Natural Resources
Conservation Service
Ecological site R010XB058OR
JD Mahogany Rockland
12-16 PZ
Last updated: 3/11/2025
Accessed: 08/16/2026
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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): 010X–Central Rocky and Blue Mountain Foothills
This MLRA is characterized by gently rolling to steep hills, plateaus, and low mountains at the foothills of the Blue Mountains in Oregon and the Central Rocky Mountains in Idaho. The geology of this area is highly varied and ranges from Holocene volcanics to Cretaceous sedimentary rocks. Mollisols are the dominant soil order and the soil climate is typified by mesic or frigid soil temperature regimes, and xeric or aridic soil moisture regimes. Elevation ranges from 1,300 to 6,600 feet (395 to 2,010 meters), increasing from west to east. The climate is characterized by dry summers and snow dominated winters with precipitation averaging 8 to 16 inches (205 to 405 millimeters) and increasing from west to east. These factors support plant communities with shrub-grass associations with considerable acreage of sagebrush grassland. Big sagebrush, bluebunch wheatgrass, and Idaho fescue are the dominant species. Stiff sagebrush, low sagebrush, and Sandberg bluegrass are often dominant on sites with shallow restrictive layers. Western juniper is one of the few common tree species and since European settlement has greatly expanded its extent in Oregon. Nearly half of the MLRA is federally owned and managed by the Bureau of Land Management. Most of the area is used for livestock grazing with areas accessible by irrigation often used for irrigated agriculture.
Ecological site concept
In reference condition, this ecological site supports a plant community dominated by curlleaf mountain mahogany (Cercocarpus ledifolius), antelope bitterbrush (Purshia tridentata) and bluebunch wheatgrass (Pseudoroegneria spicata). Idaho fescue (Festuca idahoensis) and Sandberg bluegrass (Poa secunda) are also common. Abiotically, this site is typified by occupying canyon side slopes and very shallow soils with significant stones or cobbles present. The soil climate is mesic to frigid near mesic/xeric. Historically, the ecological dynamics of this site were driven by infrequent fire and cycles of drought. Presently, reference conditions are less common and current dynamics are also influenced by the spread of invasive species, the expansion of western juniper (Juniperus occidentalis), livestock grazing pressures and fire suppression.
Associated sites
R010XB051OR JD Shallow South 9-12 PZ
South aspect, shallow soils
Similar sites
R010XB057OR JD Mahogany Rockland 9-12 PZ
lower herbaceous production
Table 1. Dominant plant species
Tree Not specified
Shrub (1) Cercocarpus ledifolius
(2) Purshia tridentataHerbaceous (1) Pseudoroegneria spicata ssp. spicata
(2) Festuca idahoensisPhysiographic features
This site typically occurs on canyon side slopes composed of basalt and tuffaceous material. Aspect is typically southerly, but may occur on other aspects with slopes typically ranging from 5 to 90 percent. Elevation typically varies from 2,100 to 4,000 feet (650 to 1,200 meters). This site is not subject to ponding or flooding and no water table is present within the soil profile.
Table 2. Representative physiographic features
Landforms (1) Upland > Hill
(2) Upland > Canyon
(3) Upland > Ridge
Flooding frequency None Ponding frequency None Elevation 2100 – 4000 ft Slope 5 – 90 % Aspect SE, S, SW Climatic features
The average annual precipitation is 12 to 16 inches (300 to 400 mm) occurring primarily as rain and snow from November through May. The soil temperature regime is mesic to frigid (near mesic) and the soil moisture regime is xeric. Occasional severe convectional storms occur during the summer. The frost-free period is approximately 40 to 100 days. The graphs below are populated from the closest available weather station to representative site locations and are provided to indicate general climate patterns.
Table 3 Representative climatic features
Frost-free period (characteristic range) 40-100 days Freeze-free period (characteristic range) Precipitation total (characteristic range) 10-20 in Frost-free period (average) 70 days Freeze-free period (average) Precipitation total (average) 10 in Characteristic rangeActual rangeBarLineFigure 1. Monthly precipitation range
Characteristic rangeActual rangeBarLineFigure 2. Monthly minimum temperature range
Characteristic rangeActual rangeBarLineFigure 3. Monthly maximum temperature range
BarLineFigure 4. Monthly average minimum and maximum temperature
Figure 5. Annual precipitation pattern
Figure 6 Annual average temperature pattern
Climate stations used
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(1) FOSSIL [USC00353038], Fossil, OR
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(2) MONUMENT 2 [USC00355711], Monument, OR
">Influencing water features
This site is not influenced by water from a wetland or stream.
