Natural Resources
Conservation Service
Ecological site R039XA137AZ
Loamy Upland
17-22" p.z.
Subirrigated
Last updated: 4/06/2020
Accessed: 09/20/2026
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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.
MLRA notes
Major Land Resource Area (MLRA): 039X–Mogollon Transition North
AZ 39.1 Mogollon Plateau Coniferous Forests
Elevations range from 7000 to 12,500 feet and precipitation averages 20 to 35 inches per year. Vegetation includes ponderosa pine, Gambel oak, Arizona walnut, sycamore, Douglas fir, blue spruce, Arizona fescue, sheep fescue, mountain muhly, muttongrass, junegrass, pine dropseed, and dryland sedges. The soil temperature regime ranges from mesic to frigid and the soil moisture regime ranges from typic ustic to udic ustic. This unit occurs within the Colorado Plateau Physiographic Province and is characterized by a sequence of flat to gently dipping sedimentary rocks eroded into plateaus, valleys and deep canyons. Sedimentary rock classes dominate the plateau with volcanic fields occurring for the most part near its margin.Associated sites
R039XA130AZ Loamy Bottom 17-22" p.z.
R039XA138AZ Clay Loam Upland 17-22 p.z.
Table 1. Dominant plant species
Tree (1) Pinus ponderosa
Shrub (1) Ericameria nauseosa ssp. nauseosa var. glabrata
Herbaceous (1) Juncus
(2) CarexPhysiographic features
This site occurs on the backslopes and breaks of basalt plateaus. The soils are deep and are saturated except in the driest conditions. The site does benefit significantly from ground water transmission, but benefits not at all or only slightly from run-on moisture from adjacent areas.
Table 2. Representative physiographic features
Landforms (1) Plateau
Elevation 6000 – 8000 ft Slope 1 – 10 % Aspect Aspect is not a significant factor Climatic features
About 40% of the moisture in this Common Resource Area (CRA), or Land Resource Unit (LRU) comes as rain from June to September. The remainder comes from October to May as snow or light rain. Extreme temperatures of 97 and -37 degrees Fahrenheit have been recorded. Some moisture is usually received every month.
Table 3 Representative climatic features
Frost-free period (average) 170 days Freeze-free period (average) 120 days Precipitation total (average) 20 in BarLineFigure 1. Monthly precipitation range
BarLineFigure 2. Monthly average minimum and maximum temperature
">Influencing water features
This site does not flood or pond but is wet due to seep discharge.
Soil features
The soils characterizing this site are deep to basalt bedrock. They are saturated by groundwater tranmission except in the driest of conditions. The surface soil textures include cobbly loam and is generally covered by about 3 inches of highly decomposed plant material. The subsurface textures include very cobbly and extremely cobbly clay loam.
Typical taxonomic units include: SSA 695 Navajo Depot - MU 12 Oxley family cobbly loam.Table 4. Representative soil features
Surface texture (1) Cobbly loam
Family particle size (1) Loamy
Drainage class Somewhat poorly drained to poorly drained Permeability class Moderately slow to slow Soil depth 40 – 60 in Surface fragment cover <=3" 10 – 15 % Subsurface fragment volume <=3"
(Depth not specified)20 – 55 % Ecological dynamics
The plant communities found on an ecological site are naturally variable. Composition and production will vary with yearly conditions, location, aspect, and the natural variability of the soils. The historical climax plant community represents the natural potential plant communities found on relict or relatively undisturbed sites. Other plant communities described here represent plant communities that are known to occur when the site is disturbed by factors such as grazing, fire, or drought.
Production data provided in this site description is standardized to air-dry weight at the end of the summer growing season. The plant communities described in this site description are based on near normal rainfall years.
NRCS uses a Similarity Index to compare existing plant communities to the plant communities described here. Similarity Index is determined by comparing the production and composition of a plant community to the production and composition of a plant community described in this site description. To determine Similarity Index, compare the production (air-dry weight) of each species to that shown in the plant community description. For each species, count no more than the maximum amount shown for the species, and for each group, count no more than the maximum shown for the group. Divide the resulting total by the total normal year production shown in the plant community description. If rainfall has been significantly above or below normal, use the total production shown for above or below normal years. If field data is not collected at the end of the summer growing season, then the field data must be corrected to the end of the year production before comparing it to the site description. The growth curve can be used as a guide for estimating production at the end of the summer growing season.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
State 1 submodel, plant communities
State 1
Grass Dominant: spike muhly, canada bluegrass, scattered ponderosa pine, and scattered rubber rabbitbrushThis state is grass dominant with scattered trees and shrubs.
