elevation of the Upper Sonoran Life Zone in the Snake Mountains. These two landscape-scale photographs depicted characteristic curl-leaf mountain mahogany scrubland in the Snake Range relative to zones (= belts) of range plant communities in these mountains. Zonal range vegetation was determined to large extent by factors (precipitation, temperture, soils, degree of slope, winds, etc. ) associated with differences in elevation and, to lesser degree, direction of slope (eg. north, south, west slopes).

Distant range vegetation that was dark green in color was tree-dominated range plant communities. That which was below (lower in elevation) this mountain-mahogany belt were various communities dominated by singleleaf pinyon pine and juniper (primarily Utah juniper). Natural plant communities above this zone of mountain mahogany scrub (higher in elevation) were vrious forest cover types (ponderosa pine-Douglas-fir, quaking aspen, Englemann spruce, limber pine, and bristle cone pine). The bare area on the distant mountain, which was Wheeler Peak, was the alpine range ecosystem above timberline.

Some of the curl-leaf mountain-mahogany plants were of heights (as tall as 15-25 feet) more typical of trees than shrubs, but almost all such plants were of the multi-stemed habit characteristic of shrubs. This woody plant-dominated (based on canopy cover, physiogonomy, plant height) vegetation was therefore defined precisely as shrubland or scrub and not woodland.

There was one-- sometimes two-- layer(s) lower layers of plants. Shrubs that were relative common in lower woody layer(s) included low sagebrush (which was the understorey dominant in the adjacent and lower Utah juniper-low sagebrush range community), viscid rabbitbrush, hairy golden aster, and fringed sagebrush (Artemisia frigida). Composites were clearly "in control" of lower shrub layer(s).

The herbaceous layer of this range vegetation was dominated by muttongrass of Fendler's bluegrass. The associate herb was the range forb, lanceleaf phacelia (Phacelia hastata= P. leucophylla). Many of the same range forb species grew on this belt of mountain-mahogany scrub range and the adjacent zone of Utah juniper-low sagebrush-grass range.

Great Basin National Park, White Pine County, Nevada. June, estival aspect. Elevation was roughly 8,000 to 8,500 feet up to as high as 9,000 feet on dry south and west slopes. FRES No. 34 (Chaparral-Mountain Shrub Shrubland Ecosystem). K- 31 (Mountain-mahogany-Oak Scrub), mountain-mahogany variant thereof. SRM 415 (Curlleaf Mountain Mahogany). Mountain-Mahogany Series 132.12 of Great Basin Montane Scrub 132.1 of Brown et al. (1998, p. 39). Cercocarpus ledifolius Shrubland Alliance is as far as can go because National Vegetation Classificatioin for Nevada (Nevada Natural Heritage Program, 26 September, 2003) did list a community (association) of this composition. Central Basin and Range- Carbonate Woodland Zone Ecoregion, 13q (Bryce et al., 2003).

 

8. Scrub range in the Snake Range- Interior of the curl-leaf mountain-mahogany-low shrub-muttongrass scrubland range presented in the two immediately preceding photographs. The multi-stemmed habit of mountain-mahogany plants was pronounced. Herbaceous and woody layers in the understorey of this range vegetation varied greatly at local (microclimate) scale. Single species of plants tended to form local populations or colonies (Clements, process of aggregation or "birds of a feather flock together"). This was particularly so for lanceleaf phacelia and muttongrass. Perhaps this was a combination of plant dispersal characteristics and considerable vriation in edaphic habitat at scale of microsites.

Several plants of fringed sage were noticable in foreground of both photographs.

Great Basin National Park, White Pine County, Nevada. June, estival aspect. Elevation was approximately 8,000 to 8,500 feet up to 9,000 feet on south and othr dry slopes. FRES No. 24 (Chaparral-Mountain Shrub Shrubland Ecosystem). K-31 (Mountain-mahogany-Oak Scrub), "pure" mountain-mahogany variant thereof. SRM 415 (Curlleaf Mountain Mahogany). Mountain-Mahogany Series 132.12 of Great Basin Montane Scrub 132.1 of Brown et al. (1998, p. 39). Cercocarpus ledifolius Shrubland Alliance is "it" because there was not an association level in National Vegetation Classification for Nevada (Nevada Natural Heritage Program, 26 September, 2003) having this composition. Central Basin and Range- Carbonate Woodland Zone Ecoregion, 13q (Bryce et al., 2003).

 

9. Curlleaf mountain-mahogany (Cercocarpus ledifolius)- Typical plant of this shrub species in the Snake Range of the Great Basin. Description of this species as to browse value was in the Range Plant Handbook (Forest Service, 1940, B50) as well as Dayton, 1931, p. 45) and Sampson and Jespersen (1963, ps. 80-81). See also Lanner (1984, ps.180-182) for a brief natural history.

Snake Range, Great Basin National Park, White Pine County, Nevada. June, pre-bloom stage..

 

10. Foothill neighbor- Another plant of cutleaf mountain-mahogany. This one was a neighbor to a population of Gambel's oak (Quercus gambelii) and a few New Mexico locusts (Robinia neomexicana) on a seep in the foothills of the Front Range of Southern Rocky Mountains.

Huerfano County, Colorado. Mid-June (late spring), pre-bloom stage.

 
11. Curlleaf mountain mahogany (Cercocarpus ledifolius)- Typical columnar habit of curlleaf mountain mahogany. According to Dayton (1931, p. 45) this is probably the largest and most treelike of the Cercocarpus species. In addition, it has evergreen leaves which increase it's browse value during winter months. Rock Canyon, Utah County, Utah. June.
 

12. Leaders of curlleaf mountain mahogany- Bark and leaves of curlleaf mountain mahogany. Rock Canyon, Utah County, Utah. June.

C. montanus and C. ledifolius were described in the various editions of North American Range Plants (Stubbendieck et al., 1981, 1982, 1986, 1992) and the Range Plant Handbook (Forest Service, 1940, B49-B51) as well as miscellaneous state and regional references on browse plants such as for California (McMinn, 1939, ps. 205-209; Sampson and Jesperson, 1963, p. 78-81) and eastern Oregon and Washington (Hayes and Garrison 1960, ps.178-180).

 
 

13. Chokecherry (Prunus virginiana)- This range and forest shrub is notable for several reasons. It is one of the most widely distributed shrubs in North America ranging from the Atlanic to the Pacific Coasts and from northern Mexico to the upper reaches of the Prairie Provinces. Within its range chokecherry grows on habitats from moist deciduous forests to canyons to prairies. Chokecherry provides useful browse and mast for wildlife, but its leaves contain hydrocyanic acid which can be highly toxic to livestock .

Cardston Muncipal District, Alberta. July.

 

14. The beauty of sexual reproduction- Single plant (first slide) and crown of two plants (second slide) of western chokecherry (Prunus virginiana var. melanocarpa) at full-bloom. Just below North La Veta Pass, Costillo County, Colorado. June, first full day of summer and what a way to start it off.
 
