Natural Resources
Conservation Service
Ecological site R010XB057OR
JD Mahogany Rockland
9-12 PZ
Last updated: 4/10/2025
Accessed: 07/13/2026
-
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.
Associated sites
R010XB051OR JD Shallow South 9-12 PZ
South aspect, shallow soils
Similar sites
R010XB051OR JD Shallow South 9-12 PZ
Table 1. Dominant plant species
Tree Not specified
Shrub (1) Cercocarpus ledifolius
(2) Purshia tridentataHerbaceous (1) Pseudoroegneria spicata ssp. spicata
(2) Poa secundaPhysiographic features
This site is on steep south facing slopes. Slopes range from 15 to 80 percent but are typically from 15 to 70 percent. Elevations range from 1300 to 3000 feet.
Table 2. Representative physiographic features
Landforms (1) Canyon
(2) Ridge
Flooding frequency None to very frequent Ponding frequency None Elevation 1300 – 3000 ft Slope 15 – 80 % Ponding depth 0 in Water table depth 60 in Aspect SE, S, SW Climatic features
The annual precipitation ranges from 9-12 inches, most of which occurs in the form of rain during the months of November through May. Localized, occasionally severe, convectional storms occur during the summer. The mean annual air temperature is 54 degrees F. Temperature extremes range from 105 to +10 degrees F. The frost-free period ranges from 116 to 135 days. The optimum period for plant growth is from April through June3
Table 3 Representative climatic features
Frost-free period (average) 130 days Freeze-free period (average) 160 days Precipitation total (average) 10 in BarLineFigure 1. Monthly precipitation range
BarLineFigure 2. Monthly average minimum and maximum temperature
">Influencing water features
Soil features
The soils of this site are typically very shallow over fractured basalt bedrock. They are well-drained with areas of rock outcrop. These soils occur on unstable positions and have little structural development. Texture is a gravelly or cobbly loam. Depth to bedrock or an indurated pan is usually less than 10 inches. Permeability is moderate. The available water holding capacity is about 2 inches for the profile. The potential for erosion is severe.
Table 4. Representative soil features
Surface texture (1) Very cobbly loamy coarse sand
Drainage class Somewhat excessively drained Permeability class Rapid Soil depth 1 – 10 in Surface fragment cover <=3" 0 – 30 % Surface fragment cover >3" 0 – 20 % Available water capacity
(0-40in)2 in Calcium carbonate equivalent
(0-40in)Not specified Electrical conductivity
(0-40in)Not specified Sodium adsorption ratio
(0-40in)Not specified Soil reaction (1:1 water)
(0-40in)7.9 – 8.4 Subsurface fragment volume <=3"
(Depth not specified)0 – 30 % Subsurface fragment volume >3"
(Depth not specified)0 – 20 % Ecological dynamics
Range in Characteristics:
Bluebunch wheatgrass increases with an increase in soil depth. Mountain Mahogany, bitterbrush, and other shrubs respond to available moisture in rock fissures and cracks. The proportion and amount of these shrubs are proportional to the extent and depth of fracturing in the bedrock. Fires on this site are very infrequent, being estimated to occur at intervals of 250 to 500 years.
Response to Disturbance:
If the conditions of the site deteriorates as a result of overgrazing, bluebunch wheatgrass decreases while Sandberg bluegrass increases. Bluebunch wheatgrass is the preferred species during the spring. With further deterioration, mountain mahogany and other shrubs become well hedged. Under deteriorated conditions excessive erosion in the bare soil interspaces markedly reduces the site productivity.
Treatment Response: none.
Reference Plant Community
State 1 – Reference State
There are three phases in the reference state. Phase 1.1 is the mountain mahogany steppe phase dominated by mountain mahogany and bluebunch wheatgrass with antelope bitterbrush being common. The mountain mahogany perennial grass and forb phase, 1.2, results from the occurrence of fire. Phase 1.3 has an increase of juniper as a result of no fire and improper grazing.
