Natural Resources
Conservation Service
Ecological site R034AY110WY
Dense Clay Green River and Great Divide Basins (DC)
Last updated: 9/28/2023
Accessed: 12/22/2024
General information
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.
Associated sites
| R034AY104WY |
Clayey Green River and Great Divide Basins (Cy) Clayey |
|---|
Similar sites
| R034AY158WY |
Shallow Clayey Green River and Great Divide Basins (SwCy) Shallow Clayey (SwCy) 7-9GR does not have extreme soil cracking and has early sage instead of low sage. |
|---|---|
| R034AY210WY |
Dense Clay Foothills and Basins West (DC) Dense Clay (DC) 10-14W has higher production. |
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. It is found on all exposures. Slopes are nearly level to 40%, but mostly 5 to 20%.
Table 2. Representative physiographic features
| Landforms |
(1)
Alluvial fan
(2) Stream terrace |
|---|---|
| Flooding frequency | None |
| Ponding frequency | None |
| Elevation | 1,829 – 2,195 m |
| Slope | 0 – 40% |
| Ponding depth | 0 cm |
| 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 late 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) | 121 days |
|---|---|
| Freeze-free period (average) | 132 days |
| Precipitation total (average) | 229 mm |
Figure 1. Monthly precipitation range
Figure 2. Monthly average minimum and maximum temperature
Influencing water features
Soil features
The soils of this site are moderately deep to very deep (greater than 20” to bedrock), 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.
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 | 38 – 152 cm |
| Surface fragment cover <=3" | 0% |
| Surface fragment cover >3" | 0% |
| Available water capacity (0-101.6cm) |
7.62 – 11.43 cm |
| Calcium carbonate equivalent (0-101.6cm) |
0 – 15% |
| Electrical conductivity (0-101.6cm) |
0 – 8 mmhos/cm |
| Sodium adsorption ratio (0-101.6cm) |
0 – 5 |
| Soil reaction (1:1 water) (0-101.6cm) |
6.6 – 8.4 |
| Subsurface fragment volume <=3" (Depth not specified) |
0% |
| Subsurface fragment volume >3" (Depth not specified) |
0% |
Ecological dynamics
As this site deteriorates from improper grazing management, low sagebrush and green rabbitbrush 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 Historic Climax 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 text
State 1 submodel, plant communities
State 2 submodel, plant communities
State 3 submodel, plant communities
State 1
Rhizomatous Wheatgrass/Low Sagebrush (Reference)
Community 1.1
Rhizomatous Wheatgrass/Low Sagebrush (Reference)
This plant community evolved with grazing by large herbivores and is suited for grazing by domestic livestock. Potential vegetation is estimated at 60% grasses or grass-like plants, 10% forbs and 30% woody plants. The major grasses include western wheatgrass, bottlebrush squirreltail, and Indian ricegrass. Other grasses and grass-like plants may include prairie junegrass and Sandberg bluegrass. Low sagebrush and bud sagebrush are the major woody plants. Other woody plants that may occur include early sagebrush, green rabbitbrush, Gardner’s saltbush, winterfat, and spineless horsebrush. A typical plant composition for this state consists of western wheatgrass 35-50%, bottlebrush squirreltail 5-15%, Indian ricegrass 5-15%, other grasses and grass-like plants 5-15%, perennial forbs 5-10%, low sagebrush 10-20%, bud sagebrush 5-10%, and 5-10% other woody species. Ground cover, by ocular estimate, varies from 45-55%. The total annual production (air-dry weight) of this state is about 350 pounds per acre, but it can range from about 200 lbs./acre in unfavorable years to about 550 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: • Nonuse will convert this plant community to the Low Sage/Bunchgrass State. • Heavy Continuous Season-long Grazing and/or Severe Hoof Compaction will convert this plant community to the Rhizomatous Wheatgrass State. • Heavy Continuous Season-long Grazing will convert this plant community to the Heavy Low Sage State
Figure 3. Annual production by plant type (representative values) or group (midpoint values)
Table 5. Annual production by plant type
| Plant type | Low (kg/hectare) |
Representative value (kg/hectare) |
High (kg/hectare) |
|---|---|---|---|
| Grass/Grasslike | 135 | 235 | 370 |
| Shrub/Vine | 67 | 118 | 185 |
| Forb | 22 | 39 | 62 |
| Total | 224 | 392 | 617 |
Figure 4. 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 |
Community 1.2
Rhizomatous Wheatgrass
This plant community is the result of brush management and/or improper grazing techniques involving severe hoof compaction of heavy clay soils. Shrubs have been removed, and rhizomatous wheatgrass is the dominant and sometime the only species present. There is a substantial amount of bare ground. 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.
