Natural Resources
Conservation Service
Ecological site R034AY118WY
Impervious Clay
Green River and Great Divide Basins (IC)
Last updated: 2/24/2025
Accessed: 07/05/2026
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Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.
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Figure 1. Mapped extent
Areas shown in blue indicate the maximum mapped extent of this ecological site. Other ecological sites likely occur within the highlighted areas. It is also possible for this ecological site to occur outside of highlighted areas if detailed soil survey has not been completed or recently updated.
Associated sites
R034AY104WY Clayey Green River and Great Divide Basins (Cy)
Clayey
R034AY144WY Saline Upland Green River and Great Divide Basins (SU)
Saline Upland
Similar sites
R034AY110WY Dense Clay Green River and Great Divide Basins (DC)
Dense Clay (DC) 7-9GR has higher production and does not have alkaline/saline properties.
Table 1. Dominant plant species
Tree Not specified
Shrub Not specified
Herbaceous Not specified
Physiographic features
This site will usually occur in a lowland position, on flat to gently sloping land, but can occur in all positions.
Table 2. Representative physiographic features
Landforms (1) Alluvial fan
(2) Stream terrace
Flooding frequency None Ponding frequency None Elevation 6000 – 7200 ft Slope 0 – 40 % Ponding depth 0 in Aspect Aspect is not a significant factor 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. Extreme storms may occur during the winter, but most severely affect ranch operations during late winter and spring.
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 April 15 and continues to about July 15. Some green up of cool season plants may occur in September if moisture is available.
For detailed information visit the Natural Resources Conservation Service National Water and Climate Center at http://www.wcc.nrcs.usda.gov/cgibin/state.pl?state=wy website. Other climate stations representative of this precipitation zone include “Bitter Creek”, ”Farson ”, “Rock Springs FAA AP”, and “Wamsutter” in Sweetwater County; “Church Buttes Gas PLT”, and Mountain View” in Uinta County; “Fontenelle”, “La Barge”, and “Sage 4 NNW” in Lincoln County; and “Big Piney” in Sublette County.
Table 3 Representative climatic features
Frost-free period (average) 120 days Freeze-free period (average) 130 days Precipitation total (average) 10 in BarLineFigure 2. Monthly precipitation range
BarLineFigure 3. Monthly average minimum and maximum temperature
">Influencing water features
There are no water features associated with this site.
Soil features
The soils of this site are moderately deep (greater than 20” to bedrock) to very deep, well drained soils formed in alluvium. The topsoil, except for thin ineffectual layers, will be heavy clays and/or soils that develop large cracks when dry and are very sticky when wet. These soils are not high in salinity and/or alkalinity but do have high concentrations of exchangeable sodium throughout the profile.
Major Soil Series correlated to this site include: Kissick and Elkol series.Table 4. Representative soil features
Surface texture (1) Clay
(2) Silty clay
Family particle size (1) Clayey
Drainage class Well drained Permeability class Very slow to slow Soil depth 15 – 60 in Surface fragment cover <=3" Not specified Surface fragment cover >3" Not specified Available water capacity
(0-40in)3 – 4.5 in Calcium carbonate equivalent
(0-40in)0 – 15 % Electrical conductivity
(0-40in)0 – 8 mmhos/cm Sodium adsorption ratio
(0-40in)0 – 5 Soil reaction (1:1 water)
(0-40in)6.6 – 8.4 Subsurface fragment volume <=3"
(Depth not specified)Not specified Subsurface fragment volume >3"
(Depth not specified)Not specified Ecological dynamics
As this site deteriorates from improper grazing management, species such as birdfoot sage and unpalatable forbs will increase. Indian ricegrass will decrease in frequency and production.
These plant communities narratives may not represent every possibility, but they probably are the most prevalent and repeatable plant communities. The plant composition tables shown above have been developed from the best available knowledge at the time of this revision. As more data is collected, some of these plant communities may be revised or removed, and new ones may be added. None of these plant communities should necessarily be thought of as “Desired Plant Communities”. According to the USDA NRCS National Range and Pasture Handbook, Desired Plant Communities (DPC’s) will be determined by the decision-makers and will meet minimum quality criteria established by the NRCS. The main purpose for including any description of a plant community here is to capture the current knowledge and experience at the time of this revision.
