Natural Resources
Conservation Service
Ecological site R010XY117OR
Mountain Swale
12-16 PZ
Last updated: 4/10/2025
Accessed: 06/29/2026
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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.
Associated sites
R010XC025OR SR Sandy 9-12 PZ
12-16" Mountain Upland Group - Gravelly Fan 12-16" PZ, Loamy Bottom
Similar sites
R010XC025OR SR Sandy 9-12 PZ
Gravelly Fan 12-16" PZ (coarser soil, deeper subsurface flows)/Loamy Bottom (perennial to near perennial subsurface flows)
Table 1. Dominant plant species
Tree Not specified
Shrub (1) Artemisia tridentata ssp. vaseyana
Herbaceous (1) Leymus cinereus
(2) Festuca idahoensisPhysiographic features
This site occurs adjacent to and on the floodplains of ephemeral drainages. It is at the upper end of drainages occuping broad to narrow swale areas. Slopes range from 2 to 12 percent. Elevations range from 3000 to 5700 feet.
Table 2. Representative physiographic features
Landforms (1) Flood plain
(2) Drainageway
(3) Swale
Elevation 3000 – 5700 ft Slope 2 – 12 % Water table depth 60 in Aspect Aspect is not a significant factor Climatic features
The annual precipitation ranges from 12 to 16 inches, most of which occurs in the form of snow during the months of November through March. Ephemeral subsurface moisture flow augments the precipitation. Localized convection storms occasionally occur during the summer. The soil temperature regime is frigid with a mean annual air temperature of 45 degrees F. Temperature extremes range from 90 to -30 degrees F. The frost-free period ranges from 30 to 90 days. The optimum period for plant growth is from April through June.
Table 3 Representative climatic features
Frost-free period (average) 90 days Freeze-free period (average) Precipitation total (average) 20 in ">Influencing water features
Soil features
The soils of this site are recent, deep to very deep and well-drained. Typically the surface layer is a silt loam about 10 inches thick. The subsoil is a silty clay loam over 40 inches thick. The substratum varies from alluvium to bedrock. Gravel content in the pedon ranges from 0 to 30 percent. Permeability is moderate. The available water holding capacity (AWC) is about 8 to 10 inches for the profile. Seasonal subsurface flows from adjacent slopes augment the available water. The potential for erosion is moderate.
Table 4. Representative soil features
Surface texture (1) Silt loam
Family particle size (1) Clayey
Drainage class Well drained Permeability class Moderate Soil depth 50 in Surface fragment cover <=3" 0 – 30 % Available water capacity
(0-40in)8 – 10 in Ecological dynamics
Range in Characteristics:
The amount of basin wildrye is dependent on the extent and duration of lateral subsurface water flows. Basin wildrye increases and Idaho fescue decreases on swales receiving subsurface flows late into the growing season. This would be on swales with large drainage areas. Conversely, Idaho fescue would increase on swales with limited drainage areas. This would typically be at the upper ends of watersheds where drainage area is limited. Production follows a similar pattern increasing on swales with large drainage areas. As a site susceptible to fire, the amount of basin big sagebrush is influenced by fire frequency.
Response to Disturbance:
If the condition of the site deteriorates as a result of overgrazing, basin wildrye and Idaho fescue decrease. Bluegrasses invade and basin big sagebrush increase. With further deterioration, annuals invade and useable forage production decreases. Streambanks become unstable from loss of vegetation and channels degrade, becoming deeper and wider in the process. Subsurface flows are affected. Peak discharges increase, the water table drops and storage of water for late season use is reduced. Erosion from concentrated flows reduces the site productivity and contributes to downstream sedimentation.State and transition model
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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
ReferenceCommunity 1.1
Reference Plant CommunityThe potential native plant community is dominated by basin wildrye and Idaho fescue. Mountain and basin big sagebrush, wax currant, bluebunch wheatgrass, and Thurber needlegrass are common. Sedges, bluegrasses, western wheatgrass, and a variety of forbs are present. Vegetative composition of the community is approximately 85 percent grasses, 5 percent forbs, and 10 percent shrubs. Approximate ground cover is 70-80 percent (basal and crown).