Pathway 1.1-1.2
Community 1.1 to 1.2
Heavy Continuous Season-long Grazing and/or Severe Hoof Compaction will convert this plant community to the Rhizomatous Wheatgrass State.
Pathway 1.2-1.1
Community 1.2 to 1.1
Prescribed Grazing will result in a plant community very similar to the Reference Plant Community (Rhizomatous Wheatgrass/Low Sage State).
State 2
Low Sagebrush/Bunchgrass
Community 2.1
Low Sagebrush/Bunchgrass
This plant community is the result of protection from grazing. Low sagebrush dominates with annual production often exceeding 20%, and herbaceous forage production is decreased. The understory of grass includes rhizomatous wheatgrass, Indian ricegrass, bottlebrush squirreltail, and Sandberg bluegrass. The total annual production (air-dry weight) of this state is about 300 pounds per acre, but it can range from about 200 lbs./acre in unfavorable years to about 500 lbs./acre in above average years. The state is stable and protected from excessive erosion. The biotic integrity of this plant community is usually intact, however forage value will decrease and wildlife values will shift toward different species. The watershed is functioning. Transitional pathways leading to other plant communities are as follows: • Chemical Brush Management followed by 1 to 2 years deferment as part of a Prescribed Grazing plan will result in a plant community very similar to the Historic Climax Plant Community (Rhizomatous Wheatgrass/Low Sage State).
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 3
Heavy Low Sagebrush
Community 3.1
Heavy Low Sagebrush
This plant community is the result of improper grazing. Low sagebrush dominates with annual production often exceeding 30-60%. There is mostly bare ground between sagebrush plants with an understory of grass and forbs limited to the protected areas under shrubs. The major grasses include Sandberg bluegrass and rhizomatous wheatgrass. 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. Soil erosion is accelerated because of increased bare ground. The biotic community has been compromised, but is relatively stable. The watershed is functioning, but is at risk of further degradation. Water flow patterns and pedestals are obvious. Infiltration is reduced and runoff is increased. Transitions or pathways leading to other plant communities are as follows: • Chemical Brush Management will convert this plant community to the 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 |
Transition T1-2
State 1 to 2
Nonuse will convert this plant community to the Low Sage/Bunchgrass State.
Transition T1-3
State 1 to 3
Heavy Continuous Season-long Grazing will convert this plant community to the Heavy Low Sage State
Restoration pathway R2-1
State 2 to 1
Chemical Brush Management followed by 1 to 2 years deferment as part of a Prescribed Grazing plan will result in a plant community very similar to the Reference Plant Community (Rhizomatous Wheatgrass/Low Sage State).
Restoration pathway R3-1
State 3 to 1
Chemical Brush Management will convert this plant community to the Rhizomatous Wheatgrass Plant Community.
