Natural Resources
Conservation Service
Ecological site R034AY112WY
Gravelly Green River and Great Divide Basins (Gr)
Last updated: 9/28/2023
Accessed: 11/21/2024
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.
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
| R034AY158WY |
Shallow Clayey Green River and Great Divide Basins (SwCy) Shallow Clayey |
|---|---|
| R034AY162WY |
Shallow Loamy Green River and Great Divide Basins (SwLy) Shallow Loamy |
| R034AY176WY |
Very Shallow Green River and Great Divide Basins (VS) Very Shallow |
Similar sites
| R034AY176WY |
Very Shallow Green River and Great Divide Basins (VS) Very Shallow (VS) 7-9GR lacks a high volume of coarse fragments. |
|---|---|
| R034AY212WY |
Gravelly Foothills and Basins West (Gr) Gravelly (Gr) 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 along terrace breaks. It is found on all exposures. Slopes vary from 1-70%, but are mostly 5 to 30%.
Table 2. Representative physiographic features
| Landforms |
(1)
Ridge
(2) Escarpment (3) Hill |
|---|---|
| Flooding frequency | None |
| Ponding frequency | None |
| Elevation | 1,829 – 2,195 m |
| Slope | 1 – 70% |
| 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 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 2. Monthly precipitation range
Figure 3. Monthly average minimum and maximum temperature
Influencing water features
Soil features
The soils of this site are very gravelly well-drained soils formed in alluvium. These soils have moderate to rapid permeability and are usually sandy loam to loam. They commonly have coarse fragments in the surface layer and have 35 to 60 percent coarse fragments between depths of 10 to 20 inches.
Major Soil Series correlated to this site include: Dunul and some phases of the Cambarge series.
Table 4. Representative soil features
| Surface texture |
(1) Gravelly sandy loam (2) Very gravelly sandy loam (3) Gravelly loam |
|---|---|
| Family particle size |
(1) Loamy |
| Drainage class | Well drained |
| Permeability class | Moderate to moderately rapid |
| Soil depth | 38 – 152 cm |
| Surface fragment cover <=3" | 20 – 40% |
| Surface fragment cover >3" | 0 – 5% |
| Available water capacity (0-101.6cm) |
5.08 – 7.11 cm |
| Calcium carbonate equivalent (0-101.6cm) |
5 – 20% |
| Electrical conductivity (0-101.6cm) |
0 – 16 mmhos/cm |
| Sodium adsorption ratio (0-101.6cm) |
0 – 13 |
| Soil reaction (1:1 water) (0-101.6cm) |
7.8 – 9 |
| Subsurface fragment volume <=3" (Depth not specified) |
25 – 50% |
| Subsurface fragment volume >3" (Depth not specified) |
0 – 15% |
Ecological dynamics
As this site deteriorates, species such as green rabbitbrush will increase. Cool season bunchgrasses such as bluebunch wheatgrass, Indian ricegrass, and needleandthread will decrease in frequency and production. Cheatgrass often invades. This site has relatively low productivity potential, and is not well suited to grazing improvement practices unless treated as part of a larger unit containing more productive areas.
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 text
Ecosystem states
State 1 submodel, plant communities
State 2 submodel, plant communities
State 1
Bluebunch Wheatgrass (Reference)
Community 1.1
Bluebunch Wheatgrass (Reference)
The interpretive plant community for this site is the Reference Plant Community. Potential vegetation is about 70% grasses or grass-like plants, 15% forbs, and 15% woody plants. The major grasses include bluebunch wheatgrass, Indian ricegrass, and needleandthread. Other grasses and grass-like plants include Sandberg bluegrass, bottlebrush squirreltail, thickspike wheatgrass, needleleaf sedge, threeawn, and prairie junegrass. Winterfat, green rabbitbrush, and skunkbush sumac are the dominant woody plants. A typical plant composition for this state consists of bluebunch wheatgrass 25-40%, needleandthread 15-30%, Indian ricegrass 15-30%, other grasses and grass-like plants 5-20%, perennial forbs 5-20%, winterfat 1-10%, green rabbitbrush 1-5%, and up to 5% skunkbush sumac. Ground cover, by ocular estimate, varies from 20-25%. 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 450 lbs./acre in above average years. The state is 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: • Severe Ground Disturbance and/or Heavy Continuous Season-Long Grazing will convert this plant community to the Cheatgrass State.
Figure 4. 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 | 157 | 275 | 353 |
| Shrub/Vine | 34 | 59 | 76 |
| Forb | 34 | 58 | 75 |
| Total | 225 | 392 | 504 |
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
Cheatgrass
Community 2.1
Cheatgrass
This plant community is a result of frequent and severe grazing followed by severe ground disturbance. Green rabbitbrush, fringed sagewort, cheatgrass, and annual forbs are significant components of this plant community. 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. The state is unstable and vulnerable to excessive erosion, however rock fragment typically prevents serious erosion from occurring. The biotic integrity of this plant community is at risk depending on how far a shift has occurred in plant composition toward cheatgrass and annual forbs. The watershed is usually at risk or nonfunctioning due to an increase in bare ground. Transitional pathways leading to other plant communities are as follows: It is not often practicable or economically feasible to convert this plant community at the present time.
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
Severe Ground Disturbance and/or Heavy Continuous Season-Long Grazing will convert this plant community to the Cheatgrass State.
