Physiographic features

The Loamy Green River Basin (Ly) ecological site (R034AB122WY) is located within LRU “B” in MLRA “34A.” 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 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%) 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 usually occurs in September with adequate fall moisture.

Table 3. Representative climatic features

Climate stations used

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

• (2) BIG PINEY MARBLETON AP [USW00024164], Big Piney, 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 light clay loam (<30% clay content) on the heavy end. The most common textures include loam, fine sandy 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.
Representative Soil Taxonomy (particle size & taxonomic subgroup): fine-loamy Ustic Haplargids, Ustic Calciargids, or Ustic Haplocambids

Table 4. Representative soil features

Animal community

LIvestock:
The following table lists suggested 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) (AUM/AC) (AC/AUM)
Big Sagebrush/Bunchgrass (Reference) 300-500-700 (.06) (16)
Bunchgrass/Big Sagebrush 300-500-700 (.07) (14)
Bunchgrass 300-500-700 (.08) (13)
Big Sagebrush/Rhizomatous Wheatgrass 200-400-600 (.03) (33)
Rhizomatous Wheatgrass/Big Sagebrush 200-400-600 (.06) (17)
Big Sagebrush/Bare Ground 100-300-400 (.01) (100)
Rabbitbrush/Rhizomatous Wheatgrass 200-400-600 (.04) (25)
Annuals/Bare Ground (.01) (100)
Reclaimed (.08) (13)
* - 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 multiply by 0.25 harvest efficiency and divide by 912 (air dried weight) 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, the forage for livestock use needs to 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% 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 (Ly) ecological site in the Green River Basin, LRU B, in MLRA 34A, Cool Central Desertic Basins and Plateaus provides suitable and valuable habitat to an array of wildlife species. including, but not limited to, suitable food, thermal, and escape cover for mule deer, elk, and pronghorn antelope. Sagebrush, which can approach 15% protein and 40-60% digestibility, provides important winter forage for the greater sage-grouse, mule deer, and antelope. Year-round habitat is provided for sage grouse and many other sagebrush obligate species such as the sage sparrow, Brewer’s sparrow, sage thrasher, pygmy rabbit, sagebrush vole, horned lizard, and pronghorn antelope. Other birds that would frequent this plant community include horned larks and golden eagles. (Stiver, Rinkes, & Naugle, 2010)
Reference State:
1.1 Big Sagebrush/Bunchgrass: This community phase provides optimal winter habitat for sage-grouse, mule deer, pronghorn, and other species that depend on shrubs that stand up through the snow for forage. A diverse suite of herbaceous species also provide important micro-nutrient 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.
1.2 Bunchgrass/WY Big Sagebrush: This community phase tends to have higher herbaceous plant diversity that may attract more diverse wildlife use. The plant community 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 sage-grouse brood­rearing habitat. It also provides high quality habitat for mule deer and pronghorn as they transition between winter and summer ranges.
1.3 Bunchgrass: This community phase provides foraging habitat for sage­grouse 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. Forb diversity is beneficial to mule deer and pronghorn during transition between winter and summer ranges. It also provides suitable habitat for burrowing animals.
Grazing Resistant State:
2.1 Big Sagebrush/Rhizomatous Wheatgrass: This community phase 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 herbaceous understory provides cover for nesting birds and small mammals. In periods of drought and low plant vigor, the herbaceous understory is short and not dense enough to provide adequate cover and habitat value declines. Diversity is low, and mat-forming forbs often occupy the space and nutrients needed for more desirable forbs such as globemallow, milkvetch, and penstemons.
2.2 Rhizomatous Wheatgrass: This community phase is variable in its value to wildlife. Value is low for species dependent on sagebrush unless in close proximity to areas with sagebrush cover. In periods of high plant vigor, herbaceous species provide cover for some birds and small mammals. In periods of drought and low plant vigor, the herbaceous community is often too short and not dense enough to provide adequate cover and habitat. Plant and animal diversity is low.
Eroded State:
3.1 Big Sagebrush/Bare Ground: This community phase provides suitable winter habitat for foraging big game and sage­grouse when sagebrush is in a healthy state and stands above winter snows. The lack of herbaceous species limits the value of the site 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.
Disturbed State:
4.1 Rabbitbrush/Rhizomatous wheatgrass: This community phase is capable of producing a high number of insects which are important for pollination and bird forage. Rabbitbrush, depending on the sub-species present, can be used heavily by wintering and transitional big game, especially when other preferred winter forages are unavailable or in poor vigor due to over-use or drought. 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.
Highly Disturbed State:
5.1 Annuals/Bare Ground: This community phase is dominated by annuals and bare ground which hold little value for wildlife due to the lack of suitable forage and cover. Furthermore, weedy species can migrate into adjacent areas, degrading wildlife habitat in adjacent areas.
5.2 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 on herbaceous plant communities for forage (elk, prairie dogs, and fox) will benefit from reclamation sooner than those species dependent on a mixed shrub/grass community. Suitable habitat for wildlife species that require tall, dense sagebrush (wintering sage-grouse, pronghorn, mule deer, and sagebrush obligate songbirds) is likely possible within a decade, 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 take longer than a decade for seed from shrubs adjacent to the area to established on-site.

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 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, with only slight movement to leeward side of shrubs. Chemical crusts do not exist. Soil biological crusts are common.

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

None

Other products

None

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. and J.R. Brown. 2005. State-and-Transition Models 101: a Fresh Look at Vegetation Change.

• 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.

• 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.

• 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.

• 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.

Other references

USDI, BLM 2015. Allotment Files. Unpublished.
Western Stockman, Feb 2, 2015.
Wyoming Department of State Parks and Cultural Resources 2014.

Contributors

Karen J. Clause
Bryan Christensen

Approval

Kirt Walstad, 9/28/2023