The Reference Plant Community (description follows the plant community diagram) has been determined by study of rangeland relic areas, or areas protected from excessive disturbance. Trends in plant communities going from heavily grazed areas to lightly grazed areas, seasonal use pastures, and historical accounts have also been used.
The following is a State and Transition Model Diagram that illustrates the common plant communities (states) that can occur on the site and the transitions between these communities. The ecological processes will be discussed in more detail in the plant community narratives following the diagram.State and transition model
More interactive model formats are also available. View Interactive Models
Click on state and transition labels to scroll to the respective textEcosystem states
State 1 submodel, plant communities
State 2 submodel, plant communities
State 3 submodel, plant communities
State 1
Birdfoot Sagebrush/Rhizomatous Wheatgrass (Reference)Community 1.1
Birdfoot Sagebrush/Rhizomatous Wheatgrass (Reference)The interpretive plant community for this site is the Reference Plant Community. Potential vegetation is estimated at 50% grasses or grass-like plants, 5% forbs and 45% woody plants.
The major grasses include western wheatgrass, bottlebrush squirreltail, Indian ricegrass, and Sandberg bluegrass. Birdfoot sagebrush is the major woody plant. Other woody plants that may occur include Gardner’s saltbush and winterfat.
A typical plant composition for this state consists of western wheatgrass 25-45%, bottlebrush squirreltail 10-20%, Indian ricegrass 10-20%, up to 5% Sandberg bluegrass, perennial forbs 1-5%, birdfoot sagebrush 25-40%, and 5-10% other woody species. Ground cover, by ocular estimate, varies from 30-45%.
The total annual production (air-dry weight) of this state is about 350 pounds per acre, but it can range from about 250 lbs./acre in unfavorable years to about 500 lbs./acre in above average years.
This state is extremely stable and well adapted to the Cool Central Desertic Basins and Plateaus climatic conditions. The diversity in plant species allows for high drought resistance. This is a sustainable plant community (site/soil stability, watershed function, and biologic integrity).
Transitions or pathways leading to other plant communities are as follows:
• Heavy Continuous Season-long Grazing or Severe Hoof Compaction will convert the plant community to the Heavy Birdfoot Sage State.Figure 4. Annual production by plant type (representative values) or group (midpoint values)
Table 5. Annual production by plant type
Plant type Low
(lb/acre)Representative value
(lb/acre)High
(lb/acre)Grass/Grasslike 125 175 250 Shrub/Vine 112 157 225 Forb 13 18 25 Total 250 350 500 Figure 5. Plant community growth curve (percent production by month). WY0401 , 7-9GR, UPLAND SITES. ALL UPLAND SITES.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec J F M A M J J A S O N D 0 0 0 10 35 40 10 0 5 0 0 0 State 2
Rhizomatous Wheatgrass/Birdfoot SagebrushCommunity 2.1
Rhizomatous Wheatgrass/Birdfoot SagebrushThis plant community is the result of mechanical treatment after frequent and severe grazing. Rhizomatous wheatgrass and bottlebrush squirreltail dominate. Birdfoot sagebrush usually comprises 10-20% of annual production.
The total annual production (air-dry weight) of this state is about 200 pounds per acre, but it can range from about 100 lbs./acre in unfavorable years to about 400 lbs./acre in above average years.
The soil is not protected and erosion will increase if management is not changed. The biotic integrity may be reduced due to low vegetative production. The watershed is functioning at risk.
Transitional pathways leading to other plant communities are as follows:
• Natural Succession will return this state to near Reference Plant Community (Birdfoot Sagebrush/Rhizomatous Wheatgrass State).Figure 6. Plant community growth curve (percent production by month). WY0401 , 7-9GR, UPLAND SITES. ALL UPLAND SITES.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec J F M A M J J A S O N D 0 0 0 10 35 40 10 0 5 0 0 0 State 3
Heavy Birdfoot SagebrushCommunity 3.1
Heavy Birdfoot SagebrushThis plant community is a result of heavy continuous season-long grazing. Severe hoof compaction typically occurs due to fine soil textures. Birdfoot sagebrush increases to 60-80% of the annual production. Cool season bunchgrasses decrease while rhizomatous wheatgrass prevails. Annual forbs increase.
The total annual production (air-dry weight) of this state is about 100 pounds per acre, but it can range from about 50 lbs./acre in unfavorable years to about 250 lbs./acre in above average years.