Additional community tables
Table 6. Community 1.1 plant community composition
| Group | Common name | Symbol | Scientific name | Annual production (kg/hectare) | Foliar cover (%) | |
|---|---|---|---|---|---|---|
|
Grass/Grasslike
|
||||||
| 1 | 138–196 | |||||
| western wheatgrass | PASM | Pascopyrum smithii | 138–196 | – | ||
| 2 | 20–59 | |||||
| squirreltail | ELEL5 | Elymus elymoides | 20–59 | – | ||
| 3 | 20–59 | |||||
| Indian ricegrass | ACHY | Achnatherum hymenoides | 20–59 | – | ||
| 4 | 20–59 | |||||
| Grass, perennial | 2GP | Grass, perennial | 0–20 | – | ||
| needle and thread | HECO26 | Hesperostipa comata | 0–20 | – | ||
| prairie Junegrass | KOMA | Koeleria macrantha | 0–20 | – | ||
| Sandberg bluegrass | POSE | Poa secunda | 0–20 | – | ||
|
Forb
|
||||||
| 5 | 20–39 | |||||
| Forb, perennial | 2FP | Forb, perennial | 0–20 | – | ||
| yarrow | ACHIL | Achillea | 0–20 | – | ||
| textile onion | ALTE | Allium textile | 0–20 | – | ||
| rosy pussytoes | ANRO2 | Antennaria rosea | 0–20 | – | ||
| milkvetch | ASTRA | Astragalus | 0–20 | – | ||
| fleabane | ERIGE2 | Erigeron | 0–20 | – | ||
| buckwheat | ERIOG | Eriogonum | 0–20 | – | ||
| aster | EUCEP2 | Eucephalus | 0–20 | – | ||
| desertparsley | LOMAT | Lomatium | 0–20 | – | ||
| tufted evening primrose | OECA10 | Oenothera caespitosa | 0–20 | – | ||
| phlox | PHLOX | Phlox | 0–20 | – | ||
| scarlet globemallow | SPCO | Sphaeralcea coccinea | 0–20 | – | ||
| woodyaster | XYLOR | Xylorhiza | 0–20 | – | ||
| deathcamas | ZIGAD | Zigadenus | 0–20 | – | ||
|
Shrub/Vine
|
||||||
| 6 | 39–78 | |||||
| little sagebrush | ARAR8 | Artemisia arbuscula | 39–78 | – | ||
| 7 | 20–59 | |||||
| bud sagebrush | PIDE4 | Picrothamnus desertorum | 20–59 | – | ||
| 8 | 20–39 | |||||
| birdfoot sagebrush | ARPE6 | Artemisia pedatifida | 0–20 | – | ||
| Gardner's saltbush | ATGA | Atriplex gardneri | 0–20 | – | ||
| yellow rabbitbrush | CHVI8 | Chrysothamnus viscidiflorus | 0–20 | – | ||
| winterfat | KRLA2 | Krascheninnikovia lanata | 0–20 | – | ||
| spineless horsebrush | TECA2 | Tetradymia canescens | 0–20 | – | ||
Interpretations
Animal community
Animal Community – Wildlife Interpretations
Rhizomatous Wheatgrass/Low Sagebrush Plant Community (HCPC): Suitable thermal and escape cover for mule deer may be limited due to the low height and density of woody plants. However, sagebrush, which can approach 15% protein and 40-60% digestibility, 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. Other birds that would frequent this plant community include horned larks and golden eagles.
Low Sagebrush/Bunchgrass 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.
Rhizomatous Wheatgrass 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 lek locations for sage grouse.
Heavy Low 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)Carrying Capacity* (AUM/ac)
Rhizomatous Wheatgrass/Low Sagebrush (HCPC)200-550 lb./ac and .09 AUM/ac
Low Sagebrush/Bunchgrass 200-500 lb./ac and .08 AUM/ac
Rhizomatous Wheatgrass 100-400 lb./ac and .06 AUM/ac
Heavy Low Sagebrush 50-250 lb./ac .03 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 is very slow. Runoff potential for this site is very high depending on ground cover. 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. 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
Inventory Data References (narrative)
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.
Inventory Data References
Data Source Number of Records Sample Period State County
SCS-RANGE-417 50 1966-1985 WY Sweetwater
& others
Contributors
Karen Clause
Approval
Kirt Walstad, 9/28/2023
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, E. Bainter |
|---|---|
| Contact for lead author | karen.clause@wy.usda.gov or 307-367-2257 |
| Date | 03/16/2007 |
| Approved by | Kirt Walstad |
| Approval date | |
| Composition (Indicators 10 and 12) based on | Annual Production |
Indicators
-
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:
Rare to nonexistent. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Bare ground can range from 30-60%. -
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. Large woody debris from sagebrush 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 3 (interspaces) to 6 (under plant canopy), but average values should be 3.5 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 Organic Matter of less than 1% is expected. -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Plant community consists of 45-80% grasses, 10% forbs, and 10-45% shrubs. An evenly distributed plant canopy (25-45%) and litter plus slow infiltration rates result in slight to moderate runoff. Basal cover typically is 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:
cool season rhizomatous grasses> perennial shrubs>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 5-25% of total canopy measurement with total litter (including beneath the plant canopy) from 10-40% 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: 200-550 lb/ac (350 lb/ac average); Metric: 224-616 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 70% is the most common indicator of a threshold being crossed. Green rabbitbrush, Sandberg bluegrass, and phlox are common increasers. Annual weeds such as halogeton, kochia, and Russian thistle are common invasive species in disturbed -
Perennial plant reproductive capability:
All species are capable of reproducing, except in drought years.
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