Natural Resources
Conservation Service
Ecological site R035XC330AZ
Sandy Terrace
10-14" p.z.
Stony
Last updated: 5/19/2025
Accessed: 04/29/2026
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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 35.3 – Colorado Plateau Sagebrush – Grasslands
Elevations range from 4500 to 6000 feet and precipitation averages 10 to 14 inches. Vegetation includes Wyoming big sagebrush, Utah juniper, Colorado pinyon - cliffrose, Mormon tea, fourwing saltbush, blackbrush Indian ricegrass, needle and thread, western wheatgrass Galleta, black grama, blue grama, and sand dropseed. 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.Ecological site concept
This site occurs on lower stream terraces. Soils are very deep. Surface texture is very cobbly sandy loam. Subsoil textures are very gravelly loamy coarse sand, cobbly fine sandy loam, cobbly coarse sand and very stony coarse sand.
Table 1. Dominant plant species
Tree (1) Juniperus osteosperma
(2) Pinus edulisShrub (1) Artemisia tridentata var. wyomingensis
(2) Ericameria nauseosa ssp. nauseosa var. bigeloviiHerbaceous (1) Achnatherum hymenoides
(2) Bouteloua gracilisPhysiographic features
This site occurs in an upland position on low stream terraces of valley floors. It neither benefits from run-in, nor suffers from excessive runoff unless denuded of its vegetation.
Table 2. Representative physiographic features
Landforms (1) Stream terrace
(2) Valley floor
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 to rare Elevation 5000 – 6400 ft Slope 2 – 5 % Aspect Aspect is not a significant factor Climatic features
Winter summer moisture ratios range from 70:30 to 60:40. Late spring is usually the driest period, and early fall moisture can be sporadic. Summer rains fall from June through September; moisture originates in the Gulf of Mexico and creates convective, usually brief, intense thunderstorms. Cool season moisture from October through May tends to be frontal; it originates in the Pacific and the Gulf of California and falls in widespread storms with longer duration and lower intensity. Precipitation generally comes as snow from December through February. Accumulations above 12 inches are not common but can occur. Snow usually lasts for 3-4 days, but can persist much longer. Summer daytime temperatures are commonly 95 - 100 F and on occasion exceed 105 F. Winter air temperatures can regularly go below 10 F and have been recorded below - 20 F.
Table 3 Representative climatic features
Frost-free period (average) 170 days Freeze-free period (average) 190 days Precipitation total (average) 10 in BarLineFigure 2. Monthly precipitation range
BarLineFigure 3. Monthly average minimum and maximum temperature
">Influencing water features
This is an upland site, and is not associated with water features or wetlands. During heavy rain events, this site may receive run-on and throughflow moisture from landforms above and contribute runoff and throughflow to landforms below.
Soil features
Soils are very deep. Surface texture is very cobbly sandy loam. Subsoil textures are very gravelly loamy coarse sand, cobbly fine sandy loam, cobbly coarse sand and very stony coarse sand. Parent material is alluvium derived from quartz diorite and sandstone. Geologic formation is alluvium from tertiary diorite and sandstone. Available water capacity is very low. Water erosion potential is slight. Wind erosion potential is moderate. Soils are non-saline, non-sodic. pH range is 7.4-8.4. Soils moisture regime is ustic aridic; temperature regime is mesic.
Typical taxonomic unit on this site:
SSA 717 Shiprock Area AZ/NM MU 315 Shoegame.Table 4. Representative soil features
Parent material (1) Alluvium – quartz-diorite
Surface texture (1) Very cobbly sandy loam
Family particle size (1) Sandy
Drainage class Somewhat excessively drained to excessively drained Permeability class Moderately rapid to rapid Soil depth 60 in Surface fragment cover <=3" 10 – 15 % Surface fragment cover >3" 20 – 30 % Available water capacity
(0-40in)0 – 2.5 in Calcium carbonate equivalent
(0-40in)5 – 10 % Electrical conductivity
(0-40in)0 – 2 mmhos/cm Sodium adsorption ratio
(0-40in)0 – 5 Soil reaction (1:1 water)
(0-40in)7.4 – 8.4 Subsurface fragment volume <=3"
(Depth not specified)5 – 10 % Subsurface fragment volume >3"
(Depth not specified)20 – 35 % 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 fire, grazing, 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 amount shown for each group. Divide the resulting total by the total normal year production shown in the plant community description. If the rainfall has ben 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 2 submodel, plant communities
State 1
Reference StateA grassland community along low stream terraces of valley floors. Soils are very deep, well drained. Major grasses include Indian ricegrass, blue grama, galleta, and sand dropseed. Shrubs are widely scattered with some trees in some areas.
