Natural Resources
Conservation Service
Ecological site R008XY226WA
Stony Foothills South Aspect bitterbrush
Last updated: 5/23/2025
Accessed: 06/20/2025
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): 008X–Columbia Plateau
MLRA 8 encompasses about 50,100 square kilometers mainly in Washington and Oregon, with a small area in Idaho. This MLRA is characterized by loess hills, surrounding scablands, and alluvial deposits. This MLRA consists mostly of Miocene Columbia River Basalt covered with up to 200 feet of loess and volcanic ash. The dominant soil order in this MLRA is Mollisols. Soils in this MLRA dominantly have a mesic temperature regime, a xeric moisture regime, and mixed minerology.
Classification relationships
Major Land Resource Area (MLRA): 8 – Columbia Plateau
LRU – Common Resource Areas (CRA):
8.1 - Channeled Scablands
8.2 - Loess Islands
8.3 - Okanogan Drift Hills
8.4 - Moist Pleistocene Lake Basins
8.5 - Moist Yakima Folds
8.7 - Okanogan Valley
Ecological site concept
Diagnostics:
Stony foothills, south aspect, bitterbrush is an upland shrub-steppe site occurring on south-facing slopes in the foothill areas below the lower tree-line of MLRA 6 (East Slope of Cascades).
The soils are deep (60 inches or greater), coarse textured and rocky. Textures are mostly sandy loam and sand with some loams. Soils are often gravelly to very gravely to extremely stony. Soils are well drained.
Fire sensitive, bitterbrush dominates the reference state overstory, while bluebunch wheatgrass is dominant in the herbaceous understory. The shrub layer is typically waist- to shoulder-height bitterbrush with a mix of other shrub steppe species scattered throughout including Wyoming sagebrush, rabbitbrush, and current.
Bitterbrush areas in MLRA 8 are east of, or adjacent to, the Ponderosa pine forests including: Klickitat and Yakima counties, and then from central Kittitas County northward to the Canadian border
Principle Vegetative Drivers:
The coarse soils and aspect drive the vegetative expression of this site. Bitterbrush prefers well drained, coarse soils. The south slope is good for bluebunch wheatgrass but is unable to support Idaho fescue.
Associated Sites:
Stony Foothills South Aspect bitterbrush is associated with Stony Foothills, Loamy and Stony in MLRA 8, and Stony Foothills South Aspect in MLRA 6 East Slope of the Cascades ecological sites.
Similar Sites:
MLRA 8 Columbia Plateau Stony Foothills, MLRA 6 East Slope of the Cascades Stony Foothills South Aspect, and Stony Foothills in MLRA 9 Palouse Prairie are also bitterbrush sites.
Associated sites
| R008XY220WA |
Stony Foothills bitterbrush |
|---|---|
| R008XY102WA |
Loamy 10-16 PZ |
Similar sites
| R008XY220WA |
Stony Foothills bitterbrush |
|---|---|
| R006XY126WA |
Stony South Aspect 4000-6000 feet |
| R009XY626WA |
Stony South Aspect |
Table 1. Dominant plant species
| Tree |
Not specified |
|---|---|
| Shrub |
(1) Purshia tridentata |
| Herbaceous |
(1) Pseudoroegneria spicata |
Physiographic features
The landscape is part of the Columbia basalt plateau. Stony foothills, south aspect, bitterbrush is commonly found on south-facing hillslopes, but not on neutral or north slopes.
Physiographic Division: Intermontane Plateau
Physiographic Province: Columbia Plateau
Physiographic Sections: Walla Walla Plateau Section
Landscapes: Hills, valleys and plateaus
Landform: Sideslopes, terraces, outwash terraces
Table 2. Representative physiographic features
| Geomorphic position, hills |
(1) Side Slope |
|---|---|
| Landforms |
(1)
Hills
(2) Valley (3) Plateau (4) Terrace (5) Outwash terrace |
| Flooding frequency | None |
| Ponding frequency | None |
| Elevation |
Not specified |
| Slope | 2 – 30% |
| Water table depth | 152 cm |
| Aspect | W, NW, NE, E, SE, S, SW |
Table 3. Representative physiographic features (actual ranges)
| Flooding frequency | Not specified |
|---|---|
| Ponding frequency | Not specified |
| Elevation | Not specified |
| Slope | 0 – 90% |
| Water table depth | Not specified |
Climatic features
Bitterbrush areas tend to be both cooler and wetter than Wyoming sagebrush areas (Daubenmire). Stony foothills, south aspect, bitterbrush, doesn’t favor Idaho fescue, has a warmer micro-climate than the northern facing Stony foothills, bitterbrush. The climate is characterized by moderately cold, wet winters, and hot, dry summers, with limited precipitation due to the rain shadow effect of the Cascades. Taxonomic soil climate is either xeric (12 to 16 inches PPT) or aridic moisture regimes (10 to 12 inches PPT) with a mesic temperature regime.