Phase 1.1 the mountain mahogany phase, the reference plant community phase (RPCP), is dominated by mountain mahogany in the overstory, antelope bitterbrush in the shrub layer and bluebunch wheatgrass in the herbaceous layer. Sandberg bluegrass and Thurber’s needlegrass are common with a minor amount of forbs. Vegetative composition of the community is approximately 30 percent grasses, 5 percent forbs, and 65 percent shrubs and trees. Approximate ground cover is 20-30 percent.
Phase 1.2, the mountain mahogany, perennial grass and forb phase results from fire that burns the understory and shrub and herbaceous species with minimal impact to the overstory mountain mahogany (1.1A). In the long interval between fires the shrub component reestablishes (1.2A) and the community moves toward phase 1.1. With no fire and improper grazing (1.1B) juniper can establish on the site and dominate or co-dominate with the mountain mahogany in the juniper-mountain mahogany phase (1.3)
Phase 1.3 the juniper-mountain mahogany phase results from phase 1.1 and 1.2 when there is no fire and improper grazing allows juniper to establish and become co-dominant with mountain mahogany with a component of shrubs and herbaceous vegetation. With the introduction of fire and prescribed grazing (1.3A) the plant community moves back to phase 1.1. Phase 1.3 is the “at risk” plant community phase in State 1. With continued improper grazing and no fire (IRT1A) the juniper becomes dominant and the site transitions to State 2 where juniper controls all of the ecological processes. A crown fire that eliminates all of the juniper and mountain mahogany (IRT1B) will move the community to State 3 a cheatgrass-shrub dominated community.
State 2 is a state dominated by juniper and mountain mahogany. Phase 2.1 maintains only a very sparse component of shrubs, grasses and forbs. As the juniper matures it becomes the juniper woodland phase (2.2) with juniper in complete control of the ecological processes. There is no potential repair pathway for this state to state 1 due to the steepness of the site, very shallow soils, low available water capacity and high erosion potential.
State 3 is cheatgrass and shrub dominated as a result of improper grazing and severe fire (IRT1B) in the juniper-mountain mahogany phase (1.3) or severe fire, improper grazing and drought (IRT2A) in the juniper woodland phase (2.2). This process eliminates the woody overstory components and allows the increase of cheatgrass which gains control of the site ecological processes. There is no potential repair pathway for this state to state 1 due to the steepness of the site, very shallow soils, low available water capacity and high erosion potential.
State 4 is the eroded state of this site. Improper grazing and fire (IRT2B and IRT3A) in the juniper woodland phase (2.2) and the cheatgrass shrub phase (3.1) exposes significant amounts of bare ground which leads to severe erosion.
State and transition model
Custom diagramStandard diagram
Figure 3. JD MAHOGANY ROCKLAND 9-12 PZ - R010XB057OR
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 reference plant community phase is dominated by curlleaf mountain mahogany, antelope bitterbrush and bluebunch wheatgrass. Sandberg bluegrass and Thurber’s needlegrass are common in the stand. Vegetative composition of the community is approximately 30 percent grasses, 5 percent forbs, and 65 percent shrubs and trees. Approximate ground cover is 20-30 percent.
Figure 4. 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)Shrub/Vine 195 385 575 Grass/Grasslike 90 180 270 Forb 15 30 45 Tree 0 5 10 Total 300 600 900 Figure 5. Plant community growth curve (percent production by month). OR4251 , B10 JD Mahog. Rockland 9-12 RPC. B10XB JD Mahog. Rockland 9-12 RPC.
