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Home , Colorado Piedmont, Halka Chronic, Southern Rocky Mountains

RANGELANDS 15(5), October 1993 213

The Rangelands of

John E. Mitchell

To understand the rangelands of border also receives very little Physlographic Colorado,one should first look at its precipitation. Note: It is not com- Physiographers have dividedColo- physiography. Colorado can right- monly known that the stretch of the the be called the"zenith" of the Uni- ColoradoRiver between Grand Lake rado into three major provinces: fully and ted States; on is the and its confluence with Green , , average, it high- the From a est state in elevation with morethan River in eastern Utah was called the Colorado Plateaus (Fig. 1). of time, these 50 peaks exceeding 14,000 ft. Moun- GrandRiver by early pioneers (Stan- perspective geological Iandforms are young.The pres- tain passes crossingthe Continental ton 1965).] quite Divide in ent Rocky Mountains were uplifted Colorado frequently are Like other western states, Colo- The Great above ft. The lowest in radois The only 60 million years ago. 11,000 point predominantly rangeland. ofalluvial mater- the state, the 1979 Assessment of the U.S. Forest Plainsare composed along ial that eroded from these where it enters is and mandated uplifting , only slightly Rangeland Situation, and were over below 3,400 ft., while about 95% of the Renewable Resources Plan- mountains deposited by thick mantles of ancient worn Colorado'sland area is morethan "a Act of estimated that 47.5 gravels ning 1974, from ancestral Rockiesformed mile The headwaters of four million ac., or 72°Jo ofthe state's lands away highl" the Paleozoic Era major rivers can be found in the are About 55%of this during (Chronic grazed. acreage and Chronic 1972). The Colorado Coloradomountains—the Colorado, is in private ownership. Of the 22 mil- North and South lion acres under Federal a Plateau is dominatedby sedimentary Platte, Arkansas, control, shales and sandstones laid down and . The watersheds of little morethan one-third is managed these rivers and during the Cretaceous Period, from their tributaries by the Bureau of Land Management and account for20% of the area of the 48 while 63% is on National Forests. 70 to 135 million years ago, the ColoradoRiver and its conterminousstates. underthe control of the carved by Rangelands tributariessince that time. Although Colorado is high in ele- Defense Department, such as the vation, it tends to be low in Pinon Maneuver Site, The rangelands of Colorado are relatively Army's Canyon linked toits precipitation except for a few comprise mostof the remaining Fed- inexorably physical geog- high- and the differences elevationpeaks along the Continen- eral land. raphy underlying tal Divide. The Sierra Madre Range near Steamboat Springs is the only mountainous area with annual pre- cipitation exceeding 50 in. In general, precipitationin the mountains ranges between 20 and 50 in/year, distrib- uted fairly even throughout all sea- sons. On the , precipita- tion is sparse, falling mostly during the spring and summermonths from convective thunderstorms. Alongthe Arkansas Rivervalley east of Pueblo, annual rainfall is less than 12 in. It rangesfrom 12 to 16 in. throughout mostof the highplains, butapproach- es 20 in. in the sandhills of northeastern Colorado. The state's driest climate,with an annual precip- itation of less than 7 in., is found in the . The Grand Val- ley between GrandJunction and the Fig. 1. Three ,na/or physiographic provinces in Colorado (adapted from Chronic and Theauthor is arange scientist, Rocky Mountain Chronic 1972). Forest and Range Experiment Station, 3825 E. Mulberry,Fort Collins, Cob. 80524. He wishesto thank Prof. Clinton Wasserfor providing back- ground informationfor this paper. 214 RANGELANDS 15(5), October 1993