Table 4. Representative climatic features
| Frost-free period (characteristic range) | 120-160 days |
|---|---|
| Freeze-free period (characteristic range) | |
| Precipitation total (characteristic range) | 254-406 mm |
| Frost-free period (actual range) | 110-190 days |
| Freeze-free period (actual range) | |
| Precipitation total (actual range) |
Influencing water features
A plant’s ability to grow on a site and overall plant production is determined by soil-water-plant relationships
1. Whether rain and melting snow runs off-site or infiltrates into the soil
2. Whether soil condition remain aerobic or become saturated and become anaerobic
3. Water drainage and how quickly the soil reaches wilting point
Stony foothills, south slope, bitterbrush receives more solar radiation and the soils dry out much more rapidly than adjacent ecological sites.
Soil features
This ecological site components are dominantly Aridic, Xeric and Vitrandic taxonomic subgroups of Haploxerolls, Argixerolls, Torripsamments great groups of the Mollisols and Entisols taxonomic orders. Soils are deep to very deep. Average available water capacity of about 4.5 inches (11.4 cm) in the 0 to 40 inches (0 to 100 cm) depth range.
Soil parent material is dominantly mixed loess, colluvium and residuum with influence of volcanic ash possible.
The associated soils are Antilon, Cashmont, Conconully, Ewall, Pogue, Quincy and similar soils.
Dominate soil surface is loam to loamy sand, with ashy modifier sometimes occurring as well.
Dominant particle-size class is ashy to sandy skeletal.
Table 5. Representative soil features
| Parent material |
(1)
Loess
(2) Colluvium (3) Residuum |
|---|---|
| Surface texture |
(1) Loam (2) Loamy sand |
| Family particle size |
(1) Sandy-skeletal (2) Ashy |
| Drainage class | Well drained to excessively drained |
| Depth to restrictive layer | 102 – 152 cm |
| Soil depth | 102 – 152 cm |
| Surface fragment cover <=3" | 15% |
| Surface fragment cover >3" | 15% |
| Available water capacity (0-101.6cm) |
13.97 cm |
| Calcium carbonate equivalent (Depth not specified) |
0 – 25% |
| Electrical conductivity (Depth not specified) |
0 – 5 mmhos/cm |
| Sodium adsorption ratio (Depth not specified) |
0 – 5 |
| Soil reaction (1:1 water) (0-25.4cm) |
5.6 – 8.4 |
| Subsurface fragment volume <=3" (Depth not specified) |
10% |
| Subsurface fragment volume >3" (Depth not specified) |
15% |
Table 6. Representative soil features (actual values)
| Drainage class | Not specified |
|---|---|
| Depth to restrictive layer | Not specified |
| Soil depth | Not specified |
| Surface fragment cover <=3" | 0 – 30% |
| Surface fragment cover >3" | 0 – 25% |
| Available water capacity (0-101.6cm) |
2.54 – 24.64 cm |
| Calcium carbonate equivalent (Depth not specified) |
Not specified |
| Electrical conductivity (Depth not specified) |
Not specified |
| Sodium adsorption ratio (Depth not specified) |
Not specified |
| Soil reaction (1:1 water) (0-25.4cm) |
Not specified |
| Subsurface fragment volume <=3" (Depth not specified) |
0 – 40% |
| Subsurface fragment volume >3" (Depth not specified) |
0 – 25% |
Ecological dynamics
Stony foothills, south aspect, bitterbrush produces about 900 to 1,300 pounds per acre of biomass annually.
Antelope bitterbrush and bluebunch wheatgrass are the primary dominant species on the Stony Foothills South Slope ecological site and warrant a degree of understanding.
Antelope bitterbrush is a very palatable, high quality shrub for big game and livestock. It is adapted to a wide range of soils and precipitation. Bitterbrush is usually two to six feet in height and up to eight feet in width. Rodents normally cache bitterbrush seed within 50 to 75 feet of an existing seed source. Following a fire, the rodent seed caches become an important source of regeneration. Another important source of regeneration are pockets of unburned rangeland that provide much needed seed to the system.
Bluebunch wheatgrass is a long-lived, mid-sized bunchgrass with an awned or awnless seed head arranged in a spike. It provides a crucial and extensive network of roots to the upper portions (up to 48” deep in soils with no root-restrictive horizons) of the soil profile. These roots create a massive underground source to stabilize the soils, provide organic matter and nutrients inputs, and help maintain soil pore space for water infiltration and water retention in the soil profile. The extensive rooting system of mid-sized bunchgrasses leave very little soil niche space available for invasion by other species. This drought resistant root can compete with, and suppress, the spread of exotic weeds.
Needle and thread is another perennial bunchgrass commonly associated with the Stony Foothills South Slope. Stems are erect, unbranched and about 4 feet in height. Needle and thread produces one seed per set of glumes in a narrow panicle. The seeds have a 4 to 5-inch long twisted awns. With wetting and drying the seed drills itself into the ground. Thus, needle and thread is one of the best seeders in the reference plant community. With grazing pressure on the dominant grass, bluebunch wheatgrass, needle and thread increases.
The stability and resiliency of the reference communities is directly linked to the health and vigor of bluebunch wheatgrass. Research has found that the community remains resistant to medusahead if the site maintains at least 0.8 mid-sized bunchgrass plants per square foot (Davies). Bluebunch wheatgrass holds the system together. If bluebunch wheatgrass is lost from the ecological site/community, the ecosystem begins to unravel.