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 1750 2388 3025 Shrub/Vine 175 363 550 Forb 75 138 200 Total 2000 2889 3775 Figure 2. Plant community growth curve (percent production by month). OR4451 , B10 SR Fan and Swale, 9-16 pz . SR Fan and Swale, 9-16 pz RPC Growth Curve.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec J F M A M J J A S O N D 0 0 5 10 25 25 20 5 5 5 0 0 Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 Perennial, deep-rooted, domiant 1500–2250 basin wildrye LECI4 Leymus cinereus 1000–1500 – basin wildrye LECI4 Leymus cinereus 1000–1500 – Idaho fescue FEID Festuca idahoensis 500–750 – Idaho fescue FEID Festuca idahoensis 500–750 – 2 Perennial, deep-rooted, sub-domiant 150–400 Thurber's needlegrass ACTH7 Achnatherum thurberianum 50–125 – bluebunch wheatgrass PSSP6 Pseudoroegneria spicata 50–125 – sedge CAREX Carex 25–75 – western wheatgrass PASM Pascopyrum smithii 25–75 – 4 Perennial, shallow-rooted, sub-dominant 25–75 bluegrass POA Poa 25–75 – 5 Other perennial grasses, all 75–300 western needlegrass ACOC3 Achnatherum occidentale 0–60 – squirreltail ELEL5 Elymus elymoides 0–60 – needle and thread HECO26 Hesperostipa comata 0–60 – prairie Junegrass KOMA Koeleria macrantha 0–60 – Sandberg bluegrass POSE Poa secunda 0–60 – Forb7 Perennial, all, dominant 50–100 buckwheat ERIOG Eriogonum 25–50 – lupine LUPIN Lupinus 25–50 – 9 Other perennial forbs, all 25–100 common yarrow ACMI2 Achillea millefolium 0–8 – white sagebrush ARLU Artemisia ludoviciana 0–8 – milkvetch ASTRA Astragalus 0–8 – tapertip hawksbeard CRAC2 Crepis acuminata 0–8 – fleabane ERIGE2 Erigeron 0–8 – stoneseed LITHO3 Lithospermum 0–8 – desertparsley LOMAT Lomatium 0–8 – bluebells MERTE Mertensia 0–8 – phlox PHLOX Phlox 0–8 – cinquefoil POTEN Potentilla 0–8 – buttercup RANUN Ranunculus 0–8 – deathcamas ZIGAD Zigadenus 0–8 – Shrub/Vine11 Perennial, evergreen, dominant 75–200 mountain big sagebrush ARTRV Artemisia tridentata ssp. vaseyana 75–200 – 12 Perennial, evergreen, sub-dominant 25–75 basin big sagebrush ARTRT Artemisia tridentata ssp. tridentata 25–75 – 14 Perennial, deciduous, dominant 25–75 wax currant RICE Ribes cereum 25–75 – 15 Other perennial shrubs, all 50–200 yellow rabbitbrush CHVI8 Chrysothamnus viscidiflorus 0–50 – golden currant RIAU Ribes aureum 0–50 – common snowberry SYAL Symphoricarpos albus 0–50 – Saskatoon serviceberry AMAL2 Amelanchier alnifolia 0–50 – Interpretations
Animal community
Livstock Grazing:
This site is suited to use by cattle, sheep, and horses in late spring, summer, and fall under a planned grazing system. Limitations in the spring are saturated wet soils and unstable banks. Use should be postponed until the soils are firm enough to prevent trampling damage and soil compaction, yet while soil moisture is adequate to allow the completion of the plant growth cycle. Improvement and/or maintenance of herbaceous bank protection should be considered during all seasons, particularly going into the winter for spring high flow periods.
Native Wildlife Associated with the Potential Climax Community:
Deer
Antelope
Elk
Hawks
Songbirds
Rodents
This site will offer food and cover for mule deer, elk, antelope, rodents, and a variety of birds. It is an important wintering area for mule deer, elk, and antelope.Hydrological functions
The soils are in hydrologic group B. The soils of this site have moderately low runoff potential. This site is potentially subject to three high flow periods: low elevation snowmelt, high elevation snowmelt, and summer cloudburst flow.
Other information
The soils of this site have excellent water holding capacities providing late season water for plant growth and slow water release to streams. When incised channels are present, rehabilitation will markedly improve production and restore good hydrologic characteristics. On altered sites the reintroduction of desirable deep rooted plants may be needed to fully restore the site potential.
Supporting information
Contributors
BLM/SCS Team - Burns
Cici Brooks
M. Parks (OSU)Approval
Kirt Walstad, 4/10/2025
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) Jeff Repp Contact for lead author State Rangeland Management Specialist for NRCS Oregon Date 11/21/2016 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
None, moderate sheet & rill erosion hazard. -
Presence of water flow patterns:
None, except following extremely high intensity storms when short (less than 1 meter) flow patterns may appear on steeper slopes. Minimal evidence of past or current soil deposition or erosion. -
Number and height of erosional pedestals or terracettes:
None. -
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
0 - 5% bare ground. -
Number of gullies and erosion associated with gullies:
None. -
Extent of wind scoured, blowouts and/or depositional areas:
None. Wind erosion hazard is moderate. -
Amount of litter movement (describe size and distance expected to travel):
Litter size is Small/Fine. Litter movement is limited, minimal, and short, associated with water flow patterns following extremely high intensity storms. Litter also may be moved during intense wind storms. -
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Site is Moderately resistant to erosion. Stability class (Herrick et al. 2001) anticipated to be 3-6 at surface under perennial vegetation. Stability class at surface in the interspaces is anticipated to be less than or equal to that under perennial vegetation. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Surface layer structure is moderate very fine granular to moderate thin platy. The A horizon has a dry color of 4 - 5 and is 3 - 15 inches thick. The Soil Organic Matter (SOM) content is low (0.2 to 2.0%). -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Plant foliar cover and basal cover with small gaps between plants should reduce raindrop impact and slow overland flow, providing increased time for infiltration to occur. High herbaceous vegetation on this site will retain more water from precipitation. High ground cover (70-80%) and gentle slopes (2-12%) limit rainfall impact and overland flow. -
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
None. -
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:
Deep rooted bunchgrassesSub-dominant:
Other perennial grasses > evergreen shrubsOther:
Perennial forbs = other shrubsAdditional:
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Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Grasses will nearly always show some mortality and decadence. Normal decadence and mortality expected on other plants. -
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):
Low 2000 lbs/acre, Representative Value 2500 lbs/acre, High 3000 lbs/acre -
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:
Western Juniper readily invades the site. Cheatgrass and Medusahead invade sites that have lost deep rooted perennial grass functional groups. -
Perennial plant reproductive capability:
All species should be capable of reproducing annually.
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