Wetland description
Not applicable
Soil features
The soils are typically very shallow, very cobble loamy coarse sand to gravelly loam over fragmental subsoil (less than 10 inches to lithic contact). The erosion hazard is very high.
Table 4. Representative soil features
Parent material (1) Colluvium – basalt
(2) Colluvium – serpentinite
(3) Residuum – volcanic rock
(4) Residuum – serpentinite
Surface texture (1) Very cobbly loamy coarse sand
(2) Gravelly loam
Family particle size (1) Sandy-skeletal
(2) Loamy-skeletal
Drainage class Well drained to somewhat excessively drained Permeability class Moderately slow to moderately rapid Depth to restrictive layer 1 – 10 in Soil depth 1 – 10 in Surface fragment cover <=3" 15 – 30 % Surface fragment cover >3" 15 – 30 % Available water capacity
(0-40in)0.2 – 1.6 in Calcium carbonate equivalent
(0-40in)Not specified Electrical conductivity
(0-40in)0 – 2 mmhos/cm Sodium adsorption ratio
(0-40in)Not specified Soil reaction (1:1 water)
(0-40in)6.6 – 8.4 Subsurface fragment volume <=3"
(4-10in)10 – 40 % Subsurface fragment volume >3"
(4-10in)20 – 30 % 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.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
T1A - Time without fire, possibly combined with improperly managed grazing T1B - Crown fire that removes overstory woody species, possibly combined with improperly managed grazing T2A - Fire, drought event or improperly managed grazing T2B - Fire, possibly combined with improperly managed grazing T3A - Catastrophic fire, possibly combined with improperly managed grazing State 1 submodel, plant communities
1.1A - Fire 1.1B - No fire, improper grazing 1.2A - No fire 1.2B - No fire, improper grazing 1.3A - Fire, prescribed grazing State 2 submodel, plant communities
P2.1A - Juniper Maturation State 3 submodel, plant communities
State 4 submodel, plant communities
State 1
Historic ReferenceThere 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.
Dominant plant species
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curl-leaf mountain mahogany (Cercocarpus ledifolius), shrub
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antelope bitterbrush (Purshia tridentata), shrub
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bluebunch wheatgrass (Pseudoroegneria spicata ssp. spicata), grass
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Idaho fescue (Festuca idahoensis), grass
Community 1.1
Reference Plant Community: Mountain Mahogany SteppeThe reference plant community phase is dominated by mountain mahogany in the overstory, antelope bitterbrush in the shrub layer and bluebunch wheatgrass in the herbaceous layer. Idaho fescue and Sandberg bluegrass are common with a minor amount of forbs. Vegetative composition of the community is approximately 55 percent grasses and grass-likes, 10 percent forbs, and 35 percent shrubs and trees. Approximate ground cover is 40 to 60 percent.
Figure 7. 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 155 310 465 Shrub/Vine 100 200 300 Forb 25 50 80 Tree 20 40 55 Total 300 600 900 Figure 8. Plant community growth curve (percent production by month). OR4261 , B10 JD Mahog. Rockland 12-16 RPC. B10XB JD Mahog. Rockland 12-16 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 10 25 25 15 5 10 5 0 0 Community 1.2
Mountain Mahogany / Perennial Grass and Forb PhasePhase 1.2, the mountain mahogany, perennial grass and forb phase results from fire that burns the understory 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)
Community 1.3
Juniper Mountain Mahogany PhasePhase 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 reduced 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. With continued improper grazing and no fire 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 will move the community to State 3 a cheatgrass-shrub dominated community.
Pathway 1.1A
Community 1.1 to 1.2Fire consumes the understory shrub and herbaceous species with minimal impact to the overstory mountain mahogany
Pathway 1.1B
Community 1.1 to 1.3With no fire and improper grazing juniper can establish on the site and dominate or co-dominate with the mountain mahogany in the juniper-mountain mahogany phase
Pathway 1.2A
Community 1.2 to 1.1In the long interval between fires the shrub component reestablishes
Pathway 1.2B
Community 1.2 to 1.3With no fire and improper grazing juniper can establish on the site and dominate or co-dominate with the mountain mahogany in the juniper-mountain mahogany phase
Pathway 1.3A
Community 1.3 to 1.1Introduction of fire and prescribed grazing
Context dependence.Prescribed grazing will only be an effective conservation tool if improper grazing impacts have not significantly altered site by severely compacting soils or severely diminishing the seed source for important herbaceous species
State 2
Tree and ShrubState 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.