The effect of fire on the main species is mixed for the Stony Foothills South Slope site. Bitterbrush is very susceptible to fire kill and is considered a weak sprouter. Needle and thread and bluebunch wheatgrass are fire tolerant in most instances. Bluebunch wheatgrass and needle and thread keep the site resistant to change, while bitterbrush makes the site more at risk.
How one answers fire return intervals for bitterbrush communities depends on the frame of reference used. Currently conditions for Stony Foothills are communities often dominated by dense canopies of bitterbrush. These shrubs are 50 to 100 years old or older due to fire suppression. These bitterbrush plants do not readily re-sprout following fire. Germinating seeds, especially from rodent caches is the primary source to bitterbrush re-establishment. The framework of current conditions suggests a fire return interval of 50 to 100 years or longer.
Miller et al, paint a totally different picture for pre-settlement mountain big sage-bitterbrush-fescue communities. These communities were dominated by the herb layer. Shrubs were widely scattered and patchy. The fire regime was high frequency (10 to 20 years), low severity, low intensity. The landscape would have been a mosaic of burned and unburned patches. In any given fire some bitterbrush plants would have survived the fire. Also, bitterbrush plants were likely much younger (10 to 30 years old), more vigorous and more likely to sprout following fire. In recent years sprouting bitterbrush after low severity fire supports the notion of sprouting bitterbrush. Seedlings from rodent caches would have also been important for the recovery of the shrub layer.
A low intensity, high frequency fire regime favors quick recovery with bitterbrush sprouting and rapid tillering by bluebunch wheatgrass. A high intensity, low frequency fire regime hinders recovery as bluebunch wheatgrass is set back and bitterbrush regeneration is limited to seedlings.
Fires with light severity will remove less bitterbrush and open smaller patches for grass and forb recovery, whereas the more severe fires will remove almost all the bitterbrush and leave vast areas open to return to bunchgrass dominance. This is how the patchy distribution occurs. So, fire resets the competitive advantage back to the bunchgrasses by removing much of the overstory. This, in turn, maintains the stability and overall resilience of the site. However, this is not always true as some fires are spotty or do not burn hot enough to fully remove the bitterbrush. Rabbitbrush and horsebrush are sprouting shrubs and may also increase following fire.
The longer the site goes without fire and the more grazing pressure is added to the bunchgrasses, the more bitterbrush cover increases, and the more bunchgrasses decline. This leaves the dense bitterbrush community phase more vulnerable to outside pressures. Invasive species take advantage of the available soil rooting spaces in the interspaces. The once extensive grass roots are largely absent. Soils are no longer receiving the organic inputs, and there is less surface cover by grass litter. Both water infiltration into the soil, and water percolation through the soil, are affected, leaving open soil space that is drier and more vulnerable to wind and water erosion, and invasion by undesirable species. Once these undesirable species have colonized, the site is at high risk of crossing a threshold if a disturbance such as fire were to occur.
Grazing is another common disturbance that occurs in this ecological site. Grazing pressure can be defined as heavy grazing intensity, or frequent grazing during reproductive period, or season-long grazing (same plants grazed more than once). As grazing pressure increases the plant community unravels in stages:
1. Bluebunch wheatgrass declines while Sandberg bluegrass, needle and thread and sagebrush increase
2. As bluebunch wheatgrass continues to decline, invasive species such as cheatgrass and knapweed colonize the site
3. With further decline the site can become a sagebrush-cheatgrass community
Managing shrub steppe to improve the vigor and health of native bunchgrasses begins with an understanding of grass physiology. New growth each year begins from basal buds. Bluebunch wheatgrass plants rely principally on tillering, rather than establishment of new plants through natural reseeding. During seed formation, the growing points become elevated and are vulnerable to damage or removal.
If defoliated during the formation of seeds, bluebunch wheatgrass has limited capacity to tiller compared with other, more grazing resistant grasses (Caldwell et al., 1981). Repeated critical period grazing (boot stage through seed formation) is especially damaging. Over several years each native bunchgrass pasture should be rested during the critical period two out of every three years (approximately April 15 to July 15). And each pasture should be rested the entire growing season every third year (approximately March 1 to July 15).
In the spring each year it is important to monitor and maintain an adequate top growth: (1) so plants have enough energy to replace basal buds annually, (2) to optimize regrowth following spring grazing, and (3) to protect the elevated growing points of bluebunch wheatgrass.
Bluebunch wheatgrass remains competitive if:
(1) Basal buds are replaced annually,
(2) Enough top-growth is maintained for growth and protection of growing points, and
(3) The timing of grazing and non-grazing is managed over a several-year period. Careful management of late spring grazing is especially critical
Antelope bitterbrush is an important browse species for big game animals and needs special management consideration with livestock in mind. There is no problem with spring grazing as livestock do not focus their attention to bitterbrush in the spring. Fall is a different story. Feeding some alfalfa every second or third day helps minimize livestock use of bitterbrush in the fall.
For more grazing management information refer to Range Technical Notes found in Section I Reference Lists of NRCS Field Office Technical Guide for Washington State.
In Washington, antelope bitterbrush / Idaho fescue /bluebunch wheatgrass communities provide habitat for big game and sharp-tailed grouse.
