Natural Resources
Conservation Service
Ecological site R047XC472UT
Mountain Very Steep Stony Loam
(bitterbrush)
Accessed: 06/26/2026
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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.
Classification relationships
Modal Soil: Ironco GRV-L, High Rainfall, Eroded — loamy-skeletal, mixed Typic Argiborolls
Type Location: See Uintah County Soil Survey
Associated sites
R047XC446UT Mountain Shallow Loam (mountain big sagebrush)
R047XC475UT Mountain Windswept Ridge (black sagebrush)
Similar sites
R047XC446UT Mountain Shallow Loam (mountain big sagebrush)
Table 1. Dominant plant species
Tree Not specified
Shrub (1) Purshia tridentata
Herbaceous (1) Hesperostipa comata
Physiographic features
Very Steep Mountainsides and Hillsides
Table 2. Representative physiographic features
Landforms (1) Mountain slope
Elevation 7200 – 9000 ft Slope 50 – 70 % Aspect NE, SW Climatic features
The climate is characterized by cool, moist summers and cold, snowy winters. Approximately 55 percent of the moisture comes as rain from May though September. On the average, October through January are the driest months and March, April, May and August are the wettest months. The soil moisture regime is ustic and soil temperatures are in the frigid regime.
Table 3 Representative climatic features
Frost-free period (average) 0 days Freeze-free period (average) 90 days Precipitation total (average) 20 in BarLineFigure 1. Monthly precipitation range
BarLineFigure 2. Monthly average minimum and maximum temperature
">Influencing water features
Soil features
Slopes are mostly 50 to 70 percent. The soil is moderately deep to deep and well drained. It formed in alluvium and colluvium derived mainly from igneous parent materials. The soil is generally loamy-skeletal with cobbles and gravels throughout the profile. Permeability is moderate and runoff is moderate to rapid. The water supplying capacity is 6.5 to 12 inches.
Table 4. Representative soil features
Surface texture (1) Loam
Drainage class Well drained Permeability class Moderate Soil depth 20 – 60 in Ecological dynamics
Because slopes are so steep, grazing by livestock does not appear to be a significant factor in altering the plant community. Fire will cause the shrubs to temporarily decrease while grasses will increase.
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 1
Reference StateCommunity 1.1
Reference StateThe general view of this site is a stand of bitterbrush and mountain big sagebrush. The composition by air-dry weight is approximately 45 percent perennial grasses, 5 percent forbs, and 50 percent shrubs.
Figure 3. 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)Shrub/Vine 325 475 625 Grass/Grasslike 293 428 563 Forb 33 48 63 Total 651 951 1251 Table 6. Ground cover
Tree foliar cover 0% Shrub/vine/liana foliar cover 50-50% Grass/grasslike foliar cover 30-30% Forb foliar cover 0-10% Non-vascular plants 0% Biological crusts 0% Litter 0% Surface fragments >0.25" and <=3" 0% Surface fragments >3" 0% Bedrock 0% Water 0% Bare ground 0% Table 7. Canopy structure (% cover)
Height Above Ground (ft) Tree Shrub/Vine Grass/
GrasslikeForb <0.5 – – – – >0.5 <= 1 – – – 4-6% >1 <= 2 – – 29-31% – >2 <= 4.5 – 49-51% – – >4.5 <= 13 – – – – >13 <= 40 – – – – >40 <= 80 – – – – >80 <= 120 – – – – >120 – – – – Additional community tables
Table 8. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Shrub/Vine0 Dominant Shrubs 350–500 antelope bitterbrush PUTR2 Purshia tridentata 200–250 – mountain big sagebrush ARTRV Artemisia tridentata ssp. vaseyana 100–150 – Utah serviceberry AMUT Amelanchier utahensis 50–100 – 3 Sub-Dominant Shrubs 140–370 Shrub (>.5m) 2SHRUB Shrub (>.5m) 50–100 – alderleaf mountain mahogany CEMO2 Cercocarpus montanus 10–30 – yellow rabbitbrush CHVIL4 Chrysothamnus viscidiflorus ssp. lanceolatus 10–30 – crispleaf buckwheat ERCO14 Eriogonum corymbosum 10–30 – slender buckwheat ERMI4 Eriogonum microthecum 10–30 – sulphur-flower buckwheat ERUM Eriogonum umbellatum 10–30 – Watson's goldenbush ERWA8 Ericameria watsonii 10–30 – creeping barberry MARE11 Mahonia repens 10–30 – mountain snowberry SYOR2 Symphoricarpos oreophilus 10–30 – Grass/Grasslike0 Dominant Grasses 250–400 needle and thread HECO26 Hesperostipa comata 150–200 – bluebunch wheatgrass PSSP6 Pseudoroegneria spicata 50–100 – 1 Sub-Dominant Grasses 130–440 Grass, annual 2GA Grass, annual 