Physiographic features

The Clayey Pinedale Plateau (Cy) ecological site (R034AC104WY: D034A02X104) is located within LRU C 02 in MLRA 34A This ecological site occurs in intermontane basin landscapes on hill, drainageway, and pediment landforms (see following definitions). The slopes range from level to 30 percent. This site occurs on all aspects.

Landscape Definitions:
intermontane basin–-A generic term for wide structural depressions between mountain ranges that are partly filled with alluvium and called "valleys" in the vernacular.

Landform Definitions:
alluvial fan--A low, outspread mass of loose materials and/or rock material, commonly with gentle slopes. It is shaped like an open fan or a segment of a cone. The material was deposited by a stream at the place where it issues from a narrow mountain valley or upland valley, or where a tributary stream is near or at its junction with the main stream. The fan is steepest near its apex, which points upstream and slopes gently and convexly outward (downstream) with a gradual decrease in gradient.

drainageway--(a) A general term for a course or channel along which water moves in draining an area. (b) [soil survey] a term restricted to relatively small, roughly linear or arcuate depressions that move concentrated water at some time, and either lack a defined channel (e.g. head slope, swale) or have a small, defined channel (e.g. low order streams).

hills–-A landscape dominated by hills and associated valleys. The landform term is singular (hill).

Table 2. Representative physiographic features

Climatic features

Annual precipitation in the Clayey Pinedale Plateau ecological site ranges from 9-12 inches per year. Wide fluctuations may occur in yearly precipitation and result in more dry years than those with more than normal precipitation. Temperatures show a wide range between summer and winter and between daily maximums and minimums. This is predominantly due to the high elevation and dry air, which permits rapid incoming and outgoing radiation. Cold air outbreaks in winter move rapidly from northwest to southeast and account for extreme minimum temperatures. Much of the precipitation accumulation (45 percent) comes in the winter in the form of snow (October to April). The wettest month is May (1.69 inches). The dominant plants (sagebrush and cool season grasses) are well adapted to these conditions. Daytime winds are generally stronger than nighttime and occasional strong storms may bring brief periods of high winds with gusts to more than 50 mph. The growing season is short (less than 60 day) and cool (critical growth period): primary growth typically occurs between May and June. Growth of native cool-season plants begins about mid-April and continues to approximately early July. Some green-up of cool-season plants usually occurs in September with adequate fall moisture.

All data is based on the 30 year average from 1981-2010.

Table 3. Representative climatic features

Climate stations used

• (1) BOULDER REARING STN [USC00480951], Boulder, WY

• (2) CORA [USC00482054], Cora, WY

• (3) PINEDALE [USC00487260], Pinedale, WY

Influencing water features

There are no influencing water features in the Clayey Pinedale Plateau ecological site.

Soil features

These are moderately deep and deep (at least 20 inches deep) well drained soils with more than 35 percent clay in the subsoil. Some soil cracking (not severe) occurs during the dry summer months, especially where the plant cover has been reduced. Water-holding capacity is high, but surface intake is restricted which causes runoff and reduces effectiveness of precipitation. A common scenario is to have a 1-2” cap of sandy loam over clay loam due to young soil development of weathered shale, mudstone, and sandstone parent materials.

Major Soil Series correlated to this site include: the Gunsone and Oysterridge series.

Typical taxonomy: Fine Torrertic Haplustepts

Soil organic matter (SOM) <2% is common. Color and structure are difficult indicators to assess in semiarid soils because SOM potential is naturally low. Typically, the soil surface consists of an A-horizon of 1-6 inches (3-16 cm) thick with strong medium granular structure and a subsurface that is medium to strong subangular blocky or prismatic structure. The surface is typically brown to grayish brown (i.e. 10YR 4/3 to 5/2) with a similar colored subsurface. Field indicators of departure from the reference condition include exposure of subsoil as evidenced by excessive pedestalling and/or surface disturbance.

