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Ecological site R047XC404UT

Mountain Clay (silver sagebrush)

Last updated: 2/11/2025
Accessed: 04/23/2025

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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.

Basemap provided by ESRI. Sources: Esri, HERE, DeLorme, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), swisstopo, MapmyIndia, © OpenStreetMap contributors, and the GIS User Community.

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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.

MLRA notes

Major Land Resource Area (MLRA): 047X–Wasatch and Uinta Mountains

MLRA 47 occurs in Utah (86 percent), Wyoming (8 percent), Colorado (4 percent), and Idaho (2 percent). It encompasses approximately 23,825 square miles (61,740 square kilometers). The northern half of this area is in the Middle Rocky Mountains Province of the Rocky Mountain System. The southern half is in the High Plateaus of the Utah Section of the Colorado Plateaus Province of the Intermontane Plateaus. Parts of the western edge of this MLRA are in the Great Basin Section of the Basin and Range Province of the Intermontane Plateaus.The MLRA includes the Wasatch Mountains, which trend north and south, and the Uinta Mountains, which trend east and west. The steeply sloping, precipitous Wasatch Mountains have narrow crests and deep valleys. Active faulting and erosion are a dominant force in controlling the geomorphology of the area. The Uinta Mountains have a broad, gently arching, elongated shape. Structurally, they consist of a broadly folded anticline that has an erosion-resistant quartzite core. The Wasatch and Uinta Mountains have an elevation of 4,900 to about 13,500 feet (1,495 to 4,115 meters).

The mountains in this area are primarily fault blocks that have been tilted up. Alluvial fans at the base of the mountains are recharge zones for the basin fill aquifers. An ancient shoreline of historic Bonneville Lake is evident on the footslopes along the western edge of the area. Rocks exposed in the mountains are mostly Mesozoic and Paleozoic sediments, but Precambrian rocks are exposed in the Uinta Mountains. The Uinta Mountains are one of the few ranges in the United States that are oriented west to east. The southern Wasatch Mountains consist of Tertiary volcanic rocks occurring as extrusive lava and intrusive crystalline rocks.

The average precipitation is from 8 to 16 inches (203 to 406 mm) in the valleys and can range up to 73 inches (1854 mm) in the mountains. In the northern and western portions of the MLRA, peak precipitation occurs in the winter months. The southern and eastern portions have a greater incidence of high-intensity summer thunderstorms; hence, a significant amount of precipitation occurs during the summer months. The average annual temperature is 30 to 50 degrees Fahrenheit (-1 to 15 C). The freeze-free period averages 140 days and ranges from 60 to 220 days, generally decreasing in length with elevation.

The dominant soil orders in this MLRA are Aridisols, Entisols, Inceptisols, and Mollisols. The lower elevations are dominated by a frigid temperature regime, while the higher elevations experience cryic temperature regimes. Mesic temperature regimes come in on the lower elevations and south facing slopes in the southern portion of this MLRA. The soil moisture regime is typically xeric in the northern part of the MLRA, but grades to ustic in the extreme eastern and southern parts. The mineralogy is generally mixed and the soils are very shallow to very deep, generally well drained, and loamy or loamy-skeletal.

LRU notes

E47C is the Uinta Mountains portion of MLRA 47 that run east and west which includes the Uinta Wilderness and The Flaming Gorge National Recreation Area and towns such as Evanston, Wyoming, Hanna and Tabiona, Utah. Structurally these mountains consist of a broadly folded anticline that has an erosion resistance quartzite core. The Duchesne River and many other tributaries to the Green River run through this range, as well as the headwaters of the Bear River.

Ecological site concept

The soils of this site formed in colluvium and slope alluvium derived from sandstone and shale or tuff. Surface textures are silty clay loams and subsurface textures are clayey. Rock fragments are not typically found on the soil surface or in the soil profile. These soils are deep, are well-drained, and have slow to moderately-slow permeability. Available water-holding capacity ranges from 5.7 to 6.7 inches of water in the upper 40 inches of soil. The soil moisture regime is ustic and the soil temperature regime is frigid.

Associated sites

R047XC430UT	Mountain Loam (mountain big sagebrush) Sites can occur adjacent to each other.

R047XC430UT

Mountain Loam (mountain big sagebrush)

Sites can occur adjacent to each other.

Similar sites

R047XC404UT	Mountain Clay (silver sagebrush) At the current time there are no documented similar sites to this one.