13. Chokecherry in full bloom- Inflorescences and leaves of western chokecherry. Rock Canyon, Utah County, Utah. June.
 

14. Enough that you can smell them- Series of three slides of western chokecherry going from leaders showing leaves as well as flower clusters (first), an entire inflorescence (second), and individual flowers (third). Just below North La Veta Pass, Costillo County, Colorado. June, first full day of summer and what a way to start it off.
 
16. Chokecherry leader- Shoots of chokecherry with ripening fruit (drupe) and leaves. Drupe is a fleshy indehiscent (not opening by fruit structures like sutures) within a single seed enclosed withi a stony endocarp. Wind Cave National Park, County, South Dakota. July.
 

17. Common serviceberry (Amelanchier alnifolia)- This is certainly one of the major browse plants across the northern half of the vast Western Range Region. It extends from the Great Lakes Region to the Pacific Coast and south to the southern Rocky Mountains. Serviceberry is an outstanding feed plant for wildlife furnishing both browse (leaves, buds, bark) and mast (the fruits). This specimen was growing in the Rocky Mountain scrub or mixed mountain brush type often designated as "soft chaparral". On this location serviceberry was associated with true mountain mahogany, mountain big sagebrush, common snowberry, and numerous forbs including Colorado columbine.

Serviceberry was discussed in all the major classic works on western browse plants (eg. Forest Service, 1940, B12) and North American Range Plants (Stubbendieck et al. 1981, 1982, 1986, 1992). Routt County, Colorado. July.

 
18. Common serviceberry- Leaves and inflorescences of common serviceberry. Rock Canyon, Utah County, Utah. June.
 
19. Fruit of common serviceberry- The Rosaceae, which is the single most important family of browse plants in North America, produce various kinds of fruit. Whereas the fruit of chokecherry is a drupe that of serviceberry is a pome which is usually defined as an indehiscent (= non-opening) and fleshy fruit derived from an inferior ovary encircled by an adnate hypanthium.The pome has been labeled a false fruit because the fleshy portion developes from the receptacle of the flower and not from the ovary. Common examples of pome fruits are apples, pears and quinces.
 
20. Low, wet mountain meadow but as a shrub-dominated community and not typical grass-sedge community- Shrubby cinquefoil (Potentilla fruticosa) and silver sagebrush (Artemisia cana) are dominant species with a varied understory of grasses in such genera as Festuca, Poa, Bromus, Danthonia.Rocky Mountain National Park, Colorado. August. FRES No. 34 (Chaparral- Mountain Shrub Ecosystem). Once again, no Kuchler units were mapped at the local scale of wetland sites. Rocky Mountain equivalent or variant of SRM 216 (Montane Meadows). Southern Rockies- Crystalline Subalpine Forests Ecoregion, 21b (Chapman et al., 2006).
 
Gambel Oak (Quercus gambellii) Scrub
There are numerous species of scrub oak (Quercus spp.) on the ranges of western North America. Some of these scrub oak species dominate and define the potential natural range vegetation thereby comprising climax shrubland (= scrubland or, simply, scrub). One (probably the major or most important one) of these scrub oak range ecosystems in the foothills up to slightly higher elevational zones of the Rocky Mountains is that dominated by Gambel oak. Some examples of this important semi-arid shrubland range type followed.
 
21. Rocky Mountain foothill scrub- This mountain brush type is dominated by Gambel oak (Quercus gambellii) with skunkbush sumac, mountain mahogany, snowberry as woody associates. Mosaic-like patches of grassland comprised of needle-and-thread, green needlegrass, blue grama, and galleta. Edge of mountain scrub type. Huerfano County, Colorado.August. FRES No. 34 (Chaparral-Mountain Brush Ecosystem). K-31 (Mountain Mahogany-Oak Scrub). Front Range variant of SRM 413 (Gambel Oak). Gambel Oak Series of Brown et al. (1998). Southern Rockies- Foothill Shrublands Ecoregion, 21d (Chapman et al., 2006).
 
22. This is a typical transition between plains grassland and foothill “soft chaparral” (= petran chaparral) with the mosaic of vegetation just described.Note broom snakeweed at lower right, snowberry in center, and mountain mahogany center background surrounded by Gambel oak. Stipa-Bouteloua mixed prairie grassland. Huerco County, Colorado. August. Likely a composite of SRM 608 (Wheatgrass-Grama-Needlegrass), 611 (Blue Grama-Buffalograss), and 715 (Grama-Buffalograss) in a mosaic of the preceding variant of SRM 413 (Gambel Oak). FRES Nos. 34 (Chaparral-Mountain Shrub Ecosystem) and 38 (Plains Grasslands Ecosystem). K-31 (Mountain Mahogany-Oak Scrub) and K-57 (Gramagrass-Needlegrass-Wheatgrass). Southern Rockies- Foothill Shrublands Ecoregion, 21d (Chapman et al., 2006).
 
23. Gambel oak- Leaves and the characteristic pattern of four acorns borne together. Huerfano County, Colorado. August.
 

Mixed scrub in the Sangre de Cristo Range. Along a small stream in the southern portions of the Sangre de Cristos a unique riparian range type dominated by New Mexico locust (Robinia neomexicana) formed a bosque palnt community complete with lower woody and herbaceous layers. Adjacent to the New Mexico locust-dominated bosque just presented and extending immediately upslope from the small stream of (supporting) this bosque (ie. contiguous with the New Mexico locust bosque) there was a seral scrub type dominated by Gambel's oak and with New Mexico locust and true or alderleaf mountain mahogany (Cercocarpus montanus) as associate species. Dick Peddie (1993, ps.125-127, 133) recognized this range vegetation as the Oak-Locust Successional Series, Quercus gambelli (undulata)-Robinia neomexicana montane scrub. This scrubland range type merged into the "pure" Gambel oak type that developed on higher, drier slopes having shallower soils and which was contiguous with the pinyon pine-juniper savannah at higher elevations and position on upslopes (see three of four photographs immediately below). The Gambel's oak range type was designated by Dick-Peddie (19993, p. 133) as Oak Successional Series, Quercus gambelli (undulata) and by the Society for Range Management (Shiflet, 1994) as the Gambel Oak rangeland cover type (SRM 413).

Note on arrangement of types: the New Mexico locust bosque was "housed" in the Miscellaneous Scrub Types under Shrublands biome of Range Types. The Gambel Oak-New Mexico Locust range type was included there also to avoid confusion even though it created redundancy. Gambel's Oak-New Mexico Locust scrubland was included here for consistency (ie. to group together all Gambel's Oak shrublands). The Gambel Oak-New Mexico Locust range type was obviously an ecotone (transitional range vegetation) between the locust-dominated bosque and Gambel Oak range types so it was included in both locations.

 

24. A unique mixed scrub- A mixed scrubland dominated by Gambel oak and with New Mexico locust and true or alderleaf mountain mahogany as associates developed between a New Mexico locust bosque below and a"straight" Gambel oak shrubland above. This transitional (ecotonal) range plant commuinity was on soils of intermediate wetness regime (chressard) between these two other range types. Immediately above (contiguous with at higher elevations) the Gambel oak scrub was a pinyon-pine-juniper savanna. There was also a transition zone between the pinyon pine-juniper savanna and the Gambel oak scrub with scattered plants of Rocky Mountain juniper (Juniperus scopulorum) and one-seed juniper ( J. osteosprma) within otherwise homogenous stands of Gambel oak. These vegetational zonation is was visible in both of these photographs which provided "phototransects" of life zones all the way to alpine (distant background of both slides).