in climatearid soils.The threeprom- inent provinces and their attendant ecosystems contain a rich diversity ofvegetation, wildlife, and otherfauna. Vegetation of the Plains The grasslands of the Great Plains are classified into three well-known divisions: the tall-grass prairie, the mid-grass prairie, andthe short-grass steppe. Two of the three have fun- damentally changedsince European settlement. In the tall-grass prairie, nativespecies have been largely re- placed by the introduced tall grass, corn. At the same time, native mid- grass prairiespecies have been exten- sively supplantedby a groupof agro- nomic mid-grasses, wheat. Only the Fig. 3. The shortgrasssteppe was considereda wastelandby travellers in the early 19th short-grass plains remains largely century,suitable only for Indiansand buffalo. Todayit is the principalran geland vegeta- under native sod. tion zone in Colorado. James A. Michener, in his classic vation of the Soil Bank. novel, Centennial, adroitly captured had been abandoned and gone into provisions a period in history when man attemp- default. Theselands were to become Whenthe Soil Bankpayments ended, ted to supplant the native short- the Pawnee and Comanche National nearly all of the acreage involved reverted to because grasseswith wheat and milo.Farmers, Grasslands, now managed by the grain production predominately were en- U.S. Forest Service. of economicconsiderations. immigrants, This is ticed to Colorado during the early During World War II, much of the process essentially repeat- 20th century by the railroads and short-grass plains wereagain plowed ing itself as a result of the Conserva- other interest with the to small This time, how- tion Reserve Program (CRP) of the groups prom- grow grains. In ise that wheatcould be grown on 12 ever, the governmentdid not buy the 1985Food Security Act. Colorado, in. of rain The Dust Bowl landwhen times laterbecame almost 2 million ac. of croplandhave per year. tough. into CAP. These years ofthe 1930's burstthat balloon, Rather, in the 1960's it contracted been placed the and the Federal with farmers to seed their lands comprise a major, if tempor- government pur- eroding incrementto chased large amounts of land that lands back into grass under conser- ary, Colorado'srange- lands(Fig. 2). Oneof the goalsof the Society for Range Management is to minimize the amount of CRP land with highly erodiblesoils that will be plowed out for row crop production at the end of the program. The tall-grass prairie is dominated by the genera Andropogon, Schiz- achyrium, Sorghastrum,and Panicum. Only remnants of this prairie are found in Colorado. However, it may have occupied much larger areas within theColorado Piedmont, agen- tle valley running north-south between the Rockiesand high plains, prior to European settlement. This depressed area tends to concentratesoil water, thereby providing suitable conditions for tall-grass communities. Numer- ous reservoirs and wetlands may be found within the today, nearlyall whichis underunder Fig.2. Extent anddistribution oflands in Colorado enrolledin the ConservationReserve irrigated agriculture or devoted to Program of the 1985Food Security Act. urbanuse. Anexcellent example of a RANGELANDS 15(5), October 1993 215

Ag. 4. Subalpinemeadow in north . These meadowsprovide muchof the availablelivestock forage in the lodgepolepine and spruce-fir zones and are also valuableto elk. true tall-grass relict area is located steppe, dominated by blue grama 1961). Today, rivers traversing the withinthe City of Boulder Open Space. and buffalo grass (Fig.3). Bluegrama Great Plains flow year-round, provid- On deep, sandysoils coveringthe was designated the state grass of ing a differentwater regimefor ripar- uplands ofextreme eastern Colorado, Colorado in 1987. Other major spe- ian ecosystems. Beforewater devel- a tall-grass prairie, represented by cies includewestern wheatgrass, sand opment, trees were widely scattered grasses such as sand bluestem, dropseed, prickly-pear cactus, and along the (Con- switchgrass, prairie sandreed and scarletglobemallow. The most com- klin 1928), but, by 1900, plains cot- side-oats grama, occurs on nearly mon shrub is four-wing saltbush. tonwoods had become increasingly 1.7 million ac. Annual precipitationis Prior to the mid-l9th Century, the established (Crouch 1961). Willows 12-16 in., 75% of which is received short-grass