Table 4. Representative soil features

Animal community

The following table lists suggested stocking rates for cattle under continuous season-long grazing under normal growing conditions with a harvest efficiency (HE) of 25 percent. These are conservative estimates that should be used only as guidelines in the initial stages of the conservation planning process. Often, the current plant composition does not entirely match any particular plant community (as described in this ecological site description). A field visit is required to document actual plant composition and production. More precise carrying capacity estimates, considering forage preference and accessibility (slope, distance to water, etc.), should be calculated using this information, particularly when grazers other than cattle are involved. Under more intensive grazing management, improved harvest efficiencies (up to 35 percent) can result in an increased carrying capacity, but recovery time for upland sites is much longer. If distribution problems occur, stocking rates should be reduced or facilitating conservation practices (i.e., cross-fencing, water development) implemented to maintain plant health and vigor.

Stocking rates are expressed in Animal Unit Months (AUMs) which is defined as the amount of forage consumed by a 1,000 lb. cow with a less than 4 month old calf at her side.

Plant Community Production (lbs./ac.) Initial Suggested Stocking Rate (AUMs/ac.)* Ac./AUM
1.1 ARTRW8/ELLAL 400-600-800 0.07 14
1.2 ELLAL 400-600-800 0.1 10
2.1 ARTRW8/BG 200-400-600 0.03 33
3.1 CHVI8/ELLAL 100-200-450 0.05 20
4.1 Annuals 100-300-600 0.04 24
4.2 Reclaimed 400-600-800 0.08 13
5.1 Dryland Pasture 500-700-900 0.19 5
5.2 Irrigated Pasture 2000-3000-4000 0.82 1.25

* Continuous, season-long grazing by cattle under average growing conditions.

Calculation for stocking rates are as follows: Using RV values for production, take forage palatable to grazing cattle and multiply by 0.25 HE and divide by 912.5 lbs./AUM air-dry weight (ADW) to arrive at the initial suggested stocking rate in AUMs/acre.

Grazing by domestic livestock is one of the major income-producing industries in the area. Rangeland in this area may provide year-long forage for cattle, sheep, or horses. During the dormant period, the forage for livestock must be supplemented with protein because the quality does not meet minimum livestock requirements.

Distance to water, shrub density, and slope can affect grazing capacity within a management unit. Adjustments should be made for the area that is considered necessary for reduction of animal numbers. For example, 30 percent of a management unit may have 25 percent slopes and distances of greater than one mile from water; therefore the adjustment is calculated for 30 percent of the unit (i.e. 50 percent reduction on 30 percent of the management unit). Fencing, slope length, management, access, terrain, kind and class of livestock, and breeds are all factors that can increase or decrease the percent of grazeable acres within a management unit. Adjustments should be made that incorporate these factors when calculating stocking rates.

Wildlife:
Reference State:
1.1 WY Big Sagebrush/Perennial Grass: This community phase provides good transitional and summer habitat for greater sage-grouse, mule deer, pronghorn, and elk. Suitable thermal and escape cover for mule deer exists. A diverse suite of herbaceous species also provide important micronutrient requirements for big game species throughout the year. These areas also provide high quality bird-nesting habitat where sagebrush canopy and residual bunchgrasses hide nests and young from predators. This community can be used as migration and stopover habitat by big game, but is generally a small component of the landscape. Spring green-up of grass is an important nutritional component of this community for migrating big game.

1.2 Rhizomatous Wheatgrass: Suitable thermal and escape cover for mule deer and pronghorn may be limited due to the low density of woody plants. However, sagebrush is a very important winter forage for mule deer and antelope. Year-round habitat is provided for greater sage-grouse and many other sagebrush obligate species such as sage sparrow, Brewer’s sparrow, sage thrasher, pygmy rabbit, sagebrush vole, horned lizard, and pronghorn. Open spaces in sagebrush canopy are potential sage grouse lek locations. Other birds that would frequent this plant community include horned larks and golden eagles.

2. Bare Ground
2.1 WY Big Sagebrush/Bare Ground: This community phase provides potential foraging habitat for big game and greater sage-­grouse when the sagebrush plants are in a healthy condition. If the sagebrush is old and has poor leader production, it may not be providing quality forage for browsing animals. The lack of herbaceous species limits the species diversity, thus the value of the site for birds and small mammals is likely less than the Reference State due to the lack of cover in the interspaces of the sagebrush plants. The lack of plant diversity also limits the diversity of insects used by wildlife species.