Dominant plant species
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western juniper (Juniperus occidentalis), tree
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curl-leaf mountain mahogany (Cercocarpus ledifolius), shrub
Community 2.1
Juniper - Mountain Mahogany PhaseCommunity 2.2
Juniper Woodland PhasePathway P2.1A
Community 2.1 to 2.2Juniper Maturation - as juniper mature, mahogany is crowded out.
State 3
InvadedState 3 is cheatgrass and shrub dominated as a result of improper grazing and severe fire in the juniper-mountain mahogany phase (1.3) or severe fire, improper grazing and drought 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.
Dominant plant species
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cheatgrass (Bromus tectorum), grass
Community 3.1
Cheatgrass Shrub PhaseState 4
ErodedState 4 is the eroded state of this site. Improper grazing and fire 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.
Dominant plant species
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curl-leaf mountain mahogany (Cercocarpus ledifolius), shrub
Community 4.1
Mountain Mahogany Eroded PhaseTransition T1A
State 1 to 2Time without fire, possibly combined with improperly managed grazing
Transition T1B
State 1 to 3Crown fire that removes overstory woody species, possibly combined with improperly managed grazing in the presence of invasive annual species
Transition T2A
State 2 to 3Fire, drought event or improperly managed grazing in the presence of invasive annual species
Transition T2B
State 2 to 4Catastrophic fire, possibly combined with improperly managed grazing
Transition T3A
State 3 to 4Catastrophic fire, possibly combined with improperly managed grazing
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 90–270 bluebunch wheatgrass PSSPS Pseudoroegneria spicata ssp. spicata 90–270 – 2 Perennial deep-rooted 45–135 Idaho fescue FEID Festuca idahoensis 45–135 – 4 Perennial shallow-rooted bunchgrass 15–45 Sandberg bluegrass POSE Poa secunda 15–45 – 5 Grass-like perennial 15–45 Geyer's sedge CAGE2 Carex geyeri 15–45 – Forb6 Perennial forbs 20–60 common yarrow ACMI2 Achillea millefolium 3–10 – arrowleaf balsamroot BASA3 Balsamorhiza sagittata 3–10 – fleabane ERIGE2 Erigeron 3–10 – buckwheat ERIOG Eriogonum 3–10 – desertparsley LOMAT Lomatium 3–10 – phlox PHLOX Phlox 3–10 – 7 Other perennial forbs 10–30 pussytoes ANTEN Antennaria 3–10 – phacelia PHACE Phacelia 3–10 – stonecrop SEDUM Sedum 3–10 – Shrub/Vine11 Perennial evergreen 60–220 curl-leaf mountain mahogany CELE3 Cercocarpus ledifolius 60–220 – 12 Perennial evergreen 30–110 antelope bitterbrush PUTR2 Purshia tridentata 30–110 – 15 Other shrubs 10–40 yellow rabbitbrush CHVI8 Chrysothamnus viscidiflorus 5–20 – currant RIBES Ribes 5–20 – 16 Perennial, deciduous 5–15 netleaf hackberry CELAR Celtis laevigata var. reticulata 5–15 – Tree18 Perennial evergreen 12–72 western juniper JUOC Juniperus occidentalis 12–60 – ponderosa pine PIPO Pinus ponderosa 0–12 – Table 7. Community 1.2 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 8. Community 1.3 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 9. Community 2.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 10. Community 2.2 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 11. Community 3.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Table 12. Community 4.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) 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: This site provides critical cover and forage for deer and elk during the fall and winter. The mountain mahogany shrubs provide suitable habitat for nesting sites for a variety of birds.Hydrological functions
The soils are in hydrologic group D. The soils of this site have high runoff potential.
Recreational uses
The larger acreage areas of this site may provide some big game hunting opportunities.
Supporting information
Type locality
Location 1: Grant County, OR Township/Range/Section T13S R28E S33 General legal description Southeast slope on ridge south of Widow Creek. References
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1980. Fire Effects Information System. http://www.fs.fed.us/database/feis/.
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. 2021 (Date accessed). USDA PLANTS Database. http://plants.usda.gov.
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
Ed Petersen, Alan Bahn
Andrew Neary - table population and edits 2021Approval
Kirt Walstad, 3/11/2025
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 Cornwell, State Rangeland Management Specialist, NRCS, Idaho (Retired) Lee Brooks, Assistant State Conservationist, NRCS, Idaho (Retired). Contact for lead author Date 09/09/2009 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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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):
Bare ground is 40 to 60 percent. -
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):
Structure is single grain and weak to moderate fine and very fine granular. The A horizon is 3 to 5 inches thick and SOM 0.5 to 3 percent. -
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
Significant cover (40-60% 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 fragmental subsoil or bedrock. -
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:
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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):
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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.
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