Physiographic features

The Loamy Calcareous Green River Basin (LyC GRB) ecological site (R034AB126WY) is located within LRU “B” in MLRA “34.” This ecological site occurs in intermontane basin landscapes on hill, draw, pediment, and fan remnant landforms (see definitions below). The slope ranges from level to 15%. This site occurs on all aspects.
fan remnant – A general term for landforms that are the remaining parts of older fan-landforms, such as alluvial fans, fan aprons, inset fans, and fan skirts, that either have been dissected (erosional fan-remnants) or partially buried (nonburied fan-remnants). An erosional fan remnant must have a relatively flat summit that is a relict fan-surface.
intermontane basin – A generic term for wide structural depressions between mountain ranges that are partly filled with alluvium and called "valleys" in the vernacular.
hills – A landscape dominated by hills and associated valleys. The landform term is singular (hill).

Table 2. Representative physiographic features

Climatic features

Annual precipitation ranges from 7-9 inches per year. Wide fluctuations may occur in yearly precipitation and result in more dry years than those with above 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%) comes in the winter in the form of snow (Oct to April). The wettest month is May (1.03 inches). The growing season is short (50-90 day average) and cool: primary growth typically occurs between May and June. 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. Growth of native cool season plants begins about mid-April and continues to approximately early-July. Some green up of cool season plants may occur in September with adequate fall moisture.

Table 3. Representative climatic features

Climate stations used

• (1) GREEN RIVER [USC00484065], Green River, WY

• (2) ROCK SPRINGS AP [USW00024027], Rock Springs, WY

• (3) FONTENELLE DAM [USC00483396], Green River, WY

Influencing water features

None

Soil features

The soils of this site are deep to moderately deep (greater than 20" to bedrock), and well-drained. Textures range from loams to very fine sandy loam on the coarse end to clay loam (<30% clay content) on the heavy end. The most common textures include loam, silt loam, and sandy clay loam. A highly common scenario is to have a 1 to 3” cap of sandy loam over a sandy clay loam due to young soil development of weathered sandstone and shale parent materials.

Major Soil Series correlated to this site include: Pepal, Chickenhill, Luhon, Piezon, Jemdillon and Polaris
Typical taxonomy: Fine-loamy Ustic Haplocalcids

Table 4. Representative soil features

Animal community

The following table lists suggested initial stocking rates for cattle under continuous season-long grazing under normal growing conditions. 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). Because of this, a field visit is recommended, in all cases, to document plant composition and production. More precise carrying capacity estimates should be calculated using field information along with animal preference data, particularly when grazers other than cattle are involved. Under more intensive grazing management, improved harvest efficiencies can result in an increased carrying capacity, but recovery time for upland sites is much longer than in a low intensity system.
If distribution problems occur, stocking rates must be reduced or facilitating conservation practices (i.e. cross-fencing, water development) used to maintain plant health and vigor.
Plant Community Production Carrying Capacity*
(lb./ac) Low-RV-High (AUM/AC) (AC/AUM)
Big Sagebrush/Bunchgrass (Reference) 200-400-500 0.06 17
Bunchgrass/Big Sagebrush 200-400-500 0.08 13
Bunchgrass 200-400-500 0.1 10
Big Sagebrush/Thickspike Wheatgrass 100-300-400 0.03 33
Thickspike Wheatgrass/Big Sagebrush 100-300-400 0.05 20
Big Sagebrush/Bare Ground 100-300-400 0.01 100
Sprounting Shrub/Thickspike Wheatgrass 100-200-250 0.05 20
Annuals/Bare Ground 30-100-200 0.01 100
Reclaimed 200-400-500 0.12 8




* - Continuous, season-long grazing by cattle under average growing conditions.
**Calculation for these stocking rates are as follows: using RV values for production, take only forage palatable to cattle and multiply by 0.25 harvest efficiency and divide by 913 (pounds of air dried weight forage per Animal Unit Month based on intake rate of 2.6%) to arrive at carrying capacity

Grazing by domestic livestock is one of the major income-producing industries in the area. Rangeland in this area may provide yearlong forage for cattle, sheep, or horses. During the dormant period, protein supplement is recommended 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% of a management unit may have 25% slopes and distances of greater than 1 mile from water; therefore the adjustment is only calculated for 30% of the unit (i.e. 50% reduction on 30% 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 graze-able acres within a management unit. Adjustments should be made that incorporate these factors when calculating stocking rates