R047XC404UT

Mountain Clay (silver sagebrush)

At the current time there are no documented similar sites to this one.

Table 1. Dominant plant species

Tree	Not specified
Shrub	(1) Artemisia cana
Herbaceous	(1) Elymus trachycaulus

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Physiographic features

This site occurs on mountain, hills and alluvial fans at elevations between 6,000 to 7,300 feet. It may be found on all aspects and on slopes ranging from 6 to 25 percent.

Table 2. Representative physiographic features

Landforms	(1) Mountain (2) Hill (3) Alluvial fan
Flooding frequency	None
Ponding frequency	None
Elevation	6,000 – 7,300 ft
Slope	6 – 25%
Aspect	Aspect is not a significant factor

Climatic features

The climate of this site is characterized by cool, moist summers and cold, snowy winters. Approximately 60 percent of the moisture comes as rain from May through October. On the average, January through April are the driest months and May through October 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 (characteristic range)
Freeze-free period (characteristic range)
Precipitation total (characteristic range)	16-22 in
Frost-free period (average)	100 days
Freeze-free period (average)	60 days
Precipitation total (average)

Soil features

The soils of this site formed in colluvium and slope alluvium derived from sandstone and shale or tuff. Surface textures are silty clay loam and subsurface textures are clayey. Rock fragments are not typically found on the soil surface or in the soil profile. These soils are deep, are well-drained, and have slow to moderately-slow permeability. Available water-holding capacity ranges from 5.7 to 6.7 inches of water in the upper 40 inches of soil. The soil moisture regime is ustic and the soil temperature regime is frigid.

Modal Soil: Skutum SiL, 10-20% — fine, montmorillonitic Argic Cryoborolls

Table 4. Representative soil features

Parent material	(1) Colluvium – sandstone and shale (2) Slope alluvium – sandstone and shale (3) Colluvium – tuff (4) Slope alluvium – tuff
Surface texture	(1) Silty clay loam
Family particle size	(1) Fine
Drainage class	Well drained
Permeability class	Slow to moderately slow
Depth to restrictive layer	60 – 80 in
Soil depth	60 – 80 in
Available water capacity (Depth not specified)	5.7 – 6.7 in
Calcium carbonate equivalent (Depth not specified)	Not specified
Electrical conductivity (Depth not specified)	2 mmhos/cm
Sodium adsorption ratio (Depth not specified)	Not specified
Soil reaction (1:1 water) (Depth not specified)	5.6 – 6.5
Subsurface fragment volume <=3" (Depth not specified)	24%

Ecological dynamics

It is impossible to determine in any quantitative detail the Historic Climax Plant Community (HCPC) for this ecological site because of the lack of direct historical documentation preceding all human influence. However, up to the 1870s the Shoshone Indians, prevalent in northern Utah and neighboring states, grazed horses and set fires to alter the vegetation for their needs. In the 1860s, Europeans brought cattle and horses to the area, grazing large numbers of them on unfenced parcels year-long. Itinerant and local sheep flocks followed, largely replacing cattle as the browse component increased.

Below is a State and Transition Model diagram that illustrates the “phases” (common plant communities), and “states” (aggregations of those plant communities) that can occur on the site. Differences between phases and states depend primarily upon observations of a range of disturbance histories in areas where this ESD is represented. These situations include grazing gradients to water sources, fence-line contrasts, patches with differing dates of fire, herbicide treatment, tillage, etc. Reference State 1 illustrates the common plant communities that probably existed just prior to European settlement.

The major successional pathways within states, (“community pathways”) are indicated by arrows between phases. “Transitions” are indicated by arrows between states. The drivers of these changes are indicated in codes decipherable by referring to the legend at the bottom of the page and by reading the detailed narratives that follow the diagram. The transition between Reference State 1 and State 2 is considered irreversible because of the naturalization of exotic species of both flora and fauna, possible extinction of native species, and climate change. There may have also been accelerated soil erosion.

When available, monitoring data (of various types) were employed to validate more subjective inferences made in this diagram. See the complete files in the office of the State Range Conservationist for more details.

Plant Community Narratives:
The plant communities shown in this State and Transition Model may not represent every possibility, but are probably the most prevalent and recurring plant communities. As more monitoring data are collected, some phases or states may be revised, removed, and/or new ones may be added. The main purpose for including descriptions of a plant community is to capture the current knowledge at the time of this revision.

