Natural Resources
Conservation Service
Ecological site F035XA121AZ
Shallow Loam
10-14" p.z.
Cobbly (JUOS)
Last updated: 5/20/2025
Accessed: 05/03/2026
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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.
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Figure 1. Mapped extent
Areas shown in blue indicate the maximum mapped extent of this ecological site. Other ecological sites likely occur within the highlighted areas. It is also possible for this ecological site to occur outside of highlighted areas if detailed soil survey has not been completed or recently updated.
MLRA notes
Major Land Resource Area (MLRA): 035X–Colorado Plateau
AZ CRA 35.1 - Colorado Plateau Mixed Grass Plains
Elevations range from 5100 to 6000 feet and precipitation averages 10 to 14 inches per year. Vegetation includes Stipa species, Indian ricegrass, galleta, and blue grama, fourwing saltbush, winterfat, and cliffrose. The soil temperature regime is mesic and the soil moisture regime is ustic aridic. 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.Table 1. Dominant plant species
Tree (1) Juniperus osteosperma
Shrub (1) Purshia stansburiana
Herbaceous (1) Bouteloua gracilis
Physiographic features
Site occurs on footslopes and summits of low hills. Depth is from very shallow to shallow. Surface textures from extremely cobble loam to very gravelly loam. Subsurface textures from very cobbly loam to very cobbly clay loam. pH from 7.4 to 8.4 and hazard of erosion is slight from water and wind.
Table 2. Representative physiographic features
Landforms (1) Hill
(2) Mesa
(3) Plateau
Flooding duration Extremely brief (0.1 to 4 hours) to very brief (4 to 48 hours) Flooding frequency None to rare Ponding duration Very brief (4 to 48 hours) Ponding frequency None Elevation 5200 – 5500 ft Slope 1 – 12 % Aspect Aspect is not a significant factor Climatic features
50-60% of moisture falls as rain Jul-Sep and is the most effective moisture for plant growth. The remaining moisture comes as snow during the winter.
Mean temperature for the hottest month (Jul) is 72 F; for the coldest month (Jan) is 32 F. Extreme temperatures of 105 F and -28F have been recorded. Long periods with little or no effective moisture are relatively common.
Table 3 Representative climatic features
Frost-free period (average) 160 days Freeze-free period (average) 180 days Precipitation total (average) 10 in BarLineFigure 2. Monthly precipitation range
BarLineFigure 3. Monthly average minimum and maximum temperature
">Influencing water features
Soil features
Soils are very shallow to shallow. Surface textures are Extremely cobbly loam to very gravelly loam. Subsurface textures from very cobbly loam to very cobbly clay loam. pH from 7.4 to 8.4 with Limestone bedrock at 17 to 28 inches and lime content at 40% plus.
Typical taxonomic units include:
SSA-699 Hualapai/Havasupai Area MU's 53 Curhollow and Winona.Table 4. Representative soil features
Parent material (1) Residuum – limestone
Surface texture (1) Extremely cobbly loam
(2) Very cobbly loam
Family particle size (1) Loamy
Drainage class Well drained Permeability class Moderate Soil depth 5 – 20 in Surface fragment cover <=3" 5 – 15 % Surface fragment cover >3" 10 – 20 % Available water capacity
(0-40in)1 – 2 in Calcium carbonate equivalent
(0-40in)15 – 35 % Electrical conductivity
(0-40in)0 – 2 mmhos/cm Soil reaction (1:1 water)
(0-40in)7.4 – 8.4 Subsurface fragment volume <=3"
(Depth not specified)2 – 15 % Subsurface fragment volume >3"
(Depth not specified)5 – 10 % 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
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Click on state and transition labels to scroll to the respective textEcosystem states
State 1 submodel, plant communities
State 1
Historic Natural Plant CommunityCommunity 1.1
Historic Natural Plant CommunityWoodland community with an overstory of Utah juniper and Colorado pinyon. Understory species include blue grama, black grama, needleandthread, globemallow, astragalus, Stansbury cliffrose, and running prickly pear.