3. Disturbed: These communities provide limited forage for pronghorn and mule deer due to low production and lack of sagebrush. They may be used as a foraging site by sage grouse if proximal to woody cover, or seasonally used by cottontail or jack rabbits. The overall dominance of rabbitbrush is generally not ideal to support a wide variety of wildlife.

4. Highly Disturbed State:
4.1 Annuals: This community phase is highly variable in its value to wildlife. It typically is less diverse, has lower forage value, and has limited structure that wildlife need for cover. This state is vulnerable to repeated disturbance which can result in a complete loss of value for wildlife. In addition, sites in this state are more susceptible to invasion of non-native species, further degrading the value for wildlife.

4.2 Reclaimed: This community phase is highly variable in its value to wildlife. Reclamation success, size and configuration of the reclaimed area, the species planted, and the time it takes for plants to establish will determine the value of the site for wildlife. A fully reclaimed site containing a diversity of herbaceous and woody native plants can eventually provide the same wildlife habitat benefits as the Reference State. In most cases, grasses and forbs establish early in the reclamation process, whereas shrubs take significantly longer to establish. Wildlife species dependent upon herbaceous plant communities for forage will benefit from reclamation sooner than those species dependent upon a mixed shrub/grass community. Suitable habitat for wildlife species that require tall, dense sagebrush (greater sage-grouse, pronghorn, mule deer, and sagebrush obligate songbirds) will likely take several decades to achieve providing appropriate shrub species were planted. It is possible to achieve successful, diverse reclamation on linear disturbances (i.e., pipelines) without seeding shrubs, but it will likely take longer than a decade for seed from shrubs adjacent to the area to establish on-site.

Hydrological functions

Water is the principal factor limiting forage production on this site. This site is dominated by soils in hydrologic group C, with localized areas in hydrologic group D. Infiltration ranges from very slow to moderately slow. Runoff potential for this site varies from moderate to high, depending upon soil hydrologic group and ground cover. In many cases, lesser sloping areas with greater than 75 percent ground cover have the greatest potential for high infiltration and lower runoff. Greater sloping areas where ground cover is less than 50 percent have the greatest potential to have reduced infiltration and higher runoff (refer to Part 630, NRCS National Engineering Handbook for detailed hydrologic information).

Rills and gullies should not typically be present. Water flow patterns should be barely distinguishable if at all present. Pedestals are only slightly present in association with bunchgrasses and shrubs. Litter typically falls in place, and signs of movement are not common. Chemical and physical crusts are sometimes present on this site.

Recreational uses

This site provides some limited recreational opportunities for hiking, horseback riding, bird watching, and upland game hunting. The forbs have a variety of colors and shapes that appeal to photographers. This site provides valuable open space when located in large, unfragmented landscapes.

Wood products

No wood products are associated with the Clayey Pinedale Plateau ecological site.

Other products

No other products are associated with the Clayey Pinedale Plateau ecological site.

Other information

Site is provisional (2019). History of site development: Range Site Clayey Foothills and Basins West (Cy 10-14W) published in 1988. Site converted to provisional Ecological Site Description in 2005 (pdf format) and entered into ESIS. Range health reference worksheet completed in 2007. Pinedale Plateau LRU designation occurred in 2012. Site concept updated for new LRU designation (provisional status) in 2019.

Inventory data references

Information presented was derived from: 1988 Range Site Descriptions - Clayey Foothills and Basins West (10-14W) MLRA 34A Cool Desertic Basins and Plateaus, historic NRCS clipping data, literature , Sublette Soil Survey field observations (based on five paired plot sampled sites in 2018 in the Reference State), observations from numerous others, and personal contacts with range-trained personnel (i.e., agency specialists, landowners, land managers, and scientists).

References

• . 2021 (Date accessed). USDA PLANTS Database. http://plants.usda.gov.