New Mexico locust and true or alderleaf mountain mahogany were in the foreground of both of these slides. The understorey of this scrub was herbaceous with naturalized smooth brome being the dominant and needle-and-thread (Stipa comata) the associate species at lower elevations with smooth brome quickly "dropping out" and being replaced by needle-and-thread as the dominant (and almost exclusive species) at slightly higher elevations.

Huerfano County, Colorado. Mid-June (late spring, vernal aspect). FRES No. 34 (Chaparral-Mountain Brush Ecosystem). K-31 (Mountain Mahogany-Oak Scrub). Variant of SRM 413 (Gambel Oak). Gambel Oak Series of Brown et al. (1998). Southern Rockies- Foothill Shrublands Ecoregion, 21d (Chapman et al., 2006).

 

25. They were associates and then they petered out- The Gambel oak-New Mexico locust scrubland range type in Sangre de Cristo Range with New Mexico locust andtrue or alderleaf mountain mahogany as associate species (first slide) and the becoming so sparse that range vegetation became more of the Gambel oak range type (second slide). The herbaceous layer was dominated by naturalized smooth bromegrass with needle-and-thread the associate herbaceous species, but at only slightly higher elevations smooth brome was no longer present at all and needle-and-thread became the herbaceous dominant.

Above the Gambel oak scrubland there was a large range community of pinyon pine-juniper savanna, but between these two range types there was a transition zone in which Rocky Mountain juniper and one-seed juniper grew within a primarily Gambel oak shrubland. There were several life zones aligned up the slopes of the Sangre de Cristo Range terminating in the alpine zone. This spatial pattern of range plant communities was presented in the second of these slides.

Huerfano County, Colorado. Mid-June (late spring, vernal aspect). FRES No. 34 (Chaparral-Mountain Brush Ecosystem). K-31 (Mountain Mahogany-Oak Scrub). Variant of SRM 413 (Gambel Oak). Gambel Oak Series of Brown et al. (1998). Southern Rockies- Foothill Shrublands Ecoregion, 21d (Chapman et al., 2006).

 
Antelope Bitterbrush (Purshia tridentata) Range
Antelope bitterbrush (Purshia tridentata) is generally regarded as the single most important browse species throughout the Western Range Region. This is such a widely recognized fact that little space was needed to elaborate on this native shrub species. Bitterbrush (and the closely related cliffrose) species are in the Rosoideae ((subfamily) of the Rosaceae.
 

The three range cover types presented immediately below (next twelve sets of photographs and captions) were on the first terrace and adjacent slopes just above the flood plain of the Cache La Poudre River in the northern part of the Front Range of the Southern Rocky Mountains. The sequential zones of vegetation going from river terrace to montane ponderosa pine woodland and/or forest were: 1) antelope bitterbrush-Parry oatgrass shrub steppe or a shrub-grass savanna, 2) foothill mixed shrubland of diverse species composition and 3) true mountain mahogany montane shrubland. These three range types were encountered more in the interior of the Front Range whereas the range type just presented (the montane or foothill mixed shrubland type of Gambel oak, skunkbush sumac, serviceberry , etc. with an understorey of grass species that were more typical of the Great Plains ) had developed on the east side of the Front Range.

There were other narrow or isolated plant communities that appeared to be transitional or "mixtures" of adjoining range communities that could perhaps be interpreted as "islands" of other range types. For example, immediately upslope from the bitterbrush-Parry oatgrass type there was a "strip" of Rocky Mountain juniper (Juniperus scopulorum)-mountain big sagebrush vegetation. This vegetation was presented in the Juniper-Pinon Pine Woodland portion of the Forests and Woodlands section elsewhere in this publication. As such it was not featured here in the Shrubland section. Likewise there were some isolated ponderosa pines that looked as if they had "wandered" from the montane or foothill ponderosa pine forest occurring at higher elevations. That forest range cover type, including examples from the Rocky Mountain Front Range, was covered in the Forests and Woodlands section.

 

26.. Antelope bitterbrush (Purshia tridentata)-Parry oatgrass (Danthonia parryii) shrub steppe- This is another of several forms of Rocky Mountain scrub or shrubland. This and the next two rangeland cover types in this section of montane shrubland had developed along the first terrace above the Cache La Poudre River. The range vegetation shown in this and the next two slides would almost certainly be an antelope bitterbrush-Parry oatgrass habitat type should such be determined for this portion of the Front Range. This vegetation is a rangeland cover type on par with the bitterbrush-bluebunch wheatgrass and bitterbrush-Idaho fescue cover types (SRM 104 and 317 and 105 and 318, respectively), but this bitterbrush-Parry oatgrass cover type was not recognized by the Society for Range Management (Shiflet, 1994). This is another suggestion for future designations and descriptions of rangeland cover types as this ever-unfolding project continues. Very few other species grew in this community. There were some isolated individuals and even a few "patches" of Sandberg bluegrass and Junegrass and rarely individual plants of mountain big sagebrush around the edges of this plant community along the bottom slope of the adjoining hills.

Larimer County, Colorado. June but in the driest single year in Colorado weather records. FRES No. 34 ( Chaparral Mountain Shrub Ecosystem). K-31 (Mountain Mahogany-Oak Scrub). No specific SRM for this combination. Bitterbrush Series of Brown et al. (1998) appeared fairly accurate. Southern Rockies- Foothill Shrublands Ecoregion, 21d (Chapman et al., 2006).

 

27 Antelope bitterbrush-Parry oatgrass montane savanna or shrub steppe- Another view of the rangeland cover type just introduced except here a closer view where this range vegetation joined the plant community that began at the start of the incline or slope of the hills adjacent to and immediately above the terrace of the Cache La Poudre River.

The foremost large shrub with brown flower stalks at far left was mountain big sagebrush which grew only along the edges of the bitterbrush-Parry oatgrass community. Mountain big sagebrush and Rocky Mountain juniper formed a transition community immediately behind the bitterbrush-Parry oatgrass cover type on a south slope.

These photographs were taken in June in what was the single driest growing season (and interpreted as part of the most extreme drought) since beginning of Colorado weather records. The cespitose Parry oatgrass had gone dormant without blooming except for rare individual plants growing on the north side of bitterbrush. These few plants that completed their annual cycle allowed positive identification of the mostly pre-bloom dormant bunchgrasses. A few plants of Sandberg bluegrass and Junegrass grew in this shrub steppe, but they did not seem to qualifiy as associate species to the exclusive (therefore dominant) Parry oatgrass.

Students will note the gravely nature of this range site on the terrace of Cache La Poudre River.