steppe was home to are found with cottonwood in ripar- between May andOctober. This prair- countless bison, antelope, prairie ian zones that are not heavily grazed ie provides excellent habitatfor small dogs and otherherbivores. The vege- during the summergrowing season mammals, upland game birds and tation present has, consequently, (Sedgwickand Knopf 1991). other animals. The dominantshrub, evolved under unmitigatedgrazing, Understoryspecies in plains ripar- sand sagebrush, also gives good cov- and is highly resistant to grazing Ian areas include prairie cordgrass, er and protection to wildlife. Endan- pressureby domestic herbivores(Klip- panicum, common reed, sedges,Can- gered species in this region include pIe and Costello 1960). Short-grass adawildrye,woods rose, goldencur- the American peregrine falcon. In communities also providegood pro- rant, and snowberry.A profusion of higher rainfall zones much of the tection from wind erosion. othergrasses, forbs and shrubsmay deepsand prairie is plantedto wheat Typical riparian zones in the east- also beencountered inthese riparian and milo. ern plains occupy flood plains and zones. Thetrue mid-grass prairie, as repre- adjacentbottomlands along braided Wildlifeare numerous on theshort- sented by different species of Agro- streamsand rivers. Prior to dam and grass steppe. Althoughthe bisonhas pyron and Stipa, is not prevalent reservoirconstruction for irrigation, been eliminated as a free-roaming within Colorado, and is notaddressed as well as water diversionsfrom west animal, thousands of antelope may in this report. of the Continental Divide, even major still be seen by travellers passing The primary ecosystem on Colo- waterways were intermittentduring through the area. Colorado's state rado's eastern plains, occupying at thelate summer andearly fall (Crouch bird, the lark bunting, is a familiar least15 million ac., is theshort-grass inhabitant.Other plains animals in- 216 RANGELANDS 15(5), October 1993

dude the coyote,black-tailed prairie dog, golden eagle, and curlew. An endangered species, the mountain plover, appears to do best in areas that have been grazed. In riparian zones, selected wildlife species com- prise birds and mammals like the great blue heron, bald eagle, white- tailed deer, and many waterfowl. Vegetation of the Rockies The mountainranges in Colorado are a subset of the (Fenneman 1931).Range- lands inthe Colorado Rockies extend from shrubby foothills communities to the subalpine zone found above timberline (Peet 1981). In general terms, they fall into five major eco- systems; foothills brush,pine/Doug- las-firforests, aspen,mountain grass- meadows and FIg. 5. Willow-dominatedriparian community near WoodlandPark, Colorado. The U.S. lands/alpine riparian Forest Service'sManitou Experimental Forest, site of many grazing studies in the ponde- areas. rosa pine zone, is nearby. The foothills brush ecosystem has broadcontrasts in species composi- The pine/Douglas-firzone is char- The valueof aspen standsfor wild- tion, depending upon location. Along acterized by low timber productivity life needs and as asource of summer theFront Range,the mountains adjoin- and moderate forage yields. How- foragefor livestockare broadlyacknow- ing western edgeof the Great Plains, ever, these sites are valuableas late ledged (Ellison and Houston 1958). it is dominatedby mountainmahog- spring or summer range for cattle They produce widelyvarying amounts any, skunkbrush, and wax currant. andwinter and early spring range for of forage, depending upon habitat On the foothills and mesas of the big game. The communities with type, however, ranging from more westernslope, the ecosystem is typi- shrub-dominated understories can than 4,500 Ib./ac. to less than 500 fied by a Gambel oak and service- be particularly important for deer lb/ac. berry overstory. Understoryspecies and elk. Rangelands inColorado sup- The extensivelodgepole pine and are quite diverse. Big bluestem, side- port more elk (200,000 head) than spruce-fir forests that grow at mid- oats grama, and needle-and-thread any other state, and nearly 600,000 elevations (around 8,000-10,000 ft.) are commongrasses along theFront deer reside there, too (Unpublished onlyprovideforagewheredisturban- Range, while Indian ricegrass, west- report, ColoradoDivision ofWildlife). ces, such as fire and logging, create ern wheatgrass, and elksedge appear Aspen communities occurthrough- openings or in natural meadows on the western slope. out the Southern Rocky Mountains, (Moir 1969). Riparian ecosystems, The pine/Douglas-fir zone is the but are most abundant west of the although not expansive in area, are lowestof the true montaneforests in and Sangre de Cristos extremely important in the montane theSouthern Rockies. From a classi- (DeByleand Winokur 1985). Stands zone for both wildlife habitat and fication perspective, it can bedivided ofaspen traditionallyhave been cate- livestock grazing. into communities having only gra- gorized as seral following fire, which Grasslands and mountain mead- minoidspecies in the understory and is often the case; however, some ows can be foundwithin all montane thosewith browsespecies, also (Alex- authors believe that aspen can be and zones above ft. ander The dominant tree is subalpine 8,000 1985). considered climax in a few habitats in the Colorado Rockies. In the pon- easily ponderosa pine. Douglas-fir (Langenheim 1962). derosapine zone, like in mesic areas within species Parry predominates Aspen community typesrange from oatgrass and sun are com- the zone, such as on sedge north-facing warm dry sites in southwestern Colo- mon. On more mesic habitats, gra- slopes. radowith understories of pachistima minoid species include tufted hair- Primary herbaceousunderstory spe- and whortleberry,to moist sites with in the grass, bluejointreedgrass, and alpine cies pine/Douglas-fir zone understories of grasses suchas blue timothy. Wet meadows tend to be includemountain muhly, sedge,June- wildrye and Thurber fescue, to wet dominated suchas Nebras- Arizonafescue and bysedges grass, Kingspike- sitesdistinguished by rich forb/grass ka sedge and rushes like millet fescue. Woody understory species understories containingmeadowrue, woodrush. Numerous forbs are com- include mountain bitter- mahogany, cowparsnip and tall larkspur. mon on wetter mountain meadows, brush, waxcurrant, sumac and woods rose. RANGELANDS15(5), October 1993 217

Fig. 6. Oakbrushvista in southern Colorado.

including solomonplume, blue-eyed black bear, mountain lion, bobcat, For nearly 100 years, much of North grass, groundsel, and Rocky Moun- bighorn sheep,and numeroussmaller Park has been irrigatedfor increased tain iris (Fig. 4). mammals. Common birds include hay production, resulting in a change Riparianareas in theSouthern Rock- blue grouse, Swainson's hawk, and in species composition to sedges, ies typically have overstories of nar- golden eagle. along with seeded cultivars liketimo- rowleaf cottonwood, often with blue Three large mountain parks, named thy, orchard grass, and clover. spruce as a co-dominant at higher North, Middle, and South, are apromi- North Park has high valueas wild- elevations. Bluespruce, of course, is nent part of the Rocky Mountain life habitat because of the luxuriant Colorado'sstate tree. The shrub layer Province in Colorado. Each is unique coverof grasses on the uplandsand is controlled by willow communities in its representativevegetation. North willow-dominatedriparian commun- unless they have been overgrazed. Park, which lies between the Park ities along its many streams and Willows, themselves, form the over- Range to its west and the Front small rivers. The National story in habitats too cold or wet for Range to its east, forms the head- WildlifeRefuge occupies severalthou- treesurvival (Fig. 5). Alderand honey- waters of the . Sit- sand acres along the Illinois River in suckle are two otherfamiliar shrubs uated at an elevation of 8,200 ft., the center of the park. In addition to in the riparian zone. Understories in North Park is epitomized by large waterfowl,upland game birds, mule montaneriparian areas includesolo- expanses ofsub-irrigated grasslands deer, and elk, morethan 600 moose monplume, baneberry, bedstraw,field