Natural Resources
Conservation Service
Ecological site R025XY022OR
SHRUBBY SOUTH SLOPES
11-13 PZ
Last updated: 4/25/2024
Accessed: 06/30/2026
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Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.
MLRA notes
Major Land Resource Area (MLRA): 025X–Owyhee High Plateau
MLRA 25 lies within the Intermontane Plateaus physiographic province. The southern half is in the Great Basin Section of the Basin and Range Province. This part of the MLRA is characterized by isolated, uplifted fault-block mountain ranges separated by narrow, aggraded desert plains. This geologically older terrain has been dissected by numerous streams draining to the Humboldt River. The northern half of the area lies within the Columbia Plateaus geologic province. This part of the MLRA forms the southern boundary of the extensive Columbia Plateau basalt flows. Deep, narrow canyons drain to the Snake River which incise the broad volcanic plain. The Humboldt River, route of a major western pioneer trail, crosses the southern half of this area. Reaches of the Owyhee River in this area have been designated as National Wild and Scenic Rivers.
Similar sites
R025XY020OR SOUTH SLOPES 11-13 PZ
Table 1. Dominant plant species
Tree Not specified
Shrub (1) Purshia tridentata
(2) Artemisia tridentata subsp. tridentataHerbaceous (1) Pseudoroegneria spicata subsp. spicata
Physiographic features
This site occurs on south-facing slopes of tablelands and canyon sideslopes. Slopes range from 15 to 70%. Elevation varies from 4,300 to 4,800 feet.
Table 2. Representative physiographic features
Landforms (1) Valley side
(2) Plateau
(3) Canyon
Elevation 4300 – 4800 ft Slope 15 – 70 % Aspect S, SW Climatic features
The annual precipitation ranges from 11 to 13 inches, most of which occurs in the form of snow during the months of December through March. Localized convection storms occasionally occur during the summer. The soil temperature regime is mesic bordering on frigid with a mean annual air temperature of 45 degrees F. Temperature extremes range from 100 to -30 degrees F. The frost free period ranges from less than 60 to 90 days. The optimum growth period for native plants is from April through July.
Table 3 Representative climatic features
Frost-free period (average) 90 days Freeze-free period (average) Precipitation total (average) 10 in ">Influencing water features
Soil features
The soils of this site are typically moderately deep to very deep and well drained. Typically, the surface layer is an extremely stony ashy fine sandy loam about 2 to 3 inches thick. The subsoil varies from a very gravelly ashy fine sandy loam to a very gravelly ashy loam that is 16 to 22 inches thick. A moderate to heaavy argillic is typically found below 20 inches. Depth to bedrock or an indurated pan varies from moderately deep to very deep. The permeability is slow to moderate. The available water holding capacity is about 4 to 6 inches for the profile. The erosion potential is moderate to severe.
Table 4. Representative soil features
Surface texture (1) Ashy fine sandy loam
(2) Extremely stony
Family particle size (1) Loamy
Drainage class Well drained Permeability class Slow to moderate Soil depth 20 – 60 in Available water capacity
(0-40in)4 – 6 in Ecological dynamics
The potential native plant community is dominated by antelope bitterbrush, basin big sagebrush and bluebunch wheatgrass. Basin wildrye, Cusick's bluegrass and Sandberg bluegrass are present. Vegetative composition of the community is approximately 70 percent grasses, 5 percent forbs and 25 percent shrubs.
Antelope bitterbrush increases on areas of deeper colluvium and fractured substratums. Production will increase at the upper end of the precipitation zone and on deeper foot slope soils. As a fire susceptible site, the amount of antelope bitterbrush and basin big sagebrush is influeneced by fire frequency.