Larimer County, Colorado. June. FRES No. 34 (Chaparral-Mountain Shrub Ecosystem). K-31 (Mountain Mahogany-Oak Scrub). No SRM specific for bitterbrush with this understorey. Bitterbrush Series of Brown et al. (1998). Southern Rockies- Foothill Shrublands Ecoregion, 21d (Chapman et al., 2006).

 

28. Antelope bitterbrush and Parry oatgrass growing on the alluvium of the Cache La Poudre River- In the single direst year on record Parry oatgrass had gone dormant without flowering while bitterbrush was "hanging in there" demonstrating the value and dependability of this extremely valuable browse plant.

Larimer County, Colorado. June. FRES No. 34 (Chaparral-Mountain Shrub Ecosystem). K-31 (Mountain Mahogany-Oak Scrub). No SRM specific for bitterbrush-Parry oatgrass. Bitterbrush Series of Brown et al. (1998). Southern Rockies- Foothill Shrublands Ecoregion, 21d (Chapman et al., 2006).

 

29. Antelope bitterbrush (Purshia tridentata)- This species has traditionally been regarded as the single most important browse on the Western Range. It is the browse equivalent of blue grama and little bluestem in being the most widely distributed and generally abundant single species of woody plant used as feed by wildlife and livetock. Bitterbrush is so valuable it needs little introduction, but it was presented in detail herein to familarize beginning students with this outstanding range browse plant.

Bitterbrush is a member of the Rosaceae (subfamily, Rosoideae) which, as was noted periodically throughout this publication, is the single most important family of browse plants in North America. Those unaware of this phenomenon have merely to scroll up and down this web page to appreciate that fact. And do not forget to read the classic literature on range plants. The following are highly recommended for coverage of antelope bitterbrush: Forest Service (1940, p. B116), Dayton (1931, ps. 52-53), and Sampson and Jespersen (1963, ps. 75-78). Probably the publication to provide nearest thing to encyclopedic coverage of bitterbrush ranges and their management was Tiedemann and Johnson (1983).

 
30. Stand of antelope bitterbrush- This is an example of the density and extent of aerial cover in which bitterbrush often grows on favorable habitats. This is browse next to none for livestock and every imaginable species of wildlife.
 

31. Leaders of antelope bitterbrush- Leaves, flowers, and immature fruit of bitterbrush were shown in these two slides. Even in the single driest year on record this plant was flowering so profusely that the tridentate apical margin of the leaves (basis for specific epithetic) were mostly obscured.

Alluvium of the floodplain of the Cache La Poudre River. Larimer County, Colorado. June.

 
Latest definitive work on bitterbrush (and a classic when it hit the press) is Young and Clements (2002).
 

32. Rocky Mountain foothill mixed shrubland- Shown here was another form of petran scrub or "soft chaparral" found in the Southern Rocky Mountain physiographic province. The vegetation seen here was in the canyon of the Cache La Poudre River on the gravely alluvium of the river terrace up to the beginning slope of hills above the canyon floor (south slope). This was a remarkably species-rich range plant community, especially when compared to the preceding bitterbrush-Parry oatgrass community growing "just up river". There was no obvious dominant species in either the shrub or herbaceous layers, but true mountain mahogany was the most common (slightly) shrub followed (in no particular order) by bitterbrush, skunkbush sumac, mountain big sagebrush, green rabbitbrush (Chrysothamnus viscidiflorus), and a Ribes species. Parry oatgrass was the most common species in the herbaceous understorey but there were "hearty" populations of little-seed ricegrass (Orysopsis micrantha). Junegrass, needle-and-thread, Sangberg bluegrass, squirreltail bottlebrush (Sitanion hystrix), and a trace of blue grama and even less cheatgrass (Bromus tectorum). At the edge of this shrubland type there were trees of ponderosa pine and Rocky Mountain juniper. These trees were growing at the very toeslope (the union of the beginning of the hill and the river terrace). They could be interpreted as being an arboreal element of this vegetation or part of an upslope commuinty that was an ecotone, a transition zone, between the montane scrub and the juniper-pinon pine woodland and ponderosa pine forest that had developed higher in the foothills.

Floor and toeslope of Cache La Poudre River Canyon, Larimer County, Colorado. June. FRES No. 34 (Chaparral-Mountain Shrub Ecosystem). K-31 (Mountain Mahogany-Oak Scrub). Variant of SRM 209 (Montane Shrubland), most generally, SRM 416 (True Mountain Mahogany), or SRM 509 (Oak-Juniper Woodland and Mahogany-Oak), none of which described the diverse vegetation of this form of Rocky Mountain shrubland. Mixed Deciduous Series of Brown et al. (1998) was most descriptive excepting the conifer layer. Southern Rockies- Foothill Shrublands Ecoregion, 21d (Chapman et al., 2006).

 

33. Rocky Mountain foothill mixed scrub- Another view of montane shrubland with a grass understorey. Most abundant shrub was true mountain mahogany (the tallest shrubs), but also in this mixed scrub were plants of bitterbrush, green rabbitbrush, mountain big sagebrush (eg. the two grayish-colored shrubs in foreground that are farthest on the left- and on the right-sides), skunkbush sumac, and a species of Ribes (eg. centermost plant in foreground). Most common grass was Parry oatgrass, but numerous other grasses were common including Sandberg bluegrass, Junegrass, needle-and-thread, squirreltail bottlebrush, and "just a tad" of blue grama with almost no cheatgrass. There were no forbs for all practical purposes. Small trees of ponderosa pine and Rocky Mountain juniper grew at the juncture of this foothill scrub and the onset of a steep slope at base of hills.

Floor of Cache La Poudre Canyon, Larimer County, Colorado. June (in the driest year to-date in Colorado weather records). FRES No. 34 (Chaparral-Mountain Shrub Ecosystem). K-31 (Mountain Magohany-Oak Scrub). No precise SRM designation but a variant of SRM 209 (Montane Shrub) in general or perhaps of SRM 416 (True Montain Mahogany) and/or SRM 509 (Oak-Juniper Woodland and Mahogany-Oak), or some combination of these. Other than conifer layer the Mixed Deciduous Series of Brown et al. (1998) seemed appropriate. Southern Rockies- Foothill Shrublands Ecoregion, 21d (Chapman et al., 2006).

 

34. True mountain mahogany-grass shrubland- Landscape view of a montane shrubland in the Front Range of the Southern Rocky Mountain physiographic province. The shrub layer of this vegetation was a "pure stand" of Cercocarpus montanus (ie. a consociation of C. montanus) with a very sparse "scattering" of young Rocky Mountain juniper or cedar at the lower elevation of the foreground and ponderosa pine on the north slope at higher elevations up the hill. Other, though very infrequent, woody species included those shrubs shown in the vegetation of the two immediately preceding slides that was designated Rocky Mountain foothill mixed shrubland. The vegetation of this and the next photograph was not a mixed mountain shrubland range type but a different type dominanted (almost exclusively populated) by true mountain mahogany.

The presence of the young juniper most likely indicated absence of fire for several years (and the belated need for a fire of cedar-killing intensity). The pines were the advancing edge of a ponderosa pine forest at higher elevations and most likely also invading downslope in absence of recent fires. The light green spots midway up the hill were of some Ribes species. Herbaceous understorey was strictly grasses of the following species: Parry oatgrass, Sandberg bluegrass, needle-and-thread, Junegrass, squirreltail, trace of blue grama, and local "hot spots" of cheatgrass. No forbs to speak of.