that are well-suited for haying opera- now live in North Park after a small horsetail, and many of the grasses tions. The native plant community number were introduced a decade associated with wet meadows. was composed primarily of the cool- ago. Besides deer and elk, montane seasonbunchgrasses fescue, MiddlePark, located just belowthe rangelands in Colorado are home to mountainmuhly, and Parryoatgrass. headwaters of the ColoradoRiver, is 218 RANGELANDS 15(5), October 1993 the onlypark of the threefound west The San Luis Valley is similar to gambel oak. Mountain muhly and of the Continental Divide. It is sur- South Park, exceptit is 1,600ft. lower bluegrama may also befound beneath rounded on the north by the Rabbit in elevation and has an annual rain- ponderosa pine overstories. Ears Range, and on the west and fall that is only two-thirds of the Fire is an importantecological fac- southwestby theGore Range. Lower park's 10—12in. This valley, situated tor in southwestern ponderosa pine in elevation than the other two parks in the rain shadow of the San Juan ecosystems, particularly in relation (i.e., approximately7,500 ft.), Middle Mountainson its west and bounded to the abundance of gambel oak Park is dominated by big by theSangre de Cristos on the east, (Brown 1958). For example, follow- sagebrush at lower elevations, basin is found in south-central Colorado, ing destructivefires, gambel oak can big sagebrush in upland swales and opening south into NewMexico. The regenerate asexually from adventi- alluvial terraces and mountain big Rio GrandeRiver passes through on tious buds, forming dense under- sagebrush at higher elevations and its way to the Gulf of Mexico. growths that will preclude pine regen- on north-facingslopes (Tiedeman et Most of the dominant species in eration. al. 1987). Herbaceous species in Mid- the San Luis Valley are the same as A foothills shrub transition zone, dle Park includewestern wheatgrass, found in South Park. The valleycon- dominated by gambel oak and moun- bluebunch wheatgrass, bottlebrush tains many deep sand sites, domi- tain mahogany, is positioned below squirreltail, and elk sedge. Much of nated by Indian ricegrass and needle- the ponderosa pine forest. Gambel Middle Park is classified as critical and-thread. Greasewood, rubber rab- oak hasdiverse growth forms in Colo- winter rangefor mule deerand elk in bitbrush and four-winged saitbush rado (Harper et al. 1985). In some addition to providing valuable graz- are found on salt flats in the valley. areas it takes a tree form, while in ing for domesticlivestock. Because of a high water table, irri- othersit establishes compact, shrub- South Park is a uniqueecosystem gated agriculture is a major land use like patches that are impenetrable to because of its high elevation and wheresalinity is nota problem (USDA man and other larger animals. Few extremelyflat topography.It is situ- Soil Conservation Service 1981). research results are at hand toexplain ated between the the reasons for such morphological and Front Range, about 55 mi. west- of the variability;however, authoritieshave northwest of Vegetation Western Colorado Springs. It is Plateaus speculated that it isa combinationof the highestof the three parks, with a environmental factors and As the west- genetic mean elevationof 9,200 ft. The head- previouslydescribed, hybridization with species ern one-thirdof Coloradois a formerly watersof the South Platte River drain region inhabitingthe area (Clary and Tiede- the park, flowing from northwest to of fairly level sedimentary rocks. Be- mann cause the area 1992). southeast beforeturning backto the has been uplifted so Gambel oak stands are not exten- far above sea therivers emanat- north and cutting through the Front level, sively grazed because of a lack of from its terrain towards Range towards . Because of ing higher available waterand their dense vege- its level terrain, runoff is extremely thewest,including theYampa, White, tation; nonetheless, and they frequently slowcompared to evaporation; there- Colorado, Dolores, Gunnison, serve as valuable habitat for