• . 2021 (Date accessed). USNVC [United States National Vegetation Classification]. 2019. United States National Vegetation Classification Database, V2.03. Federal Geographic Data Committee, Vegetation Subcommittee, Washington DC.. USNVC: http://usnvc.org/.

• . 1997. Introduction to Microbiotic Crusts. Natural Resources Conservation Service.

• . 2002. Management considerations for sagebrush (Artemisia) in the western U.S.: A selective summary of cumulative information about the ecology and biology of woody N. American sagebrush taxa. USDI-BLM, Washington, D.C..

• Bestelmeyer, B., J.R. Brown, K.M. Havstad, B. Alexander, G. Chavez, and J.E. Herrick. 2003. Development and Use of State and Transition Models for Rangelands. Jornal of Range Management 56:114–126.

• Bestelmeyer, B., J.R. Brown, J.E. Herrick, D.A. Trujillo, and K.M. Havstad. 2004. Land Management in the American Southwest: a state-and-transition approach to ecosystem complexity. Environmental Management 34:38–51.

• Bestelmeyer, B. and J. Brown. 2005. State-and-Transition Models 101: A Fresh look at vegetation change.

• Bukowski, B.E. and W.L. Baker. 2013. Historical fire regimes, reconstructed from land-survey data, led to complexity and fluctuation in sagebrush landscapes. Ecological Applications 23:546–564.

• Cagney, J., E. Bainter, B. Budd, T. Christiansen, V. Herren, and M. Holloran. 2010. Grazing Influence, Objective Development, and Management in Wyoming's Greater Sage-Grouse Habitat. 35p.

• Chambers, J.C., J.L. Beck, T.J. Christiansen, K.J. Clause, J.B. Dinkins, K.E. Doherty, K.A. Griffin, D.W. Havlina, K.F. Henke, L.L. Kurth, J.D. Maestas, M. Manning, K.E. Mayer, B.A. Mealor, C. McCarthy, M.A. Perea, and D.A. Pyke. 2016. Using resilience and resistance concepts to manage threats to sagebrush ecosystems, Gunnison sage-grouse, and Greater sage-grouse in their eastern range: A strategic multi-scale approach.. Gen. Tech. Rep. RMRS-GTR-356.. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fort Collins, CO. 1–143.

• Clause, K. and J. Randall. 2014. Wyoming Sagebrush Die-Off Report. Unpublished.

• Derner, J.D., G.E. Schuman, R.F. Follett, and G.F. Vance. 2013. Plant and Soil Consequences of Shrub Management in a Big Sagebrush-Dominated Rangeland Ecosystem.

• Miller, J.F., R.H. Frederick, and R.J. Tracey. 1973. “Precipitation-Frequency Atlas of the United States” NOAA Atlas 2, Volume 2 (Wyoming). National Weather Service, Silver Spring, Maryland.

• Rosentrater, R., M. Bowker, and J. Belnap. 2007. A Field Guide to Biological Soil Crusts of the Western U.S. Drylands. U.S. Government Printing Office, Denver, Colorado.

• Shultz, L.M. 2009. Monograph of Artemisia Subgenus Tridentatae (Asteraceae-Anthemideae). Systematic Botany Monographs 89:1–131.

• Sommers, J. 1994. Green River Drift- A History of the Upper Green River Cattle Association.

• Stiver, S., E. Rinkes, and D. Naugle. 2010. Sage-Grouse Habitat Assessment Framework. 6p.

• Stringham, T.K., W.C. Kreuger, and P.L. Shaver. 2003. State and Transition Modeling: an ecological process approach. Journal of Range Management 56:106–113.

• U. S. Environmental Protection Agency. 2010. Level III and IV ecoregions of the continental United States. U.S. EPA, National Health and Environmental Effects Research Laboratory, Corvallis, Oregon, U.S..

• Winward, A. 2007. Boulder, Squaretop Area Field Notes. Field Notes. Unpublished.

Contributors

Bryan Christensen
Karen J. Clause

Approval

Kirt Walstad, 9/28/2023