This state is unstable and vulnerable to excessive erosion. The biotic integrity of this plant community is at risk or non-functioning. The watershed is usually at risk or non-functioning as bareground increases.
Transitional pathways leading to other plant communities are as follows:
• Mechanical Treatment followed by deferment for 1 to 2 years as part of a Prescribed Grazing plan will convert this plant community to a Rhizomatous Wheatgrass/Birdfoot Sagebrush State.Figure 7. Plant community growth curve (percent production by month). WY0401 , 7-9GR, UPLAND SITES. ALL UPLAND SITES.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec J F M A M J J A S O N D 0 0 0 10 35 40 10 0 5 0 0 0 Transition T1A
State 1 to 2Natural Succession will return this state to Rhizomatous Wheatgrass/Birdfoot Sagebrush State.
Transition T1B
State 1 to 3Heavy Continuous Season-long Grazing or Severe Hoof Compaction will convert the plant community to the Heavy Birdfoot Sage State
Restoration pathway R2A
State 2 to 1Natural Succession will return this state to near Reference Plant Community (Birdfoot Sagebrush/Rhizomatous Wheatgrass State).
Restoration pathway R3A
State 3 to 2Mechanical Treatment followed by deferment for 1 to 2 years as part of a Prescribed Grazing plan will convert this plant community to a Rhizomatous Wheatgrass/Birdfoot Sagebrush State.
Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 88–158 western wheatgrass PASM Pascopyrum smithii 88–158 – 2 35–70 squirreltail ELEL5 Elymus elymoides 35–70 – 3 35–70 Indian ricegrass ACHY Achnatherum hymenoides 35–70 – 4 4–18 Grass, perennial 2GP Grass, perennial 0–18 – Sandberg bluegrass POSE Poa secunda 0–18 – Forb5 18–35 Forb, perennial 2FP Forb, perennial 0–18 – textile onion ALTE Allium textile 0–18 – rosy pussytoes ANRO2 Antennaria rosea 0–18 – milkvetch ASTRA Astragalus 0–18 – fleabane ERIGE2 Erigeron 0–18 – aster EUCEP2 Eucephalus 0–18 – desertparsley LOMAT Lomatium 0–18 – tufted evening primrose OECA10 Oenothera caespitosa 0–18 – phlox PHLOX Phlox 0–18 – woodyaster XYLOR Xylorhiza 0–18 – deathcamas ZIGAD Zigadenus 0–18 – Shrub/Vine6 88–140 birdfoot sagebrush ARPE6 Artemisia pedatifida 88–140 – 7 18–35 Gardner's saltbush ATGA Atriplex gardneri 0–18 – winterfat KRLA2 Krascheninnikovia lanata 0–18 – Table 7. Community 2.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 8. Community 3.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Interpretations
Animal community
Animal Community – Wildlife Interpretations
Birdfoot Sagebrush/Rhizomatous Wheatgrass Plant Community (HCPC): Suitable thermal and escape cover for mule deer may be limited due to the low height of woody plants. However, sagebrush provides important winter forage for mule deer and antelope. Year-round habitat is provided for sage grouse and many other sagebrush obligate species such as the sage sparrow, sage thrasher, pygmy rabbit, sagebrush vole, horned lizard, and pronghorn antelope. Open spaces in the sagebrush canopy are potential sage grouse lek locations.
Rhizomatous Wheatgrass/Birdfoot Sagebrush Plant Community: This plant community has a low level of diversity. Due to the dominance of grasses, feed for browsing animals is limited. Areas of bare ground may provide leks for sage grouse.
Heavy Birdfoot Sagebrush Plant Community: This plant community may be beneficial for the same wildlife that would use the Historic Climax Plant Community. However, the plant community composition is less diverse, and thus, less apt to meet the seasonal needs of these animals.
Animal Community – Grazing Interpretations
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 eventually be calculated using this 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.
Plant Community Production (lb./ac) and Carrying Capacity* (AUM/ac)
Birdfoot Sagebrush/Rhizomatous Wheatgrass (HCPC) 250-500 lb./ac and .08 AUM/ac
Rhizomatous Wheatgrass/Birdfoot Sagebrush 100-400 lb./ac and .04 AUM/ac
Heavy Birdfoot Sagebrush 50-250 lb./ac and .02 AUM/ac
* - Continuous, season-long grazing by cattle under average growing conditions.
