Natural Resources
Conservation Service
Ecological site R034AY318WY
Impervious Clay
High Plains Southeast (IC)
Accessed: 04/20/2026
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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
R034AY304WY Clayey High Plains Southeast (Cy)
CLayey
R034AY344WY Saline Upland High Plains Southeast (SU)
Saline Upland
Similar sites
R034AY310WY Dense Clay High Plains Southeast (DC)
Dense Clay (DC) 10-14" P.Z. High Plains Southeast has higher production and does not have high concentrations of exchangeable sodium throughout the profile.
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
Elevation 5500 – 7500 ft Slope 0 – 40 % Ponding depth 0 in Aspect Aspect is not a significant factor Climatic features
Annual precipitation ranges from 10-14 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 June 15. Some green up of cool season plants usually occurs in September.
The following information is from the “Laramie” climate station:
Minimum Maximum 5 yrs. out of 10 between
Frost-free period (days): 57 149 June 1 – September 16
Freeze-free period (days): 94 183 May 15 – September 28
Annual Precipitation (inches): 5.8 17.34
Mean annual precipitation: 11.53 inches
Mean annual air temperature: 42.2 F (30.4 F Avg. Min. to 53.9 F Avg. Max.)
For detailed information visit the Natural Resources Conservation Service National Water and Climate Center at http://www.wcc.nrcs.usda.gov/ website. Other climate station(s) representative of this precipitation zone include ”Dixon ” and “Medicine Bow”.Table 3 Representative climatic features
Frost-free period (average) 150 days Freeze-free period (average) 180 days Precipitation total (average) 10 in BarLineFigure 2. Monthly precipitation range
BarLineFigure 3. Monthly average minimum and maximum temperature
">Influencing water features
Stream type: None
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.
Table 4. Representative soil features
Surface texture (1) Clay
(2) Silty clay
Family particle size (1) Clayey
Drainage class Well drained Permeability class Slow to very slow Soil depth 15 – 60 in 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 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.
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
Custom diagramStandard diagram
More interactive model formats are also available. View Interactive Models
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
Rhizomatous Wheatgrass/ Birdfoot Sage Plant Community (HCPC)Community 1.1
Rhizomatous Wheatgrass/ Birdfoot Sage Plant Community (HCPC)The interpretive plant community for this site is the Historic Climax 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 500 pounds per acre, but it can range from about 350 lbs./acre in unfavorable years to about 700 lbs./acre in above average years.
This state is extremely stable and well adapted to the Cool Central Desertic Basins and Plateaus climate. 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 will convert the plant community to the Heavy Birdfoot Sage Plant Community.
• Moderate Continuous Season-long Grazing will convert the plant community to the Birdfoot Sage/ Rhizomatous Wheatgrass Plant Community.Figure 4. Annual production by plant type (representative values) or group (midpoint values)
Figure 5. Plant community growth curve (percent production by month). WY0901 , 34AI, 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
Birdfoot Sage/Rhizomatous Wheatgrass Plant CommunityCommunity 2.1
Birdfoot Sage/Rhizomatous Wheatgrass Plant CommunityThis plant community is the result of moderate continuous season long grazing of the HCPC. Birdfoot sage and rhizomatous wheatgrasses dominate. Birdfoot sagebrush usually comprises 50-60% of annual production. When compared to the HCPC, Indian ricegrass has decreased, rhizomatous wheatgrasses remain and birdfoot sage has increased.
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 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:
• Prescribed Grazing or Long-term Prescribed Grazing will return this state to near Historic Climax Plant Community (Rhizomatous Wheatgrass/ Birdfoot Sage Plant Community).
• Heavy Continuous Season-long Grazing will convert the plant community to the Heavy Birdfoot Sage Plant Community.Figure 6. Plant community growth curve (percent production by month). WY0901 , 34AI, 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 Sage Plant CommunityCommunity 3.1
Heavy Birdfoot Sage Plant CommunityThis plant community is a result of heavy continuous season-long grazing. Severe hoof compaction typically occurs due to fine soil textures. Birdfoot sage 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 200 pounds per acre, but it can range from about 100 lbs./acre in unfavorable years to about 300 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 bare ground increases.