50–100 – Grass, perennial 2GP Grass, perennial 50–100 – Indian ricegrass ACHY Achnatherum hymenoides 10–30 – Letterman's needlegrass ACLE9 Achnatherum lettermanii 10–30 – Geyer's sedge CAGE2 Carex geyeri 10–30 – squirreltail ELEL5 Elymus elymoides 10–30 – sheep fescue FEOV Festuca ovina 10–30 – prairie Junegrass KOMA Koeleria macrantha 10–30 – western wheatgrass PASM Pascopyrum smithii 10–30 – Sandberg bluegrass POSE Poa secunda 10–30 – Forb2 Sub-Dominant Forbs 130–410 Forb, annual 2FA Forb, annual 30–100 – Forb, perennial 2FP Forb, perennial 30–100 – silverleaf milkvetch ASAR4 Astragalus argophyllus 10–30 – Wyoming Indian paintbrush CALI4 Castilleja linariifolia 10–30 – tapertip hawksbeard CRAC2 Crepis acuminata 10–30 – blue flax LIPE2 Linum perenne 10–30 – tailcup lupine LUCAC3 Lupinus caudatus ssp. caudatus 10–30 – American vetch VIAM Vicia americana 10–30 – Interpretations
Animal community
Because slopes are so steep, livestock grazing is not significant.
This site has good values for wildlife food and cover.
Wildlife using this site include sage grouse, rabbit, coyote, mule deer and elk.
Hydrological functions
The soil series are in hydrologic group b. The hydrologic curve number is 61 when the vegetation is in good condition.
Recreational uses
This site offers color and aesthetic appeal during the growing season and the fall. Because slopes are steep this site receives limited recreation use.
Wood products
None
Supporting information
Contributors
Lars L. Rassmussen, David Somerville
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) V. Keith Wadman (NRCS Retired). Contact for lead author shane.green@ut.usda.gov Date 12/12/2012 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
Rills are fairly common. Their expression may be less defined where coarse fragments (i.e., gravels and/or channers) dominate the soil surface. Rill occurrence may increase slightly on areas located below exposed bedrock or other water shedding areas where increased runoff may occur. Rills should be <1 inches deep, somewhat long (10 to 15 feet) and somewhat widely spaced (8-12 feet). An increase in rill development may be observed immediately following major thunderstorm or spring runoff events. -
Presence of water flow patterns:
Sinuous flow patterns are common and wind around perennial plants and surface rock. Evidence of flow patterns is expected to increase somewhat as slopes approach 80%. Water flow patterns are long (20 to 30 feet), somewhat narrow (1 to 2 feet wide), and spaced widely (5 to 10 yards) and more closely spaced(3 to 6 yards) on slopes nearing 70 to 80%. -
Number and height of erosional pedestals or terracettes:
Small pedestals will form at the base of plants that occur on the edge of water flow patterns, 2 to 4% of plants show minor exposed roots. Terracettes are fairly common, forming behind debris dams of small to medium sized litter (up to 2 inches in diameter) in water flow patterns. These debris dams may accumulate smaller litter (leaves, grass and forb stems) and sediment. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
20–25%. (Soil surface is typically covered by 15-30% surface fragments). Most bare ground is associated with water flow patterns, rills, and gullies. Bare ground spaces not associated with flow patterns should not be greater than 1 to 2 feet in diameter. -
Number of gullies and erosion associated with gullies:
Few. A few gullies may occur. Any gullies preaent may extend down the length of the site until they reach a stream or other area where water and sediment is deverted or accumulates. Gullies show slightly more indication of erosion as slopes approach 80%, or where the site occurs adjacent to watershed areas with concentrated flow patterns. -
Extent of wind scoured, blowouts and/or depositional areas:
None. Perennial shrubs along with surface coarse fragments on this site help break the wind and reduce the potential for wind erosion. -
Amount of litter movement (describe size and distance expected to travel):
Because of the sites very steep slopes, some litter redistribution downslope caused by water movement is normal. Some litter removal may occur in flow channels with deposition occurring within 3 to 5 feet at points of obstruction. The majority of litter still accumulates at the base of plants. Some grass leaves, stems and small woody twigs may accumulate in soil depressions adjacent to plants. Woody stems are likely to move 1 to 2 feet. A slight increase in litter movement is expected following runoff resulting from heavy spring runoff or thunderstorms. -