State 1: Reference State:
The Reference State is a description of this ecological site just prior to Euro-American settlement but long after the arrival of Native Americans. The description of the Reference State was determined by NRCS Soil Survey Type Site Location information and familiarity with rangeland relict areas where they exist. The reference state vegetation would have been a shrub steppe. Dominant shrubs would have included silver sagebrush (Artemisia cana) and mountain snowberry (Symphoricarpos oreophilus). The understory would have been composed of grasses including slender wheatgrass (Elymus trachycaulus), mountain brome (Bromus marginatus), bluegrass (Poa spp.) and numerous forbs. The average fire return interval would have ranged from 30 to 50 years, which would have been the driving factor behind changes in abundance of shrubs relative to the associated understory. One community phase would have been an herbaceous-dominant phase (1.1) that would have been found following recent wildfire events (1.2a). As the time since fire increased (1.1a), both the shrubs and herbaceous understory would have increased (1.2). A more complete list of species by lifeform for the Reference State is available in accompanying tables in the “Plant Community Composition by Weight and Percentage” section of this ESD document.

Community Phase 1.1: herbaceous understory dominant
This plant community would have been dominated by herbaceous species such as slender wheatgrass, mountain brome, and bluegrass, along with many forb species such as sticky purple geranium, Nevada pea, slender cinquefoil, and buckwheat species.

Community Pathway 1.1a:
As the time since the last fire increased, the shrubs would have re-established, along with an increase in their herbaceous companions.

Community Phase 1.2: shrub aspect dominance/ rich herbaceous understory
This phase would have been characterized by thickened silver sagebrush and a rich herbaceous understory.

Community Pathway 1.2a:
Wildfire would temporarily reduce the shrub dominance allowing the native perennial grasses and forbs to dominate.

Transition T1a: (State 1 to State 2)
The simultaneous introduction of exotic species, both plants and animals, possible extinctions of native flora and fauna, and climate change has caused State 1 to transition to State 2. Reversal of such historic changes (i.e. a return pathway) back to State 1 is not practical.

State 2: Silver Sagebrush-Steppe/ Introduced State:
State 2 is very similar to State 1 in form and function, with the exception of the presence of non-native plants and animals, possible extinctions of some native species, and a different climate. Nevertheless, a shrub steppe persisted that should be considered the current potential. State 2 is a description of the ecological site shortly site following Euro-American settlement. Primary shrubs are silver sagebrush and mountain snowberry. Snowfield sagebrush may also be found here. Grasses include slender wheatgrass, mountain brome, and bluegrass. Forbs include sticky purple geranium, Nevada pea, slender cinquefoil, and buckwheats. A small component of non-native species may also be present such as cheatgrass (Bromus tectorum), common dandelion (Taraxacum officinale), common mullein (Verbascum thapsus), mountain tarweed (Madia glomerata), and houndstongue (Cynoglossum officinale).

Community Phase 2.1: herbaceous understory dominant
This plant community is dominated by herbaceous species such as slender wheatgrass, mountain brome, and bluegrass, along with many forb species such as sticky purple geranium, Nevada pea, slender cinquefoil, and buckwheats.

Community Pathway 2.1a:
As the length of time elapsed since last fire return lengthens, shrubs re-establish along with their herbaceous companions.

Community Phase 2.2: Shrub aspect dominance/ Rich herbaceous understory
This phase is characterized by an increased dominance of silver sagebrush and a rich herbaceous understory.

Community Pathway 2.2a:
Wildfire will temporarily reduce the shrub dominance allowing the native perennial grasses and forbs to dominate.

Transition T2a: (State 2 to State 3)
Heavy continuous season-long grazing between the 1860s and the 1950s, along with fire exclusion policies saw an increase in shrubs and a replacement of the native forb component with introduced forb species. Reduction in cover leads to accelerated soil erosion, lowering of stream channels and thus xerification and distrophication. While this site is not riparian, it is near enough to streams that it is sub-irrigated at the time of snow pack melt-off. This makes it more resilient than the adjacent uplands. If this site is to remain a productive shrub steppe, the vegetation cover should remain extensive enough so as to prevent accelerated soil erosion.

State 3: Thickened Shrubs/ Introduced Forbs State:
A thickening of shrubs, particularly of silver sagebrush and snowberry, and a reduction of native forbs was seen following a near-century long period of heavy livestock grazing during growing season of herbs. Introduced forbs such as common dandelion, common mullein, mountain tarweed, houndstongue, and snakeweed (Gutierrezia sarothrae) became abundant in the understory.