Community 1.1
Historic Climax Plant CommunityThe historic climax plant community of this site is dominated by a variety of grasses and forbs.
Figure 3. 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 720 740 760 Forb 40 60 80 Shrub/Vine 0 8 16 Tree 0 4 8 Total 760 812 864 Figure 4. Plant community growth curve (percent production by month). AZ3911 , 39.1 17-22" p.z. all sites. Growth begins in the spring, most growth occurs during the summer rainy season..
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 10 10 20 20 20 5 0 0 State 2
Shrub Dominant: rubber rabbitbrushThis state shows a decrease in grass and an increase in rubber rabbitbrush.
Transition T1A
State 1 to 2Excessive disturbance such as periodic fire, ground disturbing recreation, and continuous, season-long grazing will cause a threshold to be crossed to a rubber rabbitbrush state.
Restoration pathway R2A
State 2 to 1An increase in soil organic carbon and a decrease in bare ground will help restore the system.
Additional community tables
Table 6. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Tree0 0–6 ponderosa pine PIPO Pinus ponderosa 0–6 – Shrub/Vine0 0–30 rubber rabbitbrush ERNAG Ericameria nauseosa ssp. nauseosa var. glabrata 0–13 – pingue rubberweed HYRI Hymenoxys richardsonii 0–13 – Woods' rose ROWOW Rosa woodsii var. woodsii 0–6 – 3 6–25 aster ASTER Aster 6–13 – cinquefoil POTEN Potentilla 0–6 – sandwort ARENA Arenaria 0–6 – Grass/Grasslike0 150–375 spike muhly MUWR Muhlenbergia wrightii 98–195 – deergrass MURI2 Muhlenbergia rigens 32–65 – mountain muhly MUMO Muhlenbergia montana 0–32 – pine dropseed BLTR Blepharoneuron tricholepis 0–32 – Ross' sedge CARO5 Carex rossii 6–20 – rush JUNCU Juncus 6–20 – Grass, annual 2GA Grass, annual 6–13 – little bluestem SCSC Schizachyrium scoparium 0–6 – nodding brome BRAN Bromus anomalus 0–6 – 1 115–240 Canada bluegrass POCO Poa compressa 98–162 – slender wheatgrass ELTRT Elymus trachycaulus ssp. trachycaulus 6–20 – western wheatgrass PASM Pascopyrum smithii 6–20 – squirreltail ELELE Elymus elymoides ssp. elymoides 6–13 – Arizona fescue FEAR2 Festuca arizonica 0–6 – prairie Junegrass KOMA Koeleria macrantha 0–6 – Fendler's threeawn ARPUF Aristida purpurea var. fendleriana 0–6 – muttongrass POFE Poa fendleriana 0–6 – 2 10–65 mat muhly MURI Muhlenbergia richardsonis 0–32 – blue grama BOGR2 Bouteloua gracilis 8–20 – tufted hairgrass DECE Deschampsia cespitosa 0–13 – Forb0 25–105 iris IRIS Iris 6–13 – Lewis flax LILE3 Linum lewisii 6–13 – western yarrow ACMIO Achillea millefolium var. occidentalis 6–13 – pussytoes ANTEN Antennaria 6–13 – white sagebrush ARLU Artemisia ludoviciana 0–6 – milkvetch ASTRA Astragalus 0–6 – thistle CIRSI Cirsium 0–6 – horsetail EQUIS Equisetum 0–6 – redroot buckwheat ERRA3 Eriogonum racemosum 0–6 – strawberry FRAGA Fragaria 0–6 – lupine LUPIN Lupinus 0–6 – dock RUMEX Rumex 0–6 – Interpretations
Supporting information
Type locality
Location 1: Coconino County, AZ Township/Range/Section T21N R5E S10 General legal description Belmont, AZ quad, NE1/4, NE1/4, Section 10, T21N, R5E, Camp Navajo, Coconino County, AZ. Contributors
Larry D. Ellicott
Steve BarkerApproval
Scott Woodall, 4/06/2020
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 09/20/2026 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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