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Ecological site R028AY257UT

Semidesert Steep Gravelly Loam (Wyoming Big Sagebrush)

Last updated: 6/12/2025
Accessed: 10/19/2025

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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.

MLRA notes

Major Land Resource Area (MLRA): 028A–Ancient Lake Bonneville

MLRA 28A occurs in Utah (82 percent), Nevada (16 percent), and Idaho (2 percent). It encompasses approximately 36,775 square miles (95,246 square kilometers). A large area west and southwest of Great Salt Lake is a salty playa. This area is the farthest eastern extent of the Great Basin Section of the Basin and Range Province of the Intermontane Plateaus. It is an area of nearly level basins between widely separated mountain ranges trending north to south. The basins are bordered by long, gently sloping alluvial fans. The mountains are uplifted fault blocks with steep side slopes. Most of the valleys are closed basins containing sinks or playa lakes. Elevation ranges from 3,950 to 6,560 feet (1,204 to 2000 meters) in the basins and from 6,560 to 11,150 feet (1996 to 3398 meters) in the mountains. Much of the MLRA has alluvial valley fill and playa lakebed deposits at the surface from pluvial Lake Bonneville, which dominated this MLRA 13,000 years ago. A level line of remnant lake terraces on some mountain slopes indicates the former extent of this glacial lake. The Great Salt Lake is what remains of the pluvial lake.

Mountains in the interior of this MLRA consist of tilted blocks of marine sediments from Cambrian to Mississippian age with scattered outcrops of Tertiary continental sediments and volcanic rocks. The average annual precipitation is 5 to 12 inches (13 to 30 cm) in the valleys and ranges up to 49 inches (124 cm) in the mountains. Most of the rainfall in the southern LRU occurs as high-intensity, convective thunderstorms during the growing season (April through September). The driest period is from midsummer to early autumn in the northern LRU. Precipitation in winter typically occurs as snow. The average annual temperature is 39 to 53 °F (4 to 12 °C). The freeze-free period averages 165 days and ranges from 110 to 215 days, decreasing in length with increasing elevation. The dominant soil orders in this MLRA are Aridisols, Entisols, and Mollisols. Soils are dominantly in the mesic or frigid soil temperature regime, aridic or xeric soil moisture regime, and mixed mineralogy. The soils are generally well drained, loamy or loamy-skeletal, and very deep.

LRU notes

The Basin and Range North LRU exhibits dry summer with stronger xeric patterns than the Basin and Range South LRU. Ranges in the north LRU are about 50 percent Paleozoic sedimentary/metasedimentary (limestone/quartzite dominant) and about 10 percent Tertiary volcanics. The basin floors are between 4,200 and 5,100 feet (1,280 to 1,554 meters) in elevation. Pinyon and juniper sites have a greater percentage of Utah juniper (Juniperus osteosperma) in the plant community than pinyon pine (Pinus edulis or monophylla). The Basin and Range North have few semidesert ecological sites with Utah juniper. Cool season grasses, such as bluebunch wheatgrass (Pseudorogneria spicata), are dominant in the plant community, while warm season grasses are largely absent or a small component of the plant community.

Ecological site concept

The Semidesert Steep Gravelly Loam (Wyoming Big Sagebrush) site occurs on steep alluvial fans and hills. This site is similar to Semidesert Gravelly Loam (Wyoming big sagebrush) R028AA215UT, except that 215 occurs at gentle slopes (less than 15 percent) and the Semidesert Steep Gravelly Loam (257) occurs at slopes greater than 15 percent. This difference in slope reduces potential production on the steep site. Semidesert Steep Gravelly Loam has been correlated to soils with a small extent in the Sevier River valley, it however may occur at other unidentified locations. This site has no known vegetation data and is currently only a concept that was identified in the field with concurrent soil survey work.

Similar sites

R028AY215UT	Semidesert Gravelly Loam (Wyoming Big Sagebrush) North This site occurs at slopes less than 15 percent and has more potential production.

R028AY215UT

Semidesert Gravelly Loam (Wyoming Big Sagebrush) North

This site occurs at slopes less than 15 percent and has more potential production.

Table 1. Dominant plant species

Tree	Not specified
Shrub	(1) Artemisia tridentata ssp. wyomingensis
Herbaceous	(1) Achnatherum hymenoides

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Physiographic features

The Semidesert Steep Gravelly Loam (Wyoming Big Sagebrush) site occurs on steep alluvial fans and hills. The slope ranges from 15 to 70 percent at elevations between 5,130 to 6,710 feet.

Table 2. Representative physiographic features

Landforms	(1) Alluvial fan (2) Hill
Flooding frequency	None
Ponding frequency	None
Elevation	5,130 – 6,710 ft
Slope	15 – 70%

Climatic features

The climate is semi-arid and characterized by cold snowy winters and warm dry summers. The average annual precipitation is about 11 inches. Approximately 70 percent comes as rain from March through October. On the average, June through September are the driest months and March through May are the wettest months, however this site is influenced by summer convective storms that provide additional precipitation during the summer growing season.