Transitional pathways leading to other plant communities are as follows:
• Mechanical Treatment (Chiseling, etc.) followed by Prescribed Grazing or Long-term Prescribed Grazing may eventually return this state to near Historic Climax Plant Community (Rhizomatous Wheatgrass/ Birdfoot Sage Plant Community).Figure 7. Plant community growth curve (percent production by month). WY0901 , 34AI, 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 Additional community tables
Table 5. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 125–225 western wheatgrass PASM Pascopyrum smithii 125–225 – 2 50–100 squirreltail ELEL5 Elymus elymoides 50–100 – 3 50–100 Indian ricegrass ACHY Achnatherum hymenoides 50–100 – 4 0–25 Sandberg bluegrass POSE Poa secunda 0–25 – 5 0–25 Grass, perennial 2GP Grass, perennial 0–25 – Forb6 25–75 Forb, perennial 2FP Forb, perennial 0–25 – textile onion ALTE Allium textile 0–25 – rosy pussytoes ANRO2 Antennaria rosea 0–25 – milkvetch ASTRA Astragalus 0–25 – fleabane ERIGE2 Erigeron 0–25 – desertparsley LOMAT Lomatium 0–25 – phlox PHLOX Phlox 0–25 – woodyaster XYLOR Xylorhiza 0–25 – Shrub/Vine7 100–200 birdfoot sagebrush ARPE6 Artemisia pedatifida 100–200 – 8 25–50 Gardner's saltbush ATGA Atriplex gardneri 25–50 – 9 0–25 yellow rabbitbrush CHVI8 Chrysothamnus viscidiflorus 0–25 – 10 0–25 winterfat KRASC Krascheninnikovia 0–25 – 11 0–25 Shrub (>.5m) 2SHRUB Shrub (>.5m) 0–25 – Table 6. Community 2.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 7. Community 3.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Interpretations
Animal community
Animal Community – Wildlife Interpretations
Rhizomatous Wheatgrass/ Birdfoot Sage 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.
Birdfoot Sage/ 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 leks for sage grouse.
Heavy Birdfoot Sage 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. If distribution problems occur, stocking rates must be reduced to maintain plant health and vigor.
Plant Community Production Carrying Capacity*
(lb./ac) (AUM/ac)
Rhizomatous Wheatgrass/ Birdfoot Sage (HCPC) 350-700 .2
Birdfoot Sage/ Rhizomatous Wheatgrass 200-400 .1
Heavy Birdfoot Sage 100-300 .05
* - 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
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. 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 69 1967-1988 WY Carbon & others
Contributors
B. Brazee
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) Contact for lead author Date 05/01/2005 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
Rills should not be present -
Presence of water flow patterns:
Barely observable -
Number and height of erosional pedestals or terracettes:
Not evident -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Bare ground is 25-35%, occurring in small openings throughout the site. -
Number of gullies and erosion associated with gullies:
Active gullies should not be present. -
Extent of wind scoured, blowouts and/or depositional areas:
None -
Amount of litter movement (describe size and distance expected to travel):
Little to no plant litter movement. Plant litter remains in place and is not moved by erosional forces. -
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Plant cover and litter is at 60% or greater of soil surface and maintains soil surface integrity. Soil Stability class is anticipated to be 5 or greater. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Use Soil Series description for depth and color of A-horizon -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Grass canopy and basal cover should reduce raindrop impact and slow overland flow providing increased time for infiltration to occur. Infiltration varies with soil texture from moderately rapid to rapid. -
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
No compaction layer or soil surface crusting should be present. -
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:
Shrubs > Mid stature Grasses > Forbs = short stature grasses -
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Some plant mortality and decadence is expected -
Average percent litter cover (%) and depth ( in):
Average litter cover is 20-25% with depths of 0.10 to 0.25 inches -
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
500 lbs/ac -
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:
Birdfoot sagebrush, Annuals, and Species found on Noxious Weed List -
Perennial plant reproductive capability:
May be Limited due to effective moisture and seed to soil contact
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