Community Phase 3.1: silver sagebrush dominant/ introduced forbs (dandelion, mullein, tarweed, houndstongue, snakeweed) replacing native forbs
This plant community is characterized silver sagebrush dominance. Some introduced forbs such as common dandelion, common mullein, mountain tarweed, and houndstongue have replaced the native forbs.

Transition T3a: (State 3 to State 4)
Brush removal by either chemical means (2,4-D), or prescribed fire, and grazing deferment, will convert State 3 into a perennial forb-dominated state.

Transition T3b: (State 3 to State 5)
Plowing and drill seeding on gentler slopes will increase forage production potential by conversion to introduced grasslands (e.g. intermediate wheatgrass (Thinopyrum intermedium), smooth brome (Bromus inermis), and orchardgrass (Dactylis glomerata)).

State 4: Perennial Forb State:
This state is dominated by perennial forbs (4.1). Shrubs will re-sprout following fire or chemical applications; annuals could be replaced by perennials. If keeping the shrubs back is desirable, re-treatment using fire or chemicals may be necessary (4.1a)

Community Phase 4.1: perennial forbs dominant/ reduced annuals & shrubs
This state is characterized by a dominance of perennial forbs with reduced annuals and shrubs.

Community Pathway 4.1a:
Periodic re-treatment of brush invasion by either chemical or prescribed fire will be required to maintain introduced perennial grassland state.

Transition T4a: (State 4 to State 3)
Heavy, continuous season-long grazing will return this State 5 to State 3, a thickened shrub and introduced forbs state.

State 5: Introduced Grass State:
Intermediate wheatgrass, orchard grass, or smooth brome monocultures can result when plowing and seeding has taken place to increase herbage production.

Community Phase 5.1: introduced grasses
This phase is characterized by monocultures of introduced grasses, such as intermediate wheatgrass, orchardgrass, or smooth brome.

Transition T5a: (State 5 to State 3)
Heavy, continuous season-long grazing will return this State 5 to State 3, a thickened shrub and introduced forbs state.

State and transition model

Custom diagram

Standard 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 text

Ecosystem states

1. Reference State

State 1 submodel, plant communities

1.1. Reference Plant Community

State 1
Reference State

Community 1.1
Reference Plant Community

The dominant aspect of the plant community is grass and silver sagebrush. The composition by air-dry weight is approximately 55 percent perennial grasses, 25 percent forbs, and 20 percent shrubs.

Figure 2. 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	908	1073	1183
Forb	412	487	537
Shrub/Vine	330	390	430
Total	1650	1950	2150