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)Grass/Grasslike 110 145 180 Shrub/Vine 60 80 100 Forb 30 40 50 Tree 15 20 25 Total 215 285 355 Table 6. Canopy structure (% cover)
Height Above Ground (ft) Tree Shrub/Vine Grass/
GrasslikeForb <0.5 – – – – >0.5 <= 1 – – 0-40% – >1 <= 2 – 2-10% – 0-5% >2 <= 4.5 0-5% – 0-20% – >4.5 <= 13 – 5-20% – – >13 <= 40 25-35% – – – >40 <= 80 – – – – >80 <= 120 – – – – >120 – – – – Additional community tables
Table 7. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Tree0 12–16 Utah juniper JUOS Juniperus osteosperma 12–16 – twoneedle pinyon PIED Pinus edulis 12–16 – Shrub/Vine0 30–50 Mexican cliffrose PUME Purshia mexicana 20–40 – banana yucca YUBA Yucca baccata 16–20 – Fremont's mahonia MAFR3 Mahonia fremontii 16–20 – tulip pricklypear OPPH Opuntia phaeacantha 16–20 – Shrub (>.5m) 2SHRUB Shrub (>.5m) 12–16 – mormon tea EPVI Ephedra viridis 12–16 – spiny greasebush GLSPS Glossopetalon spinescens var. spinescens 12–16 – broom snakeweed GUSA2 Gutierrezia sarothrae 12–16 – Grass/Grasslike0 150–250 blue grama BOGR2 Bouteloua gracilis 100–140 – squirreltail ELELE Elymus elymoides ssp. elymoides 16–20 – black grama BOER4 Bouteloua eriopoda 16–20 – sand dropseed SPCR Sporobolus cryptandrus 16–20 – needle and thread HECOC8 Hesperostipa comata ssp. comata 12–16 – Grass-like, perennial 2GLP Grass-like, perennial 12–16 – Indian ricegrass ACHY Achnatherum hymenoides 12–16 – sideoats grama BOCU Bouteloua curtipendula 12–16 – Forb0 10–20 milkvetch ASTRA Astragalus 5–8 – globemallow SPHAE Sphaeralcea 5–8 – Forb, perennial 2FP Forb, perennial 4–6 – Interpretations
Animal community
This site is suitable for grazing during any period of the year by cows and calves, stocker cattle, sheep and horses. Prescribed grazing systems can benefit this site by allowing rest periods for the cool season species.
The potential plant community provides a variety of food and cover plants for wildlife. When the vegetation complex retrogresses then unpalatable shrub species increase and the site becomes less usable as a foraging area for some species. Grazing practices that encourage cool season grass species are beneficial to antelope, cottontails and rodents. Shrubs that provide both food and cover should be maintained.
Wildlife factors of Food, Cover, Topography are good but water is scarce in natural springs and potholes.Recreational uses
Site is located on gently sloping plains and mesa tops which lend themselves to activities such as horseback riding, wildlife observation and hunting.
This site has a variety of spring and summer flowers which are particularly noticeable after good moisture periods. It has good aesthetic appeal when not severely disturbed.
Winters are cold, however, relatively mild spring, fall and summer months are attractive to recreationists.
Wood products
Site Index = 35 - 40
Fuelwood (Cords/Ac) = 4 - 6
Fence Posts (7 foot) /Ac = 15 - 20
Christmas Trees/Ac = 5 - 10
CMAI* per year = 3sq ft/ac
Productivity Class = 1
*CMAI is the "Culmination of Mean Annual Increment" or highest average growth rate of the stand in the units specified.
Other information
Woodland Uses and Management Interpretations
Equipment & Operability Considerations -
Suitable Equipment for:
Harvesting: All kinds
Site Prep: All kinds
Tree Planting: Best to do by hand(shallow soil)
Precommercial Thinning: All kinds
Equipment Limitation:
Slope: None
Unsurfaced Roads: None
Stoniness/rock outcrop: Slight
Water table/flooding: None
Erosion Potential is slight for all uses.
Soil Management:
Compaction potential: Good
Rutting potential: Rutting may occur when wet
Revegetation potential:
Poor - due to shallow, droughty soil
Supporting information
Type locality
Location 1: Mohave County, AZ Township/Range/Section T25N R10W S9 General legal description Nelson Quad - 4 miles northeast of Peach Springs, north of Highway 66 on the Hualapai Indian Reservation, Arizona Contributors
Harmon Hodgkinson
Karlynn Huling
Larry D. EllicottApproval
Kendra Moseley, 5/20/2025
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 05/03/2026 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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