Table 3. Representative climatic features

Frost-free period (characteristic range)	87 days
Freeze-free period (characteristic range)	129 days
Precipitation total (characteristic range)	11 in
Frost-free period (actual range)	87 days
Freeze-free period (actual range)	129 days
Precipitation total (actual range)	11 in
Frost-free period (average)	87 days
Freeze-free period (average)	129 days
Precipitation total (average)	11 in

Characteristic range

Actual range

Bar

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Figure 1. Monthly precipitation range

Characteristic range

Actual range

Bar

Line

Figure 2. Monthly minimum temperature range

Characteristic range

Actual range

Bar

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Figure 3. Monthly maximum temperature range

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Figure 4. Monthly average minimum and maximum temperature

Figure 5. Annual precipitation pattern

Figure 6. Annual average temperature pattern

Climate stations used

(1) SALINA [USC00427557], Salina, UT

Soil features

The soil was formed in alluvium or colluvium derived from igneous rocks. The soil is deep and well drained. The surface texture is very stony, cobbly, or gravelly loam. Surface rock fragments make up between 15 to 55 percent cover and subsurface rock fragments make up between 35 to 60 percent volume.

Table 4. Representative soil features

Parent material	(1) Alluvium – igneous rock (2) Colluvium – igneous rock
Surface texture	(1) Very stony, gravelly, very cobbly loam
Drainage class	Well drained to somewhat excessively drained
Permeability class	Moderately rapid
Surface fragment cover <=3"	15 – 24%
Surface fragment cover >3"	1 – 35%
Available water capacity (Depth not specified)	1.5 – 4.3 in
Calcium carbonate equivalent (Depth not specified)	3 – 30%
Electrical conductivity (Depth not specified)	4 mmhos/cm
Sodium adsorption ratio (Depth not specified)	Not specified
Soil reaction (1:1 water) (Depth not specified)	7.9 – 9
Subsurface fragment volume <=3" (Depth not specified)	35 – 44%
Subsurface fragment volume >3" (Depth not specified)	6 – 20%

Ecological dynamics

The reference concept is typically dominated by Wyoming big sagebrush and Indian ricegrass. This site would cycle between three dominant plant communities. One community phase would occur soon after a fire, with rabbitbrush as the perennial bunch grasses as the dominant plants and the other community would develop in the absence of fire, with Wyoming big sagebrush cover increasing and reduced herbaceous cover.

The introduction of non-native species altered the trajectory of this site. Non-native species, such as cheatgrass and annual forbs, increase fine fuels and the fire recurrence interval.

The state and transition model is not based on data but on a hypothesis that the site functions similarly to R028AA215UT.

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

1. Reference State

SWAPAEH

2. Current Potential State

SWAPAEH

State 1 submodel, plant communities

1.1. Wyoming big sagebrush, bluebunch wheatgrass, Indian ricegrass

1.2. Bluebunch wheatgrass, Indian ricegrass, squirreltail

1.3. Wyoming big sagebrush

State 2 submodel, plant communities

2.1. Wyoming big sagebrush, bluebunch wheatgrass, Indian ricegrass

2.2. Bluebunch wheatgrass, Indian ricegrass

2.3. Wyoming big sagebrush

State 1
Reference State

The Reference State includes plant communities dominated by a diverse mixture of perennial grasses, and a mixture of Wyoming big sagebrush and yellow rabbitbrush. These community phases occur depending on length time since a disturbance (fire, insects, drought, or over grazing) that removes Wyoming big sagebrush from the community. Adequate duration, timing, and intensity of the disturbance is required to maintain plant vigor and health of the plant community. Note that plant communities in this state will only consist of native species.

Community 1.1
Wyoming big sagebrush, bluebunch wheatgrass, Indian ricegrass

This community is dominated by Wyoming big sagebrush and Indian ricegrass. Shadscale and ephedra are also commonly present in the shrub layer. Bluebunch wheatgrass and Indian ricegrass are the principle perennial grasses. Sandberg bluegrass (Poa secunda) is commonly present.

Community 1.2
Bluebunch wheatgrass, Indian ricegrass, squirreltail

Native perennial bunchgrasses dominate this community phase. Wyoming big sagebrush and shadscale decrease in the community. Winterfat has the ability to resprout and re-establish following a fire. Yellow rabbitbrush and horsebrush species (Nuttall, smooth, and/or spiny) may increase significantly following fire and much of the excess fine fuel accumulation is removed. Fire tolerant shrubs typically persist as dominants in the community for 30 years or longer. Bluebunch wheatgrass and other cool season bunchgrasses flourish. Western wheatgrass increases in herbaceous cover.

Community 1.3
Wyoming big sagebrush

Wyoming big sagebrush and shadscale increases significantly in percent composition. Winterfat and yellow rabbitbrush may increase also. Shrubs become decadent due to age. Bluebunch wheatgrass, Indian ricegrass, and other cool season bunchgrasses begin to lose vigor because of increased shrub competition and become dense with old vegetation. Western wheatgrass increases in herbaceous cover.

Pathway 1.1a
Community 1.1 to 1.2

Recent fire occurrence (1 – 30 years).