many San Juan, have dissected fore, soils tend to be highly calcare- it, thereby wildlifespecies, including deer(Reyn- ous and caliche layers are common. separating the province into large, olds et al. Some oak stands isolated 1970). South Park's vegetation is primar- plateaus. These substantial, have a high recreational amenityval- ilysparse grassland with and often abrupt, changes in topo- ue the fall when their tree interspersed and during islands of ponderosa pine on iso- graphy, soils, elevation havecrea- foliage turns bright shades of red latedsmall mountains. ted a diverselandscape with numer- 6). Principalspe- ous (Fig. cies consistof Indian ricegrass, blue rangeland ecosystems. Below 6,900ft., pinyon-juniper com- grama, western wheatgrass, bottle- Vegetation on top of the highest munitiesbecome theWhite about prevalent through- brush squirreltail,and winterfat. Pro- plateau, River, 11,000 outthe .Their under- ductionaverages only 500 lb/ac.Both ft. mean sea level, closely approxi- stories are primarily grasses: blue cattleand make extensiveuse mates uppermontane and subalpine sheep of grama, tobosa, side-oats grama, and of South Park during the late spring vegetation the Rocky Mountains western wheatgrass. Pinyon-juniper and summer months. to its immediate east. The other pla- woodlandoccupies about4.4 million teaus are and the montane Salt meadows occur where water lower, ac. in Colorado, substantially less accumulates in the park. Their plant zone is predominantly covered by than in , Utah, Arizona, communities are dominated by var- ponderosa pine forests (Alexander and Nevada It A (unpublisheddata). is, ious mixturesof alkali sacaton, alkali 1985). widespread rangeland com- regardless, an importantcomponent cordgrass, and western wheatgrass. munity in this zone is the ponderosa of the Colorado Plateau country. fescuehabitat On Other species often present include pine/Arizona type. Nearly all of the pinyon-juniper foxtail barley, alkali muhly,and salt- rockiersites, the understory is often zone has been by livestock, because of the of grazed grass. woody presence especiallyduring the periodbetween RANGELANDS15(5), October 1993 219

transpiration-to-precipitationratios, Conklin, E.B. 1928. A brief history ofLogan a comparatively short growing sea- County, Colorado. Welch-Haffner Print- son and ing Co., Denver,Cob. poorly-drained alkaline soils. Crouch, G.L.1961. Wildlife populationsand The most commonspecies in Colo- habitatconditions on grazed and ungrazed rado's salt desert shrub are shad- bottomlandsin LoganCounty, Colorado. scaleand the M.S. Thesis, Colorado State Univ., Fort greasewood, formeron Collins. adobe hills and benches and the lat- DeByle,Norbert V., and RobertP. Winokur. ter on alkaline flats. Other shrubby 1985. Aspen: andmanagement in species include mat saltbush, spiny the western . USDA Forest and Serv. Gen. Tech. Rep. RM-119. Rocky hop-sage, Wyoming big sage- Mountain Forest and Range Exp. Sta., brushon better-drained sites. Grasses Fort Collins, Cob. make up approximatelyone-half of Ellison, Lincoln, and Walter R. Houston. the foliar cover under conditions of 1958. Production of herbaceousvegeta- tion in openings and under canopies of favorable precipitation and proper westernaspen. Ecology39:337-345. grazing. They include bottlebrush Fenneman,Nevin M. 1931. Physiographyof squirrel tail, Indian ricegrass, wildrye, the western United McGraw-Hill States. and alkali sacaton. Book Co., Inc. New York. Harper, Kimball T., Fred J. Wagstaff, and Wildlife species in the salt desert Lynn M. Kunzler.1985. Biology and man- shrubhave adapted to little freewater agement of the Gambel oak vegetative and hot and cold type: a literature review. USDA Forest extremely tempera- Serv. Gen. Tech. INT-1 79.I ntermoun- tures can fluctute as much as Rep. (that tam Res. Sta., Ogden,Utah. 80°F during 24 hours). Black-tailed Jameson,Donald A. 1987. Climax or alter- jackrabbit, kangaroo rat, coyote, des- nativesteady states in woodland ecology, 9—13. In: Richard L. Everett 7. nearGreat ert kit fox and numerous p. (comp.) Fig. Bigsagebrush community reptiles