State and transition model
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State 1 submodel, plant communities
State 2 submodel, plant communities
State 3 submodel, plant communities
State 4 submodel, plant communities
State 1
Reference - Shrub Steppe with No Invasive Species
State 1 represents shrub steppe with no invasive or exotic weed species. All the functional, structural groups are represented by one or more native species. Reference state Community Phases: 1.1 Reference Bluebunch wheatgrass – bitterbrush 1.2 Bunchgrass Bluebunch wheatgrass 1.3 Shrub Steppe Bitterbrush – bluebunch wheatgrass 1.4 Heavy Shrub Bitterbrush – needle and thread Communities 1.1, 1,2 and 1.3 can shift to the other two communities and back again. Dominate Reference State Species: Antelope bitterbrush – bluebunch wheatgrass At-risk Communities: • All communities in the reference state are at risk of moving to State 2. The seed source of cheatgrass is nearby and blowing onto most sites annually • Community Phases 1.1, 1.2 and 1.3 have high amounts of bluebunch wheatgrass cover and are at low risk of moving to State 3 • Community Phase 1.4 is at-risk because of low density for bluebunch wheatgrass. Community 1.4 should be seeded after fire • Any community with more than 40 percent bitterbrush cover • When fire kills the Idaho fescue plants, these sites should be seeded after fire • Community 1.4, and any site with low cover of bluebunch wheatgrass, and any site with moderate to heavy cover of cheatgrass should be seeded after fire.
Community 1.1
Reference - Bluebunch Wheatgrass and Antelope Bitterbrush
70% bluebunch wheatgrass 10% antelope bitterbrush
Figure 1. Annual production by plant type (representative values) or group (midpoint values)
Community 1.2
Bunchgrass Community - Bluebunch Wheatgrass and Antelope Bitterbrush
90% bluebunch wheatgrass 0-2% antelope bitterbrush
Community 1.3
Shrub Steppe Community - Bluebunch Wheatgrass, Antelope Bitterbrush, and Needle and Thread
50% bluebunch wheatgrass 30% antelope bitterbrush 10% needle and thread
Community 1.4
Heavy Shrub Community - Antelope Bitterbrush, Needle and Thread, and Bluebunch Wheatgrass
50% antelope bitterbrush 30% needle and thread 10% bluebunch wheatgrass
Pathway 1.1A
Community 1.1 to 1.2
Result: Shift from Reference community to Bunchgrass community. Shrub cover (bitterbrush and sagebrush) is all but eliminated, while bluebunch wheatgrass has a moderate increase in cover. The community shifts from a shrub steppe to a bunchgrass appearance. Causes: Moderate-severity fire is complete enough and hot enough to remove most of the shrubs. Fire is not hot enough to affect the soil conditions. The fire removes surface vegetation but has no impact on the crown of bunchgrasses. So, bunchgrasses and forbs return post-fire with good vigor. Post-fire the bunchgrasses are now more susceptible to grazing damage. Burned rangeland pastures will need two growing seasons recovery prior to resuming grazing, or to be lightly grazed but only during dormant season the first two years post-fire. Beyond two years for the bunchgrasses to expand, moderate grazing intensity, and both critical period & growing season deferments must be implemented on burned pastures. Ecological process: Fire kills sagebrush and it does not have any sprouting ability. A few sagebrush plants remain, but only in patches that did not burn. The reduction in sagebrush releases resources and increases light for grasses and forbs. Bluebunch wheatgrass and other bunchgrasses have good vigor post-fire and expand via tillering and new seedlings.
Pathway 1.1B
Community 1.1 to 1.3
Result: shift from Bunchgrass or reference community to shrub steppe community. There is a moderate increase in bitterbrush while bunchgrasses have a moderate corresponding decrease. Causes: With excessive grazing pressure (heavy grazing intensity, season long grazing or frequent late spring grazing) and a period of no fire, bitterbrush and sagebrush increase its cover while bluebunch wheatgrass suffers a big decline. The increased shade and grazing pressure cause lower bunchgrass vigor and a decline. Ecological process: With consistent defoliation pressure plant vigor decreases to such a degree that grass roots begin to die. So, bluebunch wheatgrass experiences shrinking crowns and some plant mortality. The open niche space allows bitterbrush and sagebrush to set new seedlings and expand. Needle and thread, a prolific seeder, expands with many seedlings.
Pathway 1.2A
Community 1.2 to 1.1
Result: Shift from bunchgrass community to reference community. There is a minor reduction of bluebunch wheatgrass cover and a minor increase of bitterbrush. Causes: Over time with no fire bitterbrush and sagebrush will re-enter the community. With a slight increase in shade and some grazing pressure, perennial bunchgrasses experience a slight decline. Ecological process: With some consistent defoliation pressure Idaho fescue and bluebunch wheatgrass have lower vigor and shrinking crowns. Bitterbrush and sagebrush set new seedlings and expand. Rodents cache bitterbrush seed in the soil. Post-fire some of this cached seed will germinate. Also, spots with soil disturbance receive sagebrush seed from remnant plants in unburned patches or from adjacent sites, seed germinates in the spring and a few sagebrush seedlings establish.