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
This site should have an erosion rating of 4 or 5 under the plant canopies, and a rating of 3 to 4 in the interspaces. The average should be a 4. Vegetation cover, litter, biological soil crusts and surface rock reduce erosion. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
(Guben) Soil surface A horizon is typically 0 to 4 inches deep. Texture is a gravelly loam. Structure is weak fine granular. Color is grayish brown (10YR 5/2). A Mollic epipedon extends 10 inches into the soil profile. Use the specific information for the soil you are assessing found in the published soil survey to supplement this description. -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Good spatial distribution of well developed biological soil crusts (where present) intercept raindrops, reducing splash erosion and providing areas of increased surface detention to store water, allowing additional time for infiltration. -
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
None. Some soils may have natural textural variability within their profiles, including changes in clay and coarse fragment content, these should not be mistaken for a compaction pans. -
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:
Sprouting Shrub (bitterbrush) > Non-sprouting shrubs (Mountain big sagebrush), Utah serviceberry) > cool season perennial grasses (needle-and-thread, bluebunch wheatgrass) >> rhizomatous grasses (western wheatgrass).Sub-dominant:
Sprouting shrubs (alderleaf mountain mahogany, green rabbitbrush) > cool season perennial grasses (Nevada bluegrass, Letterman needlegrass) = > forbs (spurred lupine) > biological soil crusts (where present).Other:
Functional/structural groups may appropriately contain non-native species if their ecological function is the same as the native species in the reference state. Biological soil crust is variable in its expression where present on this site and is measured as a component of ground cover. Forbs can be expected to vary widely in their expression in the plant community based upon departures from average growing conditions.Additional:
Factors contributing to temporal variability include insects and other pathogens (mistletoe), drought, extreme precipitation events, etc. Factors contributing to spatial variability include slope, amount of rock fragments, aspect, etc. Following a recent disturbance such as fire, drought or insects, that may remove the woody vegetation, forbs and perennial grasses (herbaceous species) may become more dominate in the community. These conditions may reflect different functional community phases within the reference state. -
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
During years with average to above-average precipitation, there should be very little recent mortality or decadence apparent on shrubs, or grasses. There may be partial mortality on individual bunchgrasses and shrubs during drought periods, and complete mortality of individual plants during severe drought periods. -
Average percent litter cover (%) and depth ( in):
Cover should be composed mostly of fine litter. Depth should vary from a 1/2 thickness in the interspaces, to up to 1 under herbaceous canopies, and up to 1 1/2” under shrub canopies. Litter cover may increase to 30% on some years due to increased production of plants. -
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
Annual production in air-dry herbage should be approximately 900 - 1000#/acre on an average year, but could range from 600 to 1300#/acre during periods of prolonged drought or above average precipitation. -
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:
Few invasive species are capable of dominating this site. When invasion does occur, cheatgrass, alyssum, and mustard species are the most likely species to invade. -
Perennial plant reproductive capability:
All perennial plants should have the ability to reproduce in all years, except in extreme drought years. There are no restrictions on either seed or vegetative reproduction. Some seedling recruitment of major species is present during average and above average growing years.
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