Natural Resources
Conservation Service
Ecological site R010XY125OR
Gravelly Fan
12-16 PZ
Last updated: 4/10/2025
Accessed: 07/14/2026
-
Search
Major Land Resource Area or ecological site by name and/or ID.
PreviousSectionsNextGeneral 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.
Table 1. Dominant plant species
Tree Not specified
Shrub (1) Artemisia tridentata ssp. tridentata
Herbaceous (1) Leymus cinereus
(2) Pseudoroegneria spicata ssp. spicataPhysiographic features
This site occurs on fans near and at the outlets of ephemeral streams. Braiding is common. It often occurs along major rivers and streams as a series of coalescing fans. Slopes range from 2 to 15 percent. Elevation varies from 2100 to 4500 feet.
Table 2. Representative physiographic features
Landforms (1) Fan
(2) Braided stream
Elevation 2100 – 4500 ft Slope 2 – 15 % 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. A seasonal supply of deep subsurface moisture augments the precipitation. Localized convectional storms occasionally occur during the summer. The soil temperature regime is typically near frigid with a mean annual air temperature of 50 degrees F. Temperature extremes range from 100 to -20 degrees F. The frost-free period ranges from 60 to 130 days. The optimum growth period for native plants is from April through June.
Table 3 Representative climatic features
Frost-free period (average) 130 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, skeletal and well-drained. Typically the surface layer is a gravelly or shaly loam about 30 inches thick. The subsoil is a gravelly or shaly loam over 20 inches thick. The substratum is alluvium. Permeability is moderate. The available water holding capacity (AWC) is about 8 to 10 inches for the profile. Deep seasonal subsurface flows augment the availabe water. The potential for erosion is moderate.
Table 4. Representative soil features
Surface texture (1) Gravelly fine sandy loam
Family particle size (1) Loamy
Drainage class Well drained Permeability class Moderate Soil depth 50 in Available water capacity
(0-40in)8 – 10 in Ecological dynamics
Range in Characteristics:
Basin wildrye is dominant with production dependent on the extent and duration of lateral subsurface water flows. Bluebunch wheatgrass increases on drier areas with limited subsurface flows. Production follows a similar pattern, increasing on fans that receive late subsurface flows from large drainage areas. Idaho fescue increases on northerly aspects. As a fire susceptible site, the amount of basin big sagebrush and juniper, 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. Bluebunch wheatgrass and bluegrasses increase. With further deterioration, basin big sagebrush continues to increase and annuals and juniper invade. Basin big sagebrush effectively replaces basin wildrye in the use of deep moisture. Streambanks become unstable from loss of vegetation and channels degrade, becoming wider in the process. Bareground increases, filtering capacity is lost, and downstream sedimentation increases.State and transition model
Custom diagramStandard diagram
More interactive model formats are also available. View Interactive Models
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 bluebunch wheatgrass. Basin big sagebrush, Idaho fescue, and Thurber needlegrass are common in the stand. Rabbitbrush, bluegrasses, and a variety of forbs are present. Vegetative composition of the community is approximately 90 percent grasses, 2 percent forbs, and 8 percent shrubs. Approximate ground cover is 80-90 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 2370 3060 3750 Shrub/Vine 60 135 210 Forb 90 150 210 Tree 30 45 60 Total 2550 3390 4230 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, dominant 1800–2400 basin wildrye LECI4 Leymus cinereus 1800–2400 – 2 Perennial, deep-rooted, sub-dominant 510–1200 bluebunch wheatgrass PSSP6 Pseudoroegneria spicata 300–600 – Idaho fescue FEID Festuca idahoensis 150–450 – Thurber's needlegrass ACTH7 Achnatherum thurberianum 60–150 – 5 Other perennial grasses, all 60–150 squirreltail ELEL5 Elymus elymoides 0–50 – prairie Junegrass KOMA Koeleria macrantha 0–50 – Sandberg bluegrass POSE Poa secunda 0–50 – Forb7 Perennial, all, dominant 60–120 milkvetch ASTRA Astragalus 30–60 – lupine LUPIN Lupinus 30–60 – 9 Other perennital forbs, all 30–90 common yarrow ACMI2 Achillea millefolium 0–10 – white sagebrush ARLU Artemisia ludoviciana 0–10 – arrowleaf balsamroot BASA3 Balsamorhiza sagittata 0–10 – tapertip hawksbeard CRAC2 Crepis acuminata 0–10 – fleabane ERIGE2 Erigeron 0–10 – buckwheat ERIOG Eriogonum 0–10 – stoneseed LITHO3 Lithospermum 0–10 – desertparsley LOMAT Lomatium 0–10 – phlox PHLOX Phlox 0–10 – Shrub/Vine11 Perennial, evergreen, dominant 30–150 basin big sagebrush ARTRT Artemisia tridentata ssp. tridentata 30–150 – 12 Perennial, evergreen, sub-dominant 30–60 rabbitbrush CHRYS9 Chrysothamnus 30–60 – Tree16 Perennial, evergreen, dominant 30–60 western juniper JUOC Juniperus occidentalis 30–60 – Interpretations
Animal community
Livestock Grazing:
This site is suited to use by cattle, sheep, and horses in all seasons under a planned grazing system. Limitations in the spring are 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. As a sediment deposition area, improvement and/or maintenance of herbaceous cover should be considered during all seasons, particularly in the fall and winter for spring runoff protection and sediment deposition.
Native Wildlife Associated with the Potential Climax Community:
Deer
Antelope
Elk
Hawks
Songbirds
Rodents
This site will offer food and cover for mule deer, antelope, elk, rodents, and a variety of birds. It is an important wintering area for mule deer and elk.
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.
Wood products
This site is susceptible to increase in western juniper. Where this has occurred, the site will yield fence posts, firewood, and specialty products.
Other information
The soils in this site have good water holding capacities providing late season water for plant growth and slow water release to streams. Increase in western juniper and the subsequent competition for moisture will lead to a reduction of availabe forage. Overgrazing can easily reduce ground cover and accelerate soil loss. Improving infiltration and permeability, and reducing runoff should be the immediate goal of juniper control. When incised channels are present, rehabilitation will markedly improve production, reduce downstream sedimentation and restore good hydrologic characteristics. On altered sites, the reintroduction of basin wildrye may be needed to fully restore the site potential.
Supporting information
Contributors
Cici Brooks
J. Thompson, A. Bahn
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) Contact for lead author Date 07/14/2026 Approved by 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:
Print Options
Sections
Font
AAAAOther
PrintThe Ecosystem Dynamics Interpretive Tool is an information system framework developed by the USDA-ARS Jornada Experimental Range, USDA Natural Resources Conservation Service, and New Mexico State University.
Accessibility statement