Pathway 1.3A
Community 1.3 to 1.1
Result: Shift from shrub steppe community to reference community or to bunchgrass community. Shrub cover is reduced by two-thirds which is coupled with a significant increase in the cover of native bunchgrasses. Causes: Moderate-severity fire is patchy and dependent on temperature, wind, fuel load and fuel moisture. Some areas burn completely while other areas are unburned to lightly burned. Fire is not hot enough to affect the soil conditions. Fire removes surface vegetation but has no impact on the root crown of bunchgrasses. So, bunchgrasses and forbs return post-fire. Post-fire the bunchgrasses are now more susceptible to grazing damage. Burned rangeland pastures will need two growing seasons recovery prior to resuming grazing, or to be lightly grazed but only during dormant season the first two years post-fire. Beyond two years, for the bunchgrasses to continue to expand, the grazing plan must consider moderate grazing intensity, and both critical period & growing season deferments. Ecological process: Bluebunch wheatgrass and other bunchgrasses have good vigor post-fire and expand via tillering and new seedlings. The reduction in bitterbrush releases resources and increases light for grasses and forbs. Bunchgrasses must have high vigor both pre- and post-fire, to expand its cover.
Pathway 1.3B
Community 1.3 to 1.4
Result: Shift from shrub steppe community to heavy shrub community. Bitterbrush and needle and thread have a big increase in cover while bluebunch wheatgrass is reduced significantly. Invasive annual grasses have not invaded but Community 1.4 is most at risk and, is the segue between Reference State and States 2 & 3. Causes: With no fire, more shade and grazing pressure (heavy grazing intensity, season long grazing or frequent late spring grazing), the bunchgrasses experience weakened vigor and declining crowns. Grazing animals selectively target and eliminate most of the remaining bluebunch wheatgrass plants from the community. Bitterbrush and needle and thread both expand. Ecological process: With consistent defoliation pressure plant vigor decreases to such a degree that grass roots die. Bluebunch wheatgrass experiences shrinking crowns and a lot of plant mortality. Bitterbrush and needle and thread, however, set new seedlings and expand. The open niche space gives bitterbrush and sagebrush opportunity to set new seedlings. Needle and thread, a prolific seeder, expands with many seedlings.
State 2
Shrub Steppe with Invasive Species
State 2 represents invasion by annual grasses and is the gradation between Reference state and state 3. State 2 is shrub steppe with the inclusion of invasive annual grasses such as cheatgrass. The loss if soil biological crusts and annual grass seed blowing onto the site annually contributes to the annual grass invasion. All the native functional, structural groups are still represented by one or more species. This state can occur with or without bitterbrush. For communities 2.1, 2.2, and 2.3 the amount of cheatgrass is minor. Cheatgrass is more prominent in community 2.4. Once a community has been invaded by cheatgrass the chance of going back to State 1 is small. This state can occur with or without bitterbrush. Community Phases for state 2: Same four communities as for Reference state. Dominate State 2 Species: Bitterbrush, bluebunch wheatgrass Pathways within State 2: Same as for Reference state
Community 2.1
Reference with Invasives
Community 2.2
Bunchgrass with Invasives
Community 2.3
Shrub Steppe with Invasives
Community 2.4
Heavy Shrub with Invasives
Pathway 2.1A
Community 2.1 to 2.2
Result: Shift from reference community to bunchgrass community. Shrub cover (bitterbrush and sagebrush) is all but eliminated, while bluebunch wheatgrass has a moderate increase in cover. The community shifts from a shrub steppe to a bunchgrass appearance. Causes: Moderate-severity fire is complete enough and hot enough to remove most of the shrubs. Fire is not hot enough to affect the soil conditions. The fire removes surface vegetation but has no impact on the crown of bunchgrasses. So, bunchgrasses and forbs return post-fire with good vigor. Post-fire the bunchgrasses are now more susceptible to grazing damage. Burned rangeland pastures will need two growing seasons recovery prior to resuming grazing, or to be lightly grazed but only during dormant season the first two years post-fire. Beyond two years for the bunchgrasses to expand, moderate grazing intensity, and both critical period & growing season deferments must be implemented on burned pastures. Ecological process: Fire kills sagebrush and it does not have any sprouting ability. A few sagebrush plants remain, but only in patches that did not burn. The reduction in sagebrush releases resources and increases light for grasses and forbs. Bluebunch wheatgrass and other bunchgrasses have good vigor post-fire and expand via tillering and new seedlings.
Pathway 2.1B
Community 2.1 to 2.3
Result: shift from bunchgrass or reference community to shrub steppe community. There is a moderate increase in bitterbrush while bunchgrasses have a moderate corresponding decrease. Causes: With excessive grazing pressure (heavy grazing intensity, season long grazing or frequent late spring grazing) and a period of no fire, bitterbrush and sagebrush increase its cover while bluebunch wheatgrass suffers a big decline. The increased shade and grazing pressure cause lower bunchgrass vigor and a decline. Ecological process: With consistent defoliation pressure plant vigor decreases to such a degree that grass roots begin to die. So, bluebunch wheatgrass experiences shrinking crowns and some plant mortality. The open niche space allows bitterbrush and sagebrush to set new seedlings and expand. Needle and thread, a prolific seeder, expands with many seedlings.