Canyon of the Cache La Poudre River, Larimer County, Colorado. June. This was the driest year in history of Colorado weather records. FRES No. 34 (Chaparral-Mountain Shrub Ecosystem). K-31 (Mountain Mahogany-Oak Scrub). SRM 416 (True Mountain Mahogany). Mountain-Mahogany Series of Brown et al. (1998). Southern Rockies- Foothill Shrublands Ecoregion, 21d (Chapman et al., 2006).

 

35. True mountain mahogany scrubland- Interior view of the true mountain mahogany-grass shrubland range type seen at landscape scale in the preceding slide. This was on the first bench or beginning of the slope of hills immdediately above the terrace of the Cache La Poudre River. This was a consociation of C. montanus, but other (and isolataed) shrub species included a Ribes species (the prominent light green, low shrubs in left background), antelope bitterbrush, skunkbush sumac, and green rabbitbrush. The dominant grass was Parry oatgrass, but other common Gramineae members included Sandberg bluegrass, Junegrass, needle-and-thread, little-seed ricegrass, squirreltail, and cheatgrass. The latter was very infrequent-- almost nonexistant-- except for localized spots (perhaps microsites). For instance, some cheatgrass was visible in the immediate left foreground but even here Parry oatgrass was the most common grass species. There were no notable forbs.

Rocky Mountain juniper was common enough to "stick out" and in absence of fire will likely add an arboreal element eventually.

Larimer County, Colorado. June (of most extreme drought in history of recorded weather). FRES No. 34 (Chaparral-Mountain Shrub Ecosystem). K-34 (Mountain Mahogany-Oak Scrub). SRM 416 (True Mountain Mahogany). Mountain-Mahogany Series of Brown et al. (1998). Southern Rockies- Foothill Shrublands Ecoregion, 21d (Chapman et al., 2006).

 
36. True mountain mahogany (Cercocarpus montanus)- Along bank of Cache La Poudre River. Larimer County, Colorado. June.
 

37. Ecotone- Transition zone between the Rocky Mountain foothill mixed shrubland (dominated by true mountain mahogany) presented above and the juniper-pinon pine woodland and ponderosa pine forest of the general montane zone. Shrub and grass species were those given in the captions of the last four slides of vegetation (the Rocky Mountain foothill mixed shrubland and the true mountain mahogany range cover types). In the vegetation presented in this slide the mixed shrubland (or a composite of the mixed montane scrub and the true mountain mahogany) has an added layer , an arboreal component of such density and cover as to include a tree layer.

The plant community viewed in this photograph was clearly ecotonal in nature being transitory between montane forest and lower elevation shrubland. The range vegetation observed in the immediate last six slides can be compared to the juniper-pinon pine woodland and ponderosa pine forest given in the Forest and Woodlands section. If all of these were compared with the lodgepole pine and Englemann spruce-subalpine fir of the Forest and Woodland section, Great Plains mixed prairie grassland of the Grassland section, and the vegetation of the Alpine section the student will see the entire elevational array of Colorado vegetation east of the Continental Divide. This will include all the Life Zones of C. Hart Merriam.

Outstanding recent reference on shrubland ecotones is the publication of that name by the Shrub Research Consortium (McArthur et al., 1999).

Cache La Poudre Canyon, Larimer County, Colorado. June. A hybrid of multiple FRES, Kuchler, and SRM units. Southern Rockies- Foothill Shrublands Ecoregion, 21d (Chapman et al., 2006).

 
Another example of antelope bitterbrush foothill range was provided by the Northern Cascades and presented immediately below. This was--as is often typical of bitterbrush ranges--a shrub-grass savanna. This one even included an arboreal element.
 

38. Antelope bitterbrush-bluebunch wheatgrass foothill range- Two photographs of range vegetation in foothills of the Northern Cascades that was a mixed shrub-bunchgrass shrub-steppe dominated by antelope bitterbrush and bluebunch whaetgrass with several other species of shrubs, cespitose grasses and forbs. Other shrubs included mountain big sagebrush (Artemisia tridentata ssp. vaseyana), Virginia or western chokecherry, commmon or western serviceberry, a species of wild-buckwheat that was not blooming but appeared to be snow wild-buckwheat (Erigonum niveum), syria (Philadelphus lewisii), even a few quaking aspen (Populus tremuloides) and black cottonwood (P. trichocarpa). The second most common grass (cover-wise) was western, Nelson's or Columbia needlegrass (Stipa occidentalis subsp. nelsonii) followed by Sandberg's bluegrass, cheatgrass, and trace of needle-and-thread (S. comata). Most common forb was arrowleaf balsamroot (Balsamorhiza sagittata). There were some scattered individuals of narrowleaf skeleton weed or bush wire-lettuce (Stephanomeria tenuifolia var. tenuifolia), as in left foreground of first photograph.

These two slides featured conspicuous bluebunch wheatgrass. The immediately following slides presented views of this same range contrasting the antelope bitterbursh-bunchgrass shrub-steppe with parts of the same range that were more of a montain chaparral vegetation.

This land was extremely stoney, including local small boulder fields, a feature consistent with that reported by Daubemnire (1968,p. 61).

Franklin and Dryness (1973, ps. 211) listed nine climatic climaxes that comprised zonal associations in the Columbia Basin Province (Daubenmire, 1968). Another zonal association that was not listed in Franklin and Dryness (1973, p. 223), but one that was cited by them from Daubenmire (1968, p.iii, ps.60-61) was "a closely related Purshia/Agropyron spicatum coummunity from which Festuca idahoensis is absent". That was natural vegetation was the range plant community featured in photographs of this Northern Cascades foothill range and those in the next series of five slides.

Okanogan County, Washington. June (early summer). FRES No. 29 (Sagebrush Shrubland Ecosystem). K-50 (Wheatgrass-Needlegrass Shrubsteppe). SRM 104 (Antelope Bitterbrush-Bluebunch Wheatgrass). Closest biotic community in Brown et al. (1998) was Great Basin Shrub-Grassland 142.2- Mixed Bunchgrass-Shrub Series 142.22, but should be a Columbia Plateau Shrub-Grassland unit. Purshia tridentata-Agropyron spicatum habitat type (Daubenmire, 1968, ps. iii, 60-61). Chelan Tephra Hills Ecoregion, 77f (Environmental Protection Agency, undated).

 

39. Antelope bitterbrush-bluebunch wheatgrass-dominated shrub-steppe- Two more views of the Northern Cascades foothills shrub-bunchgrass range introduced in the two preceding photographs. First of these two slides presented physiogonomy, structure, and species composition of the bitterbrush-bunchgrass shrub-steppe while the second slide featured a local range community made up of numerous shrub species (ie. a shrubland with understorey of bunchgrass species and some range forbs). In addition to antelope bitterbrush, the dominant shrub, other woody species included mountain big sagebrush Virginia or western chokecherry, commmon or western serviceberry, syria, black cottonwood a some "lost" quaking aspen. Western (= Nelson's or Columbia, depending on authority) was the second most important and abundant grass, but there were some plants of Sandberg's bluegrass and, as always, some cheatgrass or downy bromegrass.Grasses were much abundant in understorey of the dense scrub preented in second photograph.

