Natural Resources
Conservation Service
Ecological site R009XY007OR
Cold Swale
17-24 PZ
Last updated: 5/05/2025
Accessed: 04/22/2026
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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.
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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.
Associated sites
R009XY008OR Cold Wet Swale 17-24 PZ
Wet Mountain Swale 17-24 PZ
Table 1. Dominant plant species
Tree Not specified
Shrub Not specified
Herbaceous Not specified
Physiographic features
This site occurs as narrow open drainage areas in forestslands on mountian plateaus. It occurs along the shallow edges and upper ends of coalescing swales. Slopes range form 2-15%. Elevation varies from 3400 to 4500 feet.
Table 2. Representative physiographic features
Landforms (1) Mountain
(2) Swale
Elevation 1036 – 1372 m Slope 2 – 15 % Aspect Aspect is not a significant factor Climatic features
The annual precipitation ranges from 17 to 24 inches. It occurs primarily as snow during the monthes of November through March. Spring rainfall is ample followed by occansional summer convection storms. Ephemeral subsurface moisture flow augments the precipitation. The mean annual air temperature is approximately 43 degrees F. Extreme temperatures range from 90 degrees F to -30 degrees F. Soil temperature regimes are frigid. The frost-free period ranges from 30 to 100 days. The period of optimum plant growth is from late April through July.
Table 3 Representative climatic features
Frost-free period (average) 100 days Freeze-free period (average) Precipitation total (average) 610 mm ">Influencing water features
Soil features
The soils of this site are formed in alluvium and loess over basalt. They are shallow and stony. Typical the surface layer is a stony silt loam over a silty clay loam to clayey subsoil. Surface intake rates are moderate. Subsoil permeability rates are low with a seasonal water table. Classification is somewhat poorly drained. The available water holding capacity (AWC) is 2 to 4 inches. The potential for erosion is moderate.
Table 4. Representative soil features
Surface texture (1) Stony silt loam
(2) Silty clay loam
Family particle size (1) Clayey
Drainage class Poorly drained Permeability class Slow Ecological dynamics
Range in Characteristics:
As a shallow site, variabilty in plant compostion and yeild is dependent primarily on the extent and duration of both surface and lateral subsurface water flows. California oatgrass, rushes and sedge increase on soils that recieve longer duration surface and subsurface flows. Bluegrasses, fescues and needlegrassincrease on soils that recieve limited surface and subsurface flows. Production follows a similar pattern, increasing or decreasing with flow duration.
Response to Disturbance:
If the condition of the site deteriorates as a result of overgrazing, California oatgrass and palatable rushes and sedges decrease. Unpalatable rushes, annual hairgrass and forbs increase. Kentucky bluegrass, other bluegrass and annuals invade. With further deterioration annual hairgrass continues to increase, Japanese brome and other annuals strongly invade and usable forage production decreases. Bare ground increases and intermittent streambeds and banks become unstable from loss of vegetation. Peak discharge increases and seasonal watertables are lowered reducing water for late season use. Erosion from concentated flows increase, sediment yields increase and the inherent productivity of the site decreases.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
Historic Climax Plant CommunityCommunity 1.1
Historic Climax Plant CommunityThe potential native plant community is dominated by California oatgrass. Timber oatgrass, and a variety of rushes, sedges, bunchgrasses, bluegrasses and forbs are present. The potential vegetative composition is approximately 95 percent grasses and 5 percent forbs.