Community 1.1
Reference Plant CommunityThis range site is a grassland community on stream terraces with a cobbly and stoney soil surface. Shrubs are present with scattered trees (Utah juniper, Colorado pinyon) in some areas. Major grasses species include Indian ricegrass, blue grama, galleta and sand dropseed.
With severe disturbance, Fendler threeawn, broom snakeweed, Wyoming big sagebrush and Bigelow rubber rabbitbrush will increase; cheatgrass and Russian thistle will also invade.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 240 370 580 Shrub/Vine 60 90 140 Tree 30 40 60 Forb 10 20 20 Total 340 520 800 Table 6. Ground cover
Tree foliar cover 0-0% Shrub/vine/liana foliar cover 0-10% Grass/grasslike foliar cover 10-20% Forb foliar cover 0-0% Non-vascular plants 0% Biological crusts 0% Litter 0% Surface fragments >0.25" and <=3" 0% Surface fragments >3" 0% Bedrock 0% Water 0% Bare ground 0% Table 7. Canopy structure (% cover)
Height Above Ground (ft) Tree Shrub/Vine Grass/
GrasslikeForb <0.5 – – 2-5% 0-2% >0.5 <= 1 – – – – >1 <= 2 – – 10-20% – >2 <= 4.5 – 1-5% – – >4.5 <= 13 0-2% – – – >13 <= 40 – – – – >40 <= 80 – – – – >80 <= 120 – – – – >120 – – – – Figure 5. Plant community growth curve (percent production by month). AZ3503 , 35.3 10-14" p.z. galleta. Growth begins in spring, most growth occurs during summer and early fall rainy season. Plants will green up again in the fall..
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 0 0 5 20 15 20 30 10 0 0 Figure 6. Plant community growth curve (percent production by month). AZ3505 , 35.3 10-14" p.z. Indian ricegrass. Growth begins in spring, with semi-dormancy occurring during July through August. Plants will green up again in the fall..
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 10 20 25 20 5 5 10 5 0 0 Figure 7. Plant community growth curve (percent production by month). AZ3508 , 35.3 10-14" p.z. Wyoming big sagebrush. Most growth occurs in spring and early summer. Stem elongation and seed set occur in the fall..
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 0 5 15 30 20 10 10 10 0 0 Figure 8. Plant community growth curve (percent production by month). AZ3531 , 35.3 10-14" p.z. all sites. Growth begins in the spring and continues through the summer..
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 1 3 17 18 10 19 20 10 1 1 0 Figure 9. Plant community growth curve (percent production by month). AZ3567 , 35.3 10-14" p.z. blue grama. Growth occurs mostly 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 0 0 5 5 30 55 5 0 0 0 State 2
Shrub and Annual StateThe aspect of this site is a shrub dominated plant community with broom snakeweed, rubber rabbitbrush, and Wyoming big sagebrush. Dominant grasses include threeawns and warm season grassed including blue grama and dropseeds.
Community 2.1
Shrubland with AnnualsThis plant community is comprised mostly shrubs, including broom snakeweed, Bigelow sagebrush, Wyoming big sagebrush and rubber rabbitbrush. Perennial cool season grasses are reduced with a increase of threeawn and other warm season grasses. Other plants that increase with disturbance are introduced annuals including cheatgrass and Russian thistle.
Transition T1A
State 1 to 2Season-long grazing providing little rest and recovery for preferred grazed plants during critical growing periods, coupled with high utilization. This is coupled or proceeded by prolonged drought and the establishment of introduced annuals.