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.Hydrological functions
Water is the principal factor limiting forage production on this site. This site is dominated by soils in hydrologic group D. Infiltration ranges from slow to very slow. Runoff potential for this site varies from high to very high depending on ground cover (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. Litter typically falls in place, and signs of movement are not common. Chemical and physical crusts are rare to non-existent. Cryptogrammic crusts are present, but only cover 1-2% of the soil surface.Recreational uses
This site provides limited hunting opportunities.
Wood products
No appreciable wood products are present on the site.
Other products
None noted.
Supporting information
Inventory data references
Information presented here has been derived from NRCS clipping data and other inventory data. Field observations from range trained personnel were also used. Those involved in developing this site include: Bill Christensen, Range Management Specialist, NRCS; Karen Clause, Range Management Specialist, NRCS; and Everet Bainter, Range Management Specialist, NRCS. Other sources used as references include: USDA NRCS Water and Climate Center, USDA NRCS National Range and Pasture Handbook, and USDA NRCS Soil Surveys from various counties.
Contributors
Karen Clause
Approval
Kirt Walstad, 2/24/2025
Rangeland health reference sheet
Interpreting Indicators of Rangeland Health is a qualitative assessment protocol used to determine ecosystem condition based on benchmark characteristics described in the Reference Sheet. A suite of 17 (or more) indicators are typically considered in an assessment. The ecological site(s) representative of an assessment location must be known prior to applying the protocol and must be verified based on soils and climate. Current plant community cannot be used to identify the ecological site.
Author(s)/participant(s) K. Clause, B. Brazee, E. Bainter Contact for lead author karen.clause@wy.usda.gov or 307-367-2257 Date 03/16/2007 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
Rare to nonexistent. Where present, short and widely spaced. -
Presence of water flow patterns:
Barely observable. -
Number and height of erosional pedestals or terracettes:
Slight to moderate pedestalling evident on this site. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Bare ground can range from 40-80%. -
Number of gullies and erosion associated with gullies:
Active gullies should not be present. -
Extent of wind scoured, blowouts and/or depositional areas:
Minimal to nonexistent. -
Amount of litter movement (describe size and distance expected to travel):
Herbaceous litter expected to move only in small amounts (to leeward side of shrubs) due to wind. Woody debris will show no movement. -
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Soil Stability Index ratings range from 1 (interspaces) to 4 (under plant canopy), but average values should be 3.0 or greater. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Currently no soil series are correlated to this ecological site. Soil OM of less than .5% is expected. -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Plant community consists of 45-85% grasses, 5% forbs, and 10-50% shrubs. A sparse plant canopy (20-40%) and litter plus very slow infiltration rates result in slight to moderate runoff. Basal cover is typically less than 5% for this site and does very little to effect runoff on this site. -
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
No compaction layer exists, but severe soil crusting in dry conditions is typical. -
Functional/Structural Groups (list in order of descending dominance by above-ground annual-production or live foliar cover using symbols: >>, >, = to indicate much greater than, greater than, and equal to):
Dominant:
Sub-dominant:
Other:
Additional:
perennial shrubs>cool season rhizomatous grasses>mid-size, cool season bunchgrasses>short, cool season bunchgrasses>perennial forbs -
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Some decadence expected, typically associated with shrub component. -
Average percent litter cover (%) and depth ( in):
Litter ranges from 5-15% of total canopy measurement with total litter (including beneath the plant canopy) from 10-30% expected. Herbaceous litter depth is typically very shallow, ranging from 1-5mm. Woody litter can be up to a couple inches (4-6 cm). -
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
English: 250-500 lb/ac (350 lb/ac average); Metric: 280-560 kg/ha (392 kg/ha average). -
Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize degraded states and have the potential to become a dominant or co-dominant species on the ecological site if their future establishment and growth is not actively controlled by management interventions. Species that become dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the ecological site:
Bare ground greater than 90% is the most common indicator of a threshold being crossed. Birdfoot sagebrush, Sandberg bluegrass, and phlox are common increasers. Annual weeds such as halogeton, kochia, and Russian thistle are common invasive species in disturbed sites. -
Perennial plant reproductive capability:
All species are capable of reproducing, except in drought years.
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