Figure 2. Annual production by plant type (representative values) or group (midpoint values)
Table 5. Annual production by plant type
Plant type Low
(kg/hectare)Representative value
(kg/hectare)High
(kg/hectare)Grass/Grasslike 982 1365 1749 Forb 27 81 135 Total 1009 1446 1884 Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike2 Perennial Deep-rooted Subdominant 457–726 smallwing sedge CAMI7 Carex microptera 67–108 – sedge CAREX Carex 67–108 – toad rush JUBU Juncus bufonius 40–67 – Colorado rush JUCO2 Juncus confusus 40–67 – common rush JUEF Juncus effusus 40–67 – swordleaf rush JUEN Juncus ensifolius 40–67 – Bolander's spikerush ELBO Eleocharis bolanderi 40–54 – fewflower spikerush ELQU2 Eleocharis quinqueflora 40–54 – 3 Perennial Shallow-rooted Dominant 336–538 California oatgrass DACA3 Danthonia californica 336–538 – 4 Perennial Shallow-rooted subdominant 40–108 Sandberg bluegrass POSE Poa secunda 67–135 – timber oatgrass DAIN Danthonia intermedia 40–108 – 5 PPGG 81–242 Letterman's needlegrass ACLE9 Achnatherum lettermanii 7–19 – western needlegrass ACOC3 Achnatherum occidentale 7–19 – bentgrass AGROS2 Agrostis 7–19 – pinegrass CARU Calamagrostis rubescens 7–19 – onespike danthonia DAUN Danthonia unispicata 7–19 – bearded wheatgrass ELCA11 Elymus caninus 7–19 – blue wildrye ELGL Elymus glaucus 7–19 – red fescue FERU2 Festuca rubra 7–19 – prairie Junegrass KOMA Koeleria macrantha 7–19 – pullup muhly MUFI2 Muhlenbergia filiformis 7–19 – tall trisetum TRCA21 Trisetum canescens 7–19 – western fescue FEOC Festuca occidentalis 7–19 – Forb9 PPFF 27–135 common yarrow ACMI2 Achillea millefolium 2–11 – agoseris AGOSE Agoseris 2–11 – twin arnica ARSO2 Arnica sororia 2–11 – camas CAMAS Camassia 2–11 – larkspur DELPH Delphinium 2–11 – aster EUCEP2 Eucephalus 2–11 – desertparsley LOMAT Lomatium 2–11 – lupine LUPIN Lupinus 2–11 – beardtongue PENST Penstemon 2–11 – yampah PERID Perideridia 2–11 – cinquefoil POTEN Potentilla 2–11 – ragwort SENEC Senecio 2–11 – Interpretations
Animal community
Livestock Grazing:
Thsi site is well suited to late summer and fall use by livestock under a planned grazing system. The key species are California oatgrass and rush flowering and seed information when root reserves are low. Palatable rushes, sedge and bunchgrasses provide excellent standing forage during late summer and fall dormancy. Grazing system design and implementation should consider the improvement and maintenenace of streambed and bank cover during all seasons. Use in late spring and early summer should be postponed until soils and streambanks are firm enough to withstand trampling damage. In the fall it is particularly important toleave enough residue in the swale and on the banks for protection during early spring runoff events.
Wildlife:
When the ecological condition is high this site provides excellent forage for elk, deer and various other mammals. IT si and important summer and fall use area for elk and mule deer.
Native Wildlife Associated with the Potential Climax Community:
Elk, mule deer, whitetail deer, rodents and various upland birds use this site for food and limited cover.Hydrological functions
The soils of this site have slow intake and permeability rates. Water holding capacities are good and depending on soil depth, provide limited late season water for plant growth and water release to streams. The hydrologic cover conditon is good when the ecological conditon is high. Under high ecological conditons the primary channel is shallow and not well defined. Adequate vegetative cover protects the swale from incision during runoff events. Flows are broad and shallow across vegetative cover which flattens, catches sediment and protects the soil surface from erosion.
Other information
In fair conditon this site responds rapidly to good management. Periodic deferment allows seed production and rapid improvement of California oatgrass and rushes. If incised channels are present, periodic rest and/or deferment will restore good hydrologic charateristics.
Supporting information
Contributors
AV Bahn
Cici Brooks
Justin GredvigApproval
Kirt Walstad, 5/05/2025
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 Oregon NRCS State Rangeland Management Specialist Date 07/30/2012 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
None to some, moferate sheet & rill erosion hazard -
Presence of water flow patterns:
Frequent flooding with seasonal high water table -
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):
10-15% -
Number of gullies and erosion associated with gullies:
Poor resistance to erosion when cover is lacking - subject to incision and downcutting -
Extent of wind scoured, blowouts and/or depositional areas:
none, slight wind erosion hazard -
Amount of litter movement (describe size and distance expected to travel):
Fine - limited movement -
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Moderately resistant to erosion with adequate cover; aggregate stability = 2-4 -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Shallow, somewhat poorly drained alluvium with a stony silt loam surface; low OM (1-2%) -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Significant ground cover (90-100%) and gentle slopes (0-15%) effectively 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:
California oatgrass > rushes > other perennial grasses > sedges > Sandberg bluegrass > forbs > Timber oatgrass = spikegrassSub-dominant:
Other:
Additional:
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Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Normal decadence and mortality expected -
Average percent litter cover (%) and depth ( in):
-
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
Favorable: 1500, Normal: 1200, Unfavorable: 800 lbs/acre/year at high RSI (HCPC) -
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:
With deterioration of plant community, bluegrasses 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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