Natural Resources
Conservation Service
Ecological site R023XY612OR
PUMICE SOUTH SLOPES
10-14 PZ
Last updated: 4/10/2025
Accessed: 04/20/2026
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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.
Ecological site concept
Currently there is only a draft of the initial concept for this ecological site. The initial concept for this site places it within the Loamy 10-20 PZ Mountain Big Sagebrush and Bluebunch Wheatgrass Ecological Site Group. To view the General STM and other information available for this ESG please go to https://edit.jornada.nmsu.edu/catalogs/esg/023X/R023XY905NV
Table 1. Dominant plant species
Tree Not specified
Shrub Not specified
Herbaceous Not specified
Physiographic features
This site occurs on moderately steep south facing slopes of canyons, buttes, and ridges. Slopes range from 15-65% but are typically from 30-60%. Elevations range from 2500-4500 feet.
Table 2. Representative physiographic features
Landforms (1) Canyon
(2) Butte
(3) Ridge
Elevation 2500 – 4500 ft Slope 15 – 65 % Aspect S Climatic features
The annual precipitation averages 10-15 inches, most of which occurs during the months of October through March. The mean annual air temperature is 48 degrees F. Temperature extremes range from 110 to -30 degrees F. The period for optimum plant growth is from April through July.
Table 3 Representative climatic features
Frost-free period (average) 120 days Freeze-free period (average) 150 days Precipitation total (average) 10 in ">Influencing water features
Soil features
The soils of this site have sandy loam surface layers and subsoils. They are usually stony to very stony on the surface and throughout the profile. Colluvial rock material limits the effective depth to less than 30 inches. Depth to bedrock ranges from 10-40 inches. Permeability is moderate to rapid and the available water holding capacity is 2-6 inches for the profile. The potential for water erosion is high.
Table 4. Representative soil features
Surface texture (1) Stony sandy loam
Family particle size (1) Loamy
Drainage class Well drained Permeability class Moderate to rapid Soil depth 10 – 40 in Available water capacity
(0-40in)2 – 6 in Calcium carbonate equivalent
(0-40in)2 % Electrical conductivity
(0-40in)Not specified Sodium adsorption ratio
(0-40in)Not specified Soil reaction (1:1 water)
(0-40in)7 Ecological dynamics
Five states have been identified for this site: a reference state; a state with the presence of annuals; a state that has Juniper dominating site resources; a state that is Juniper dominant; and a state with annual dominance.
Reference: Plant community phase change is driven by fire. Mountain and basin big sagebrush declines after fire while Idaho fescue, Thurber’s needlegrass and other grasses increase. May see a temporary increase in rabbitbrush after fire. Time facilitates the reintroduction of sagebrush. The introduction of invasive annual grasses and forbs transitions into the state 2.
State 2: Compositionally similar to the reference state with a trace of cheatgrass and the annual weeds. Ecological function has not changed, however the resiliency of the state has been reduced by the presence of invasive weeds. Prescribed grazing maintains state dynamics. Mismanagement of grazing favors sagebrush and Sandberg’s bluegrass. Cheatgrass increases. Prescribed grazing can reverse the trend. Reduction in fire frequency facilitates juniper encroachment in both poor and good condition communities. Fire reduces or eliminates juniper and with time sagebrush reestablishes. Juniper is out-competing sagebrush and the herbaceous plant community which brings the site to state 3.
State 3: Juniper dominates site resources. Sagebrush is dead or dying and bitterbrush lacks vigor. Sandberg’s bluegrass is the dominant species in the interspace and bare ground is significant. The perennial grass component is significantly reduced in both density and productivity. Idaho fescue may be present under the canopy of trees (north slope typically). Spatial and temporal energy capture and nutrient cycling has been truncated. Infiltration may be reduced due to lack of ground cover. Juniper woodland development is complete and soil loss and erosion drive site processes as the site goes into state 4.
State 4: Juniper dominated state. Soil loss is evident and erosion is active. All ecological processes, hydrologic cycle, nutrient cycle and energy capture have been significantly changed preventing the establishment of perennial plants. An abiotic threshold has been crossed. With catastrophic wildfire, state 5 is achieved.
State 5: Cheatgrass dominated plant community with limited to no shrub or perennial grass component. Soil erosion and redistribution along with changes in dynamic soil properties affect the hydrologic cycle and thus the nutrient cycle. Harsh environmental factors increase state resiliency to change.
State and transition model
Custom diagramStandard diagram
Figure 1. Group 8, STM
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
Historic Climax Plant CommunityCommunity 1.1
Historic Climax Plant CommunityHCPC
Figure 2. 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 490 525 560 Shrub/Vine 105 140 175 Forb 18 35 53 Total 613 700 788 Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 263–368 Idaho fescue FEID Festuca idahoensis 210–263 – bluebunch wheatgrass PSSPS Pseudoroegneria spicata ssp. spicata 53–105 – 2 53–131 Sandberg bluegrass POSE Poa secunda 26–53 – Thurber's needlegrass ACTH7 Achnatherum thurberianum 5–26 – squirreltail ELEL5 Elymus elymoides 11–26 – prairie Junegrass KOMA Koeleria macrantha 11–26 – Forb3 0–16 common yarrow ACMI2 Achillea millefolium 0–2 – woollypod milkvetch ASPU9 Astragalus purshii 0–2 – tapertip hawksbeard CRAC2 Crepis acuminata 0–2 – fleabane ERIGE2 Erigeron 0–2 – buckwheat ERIOG Eriogonum 0–2 – desertparsley LOMAT Lomatium 0–2 – phacelia PHACE Phacelia 0–2 – phlox PHLOX Phlox 0–2 – Shrub/Vine4 7–21 mountain big sagebrush ARTRV Artemisia tridentata ssp. vaseyana 7–14 – antelope bitterbrush PUTR2 Purshia tridentata 0–7 – 5 12–28 yellow rabbitbrush CHVI8 Chrysothamnus viscidiflorus 3–7 – buckwheat ERIOG Eriogonum 3–7 – rubber rabbitbrush ERNA10 Ericameria nauseosa 3–7 – desert gooseberry RIVE Ribes velutinum 3–7 – Interpretations
Animal community
Livestock- This site is suited for use by cattle, sheep, and horses under a planned grazing system in the spring and fall.
Wildlife- This site is commonly used by mule deer, rabbits, rodents, an assorted variety of birds and their associated avian and terrestrial predators.Hydrological functions
The soils of this site have slow to very rapid runoff potential. The hydrologic cover is fair when ecological condition is high. The hydrologic soil group is B.
Wood products
This site is susceptible to invasion by western juniper. If this occurs, it can provide firewood and fence posts.
Other information
Bluebunch wheatgrass is the dominant grass, but Thurber needlegrass increases with more sandy surface textures. Antelope bitterbrush may increase as precipitation approaches 12 inches.
Fires causes a decline in sagebrush, but increases in rabbitbrush due to resprouting. Cheatgrass may invade in burned areas.
Supporting information
Contributors
C Tackman
Approval
Kendra Moseley, 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 04/20/2026 Approved by Approval date Composition (Indicators 10 and 12) based on Annual Production Indicators
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Number and extent of rills:
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Presence of water flow patterns:
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Number and height of erosional pedestals or terracettes:
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Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
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Number of gullies and erosion associated with gullies:
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Extent of wind scoured, blowouts and/or depositional areas:
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Amount of litter movement (describe size and distance expected to travel):
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Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
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Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
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Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
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Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
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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:
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Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
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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):
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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:
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Perennial plant reproductive capability:
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