The shrub-dominated range community in the second slide was in a small draw (perhaps qualified as a coulee) that had an ephemeral stream still trickling into early summer.

This was mule deer range par excellance (as was the next foothill range featured immediately below).

Okanogan County, Washington. June (early summer). FRES No. 29 (Sagebrush Shrubland Ecosystem). K-50 (Wheatgrass-Needlegrass Shrubsteppe). SRM 104 (Antelope Bitterbrush-Bluebunch Wheatgrass). Closest biotic community in Brown et al. (1998) was Great Basin Shrub-Grassland 142.2- Mixed Bunchgrass-Shrub Series 142.22, but should be a Columbia Plateau Shrub-Grassland unit. Purshia tridentata-Agropyron spicatum habitat type (Daubenmire, 1968, ps. iii, 60-61). Chelan Tephra Hills Ecoregion, 77f (Environmental Protection Agency, undated).

 

40. Antelope bitterbrush-bluebunch wheatgrass-dominated shrub-steppe with a sporadic arboreal component- Another range in the foothills of the Northern Cascades that was within approxomately ten miles of the foothill range described immediately above. The range featured and in the next set of two photographs and then the single photograph that followed these was much steeper, less stoney (though still plenty of rocks), had fewer shrub species and more forb cover, and, most conspicuously, included some ponderosa pines.Bluebunch wheatgrass was still the dominant herbaceous species. Other important grasses included western or Nelson's needlegrass, Sandberg's bluegrass, and cheatgrass. Cover of arrowleaf balsamroot, the obviously dominant forb, was greater than in the Northern Cascades foothill range treated immediately above as was western yarrow (Achillea millefolium var. lanulosa), here the associate forb, which was very sparse on the foothill range covered above.

Besides presence of a conifer component on this foothill range the most conspicuous differences between these two ranges was less shrub cover and fewer shrub species on this range (syria, quaking aspen, and western chokecherry were not present in this range vegetation; black cottonwood had seeded in from the nearby Methow River and was present--sort of--though rare). Ponderosa pine furnished a tree aspect that resulted in a different structure and gross visual appearance to the otherwise same physiogonomy and structure of this shrub-bunchgrass savannah.

The associate shrub (to dominant bitterbrush) varied locally, but was most frequently common serviceberry, snow wild-buckwheat or, mountain big sagebrush, though this latter species appeared to be less common overall. These three shrub species were less abundant on upper portions of this east slope.

Okanogan County, Washington. June (early summer). FRES No. 29 (Sagebrush Shrubland Ecosystem). K-50 (Wheatgrass-Needlegrass Shrubsteppe). SRM 104 (Antelope Bitterbrush-Bluebunch Wheatgrass). Closest biotic community in Brown et al. (1998) was Great Basin Shrub-Grassland 142.2- Mixed Bunchgrass-Shrub Series 142.22, but should be a Columbia Plateau Shrub-Grassland unit. Purshia tridentata-Agropyron spicatum habitat type (Daubenmire, 1968, ps. iii, 60-61). Chelan Tephra Hills Ecoregion, 77f (Environmental Protection Agency, undated).

 

41. Northern Cascades foothill range dominated by antelope bitterbrush and bluebunch wheatgrass (and with some trees)- The range presented in these two photographs and the two immediately above was very similar to the foothill range described immediately before this foothill range. Bluebunch wheatgrass was the dominant herbaceous plant.Western (Nelson'sor Colu;mbia) needlegrass was locally common and more abundant than either Sandberg's bluegrass or cheatgrass which were also present.

The range shown here (and in the two immediately preceding slides) had less shrub cover and fewer species of shrubs. Syria, quaking aspen, and western chokecherry were absent from this range. A few "barely holding on" black cottonwood had seeded from large groves of this species in the floodplain of the Methow River that flowed just below this east slope.There was, however, the tree component provided by ponderosa pine, which clearly changed physiogonomy and species composition of this antelope bitterbursh-bunchgrass savanna.

The associate shrub species varied at local scale, but was typically common serviceberry or snow wild-buckwheat (less commonly, mountain big sagebrush). Dominant forb was arrowleaf balsamroot; western yarrow was associate range forb.

Okanogan County, Washington. June (early summer). FRES No. 29 (Sagebrush Shrubland Ecosystem). K-50 (Wheatgrass-Needlegrass Shrubsteppe). SRM 104 (Antelope Bitterbrush-Bluebunch Wheatgrass). Closest biotic community in Brown et al. (1998) was Great Basin Shrub-Grassland 142.2- Mixed Bunchgrass-Shrub Series 142.22, but should be a Columbia Plateau Shrub-Grassland unit. Purshia tridentata-Agropyron spicatum habitat type (Daubenmire, 1968, ps. iii, 60-61). Chelan Tephra Hills Ecoregion, 77f (Environmental Protection Agency, undated).

 

42. Structure of a Northern Cascades foothill shrub-steppe range- View of the antelope bitterbrush-bluebunch wheatgrass-dominated savannah described in the last two two-photograph discussions. In this photo-quadrant western or common serviceberry "joined" the dominant bitterbrush and snow wild-buckwheat, one of two local associate shrub species, to form a three shrub-layered structure in this shrub-steppe, a foothill savannah. Bluebunch wheatgrass was still the conspicuous dominant. The forb component comprised of arrowleaf balsamroot, the dominant, and western yarrow, the associate, was represented much less prominently in the herbaceous layers in this view of range vegetation.

It was remarked earlier that both of the antelope bitterbrush-bluebunch wheatgrass-dominated foothill ranges featured here were excellent big game range, mule deer being the most common of these.

Okanogan County, Washington. June (early summer). FRES No. 29 (Sagebrush Shrubland Ecosystem). K-50 (Wheatgrass-Needlegrass Shrubsteppe). SRM 104 (Antelope Bitterbrush-Bluebunch Wheatgrass). Closest biotic community in Brown et al. (1998) was Great Basin Shrub-Grassland 142.2- Mixed Bunchgrass-Shrub Series 142.22, but should be a Columbia Plateau Shrub-Grassland unit. Purshia tridentata-Agropyron spicatum habitat type (Daubenmire, 1968, ps. iii, 60-61). Chelan Tephra Hills Ecoregion, 77f (Environmental Protection Agency, undated).

 
Black Greasewood (Sarcobatus vermiculatus) Range
Black greasewood, or, usually, the more simple greasewood (Sarcobartus vermiculatus) is a major woody chenopod species throughout much of the Western Range, especially throughout the Intermountain West (including the Colorado Plateau, Basin and Range, especially the Great Basin, and Columbia Plateau) of North America. Other examples of shrubland or scrub range dominated by greasewood were presented in the chapter devoted to the Great Basin Desert. Coverage here was limited to greasewood-dominated range vegetation within mountains, especially the Rocky Mountains.
 