Additional community tables
Table 8. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Tree0 30–50 Utah juniper JUOS Juniperus osteosperma 20–50 – twoneedle pinyon PIED Pinus edulis 6–13 – Shrub/Vine0 50–80 blue grama BOGR2 Bouteloua gracilis 17–34 – James' galleta PLJA Pleuraphis jamesii 17–34 – sand dropseed SPCR Sporobolus cryptandrus 17–34 – Wyoming big sagebrush ARTRW8 Artemisia tridentata ssp. wyomingensis 5–26 – rubber rabbitbrush ERNAB2 Ericameria nauseosa ssp. nauseosa var. bigelovii 5–26 – broom snakeweed GUSA2 Gutierrezia sarothrae 5–26 – 2 20 Shrub (>.5m) 2SHRUB Shrub (>.5m) 0–26 – fourwing saltbush ATCA2 Atriplex canescens 0–11 – arctic alpine forget-me-not ERNAC Eritrichium nanum var. chamissonis 0–11 – plains pricklypear OPPO Opuntia polyacantha 0–11 – narrowleaf yucca YUAN2 Yucca angustissima 0–5 – mormon tea EPVI Ephedra viridis 0–5 – alkali sacaton SPAI Sporobolus airoides 0–3 – Grass/Grasslike0 300–340 Indian ricegrass ACHY Achnatherum hymenoides 53–105 – James' galleta PLJA Pleuraphis jamesii 26–53 – sand dropseed SPCR Sporobolus cryptandrus 26–53 – blue grama BOGR2 Bouteloua gracilis 26–53 – squirreltail ELELE Elymus elymoides ssp. elymoides 5–26 – Fendler's threeawn ARPUF Aristida purpurea var. fendleriana 5–26 – Fendler's sandwort ARFE3 Arenaria fendleri 3–17 – squirreltail ELELE Elymus elymoides ssp. elymoides 3–17 – 1 40–50 Grass, perennial 2GP Grass, perennial 0–26 – needle and thread HECOC8 Hesperostipa comata ssp. comata 0–16 – muttongrass POFE Poa fendleriana 0–11 – spike dropseed SPCO4 Sporobolus contractus 0–11 – needle and thread HECOC8 Hesperostipa comata ssp. comata 0–10 – alkali sacaton SPAI Sporobolus airoides 0–5 – Forb0 0–30 Forb, perennial 2FP Forb, perennial 5–16 – Forb, annual 2FA Forb, annual 5–11 – muttongrass POFE Poa fendleriana 0–7 – spike dropseed SPCO4 Sporobolus contractus 0–7 – Table 9. Community 2.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Interpretations
Animal community
This site is suitable for yearlong grazing by either cows and calves or stocker cattle but is not easily traversed because of the Cobbles and Boulders. Prescribed grazing systems can benefit this site by allowing rest periods for the cool season species. Soils on this site have high wind erosion hazard, particularly on overgrazed areas, roads, cattle trails and concentration areas.
This site offers a fair diversity in the vegetative complex for wildlife. In higher condition classes the site is most suitable to grassland wildlife species. As retrogression occurs the woody species increase and wildlife species utilizing the site may change.
Wildlife includes ground squirrel, lizards, cottontail rabbit, snakes, blacktail jackrabbit and mule deer.Recreational uses
This site is typified by Cobbly cover and sandstone breaks, usually on stream terraces or near sandstone outcropping.
It has shrubby grasslands on areas with weathered sandstone outcrops. Winters are cold, however, moderate spring, fall and summer temperatures are attractive to recreational users. Site lends itself to activities such as hunting, horseback riding, photography, hiking, rock collecting, and wildlife observation.
Supporting information
Type locality
Location 1: Apache County, AZ Township/Range/Section T40N R31E S18 General legal description Beclabito quad - 3 mi NW of Beclabito along Shoegame Wash, Navajo Indian Reservation, Arizona Contributors
HSH
Larry D. Ellicott
Steve BarkerApproval
Kendra Moseley, 5/19/2025
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 04/29/2026 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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