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 | 99–157 | |||||
| bluebunch wheatgrass | PSSP6 | Pseudoroegneria spicata | 99–157 | – | ||
| 2 | 59–118 | |||||
| needle and thread | HECO26 | Hesperostipa comata | 59–118 | – | ||
| 3 | 59–118 | |||||
| Indian ricegrass | ACHY | Achnatherum hymenoides | 59–118 | – | ||
| 4 | 20–78 | |||||
| Grass, perennial | 2GP | Grass, perennial | 0–20 | – | ||
| threeawn | ARIST | Aristida | 0–20 | – | ||
| needleleaf sedge | CADU6 | Carex duriuscula | 0–20 | – | ||
| squirreltail | ELEL5 | Elymus elymoides | 0–20 | – | ||
| thickspike wheatgrass | ELLAL | Elymus lanceolatus ssp. lanceolatus | 0–20 | – | ||
| prairie Junegrass | KOMA | Koeleria macrantha | 0–20 | – | ||
| Sandberg bluegrass | POSE | Poa secunda | 0–20 | – | ||
|
Forb
|
||||||
| 5 | 20–78 | |||||
| Forb, perennial | 2FP | Forb, perennial | 0–20 | – | ||
| common yarrow | ACMI2 | Achillea millefolium | 0–20 | – | ||
| rosy pussytoes | ANRO2 | Antennaria rosea | 0–20 | – | ||
| sandwort | ARENA | Arenaria | 0–20 | – | ||
| milkvetch | ASTRA | Astragalus | 0–20 | – | ||
| Indian paintbrush | CASTI2 | Castilleja | 0–20 | – | ||
| fleabane | ERIGE2 | Erigeron | 0–20 | – | ||
| buckwheat | ERIOG | Eriogonum | 0–20 | – | ||
| aster | EUCEP2 | Eucephalus | 0–20 | – | ||
| blue flax | LIPE2 | Linum perenne | 0–20 | – | ||
| granite prickly phlox | LIPU11 | Linanthus pungens | 0–20 | – | ||
| tufted evening primrose | OECA10 | Oenothera caespitosa | 0–20 | – | ||
| nailwort | PARON | Paronychia | 0–20 | – | ||
| beardtongue | PENST | Penstemon | 0–20 | – | ||
| phacelia | PHACE | Phacelia | 0–20 | – | ||
| spiny phlox | PHHO | Phlox hoodii | 0–20 | – | ||
| buttercup | RANUN | Ranunculus | 0–20 | – | ||
| stonecrop | SEDUM | Sedum | 0–20 | – | ||
| stemless mock goldenweed | STAC | Stenotus acaulis | 0–20 | – | ||
| clover | TRIFO | Trifolium | 0–20 | – | ||
| violet | VIOLA | Viola | 0–20 | – | ||
|
Shrub/Vine
|
||||||
| 6 | 4–39 | |||||
| winterfat | KRLA2 | Krascheninnikovia lanata | 4–39 | – | ||
| 7 | 20–39 | |||||
| prairie sagewort | ARFR4 | Artemisia frigida | 0–20 | – | ||
| big sagebrush | ARTR2 | Artemisia tridentata | 0–20 | – | ||
| yellow rabbitbrush | CHVI8 | Chrysothamnus viscidiflorus | 0–20 | – | ||
| skunkbush sumac | RHTR | Rhus trilobata | 0–20 | – | ||
Interpretations
Animal community
Animal Community – Wildlife Interpretations
Bluebunch Wheatgrass Plant Community (HCPC): This plant community does not contribute much forage to wildlife nor is it typically inhabited by burrowing animals due to the high volume of coarse fragments in the profile. It is mostly used by wildlife in transit to other habitats. When found proximal to taller sagebrush, these sites are suitable locations for sage grouse leks. When occurring near perennial water, it may be used by killdeer for nesting.
Cheatgrass Plant Community: This plant community exhibits a low level of plant species diversity. In most cases, it is not a desirable plant community to select as a wildlife habitat management objective.
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)
Bluebunch Wheatgrass (HCPC)200-450 lb./ac and .1 AUM/ac
Cheatgrass 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 and coarse fragments are the principal factors limiting forage production on this site. This site is highly variable and is dominated by soils in hydrologic group B and D, with localized areas in hydrologic group A and C. Infiltration ranges from slow to very rapid. Runoff potential for this site varies from moderate to high depending on soil hydrologic group, depth and fracturing of bedrock, slope, and ground cover (refer to Part 630, NRCS National Engineering Handbook for detailed hydrology information).
Rills and gullies may be present, but should be small. Water flow patterns should be barely distinguishable. Pedestals are only slightly present in association with bunchgrasses such as bluebunch wheatgrass. 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, 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:
Some 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 25-50%. -
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 in moderate amounts. Large woody debris will show only slight movement down slope. -
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 2 (interspaces) to 5 (under plant canopy), but average values should be 2.0 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 60-70% grasses, 20% forbs, and 10-20% shrubs. Minimal plant canopy (10-40%) and litter plus moderate infiltration rates result in slight to moderate runoff. Basal cover is typically less than 5% and does very little to effect runoff on this site. Surface rock fragments of 20-50% provide site stability from erosion, but decrease infiltration. -
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 large amounts of subsurface coarse fragments may be mistaken for a compaction layer. -
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:
mid-size, cool season bunchgrasses>> perennial forbs=perennial shrubs>short, cool season bunchgrasses>cool season rhizomatous grasses -
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Minimal decadence, typically associated with shrub component. -
Average percent litter cover (%) and depth ( in):
Litter ranges from 0-15% of total canopy measurement with total litter (including beneath the plant canopy) from 5-30% 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: 200-450 lb/ac (350 lb/ac average); Metric: 224-504 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:
Rabbitbrush, Sandberg bluegrass, and phlox are common increasers. Annual weeds such as cheatgrass, 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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