Pathway 2.2A
Community 2.2 to 2.1
Result: Shift from bunchgrass community to reference community. There is a minor reduction of bluebunch wheatgrass cover and a minor increase of bitterbrush. Causes: Over time with no fire bitterbrush and sagebrush will re-enter the community. With a slight increase in shade and some grazing pressure, perennial bunchgrasses experience a slight decline. Ecological process: With some consistent defoliation pressure Idaho fescue and bluebunch wheatgrass have lower vigor and shrinking crowns. Bitterbrush and sagebrush set new seedlings and expand. Rodents cache bitterbrush seed in the soil. Post-fire some of this cached seed will germinate. Also, spots with soil disturbance receive sagebrush seed from remnant plants in unburned patches or from adjacent sites, seed germinates in the spring and a few sagebrush seedlings establish.
Pathway 2.3A
Community 2.3 to 2.1
Result: Shift from shrub steppe community to the near reference community or to bunchgrass community. Shrub cover is reduced by two-thirds which is coupled with a significant increase in the cover of native bunchgrasses. Causes: Moderate-severity fire is patchy and dependent on temperature, wind, fuel load and fuel moisture. Some areas burn completely while other areas are unburned to lightly burned. Fire is not hot enough to affect the soil conditions. Fire removes surface vegetation but has no impact on the root crown of bunchgrasses. So, bunchgrasses and forbs return post-fire. Post-fire the bunchgrasses are now more susceptible to grazing damage. Burned rangeland pastures will need two growing seasons recovery prior to resuming grazing, or to be lightly grazed but only during dormant season the first two years post-fire. Beyond two years, for the bunchgrasses to continue to expand, the grazing plan must consider moderate grazing intensity, and both critical period & growing season deferments. Ecological process: Bluebunch wheatgrass and other bunchgrasses have good vigor post-fire and expand via tillering and new seedlings. The reduction in bitterbrush releases resources and increases light for grasses and forbs. Bunchgrasses must have high vigor both pre- and post-fire, to expand its cover.
Pathway 2.3B
Community 2.3 to 2.4
Result: Shift from shrub steppe community to heavy shrub community. Bitterbrush and needle and thread have a big increase in cover while bluebunch wheatgrass is reduced significantly. Invasive annual grasses have not invaded but Community 1.4 is most at risk and, is the segue between Reference State and States 2 and 3. Causes: With no fire, more shade and grazing pressure (heavy grazing intensity, season long grazing or frequent late spring grazing), the bunchgrasses experience weakened vigor and declining crowns. Grazing animals selectively target and eliminate most of the remaining bluebunch wheatgrass plants from the community. Bitterbrush and needle and thread both expand. Ecological process: With consistent defoliation pressure plant vigor decreases to such a degree that grass roots die. Bluebunch wheatgrass experiences shrinking crowns and a lot of plant mortality. Bitterbrush and needle and thread, however, set new seedlings and expand. The open niche space gives bitterbrush and sagebrush opportunity to set new seedlings. Needle and thread, a prolific seeder, expands with many seedlings.
State 3
Annual Grasses
State 3 represents communities dominated by invasive annual species and has crossed a biological threshold. Virtually all the native functional, structural groups are missing. This state can occur with or without shrubs. Important species can include cheatgrass, Japanese brome, medusahead, ventenata, mustard, prickly lettuce and diffuse knapweed. Community Phases for state 3: 3.1 Shrub – Annual Grass Bitterbrush – Annual bromes 3.2 Annual Grass Annual bromes Dominate state 3 Species: Annual grasses such as cheatgrass, with or without shrubs The main species can include Japanese brome, medusahead, ventenata, mustard, prickly lettuce and diffuse knapweed. This state can occur with or without shrubs.
Community 3.1
Shrubs and Annual Brome
50% shrubs 40% annual grass
Community 3.2
Annual Brome
90% annual grass
Pathway 3.1A
Community 3.1 to 3.2
Result: shift from shrub-annual brome community to annual brome community Causes: Moderate intensity fire kills most or all sagebrush. Annual bromes and other invasive species fully occupy the site.
State 4
Seeded Grass
State 4 represents a site that has been seeded to desirable grasses such as Secar Snake River wheatgrass, Sherman big bluegrass, crested wheatgrass or intermediate wheatgrass. The communities in State 4 are stable as long as they maintain 0.8 plant per square feet or greater of the desired grasses Dominate Species for State 4: Desirable seeded grass species with or without shrubs and legumes Community Phases for State 4: 4.1 Seeded Grass 4.2 Shrub – Seeded Grass
Community 4.1
Seeded Grass
85% seeded grass
Community 4.2
Shrubs and Seeded Grass
50% shrubs 40% seeded grass
Pathway 4.1A
Community 4.1 to 4.2
Result: Shift from seeded grass to shrub-grass community. Shrubs colonize the site and increase cover and density while seeded grasses decline Causes: Excessive grazing pressure (heavy grazing intensity, season long grazing or frequent late spring grazing) on seeded grasses reduce plant vigor. Grass root crowns shrink in size and some grasses die allowing shrubs to re-enter the site. Ecological Process: With consistent defoliation pressures seeded grasses experiences poor plant vigor to such a degree that grass roots begin to die. So, the seeded grasses experience shrinking crowns and some mortality. This gives shrubs the opportunity to set new seedlings and expand its cover. Increased shade from the new sagebrush plants also plays a role in this process.