Table 6. Ground cover

Tree foliar cover	0%
Shrub/vine/liana foliar cover	19-21%
Grass/grasslike foliar cover	39-41%
Forb foliar cover	14-16%
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/ Grasslike	Forb
<0.5	–	–	–	–
>0.5 <= 1	–	–	–	–
>1 <= 2	–	–	–	14-16%
>2 <= 4.5	–	19-21%	39-41%	–
>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 (lb/acre)	Foliar cover (%)
Shrub/Vine
1	Dominant Shrubs			460–600
	silver sagebrush	ARCA13	Artemisia cana	400–600	–
	mountain snowberry	SYOR2	Symphoricarpos oreophilus	60–100	–
3	Sub-Dominant Shrubs			120–220
	Shrub (>.5m)	2SHRUB	Shrub (>.5m)	60–100	–
	yellow rabbitbrush	CHVIV4	Chrysothamnus viscidiflorus ssp. viscidiflorus var. viscidiflorus	20–40	–
	creeping barberry	MARE11	Mahonia repens	20–40	–
	blue elderberry	SANIC5	Sambucus nigra ssp. cerulea	20–40	–
Grass/Grasslike
2	Dominant Grasses			600–900
	slender wheatgrass	ELTR7	Elymus trachycaulus	400–500	–
	Sandberg bluegrass	POSE	Poa secunda	100–200	–
	mountain brome	BRMA4	Bromus marginatus	100–200	–
1	Sub-Dominant Grasses			520–1200
	Grass, annual	2GA	Grass, annual	200–300	–
	Grass, perennial	2GP	Grass, perennial	200–300	–
	Letterman's needlegrass	ACLE9	Achnatherum lettermanii	20–100	–
	Columbia needlegrass	ACNE9	Achnatherum nelsonii	20–100	–
	Geyer's sedge	CAGE2	Carex geyeri	20–100	–
	oniongrass	MEBU	Melica bulbosa	20–100	–
	nodding bluegrass	PORE	Poa reflexa	20–100	–
Forb
3	Dominant Forbs			160–300
	sticky purple geranium	GEVI2	Geranium viscosissimum	100–200	–
	Nevada pea	LALA3	Lathyrus lanszwertii	60–100	–
2	Sub-Dominant Forbs			600–1200
	Forb, annual	2FA	Forb, annual	100–200	–
	Forb, perennial	2FP	Forb, perennial	100–200	–
	common yarrow	ACMI2	Achillea millefolium	20–40	–
	pale agoseris	AGGL	Agoseris glauca	20–40	–
	nettleleaf giant hyssop	AGUR	Agastache urticifolia	20–40	–
	western mountain aster	SYSPS	Symphyotrichum spathulatum var. spathulatum	20–40	–
	Wyoming Indian paintbrush	CALI4	Castilleja linariifolia	20–40	–
	tapertip hawksbeard	CRAC2	Crepis acuminata	20–40	–
	twolobe larkspur	DENU2	Delphinium nuttallianum	20–40	–
		DEOC	Delphinium ×occidentale	20–40	–
	darkthroat shootingstar	DOPU	Dodecatheon pulchellum	20–40	–
	shortstem buckwheat	ERBR5	Eriogonum brevicaule	20–40	–
	Eaton's fleabane	EREA	Erigeron eatonii	20–40	–
	woodland strawberry	FRVE	Fragaria vesca	20–40	–
	common sneezeweed	HEAU	Helenium autumnale	20–40	–
	Tolmie's owl's-clover	ORTO	Orthocarpus tolmiei	20–40	–
	lobeleaf groundsel	PAMU11	Packera multilobata	20–40	–
	low beardtongue	PEHU	Penstemon humilis	20–40	–
	slender cinquefoil	POGR9	Potentilla gracilis	20–40	–
	Fendler's meadow-rue	THFE	Thalictrum fendleri	20–40	–
	Parry's clover	TRPA5	Trifolium parryi	20–40	–
	American vetch	VIAM	Vicia americana	20–40	–

Interpretations

Animal community

This site has moderately high values for summer use by cattle, sheep, and horses. It provides green forage when vegetation of sites at lower elevations is dry and mature. Sufficient livestock water is usually close by.

The potential is poor for openland habitat, good for woodland habitat, very poor for wetland habitat, and good for rangeland habitat.

It is good habitat for summer use by elk, mule deer, and moose, and good all around habitat for bear, coyote, cougar, bobcat, snowshoe hare, songbirds, pine grouse, squirrels, golden eagle, bald eagle, and hawks.

Hydrological functions

The hydrologic soil group is C and the hydrologic curve number is 74 when vegetation is in good condition.

Recreational uses

The potential natural plant community has high values for aesthetics and natural beauty. Wildflowers bloom from early summer through fall. Hunting is fair and fishing is opportune on streams, lakes, and reservoirs through and adjacent to this site.

Wood products

None

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	11/09/2012
Approved by	Sarah Quistberg
Approval date
Composition (Indicators 10 and 12) based on	Annual Production