Pathway 1.1b
Community 1.1 to 1.3

Extended period of time without a major disturbance such as fire; insect damage; or prolonged drought. Fire frequency extends well beyond the 40 to 50 year average for the site.

Pathway 1.2a
Community 1.2 to 1.1

Normal fire frequency of about 100 years returns on the site.

Pathway 1.3a
Community 1.3 to 1.2

Recent fire occurrence.

State 2
Current Potential State

This state includes plant communities dominated by a diverse mixture of perennial grasses, a mixture of Wyoming big sagebrush and perennial grasses, and a community dominated by Wyoming big sagebrush. These community phases occur depending on the time since a disturbance that kills Wyoming big sagebrush has occurred, such as fire, insects, or drought, and grazing that provides adequate duration, timing, and intensity that maintain plant vigor and health of the plant community. Plant communities in this state can include native, acclimatized, naturalized and invasive non-native species. This state is irreversibly changed from the reference state because these non-native species will now remain a permanent part of the community. This plant community has the composition, structure and cover present that facilitates the capture, storage, and safe release of precipitation, nutrients are being cycled through deep rooted perennial grasses, forbs, and evergreen shrubs, and cool season energy capture throughout the entire growing season (March to October) such that this plant community and site resiliency is maintained. With a lengthened fire return interval (greater than 60 years), an increase in sagebrush canopy occurs until sagebrush dominates resource use. This results in a decrease in vigor, cover and reproduction of perennial bunch grasses, and results in an increase in invasive annuals such as cheatgrass.

Community 2.1
Wyoming big sagebrush, bluebunch wheatgrass, Indian ricegrass

This community is dominated by Wyoming big sagebrush. Shadscale and ephedra are also commonly present in the shrub layer. Bluebunch wheatgrass and Indian ricegrass are the principle perennial grasses. Sandberg bluegrass is commonly present. This community is dominated by native species, but may include acclimatized, naturalized and invasive non-native species.

Community 2.2
Bluebunch wheatgrass, Indian ricegrass

Wyoming big sagebrush and shadscale decrease in the community. Winterfat resprouts following the fire. Yellow rabbitbrush and horsebrush species (Nuttall, smooth and/or spiny) may increase significantly in the community following fire. Several native grasses dominate the understory. Fire tolerant shrubs typically persist as dominants in the community for 30 years or longer. This community is dominated by native species, but may include acclimatized, naturalized and invasive non-native species.

Community 2.3
Wyoming big sagebrush

Wyoming big sagebrush and shadscale increase significantly in percent composition. Winterfat and yellow rabbitbrush may increase also. Shrubs become decadent due to age. Bluebunch wheatgrass, Indian ricegrass, and other cool season bunchgrasses begin to lose vigor because of improper grazing (including, season long overstocking, wrong season, etc.) and/or increased shrub competition and become dense with old vegetation. Western wheatgrass increases in herbaceous cover. This community is dominated by native species, but may include acclimatized, naturalized and invasive non-native species. Utah Juniper can encroach in this community phase and is small and low in cover.

Pathway 2.1a
Community 2.1 to 2.2

Fire removes non-sprouting shrubs from the community. Yellow rabbitbrush and/or horsebrush species may be dominant. Recent fire occurrence (1 to 30 years).

Pathway 2.1b
Community 2.1 to 2.3

Improper grazing (including season long, overstocking, wrong season, etc.) and/or drought remove annual and perennial fine fuels from the site lessening the potential for fire to occur. Fire frequency extends beyond the 100 year average for the site. Utah juniper may invade the site in drainageways if a seed source is available.

Pathway 2.2a
Community 2.2 to 2.1

Native perennial vegetation is recovering. Fire frequency returns to within the normal range for the state. 100 years or more without a fire occurrence (normal fire frequency).

Pathway 2.3a
Community 2.3 to 2.2

Fire removes non-sprouting shrubs from the community. Yellow rabbitbrush and/or horsebrush species become dominant. Recent fire occurrence (1 to 30 years).

Transition T1A
State 1 to 2

The threshold is crossed when there is an introduction of non-native species, primarily cheatgrass and various annual mustards, that become established in the community.

Additional community tables

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	06/14/2025
Approved by	Kendra Moseley
Approval date
Composition (Indicators 10 and 12) based on	Annual Production

Indicators

Number and extent of rills:
Presence of water flow patterns:
Number and height of erosional pedestals or terracettes:
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Number of gullies and erosion associated with gullies:
Extent of wind scoured, blowouts and/or depositional areas:
Amount of litter movement (describe size and distance expected to travel):
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
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:
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Average percent litter cover (%) and depth ( in):
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
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:
Perennial plant reproductive capability:

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Natural ResourcesConservation Service

Ecological site R028AY257UT

Semidesert Steep Gravelly Loam (Wyoming Big Sagebrush)

Last updated: 6/12/2025 Accessed: 10/19/2025

General information

MLRA notes

LRU notes

Ecological site concept

Similar sites

Table 1. Dominant plant species

Ecosystem states

State 1 submodel, plant communities

State 2 submodel, plant communities

Natural Resources
Conservation Service

Last updated: 6/12/2025
Accessed: 10/19/2025