43. Greasewood-saltgrass shrubland- Saline sink in North Park of the Southern Rocky Mountains with a shrub overstorey comprised exclusively of black greasewood (Sarcobartus vermiculatus) and an inland saltgrass-dominated understorey accompanied with isolated individuals of threadleaf sedge (Carex filifolia). This depression usually has standing water for a period during spring after which the soil water content remains relatively high on the low permeability soil. This both supplies adequate water for greasewood and dilutes the salt concentration in the soil of this small basin thereby reducing salt stress to plants. As with most members of the Chenopodiaceae, greasewood posses salt-extruding glands that prevent salt toxicity.

These photographs were taken during the single driest growing season to-date in Colorado weather records (2002) and the greasewood, which is not well-adapted to prolongued drought, showed drought stress as did the graminoids.

It was not known whether the cover of greasewood was excessive and was a brush problem due to mismanagement (perhaps an increase in shrub density, cover, etc. with past overgrazing maybe even tracing back to the open range era) or if this was the ecological potential or climax vegetation. Certainly enough has been learned to identify or "map" this as a naturally Sarcobatus vermiculatus-dominated shrubland with a saltgrass understorey. This vegetation was described by Knight (1994, ps. 108-113). Franklin and Dryness (1973, p. 227) designated this community the Sarcobatus vermiculatus/ Distichlis stricta association of shrub steppe in the Columbia Basin of eastern Oregon and Washington.

The climate under which this range type developed was semiarid and the composition of the plant community was such that this was semidesert shrub steppe and not a cold desert saltbush-greasewood scrub. An example of that community on the Red Desert of Wyoming-- and not in a drought-- was presented under the Great Basin Desert portion here in the Shrubland section. The range plant community shown here was one range cover type among several of the Rocky Mountain scrub or "soft chaparral".

Arapaho National Wildlife Refuge, Jackson County, Colorado. North Park. June. No appropriate FRES or Kuchler designations because those units were too large for this vegetation, but this was a legitimate range cover type of shrub steppe. This was another example of the incompleteness-- and need for on-going research into-- vegetation mapping and classification. In the author's judgment this was climax or potential natural vegetation. Franklin and Dryness (1973, 227) clearly designated it (the black greasewood-inland saltgrass association) as natural vegetation. It is definitely the black greasewood shrub steppe and on equivalent ecological standing with the big sagebrush shrub steppe. It has yet to be designated and described. One important function of technical writing is to point out deficiencies or "missing pieces" in the existing literature. That was just done here. Southern Rockies- Sagebrush Parks Ecoregion, 21i (Chapman et al., 2006).

 
44. Greasewood- Greasewood is a chenopod shrub that is a dominant on various range sites throughout the desert scrub communities of the Great Basin and in isolated depressions such as in the parks of the Rocky Mountains as well as along drainages and bottomland grasslands in the Great Plains. Note the green color of this plant that was not suffering from water-deprivation like those in extreme drought shown immediately above. Crowley County, Colorado, July.
 
45. Greasewood- Leaves and staminate flower clusters of greasewood. Crowley County, Colorado, July.
 
46. Leader of male black greasewood- Greasewood is a dioecious species. This was a primary lower limb on a male plant bearing an abundant crop of staminate flowers. Costillo County, Colorado. Late June, immediate stage before anthesis (pre-pollen release).
 

47. Boys' club- Leader of a male plant of black greasewood with staminate inflorescences and leaves (first slide) and details of staminate flowers (second slide). These flowers were on the same main leader (limb or primary branch) shown in the preceding slide. Costillo County, Colorado. Late June, immediately prior to pollen release. .
 
 
Mountain Big Sagebrush (Artemisia tridentata var. vaseyana) Range
Mountain big sagebrush (Artemisia tridentata var. vaseyana= A. vaseyana) is one of four varieties or subspecies (depending on author) of big sagebrush (A. tridentata) that dominate (or is at least a defining shrub) across much of the Western Range Region. Other of these big sagebrush subunits (and, in fact, other examples of mountain big sagebrush) were provided elsewhere in this publication. Coverage in this chapter was limited to the mountain big sagebrush range in the Central Rocky Mountains.
 

48. *Mountain big sagebrush shrub steppe- Large-scale view of a shrub steppe dominated by mountain big sagebrush (Artemisia tridentata var. vaseyana= A. vaseyana) and with a grass understorey primarily of Idaho fescue and Sandberg bluegrass. The dominant forb was western false helleborne (Veratrum californicum). The cover of Artemisia was almost certainly excessive with a commensurate reduction in cover and productivity of the bunchgrasses so as to constitute range retrogression. This was yet another example of "Deserts on the March" with a mountain big sagebrush shrub steppe (a shrub savanna) having been (or in process of being) converted into a sagebrush shrubland approaching the climax big sagebrush cold desert of the Great Basin farther to the west in an arid zone. The species are the same in both climax range types but the relative proportions are "supposed to be" different, and they have become less so. This mountain big sagebrush-bunchgrass range was not so severely depleted-- not yet at least-- as to be an extreme departure from it's ecological (= successional) potential. Understorey species were still mostly those of climax shrub steppe with relatively little cheatgrass or downy brome (Bromus tectorum). From perspective of physiogonomy there was enough big sagebrush to indicate that it was a shrub steppe. (Ha!)

*Technical note on taxonomy: Knight (1994, ps. 90-99 passim) discussed the sagebrush steppe of Wyoming, complete with inclusion of maps of eight species, in which he noted that "[m]ountain big sagebrush is found in the foothills at higher, cooler elevtions" (Knight, 1994, p. 91). Otherwise the most common A. tridentata taxon of the sagebrush steppe other than in alluvian basins was Wyoming big sagebrush (A. tridentata var. wyomingensis). Beetle (1960, p. 41) mapped the area in which the vegetation shown in these slides grew as A. tridentata subsp. vaseyana (note that Beetle used the taxon of subspecies rather than variety). Beetle (1960) did not recognize the taxon of wyomingensis. Weber and Wittmann (2001) noted presence of a subspecies of wyomingensis along the Colorado-Wyoming state line, but they interpreted the big sagebrush taxon of North Park as Seriphidium vaseyanum. Mutel and Emerick (1992, ps. 94, 103) used this latter species name. The current author designated the vegetation shown here as mountain big sagebrush, but noted that this A. tridentata var. vaseyana attained nothing of the stature or general large size of those individuals found in the foothills or up in the montane zone.

Grand County, Colorado. June (most extreme drought for a one-year period in Colorado weather records). FRES No. 29 (Sagebrush Shrubland Ecosystem). K-49 (Sagebrush Steppe). Variant SRM 612 (Sagebrush-Grass). Sagebrush Series of Brown et al. (1998). Southern Rockies- Sagebrush Parks Ecoregion, 21i (Chapman et al., 2006).