Pinyon-juniperconference, proceedings. Divide, an expansive plateau in north- inhabit these desert areas. USDAForest Serv. Gen. Tech. INT- western Colorado. The individual in the Rep. So, there you have it. From the 215. Intermountain Res. Sta. Ogden, picture isClint Wasser, apioneering range Utah. ecologist and teacher at Colorado State vastness of the Great Plains to her Kuchler,A.W. 1964. Potential natural University. rampart-likemountains and colorful tation of the conterminousvege- western plateaus, the rangelands of United States. Amer. Geogr. Soc. Spec. 1880 and the end of I World War Coloradoare a broad representation Pub. 36. with and (West 1984). Grazing, coupled of the diversityand vistas of western Langenhelm,Jean H. 1962. Vegetation environmental patterns in the Crested unquantified(in Colorado) effects of . a means fire, have contributed They provide Butte area, Gunnison County, Colorado. undoubtedly of livelihood to some, a source of Ecol. Mono. 32:249-285. to shifts in distribution geographical clean air, water and food to many, Moir,William H. 1969. The lodgepole pine and communitystructure of this type zone in Colorado. Amer. Midland Natur. and a sense of enjoyment to us all. 81:87-98. (Jameson 1987). Our is to work towards the en- job Peet, Robert K. 1981. Forest vegetation of sagebrush ecosystems hancement of all these benefits. the Colorado Front Range: composition (Kuchler 1964) are another impor- and dynamics.Vegetatio 45:3-75. tant foothills componentof the Colo- LIterature CIted Reynolds,H.G., W.P. Clary, and P.F. Ff0111- ott. 1970. Gambel oak for southwestern radoplateau. The three primarysub- Alexander, Robert R. 1985. Major habitat wildlife. J. Forest. 68:545—547. species of big sagebrush, mountain, types, community types, and plant com- Sedgwick, James A., and Fritz L. Knopt. basin and Wyoming, are all present. munities in the Rocky Mountains.USDA 1991. Prescribedgrazing as a secondary Soil factors, fire, and grazingappear Forest Serv. Gen. Tech. Rep. RM-123. impact in a westernriparian floodplain. J. to control the Rocky Mountain Forest and Range Exp. Range Manage. 44:369—373. relative distributionof Sta., Fort Collins, Cob. Stanton, Robert Brewster. 1965. Down the pinyon-juniperand the 3 sagebrush Bonham, C.D., T.R. Cottrell, and J.E. MIt- Colorado.Univ. Oklahoma Press, Norman. subspecies (Bonham et al. 1991). chell. 1991. Inferences for life history Tledemann, James A., Richard E. Francis, The watersheds of the White and strategiesof Artemisia tridentatasubspe- Charles Terwilliger, Jr., and Len H. Car- cies. J. VegetationSci. 2:339—344. penter. 1987. Shrub-steppehabitat types YampaRivers in northwestern Colo- Brown, HarryE. 1958. Gambeloak in west- of Middle Park, Colorado. USDA Forest rado, known for their large reserves central Colorado.Ecology 39:317-327. ServiceRes. PaperRM-273. RockyMoun- of coal, naturalgas, andoil shale, are Chronic, John, and Halka ChronIc. 1972. tain Forestand Range Exp. Sta., FortCol- across Prairie, peak and plateau:a guide to the lins, Cob. occupied by sagebrush nearly of Colorado. Cob. Geol. Surv. USDASoil Conservation Service.1981. Land 5 million acres (Fig. 7). Bull. 32, Colorado Geol. Surv., Denver. resource regionsand major land resource One encounterssalt desert shrub Clary, WarrenP., and Arthur R. Tledemann. areas of the United States. Agr. Hand- ecosystems, dominatedby members 1992. Ecology and valuesof Gambeloak book 296. Washington,D.C. ofthe woodlands, p. 87-95. In: Ecology and West, Nell E. 1984. Successional patterns family Chenopodiaceae, atthe management ofoak and associatedwood- and productivity potentials of pinyon- lowest elevations within the Colo- lands: perspectivesin the southwestern juniper ecosystems, p.1301 -1332.In: Nat. radoplateau province. The saltdesert UnitedStates andnorthern Mexico. USDA Res. Council/Nat. Acad.Sci. Developing shrub can be consideredas a Forest Serv. Gen. Tech. Rep. RM-219. strategies for rangeland man- high, RockyMountain Forest and Range Exper- agement.Westview Press, Boulder, Cob. cold desert, typified by high evapo- iment Station, Fort Collins, Cob.