If the condition of the site deteriorates as a result of overgrazing, antelope bitterbrush and bluebunch wheatgrass will decrease while basin big sagebrush increases and annuals invade. Cheatgrass is a strong invader. With further deterioration, bare ground increases and excessive erosion in the bare soil interspaces reduces the stie productivity and contributes to downstream sedimentation.State and transition model
More interactive model formats are also available. View Interactive Models
Click on state and transition labels to scroll to the respective textEcosystem states
State 1 submodel, plant communities
State 1
Historic Climax Plant CommunityCommunity 1.1
Historic Climax Plant CommunityThe potential native plant community is dominated by antelope bitterbrush, basin big sagebrush and bluebunch wheatgrass. Basin wildrye, Cusick's bluegrass and Sandberg bluegrass are present. Vegetative composition of the community is approximately 70 percent grasses, 5 percent forbs and 25 percent shrubs.
Figure 1. 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 700 840 980 Shrub/Vine 250 300 350 Forb 50 60 70 Total 1000 1200 1400 Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 Dominant deep rooted perennial grasses 480–720 bluebunch wheatgrass PSSPS Pseudoroegneria spicata ssp. spicata 480–720 – 2 Subdominant deep rooted perennial grasses 24–60 basin wildrye LECI4 Leymus cinereus 24–60 – 3 Sub-dominant shallow rooted perennial grasses 24–60 Sandberg bluegrass POSE Poa secunda 24–60 – 4 Other perennial grasses 48–96 Thurber's needlegrass ACTH7 Achnatherum thurberianum 12–24 – squirreltail ELEL5 Elymus elymoides 12–24 – Idaho fescue FEID Festuca idahoensis 12–24 – Cusick's bluegrass POCU3 Poa cusickii 12–24 – Forb5 Dominant, perennial forbs 48–96 milkvetch ASTRA Astragalus 12–24 – arrowleaf balsamroot BASA3 Balsamorhiza sagittata 12–24 – tapertip hawksbeard CRAC2 Crepis acuminata 12–24 – lupine LUPIN Lupinus 12–24 – 6 Other perennial forbs 9–57 common yarrow ACMI2 Achillea millefolium 1–7 – desertparsley LOMAT Lomatium 1–7 – phacelia PHACE Phacelia 1–7 – phlox PHLOX Phlox 1–7 – deathcamas ZIGAD Zigadenus 1–7 – fleabane ERIGE2 Erigeron 1–7 – buckwheat ERIOG Eriogonum 1–7 – stoneseed LITHO3 Lithospermum 1–5 – agoseris AGOSE Agoseris 1–5 – onion ALLIU Allium 1–5 – Shrub/Vine7 Dominant, perennial shrubs 180–240 antelope bitterbrush PUTR2 Purshia tridentata 180–240 – 8 Sub-dominant, perennial shrubs 60–120 basin big sagebrush ARTRT Artemisia tridentata ssp. tridentata 60–120 – 9 All other perennial shrubs 14–68 Wyoming big sagebrush ARTRW8 Artemisia tridentata ssp. wyomingensis 7–14 – yellow rabbitbrush CHVI8 Chrysothamnus viscidiflorus 7–14 – rubber rabbitbrush ERNA10 Ericameria nauseosa 7–14 – wax currant RICE Ribes cereum 7–14 – Interpretations
Animal community
This site offers food and cover for antelope, mule deer, rodents and a variety of birds. It is an important wintering area for mule deer.
Hydrological functions
The soils are in hydrologic group C. The soils of this site have moderately high runoff potential.
Other products
This site is suited to use by cattle, sheep and horses in late spring, summer and fall under a planned grazing system. Use should be postponed until the soils are firm enough to prevent trampling damage and soil compaction.
Supporting information
Contributors
C.D. Tackman, R.B. Williams & A.V. Bahn
Approval
Kendra Moseley, 4/25/2024
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 06/30/2026 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
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Presence of water flow patterns:
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Number and height of erosional pedestals or terracettes:
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Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
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Number of gullies and erosion associated with gullies:
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Extent of wind scoured, blowouts and/or depositional areas:
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Amount of litter movement (describe size and distance expected to travel):
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Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
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Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
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Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
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Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
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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:
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Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
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Average percent litter cover (%) and depth ( in):
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Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
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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:
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Perennial plant reproductive capability:
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