 

49. Mountain big sagebrush-bunchgrass shrub steppe- General appearance of a shrub steppe having mountain big sagebrush as the dominant shrub (no other woody species were encountered) and the dominant species of this vegetation with an herbaceous layer of golden-aster or goldeneye (Heterotheca villosa= Chrysopsis villosa) and perennial bunchgrasses. The grasse species were also limited with Idaho fescue and Sandberg bluegrass the dominant and associate species, respectively. Western wheatgrass was the third-- a distant third-- major grass. It was nowhere common enough to add a sod-forming grass component. There was cheatgrass but at extremely infrequent occurrence. The golden-aster was in pre-bloom stage and not conspicuous, but many of the small grayish-green clumps are of this composite forb, and not bunchgrasses. This range was in some state of retrogression but not to the point that the species present were other than those of the climax. Proportions of bunchgrasses had probably declined while cover of the composites had increased, but the dominant grasses were still climax species and the cover and density of the Eurasian cheatgrass did not begin to approach the quantities associated with range depletion.

This was appearance of the range following a grazing period in the driest growing season on record in Colorado.

North Park, Jackson County, Colorado. June. FRES No. 29 (Sagebrush Shrubland Ecosystem). K-49 (Sagebrush Steppe). Variant of SRM 612 (Sagebrush-Grass). Southern Rockies- Sagebrush Parks Ecoregion, 21i (Chapman et al., 2006).

 

50. Detail of mountain big sagebrush-bunchgrass shrub steppe- Close-up view of A. tridentata var. vaseyana- dominated range with golden-aster as the most common forb and Idaho fescue the dominant grass. In this worst drought on record in Colorado the Idaho fescue had gone dormant after completing it's annual cycle, but the golden-aster was pre-bloom stage. The flowering stalks of Idaho fescue are visible in immediate foreground by the sagebrush.

North Park, Jackson County, Colorado. June. FRES No.29 (Sagebrush Shrubland Ecosystem). K-49 (Sagebrush Steppe). Variant of SRM 612 (Sagebrush-Grass). Southern Rockies- Sagebrush Parks Ecoregion, 21i (Chapman et al., 2006).

 
Mixed Montane "Brush" (Shrubland) Range
The shrublands (= scrub) range vegetation throughout the greater Rocky Mountains (including affilitated mountain ranges) exhibit tremendous variety. These various forms or types of range vegetation have often been designated as the "soft chaparral" (as distinguished from the "hard chaparral" used to designated the broad-sclerophyllous chaparral of California that is defined/determined by Mediterranean climate). "Soft chaparral" refers generally to the Petran Chaparral Association of Clements. The example of range vegetation from Rock Canyon, Utah County, Utah presented immediately below was an example of the the Subclimax Chaparral (Rhus-Quercus Associes) of Clements (1920, ps. recognized ps. 187-190).
 
51.Vegetation of the Wasatch Range- Cliffrose or, often, Stansbury cliffrose (Cowania stansburyana= Cowania mexicana var. stansburyana= Purshia mexicana var. stansburyana) and bluebunch wheatgrass on south slope (foreground) and three cover types in background (lowest to highest): 1) Gambel oak type, 2) bigtooth or canyon maple (Acer grandidentatum) scrub type, and 3) Douglas fir (Pseudotsuga menziesii) type. Provo Peaks above Rock Canyon, Utah County, Utah. June. South slope type is a variant form of FRES 29 No. (Sagebrush Ecosystem), K-50 (Wheatgrass-Needlegrass Shrubsteppe), while the oak and maple types are of FRES No. 34 (Chaparral-Mountain Shrub Ecosystem), K-31 (Mountain Mahogany-Oak Scrub), and Douglas fir is FRES No. 20 (Douglas-fir Ecosystem), local site of K-11 (Douglas-fir Forest). First type not described by SRM (resembles SRM 322); SRM 413 (Gambel Oak), 418 (Bigtooth Maple), and one form of SAF 210 (Douglas-fir). Edge of Central Basin and Range- Moist Wasatch Front Footslopes Ecoregion, 13f (Woods et al., 2001) in foreground and Wasatch and Uinta Mountains- Semiarid Foothills Ecoregion, 19f (Woods et al., 2001) in background. This landscape demonstrates that "ecosystems" or cover types which are zonal (= regional) in scale on the plains and prairies can become highlylocalized in mountains due to combinations of elevational, aspect, and edaphic features.
 
 
52. Cliffrose- bluebunch wheatgrass shrub steppe type- Smooth sumac (Rhus glabra) in foreground. Rock Canyon, Utah County, Utah. June. FRES No. 34 (Chaparral-Mountain Shrub Ecosystem). No specific K- unit. No SRM type description. Rhus glabra-Agropyron spicatum habitat type (Daubenmire, 1968, ps. 72-73). Central Basin and Range- Moist Wasatch Front Footslopes Ecoregion, 13f (Woods et al., 2001)
 
53. Flowers and young fruit of cliffrose- This is one species in the large and diverse Rosaceae. Synonyms for the binominal of this species have varied by various authorities (some synonyms provided in the caption above the preceding one). A Utah Flora (Welsh et al., 1993, p. 611) regarded this species of cliffrose (cliff-rose) as Purshia mexicana var. stansburyana. Various The rose family has more species that provide browse for game and livestock than any other family of range plants. Cliffrose has received considerably less coverage in the literature than to the closely related antelope bitterbursh. The proceedings edited by Tiedemann and Johnson (1983) furnished some treatment regarding ecology and management of this Stansbury cliffrose. Rock Canyon, Utah County, Utah, June.
 

54. Gambel oak form of mountain scrub in foreground and bigtooth maple in background- FRES No. 34 (Chaparral-Mountain Shrub Ecosystem). No Kuchler units specific for these; could be viewed as variants of K-31 (Mountain Mahogany-Oak Scrub). SRM Types 413 (Gambel Oak)and 418 (Bigtooth Maple), respectively. Mixed Deciduous Series of Brown et al. (1998) could be applied. Scattered specimens of blue elder (Sambucus cerulea), skunkbush sumac, netleaf hackberry (Celtis reticulata), and curlleaf mountain mahogany (Cercocarpus ledifolius) especially at lower elevations. Wasatch and Uinta Mountains- Semiarid Foothills Ecoregion, 19f (Woods et al., 2001).Rock Canyon, Utah County, Utah. June.

 
55. Gambel oak type- FRES No. 34 (Chaparral-Mountain Shrub). No specific Kuchler unit for a type described in the standard and classical literature. SRM Type 413 (Gambel Oak). Gambel Oak Series of Brown et al. (1998). Wasatch and Uinta Mountains- Semiarid Foothills Ecoregion, 19f (Woods et al., 2001). Rock Canyon, Utah County, Utah. June.
 
56. Canyon Maple Cover Type- Rock Canyon, Utah County, Utah. June. FRES No. 34 (Chaparral-Mountain Shrub Ecosystem). No Kunchler designation for another scrub type traditionally recognized in the literature. SRM Type 418 (Bigtooth Maple). Maple-Scrub Series of Brown et al. (1998). Wasatch and Uinta Mountains- Semiarid Foothills Ecoregion, 19f (Woods et al., 2001).
 
57. Canyon Maple with scattered Douglas fir higher up.
 

[ Home ]