Pathway 4.2A
Community 4.2 to 4.1
Result: Shift from shrub-grass to seeded grass community. The shrub layer is decreased to all but eliminated and grasses increase to dominate the community. Causes: (1) For communities with fire sensitive shrubs (sagebrush, bitterbrush) and a good population of desirable grasses, the best course of action is to reduce the shrubs by fire, chemical or mechanical treatment, and to use proper grazing management to ensure grasses recover. (2) For communities with fire tolerant shrubs (rabbitbrush, three-tip sage) and a good population of desirable grasses, the best course of action is to reduce the shrubs by chemical treatment and use proper grazing management to ensure grasses recover. (3) Communities that do not have much seeded grass remaining will require a seedbed to be prepared and a seeding operation. Seedbed preparation can use a combination of fire, mechanical tillage and chemical application. Post-seeding the site will need 1-2 years of rest while the seeded grasses are established. Broadleaf weed control may also be necessary. Afterward, proper grazing must be used to maintain the stand.
Transition T1A
State 1 to 2
Result: shift from Reference State to State 2 with a few annual grasses. Ecological process: annual grass seeds blow onto the site awaiting an opportunity to colonize. Loss of soil biological crusts also contributes to the invasion be annual grasses. Primary trigger: soil disturbances from rodent or badger activity provide great opportunity for invasive annual species. Fire, drought and grazing pressure can create holes in the plant community. Indicators: A few annual grasses have colonized the site.
Transition T2A
State 2 to 3
Result: shift from State 2 with a few annuals to State 3 which is dominated by annual grasses. This transition occurs once the cover of bluebunch wheatgrass declines to less than 10% and invasive species cover is greater than 40%. Primary trigger: Grazing pressure (heavy grazing, season long grazing or frequent late spring grazing) causes low vigor and reduced cover of bluebunch wheatgrass. Initially both needleandthread and the annual grasses increase. As the grazing pressure continues, needleandthread will also decrease. Secondary trigger: repeated fire which is not a common occurrence in MLRA 8. Ecological process: With consistent defoliation pressures bluebunch wheatgrass and needleandthread experience poor plant vigor to such a degree that grass roots begin to die. So, bunchgrasses have shrinking crowns and some mortality. This gives invasive annual grasses opportunity to expand its cover to a position of dominance. Indicators: Significant decline in vigor and cover of one or more of the dominant reference state species – bluebunch wheatgrass, bitterbrush. Increasing cover of annual grasses. Increasing canopy gaps between bluebunch wheatgrass plants.
Restoration pathway R3A
State 3 to 4
Equipment limitations from surface rock and rock in the profile will cause issues and some treatment options may not be feasible on some sites. R3A Result: shift from State 3 dominated by annual grasses to State 4 seeded grasses. This restoration transition is not likely to occur without significant time and inputs for weed control, seedbed preparation, seeding operation and post-seeding management & weed control. Two years of weed control, 1-2 years of deferment post-seeding, and proper grazing management afterward.
Restoration pathway R4A
State 4 to 2
Result: Shift from State 3 back to State 2. This restoration transition does not occur without a significant commitment of time & resource inputs to restore ecological processes, native bunchgrasses, bitterbrush and native forb species. Attention needs to be paid to each step of the process: weed control, seedbed preparation, seeding and planting operations and post-seeding management. Shifting from State 3 to State 4: If the goal is to restore back to a native plant community, State 3 must first be shifted to State 4. It will take two years or longer to kill annual species and to exhaust the seedbank of invasive species. Site will then need to be seeded to perennial species such as crested wheatgrass to restore soil properties before native species can survive and thrive on site. The seeded species rebuild some of the basic soil properties including increased soil organic matter, increased soil moisture, and likely would also require the soil’s pore spaces, bulk density and soil microorganisms to return before the native species that used to survive in this ecological site can return. The site would also need several years of no significant fires and proper grazing management as well. See narrative for R3A transition above. Shifting from State 4 to State 2: This assumes that the shift from State 3 to State 4 has been successful. Introduced grasses must be killed before seeding native species. The seeding of native species should occur in two steps: (1) a seeding of native bunchgrasses so that broadleaf weeds may be controlled, (2) a re-introduction of sagebrush and native forbs. The site would also need several years of no significant fires and proper grazing management as well to ensure plant establishment and vigor. Shrubs and native forbs should not be planted until broadleaf weeds have been controlled.
Transition T4A
State 4 to 3
Transition from State 4 seeded grass to State 3 annual grasses. This transition occurs when the desirable seeded grasses become minor to the dominant annual grasses. Primary trigger: grazing pressure on the seeded grasses reduce the vigor and density of key bunchgrass species. Ecological process: the unraveling of the seeded grass community begins with weakened vigor and less cover of the seeded grasses. Invasive annual grasses colonize the site and become more and more common with the loss of each bunchgrass. Ecological process: consistent defoliation pressure causes weakened vigor, roots dying and less cover for the seeded grasses. Invasive annual grasses colonize the site and become more and more common with the loss of each bunchgrass plant. Indicators: shrinking crowns and mortality of desirable species, increasing caps gaps between seeded plants, increasing cover by annual grasses.