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 15 35 25 5 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 70–180 bluebunch wheatgrass PSSP6 Pseudoroegneria spicata 70–180 – 2 Perennial, deep-rooted 12–42 Thurber's needlegrass ACTH7 Achnatherum thurberianum 8–30 – Idaho fescue FEID Festuca idahoensis 4–12 – 4 Perennial, shallow-rooted 8–48 Sandberg bluegrass POSE Poa secunda 8–48 – Forb5 12–24 buckwheat ERIOG Eriogonum 3–6 – desertparsley LOMAT Lomatium 36–6 – beardtongue PENST Penstemon 3–6 – phlox PHLOX Phlox 3–6 – 7 Other perennial forbs 3–9 common yarrow ACMI2 Achillea millefolium 0–3 – pussytoes ANTEN Antennaria 0–3 – erigenia ERIGE Erigenia 0–3 – phacelia PHACE Phacelia 0–3 – stonecrop SEDUM Sedum 0–3 – Shrub/Vine11 Perennial, evergreen 160–430 curl-leaf mountain mahogany CELE3 Cercocarpus ledifolius 160–430 – 12 Perennial, evergreen 20–100 antelope bitterbrush PUTR2 Purshia tridentata 20–100 – 14 Perennial, deciduous 5–15 hackberry CELTI Celtis 5–15 – 15 Other shrubs 10–30 yellow rabbitbrush CHVI8 Chrysothamnus viscidiflorus 5–15 – currant RIBES Ribes 5–15 – Tree16 Perennial, evergreen 0–10 western juniper JUOC Juniperus occidentalis 0–10 – Interpretations
Animal community
Livestock Grazing:
This site is not suited for use by livestock. Limitations are unstable soils, steep and rocky slopes.
Native Wildlife Associated with the Potential Climax Community:
Mule deer
Hawks
Rodents
Songbirds
This site provides critical cover and forage for deer during winter.Hydrological functions
The soils are in hydrologic group D. The soils of this site have high runoff potential.
Supporting information
Type locality
Location 1: Grant County, OR Township/Range/Section T12S R26E S18 General legal description Hwy 26 and Hwy 19 junction, Picture Gorge Area-John Day Fossil Beds National Monument. Other references
Stringham, Tamzen, 2007. Final Report for USDA Ecological Site Description. Oregon State University, Corvallis, Oregon.
USDI Bureau of Land Management, US Geological Survey; USDA Natural Resources Conservation Service, Agricultural Research Service; Interpreting Indicators of Rangeland Health. Technical Reference 1734-6; Version 4-2005.
Contributors
A. Bahn, J. Thompson, H. Barrett
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) James A. Cornwell, State Rangeland Management Specialist, NRCS, Idaho (Retired) Lee Brooks, Assistant State Conservationist, NRCS, Idaho (Retired). Contact for lead author State Rangeland Management Specialist for NRCS – Oregon Date 09/09/2009 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
-
Number and extent of rills:
Rills can occur on this site, especially on the steeper slopes. -
Presence of water flow patterns:
None -
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):
70 to 80%. -
Number of gullies and erosion associated with gullies:
None. -
Extent of wind scoured, blowouts and/or depositional areas:
Does not occur on this site. -
Amount of litter movement (describe size and distance expected to travel):
Fine. Litter movement, typically would be < two feet. -
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
stability values should range from 3 to 5, but needs to be verified. -
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Soil surface structure is single grained. SOM ranges from 0.5 to 1.0 percent. -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Moderate plant cover (20-30% basal and crown) mediates the rainfall impact even on steeper slopes (40-80%). The root mass of perennial bunchgrasses provides significant soil stability. -
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
The soils are shallow to bedrock or an indurated pan. -
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:
Tall shrubs>Sub-dominant:
Deep-rooted, perennial, cool season bunchgrasses>Other:
Shallow-rooted, perennial, cool season bunchgrasses > Forbs > treesAdditional:
-
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Normal decadence would be expected in both the mountain mahogany and the bunchgrasses. -
Average percent litter cover (%) and depth ( in):
-
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
Favorable: 900; Normal: 600; Unfavorable: 300 lbs/ac/yr. -
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:
Russian, diffuse, and spotted knapweed and cheatgrass. -
Perennial plant reproductive capability:
All species should be capable of reproducing annually. Mountain mahogany is a prolific seed producer.
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