Wildlife
The Loamy Calcareous ecological site in the Green River Basins provides suitable and valuable habitat for a variety of wildlife species. In most cases, the greater the density and diversity of native forbs, grass and shrub species within the site, the greater the diversity of wildlife the site can support including insects which many wildlife species depend on for their dietary requirements. Mid-sized cool season bunchgrasses provide forage and cover for big game species, small mammals, birds and reptiles. Wildlife such as pronghorn, elk, cottontails, and jackrabbits depend largely on grass for forage. Birds nest among the bunchgrasses and utilize grass as screening cover from predatory wildlife. Mule deer, pronghorn, greater sage grouse, and songbirds utilize the taller grass amongst the shrubs as hiding cover for their young. Sagebrush provides important winter forage for greater sage grouse, mule deer, and pronghorn. Year-round habitat is provided for sagebrush obligate species such as greater sage grouse, cottontails, pygmy rabbit, sagebrush vole, short-horned lizard, and pronghorn. Seasonal habitat needs are provided for migrants such as sage sparrow, Brewer’s sparrow, Vesper’s sparrow, sage thrasher, and other sagebrush obligate songbirds. Other birds that frequent this plant community include horned larks and golden eagles.
Although not a dominant part of this community, forbs are an important component of this habitat type, providing an early food source for sage grouse chicks both nutritionally and via the insects that forbs attract. Forbs provide necessary moisture to wildlife in arid landscapes. Pronghorn depend on abundant forbs to aid in the production of milk to nurse fawns and as forage for fawn development and health. Dietary overlap between wildlife and wild horses in this ecological site can significantly reduce the quantity and quality of habitat for wildlife.
Reference State:
1.1 Big Sagebrush/Bunchgrass Plant Community
This plant community provides optimal winter habitat for greater sage grouse, mule deer, pronghorn, and other species that depend on shrubs that stand up through the snow for forage. These areas also provide high quality bird nesting habitat where sagebrush canopy and residual bunchgrasses hide nests and young from predators. Forbs, although sparse, are necessary in the understory of this plant community to attract insects that are a highly nutritious spring food source for greater sage grouse chicks and other sagebrush obligate bird species. Winter use by mule deer and pronghorn may be significant and some shrubs may become hedged over time with excessive browsing.
1.2 Bunchgrass/Big Sagebrush Plant Community
This vegetation community tends to have higher herbaceous plant density that may attract more diverse wildlife use. The state provides suitable forage and cover for sagebrush obligate species. The more open canopy promotes higher diversity and quantity of forbs that are important for early greater sage grouse brood rearing habitat. A reduced sagebrush canopy may result in a slightly lower nesting frequency by greater sage grouse and songbirds. Winter use by mule deer and pronghorn may be significant and some shrubs may become hedged over time with excessive browsing.
1.3 Bunchgrass Plant Community
This plant community provides foraging habitat for greater sage grouse when in proximity to areas with denser sagebrush cover. Due to the higher production of perennial cool-season grasses, this vegetation type provides high forage value for wintering elk. Mule deer and pronghorn transition through these habitats during annual migrations between summer and winter ranges. It also provides suitable habitat for burrowing animals.
Grazing Resistant State:
This State is variable in its value to wildlife. The value of the sagebrush community is similar to the reference state but the value of the grass community decreases. In periods of high plant vigor, the grass plants can provide cover for nesting birds and small mammals. In periods of drought and low plant vigor and diversity, especially low forb availability, grass plants are too short and not dense enough to provide adequate cover and the wildlife value of these areas declines. Mat-forming forbs often occupy the space and nutrients needed for more desirable forbs such as globemallow, penstemon, milk vetches and composites.
Bare Ground State:
This State provides suitable winter habitat for foraging big game and greater sage grouse when sagebrush is in a healthy state and stands above winter snow. The lack of herbaceous species limits the value of this state for birds and small mammals due to the lack of cover in the interspaces of the sagebrush plants. The lack of plant diversity limits the diversity of insects used by wildlife species. Bare ground provides essentially no habitat value for wildlife. In addition, bare ground may be more susceptible to invasion of non-native species, further degrading the value for wildlife.
Disturbed State:
This State is capable of producing a high number of insects which are important for pollination and bird forage at times of the year. Depending on the subspecies, rabbitbrush can be used heavily by wintering mule deer and pronghorn, especially when other preferred winter forages are unavailable or in poor vigor due to over-use or drought. The lack of an herbaceous community limits the value as bird and small mammal hiding cover and forage for grazing animals. Annual plants have little nutritive value and are typically too short to provide hiding cover for wildlife.
Highly Disturbed Site:
As described in the Bare Ground State, annuals and bare ground hold little value for wildlife due to the lack of suitable forage and cover. This State is vulnerable to an increase in weedy species that can migrate into adjacent areas, degrading the adjacent areas’ value for wildlife. Suitable habitat for wildlife species which require tall, dense sagebrush (greater sage grouse, pronghorn, mule deer, and sagebrush obligate songbirds) will likely not benefit from reclamation efforts for a decade or longer, providing shrub species were planted and/or seeded from shrubs adjacent to the area and have established onsite.

Hydrological functions

Water is the principal factor limiting forage production on this site. This site is dominated by soils in hydrologic group B (infiltration rate of 0.15-0.3 in/hr), with localized areas in hydrologic groups A (infiltration rate of >0.3 in/hr) and C (infiltration rate of 0.05-0.15 in/hr). Infiltration ranges from moderately rapid to moderate. Runoff potential for this site varies from low to moderate depending on soil hydrologic group and ground cover. In many cases, areas with greater than 75% ground cover have the greatest potential for high infiltration and lower runoff. Areas where ground cover is less than 50% have the greatest potential to have reduced infiltration and higher runoff (refer to Part 630, NRCS National Engineering Handbook for detailed hydrology 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 rare to non-existent. Biological crusts should be present, and play an important role in soil stability.

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, un-fragmented landscapes.

Wood products

NONE

Other products

NONE

Other information

Similarity Index is based on species composition by air-dry weight. Calculations of allowable pounds per acre for each species are based on the sum of the maximum end of the production range or actual production (whichever is less) in the plant table for the Desired Plant Community until the maximum allowable is reached for the plant grouping. The sum is then divided by the Representative Value (RV) of total annual production for the Desired Plant Community.

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.

• LLC, . 2009. Greater Sage-Grouse Focused Herbaceous Monitoring of Moxa Arch Sagebrush Vegetation Treatments.

• 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.

• 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.

• Tanner, R.L. 2016 (Date accessed). Leasing the Public Range: The Taylor Grazing Act and the BLM. http://www.wyohistory.org/encyclopedia/leasing-public-range-taylor-grazing-act-and-blm.

• 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.

Other references

USDI, B. o. (2015). Allotment files. Rock Springs, WY: unpublished.

Contributors

Bryan Christensen
Karen J. Clause

Approval

Kirt Walstad, 9/28/2023

Acknowledgments

Jill Randell, Wyoming Game and Fish
Shari Meeks, Sublette County Conservation District
Bailey Terry, BLM