Additional community tables
Table 7. Community 1.1 plant community composition
| Group | Common name | Symbol | Scientific name | Annual production (kg/hectare) | Foliar cover (%) | |
|---|---|---|---|---|---|---|
|
Shrub/Vine
|
||||||
| 1 | Non-Sprouting Shrubs - Subdominant | 146– | ||||
| antelope bitterbrush | PUTR2 | Purshia tridentata | – | – | ||
| Wyoming big sagebrush | ARTRW8 | Artemisia tridentata ssp. wyomingensis | – | – | ||
| basin big sagebrush | ARTRT | Artemisia tridentata ssp. tridentata | – | – | ||
| 2 | Sprouting Shrubs - Minor | 56– | ||||
| rabbitbrush | CHRYS9 | Chrysothamnus | – | – | ||
| currant | RIBES | Ribes | – | – | ||
| rose | ROSA5 | Rosa | – | – | ||
| threetip sagebrush | ARTR4 | Artemisia tripartita | – | – | ||
|
Grass/Grasslike
|
||||||
| 3 | Dominant Mid-Size Bunchgrass | 1037– | ||||
| bluebunch wheatgrass | PSSP6 | Pseudoroegneria spicata | – | – | ||
| 4 | Other Mid-Size Bunchgrasses - Minor | 56– | ||||
| squirreltail | ELEL5 | Elymus elymoides | – | – | ||
| Thurber's needlegrass | ACTH7 | Achnatherum thurberianum | – | – | ||
| needle and thread | HECOC8 | Hesperostipa comata ssp. comata | – | – | ||
| 5 | Short Grass - Minor | 56– | ||||
| Sandberg bluegrass | POSE | Poa secunda | – | – | ||
| 6 | Other Graminoids - Trace to Minor | – | ||||
| threadleaf sedge | CAFI | Carex filifolia | – | – | ||
|
Forb
|
||||||
| 7 | Native Forbs - Minor | 146– | ||||
| arrowleaf balsamroot | BASA3 | Balsamorhiza sagittata | – | – | ||
| lupine | LUPIN | Lupinus | – | – | ||
| hawksbeard | CREPI | Crepis | – | – | ||
| fleabane | ERIGE2 | Erigeron | – | – | ||
| buckwheat | ERIOG | Eriogonum | – | – | ||
| Indian paintbrush | CASTI2 | Castilleja | – | – | ||
| granite prickly phlox | LIPU11 | Linanthus pungens | – | – | ||
| trumpet | COLLO | Collomia | – | – | ||
| woolly plantain | PLPA2 | Plantago patagonica | – | – | ||
| silverpuffs | MICRO6 | Microseris | – | – | ||
| mariposa lily | CALOC | Calochortus | – | – | ||
| longleaf phlox | PHLO2 | Phlox longifolia | – | – | ||
| desertparsley | LOMAT | Lomatium | – | – | ||
| milkvetch | ASTRA | Astragalus | – | – | ||
| low pussytoes | ANDI2 | Antennaria dimorpha | – | – | ||
| spiny phlox | PHHO | Phlox hoodii | – | – | ||
| western stoneseed | LIRU4 | Lithospermum ruderale | – | – | ||
| common yarrow | ACMI2 | Achillea millefolium | – | – | ||
Interpretations
Supporting information
Other references
Boling M., Frazier B., Busacca, A., General Soil Map of Washington, Washington State University, 1998 Daubenmire, R., Steppe Vegetation of Washington, EB1446, March 1968
Davies, Kirk, Medusahead Dispersal and Establishment in Sagebrush Steppe Plant Communities, Rangeland Ecology & Management, 2008 Environmental Protection Agency, map of Level III and IV Ecoregions of Washington, June 2010
Miller, Baisan, Rose and Pacioretty, “Pre and Post Settlement Fire regimes in mountain Sagebrush communities: The Northern Intermountain Region Natural Resources Conservation Service, map of Common Resource Areas of Washington, 2003 Rapid Assessment Reference Condition Model for Wyoming sagebrush, LANDFIRE project, 2008
Rocchio, Joseph & Crawford, Rex C., Ecological Systems of Washington State. A Guide to Identification. Washington State Department of Natural Resources, October 2015. Pages 156-161 Inter-Mountain Basin Big Sagebrush
Rouse, Gerald, MLRA 8 Ecological Sites as referenced from Natural Resources Conservation Service-Washington FOTG, 2004 Soil Conservation Service, Range Sites for MLRA 8 from 1980s and 1990s
Tart, D., Kelley, P., and Schlafly, P., Rangeland Vegetation of the Yakima Indian reservation, August 1987, YIN Soil and Vegetation Survey
Contributors
Kevin Guinn
K. Moseley
G. Fults
R. Fleenor
W. Keller
C. Smith
K. Bomberger
C. Gaines
K. Paup-Lefferts
Approval
Kirt Walstad, 5/23/2025
Acknowledgments
Provisional Site Author: Kevin Guinn
Technical Team: K. Moseley, G. Fults, R. Fleenor, W. Keller, C. Smith, K. Bomberger, C. Gaines, K. Paup-Lefferts
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 | 05/07/2025 |
| Approved by | Kirt Walstad |
| 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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