Indicators

Number and extent of rills:
Rare to very few. Some very minor rill development may occur on steeper slopes (>10%) or on areas located below exposed bedrock or other water shedding areas where increased runoff may occur. Any rills present should be <1 inch deep, fairly short (<6 feet long) and somewhat widely spaced (8-10 feet). Minor rill development may be observed following major thunderstorm or spring runoff events, but they should heal during the next growing season. Vertical cracking and slickensides are natural components of the soils on this site and should not be mistaken for rills.
Presence of water flow patterns:
Slight. Some very minor evidence of water flow patterns may be found around perennial plant bases. They show little evidence of current erosion. They are expected to be somewhat short (3-6 feet), stable, sinuous and not connected. There may also be very minor evidence of deposition. Evidence of water flow may increase somewhat with slope.
Number and height of erosional pedestals or terracettes:
None to Slight. Perennial vegetation shows little evidence of erosional pedestalling (2 to 3% of individual plants). Plant roots are covered and litter remains in place around plant crowns. Terracettes should be absent or, if present, stable. A slight increase in both pedestal and terracette development may occur with increasing slope. Gilgai micro-relief may be evident and is natural on this site.
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
20-25% bare ground. Soil surface is typically covered by < 5% coarse fragments. Bare ground spaces should not be greater than 2 to 3 feet in diameter and should not be connected.
Number of gullies and erosion associated with gullies:
None to Very Few. A few gullies may be present in landscape settings where they transport runoff from areas of greater water flow such as exposed bedrock. These gullies will be limited to slopes exceeding 20% slope and adjacent to sites where this runoff accumulation occurs. Any gullies present should show little sign of accelerated erosion and should be stabilized with perennial vegetation.
Extent of wind scoured, blowouts and/or depositional areas:
None. No evidence of wind generated soil movement is expected. No blowouts or depositional materials are present.
Amount of litter movement (describe size and distance expected to travel):
Most litter resides in place with some redistribution caused by water movement. Minor litter removal may occur in flow channels with deposition occurring within 1 to 2 feet at points of obstruction. The majority of litter accumulates at the base of plants. Some grass leaves and small twigs (grass stems) may accumulate in soil depressions adjacent to plants. Woody stems are not likely to move. However, some litter movement is expected (up to 6 feet) with increases in slopes > 10% and/or increased runoff resulting from heavy 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 a soil stability rating of 5 or 6 under the plant canopies, and a rating of 4 to 5 in the interspaces. The average rating should be a 5. Soil surface texture is typically a silty clay.
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
(Obray) Soil surface 0-7 inches. Texture is a silty clay; color is dark grayish brown (10YR 4/2); structure is weak medium subangular blocky parting to weak fine and medium granular. Mollic epipedon ranges from 31 to more than 45 inches. 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:
The clay content within the soil profile may limit infiltration during all but the most gentle storms and snowmelt periods. Perennial vegetation provides sufficient cover and spatial arrangement to intercept most raindrops and reduce raindrop splash erosion. Litter on soil surface and cryptogamic crusting, where present, protect soil surface from splash erosion and encourages a higher rate of infiltration. Good plant spatial distribution will slow runoff, allowing additional time for infiltration. Bare spaces are expected to be small and irregular in shape and are usually not connected. Vegetative structure is usually adequate to capture snow and ensure that snowmelt occurs in a controlled manner, allowing time for good infiltration, reducing runoff and erosion. When perennial grasses and shrubs decrease due to natural events, including drought, insect damage, etc., which may reduce ground cover, runoff is expected to increase and infiltration be reduced.
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 content, these should not be mistaken for a compaction pan.
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:
Rhizomatous grasses (slender wheatgrass) > Sprouting shrubs (silver sagebrush, mountain snowberry), > Perennial bunchgrasses (mountain brome, Nevada bluegrass) > Perennial Forbs (purple germanium).

Sub-dominant:
Other perennial bunchgrasses and grasslikes (sheep fescue, Geyer sedge) > Rhizomatous grasses (western wheatgrass) >> Sprouting Shrubs (green rabbitbrush) >> Perennial forbs (thickleaf peavine).

Other:
Perennial and annual forbs can be expected to vary widely in their expression in the plant community based upon departures from average growing conditions.

Additional:
Natural disturbance regimes include fire, drought, and insects. Assumed fire cycle of 40 to 60+ years. Functional/structural groups may appropriately contain non-native species if their ecological function is the same as the native species in the reference state. Following a disturbance such as fire, drought, rodents or insects that remove woody vegetation, forbs and perennial grasses (herbaceous species) may dominate the community for a period of time. If a disturbance has not occurred for an extended period of time, woody species may continue to increase. These conditions would reflect a functional community phase within the reference state.
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
All age classes of perennial grasses should be present under average to above average growing conditions with age class expression likely subdued during periods of extended drought. Slight decadence in the principle shrubs could occur near the end of the fire cycle or during periods of extended drought, or insect infestations. In general, a mix of age classes should be expected with some dead and decadent plants present.
Average percent litter cover (%) and depth ( in):
Litter cover will be heavier under plants. Most litter will be herbaceous and depths of 1 to 2.5 inches would be considered normal. Perennial vegetation should be well distributed on the site.
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 1900 - 2000#/acre on an average year, but could range from 1600 to 2200#/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:
Cheatgrass, Canada thistle, morningglory, Russian thistle, alyssum, dock & mustard species.
Perennial plant reproductive capability:
All perennial plants should have the ability to reproduce in all years, except in extreme drought years. Green rabbitbrush sprouts vigorously following fire. There are no restrictions on either seed or vegetative reproduction. Some seedling recruitment of major species should be present during average and above average growing years.

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