Natural Resources
Conservation Service
Ecological site R030XB231AZ
Loamy Wash
6-9" p.z.
Last updated: 10/21/2024
Accessed: 08/11/2026
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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): 030X–Mojave Basin and Range
This unit occurs within the Basin and Range Province and is characterized by broad basins, valleys, and old lakebeds. Widely spaced mountains trending north to south occur throughout the area. Isolated, short mountain ranges are separated by an aggraded desert plain. The mountains are fault blocks that have been tilted up. Long alluvial fans coalesce with dry lakebeds between some of the ranges.
LRU notes
AZ LRU 30-2 – Middle Mohave Desert
Elevations range from 1500 to 3200 feet and precipitation averages 6 to 9 inches per year. Vegetation includes creosotebush, white bursage, yucca, prickly pear and cholla species, Mormon tea, flattop buckwheat, ratany, winterfat, bush muhly, threeawns, and big galleta. The soil temperature regime is thermic and the soil moisture regime is typic aridic.Ecological site concept
This site is located in bottoms. Soils are deep loams.
Associated sites
R030XB205AZ Sandy Loam Upland 6-10" p.z. Limy Subsurface, Gravelly
R030XB229AZ Loamy Swale 6-9" p.z. Sodic
Table 1. Dominant plant species
Tree Not specified
Shrub (1) Atriplex canescens
Herbaceous (1) Pleuraphis rigida
(2) Sporobolus airoidesPhysiographic features
This ecological site is found in a bottom position in stream channels and low stream terraces of floodplains. It receives additional run-in moisture from surrounding ecological sites.
Table 2. Representative physiographic features
Landforms (1) Flood plain
(2) Channel
(3) Terrace
Flooding duration Very brief (4 to 48 hours) to brief (2 to 7 days) Flooding frequency Frequent Ponding duration Very brief (4 to 48 hours) to brief (2 to 7 days) Ponding frequency Rare to occasional Elevation 2800 – 4200 ft Slope 0 – 3 % Aspect Aspect is not a significant factor Climatic features
The climate is arid and warm. Annual precipitation ranges from 6 to 9 inches. About 65 percent of the rainfall comes from October through May as gentle rain from Pacific storms which may last for a couple of days. The rest of the rainfall comes during the summer monsoon season from July through September as spotty, brief, intense thunderstorms. Snow rarely falls, and only remains on the ground a few hours at most. Annual air temperature ranges from 59 to 70 degrees F. The average frost-free period ranges from 156 to 259 days.
Table 3 Representative climatic features
Frost-free period (average) 260 days Freeze-free period (average) 290 days Precipitation total (average) 10 in BarLineFigure 2. Monthly precipitation range
BarLineFigure 3. Monthly average minimum and maximum temperature
">Influencing water features
Soil features
The soil of this ecological site is deep to very deep with very fine sandy loam, loamy fine sand, silty clay loam or silt loam surface textures. Subsoil textures are fine sand, very fine sandy loam, fine sandy loam, silt loam, loamy fine sand and silty clay.
The soil's parent material is stratified alluvium from sedimentary rocks of varied geologic formation. The available water capacity is low to high. The soil's erosion hazard by water is slight to severe and by wind is slight to very high.
The soil is non-saline, non-sodic with pH range of 7.9-8.6. The soil moisture regime is typic aridic and temperature regime is thermic.
A typical soil profile is:
A-0 to 4 inches; silty clay loam
C-4 to 16 inches; silty clay loam
Dn1-16 to 23 inches; silty clay loam
Cn2-23 to 44 inches; silt loam
C'-44 to 60 inches; sandy clay loam
This ecological site has been correlated to map units 697119 and 697120, Rift soil, Mohave County, AZ, Central Part SSA.Table 4. Representative soil features
Surface texture (1) Fine sandy loam
(2) Fine sand
(3) Sandy clay loam
Family particle size (1) Clayey
Drainage class Well drained Permeability class Slow to moderately rapid Soil depth 60 – 0 in Surface fragment cover <=3" 0 – 5 % Surface fragment cover >3" Not specified Available water capacity
(0-40in)11.5 – 12.5 in Calcium carbonate equivalent
(0-40in)1 – 10 % Electrical conductivity
(0-40in)0 – 10 mmhos/cm Sodium adsorption ratio
(0-40in)0 – 30 Soil reaction (1:1 water)
(0-40in)7.9 – 9 Subsurface fragment volume <=3"
(Depth not specified)0 – 5 % Subsurface fragment volume >3"
(Depth not specified)Not specified Ecological dynamics
Loamy Wash, 6"-9" p.z., is a shrub-grassland. Annual forbs and grasses flourish following rainfall. Natural disturbances are rare. After introduction of non-native annuals (forbs and/or grasses), the shift in total productivity is shift increased seasonal herbaceous production following periods of rain. Dominant shrubs are creosote and white bursage. Assorted half-shrubs are widely scattered.
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
Historic Climax Plant CommunityCommunity 1.1
Historic Climax Plant CommunityThe dominant aspect of this plant community is a grass-shrub mix. Major grasses are big galleta, alkali sacaton and bush muhly. Dominant shrubs are fourwing saltbush, shadscale and Anderson wolfberry.
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 176 335 709 Shrub/Vine 106 215 473 Forb 18 50 118 Total 300 600 1300 Table 6. Ground cover
Tree foliar cover 0% Shrub/vine/liana foliar cover 0-0% Grass/grasslike foliar cover 0-0% Forb foliar cover 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 – – – 0-2% >0.5 <= 1 – – 9-11% – >1 <= 2 – – – – >2 <= 4.5 – 13-17% – – >4.5 <= 13 – – – – >13 <= 40 – – – – >40 <= 80 – – – – >80 <= 120 – – – – >120 – – – – Figure 5. Plant community growth curve (percent production by month). AZ3022 , 30.2 6-9" p.z. upland sites. Growth begins in the late winter, most growth occurs in the spring..
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 2 19 33 18 7 7 11 3 0 0 0 State 2
Historic Native Plant Community plus Introduced AnnualsCommunity 2.1
Non-Native AnnualsNon-native annual grasses and forbs like; red brome, cheatgrass, kochia, tumble pigweed, russian thistle, tumble mustard, yellow starthistle, wild oats and filaree, can invade and dominate areas of the site with very low tobosa cover. Perennial forbs like russian knapweed and leafy spurge could invade and, perhaps, dominate this site. These species can, over time, reduce the seed-bank of native annual grasses and forbs.
Transition T1A
State 1 to 2Introduction of non-native annual forb and grass seed.
Additional community tables
Table 8. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 60–90 big galleta PLRI3 Pleuraphis rigida 60–90 – 2 90–120 alkali sacaton SPAI Sporobolus airoides 90–120 – 3 6–30 sand dropseed SPCR Sporobolus cryptandrus 6–30 – 4 30–60 bush muhly MUPO2 Muhlenbergia porteri 30–60 – 5 6–30 Indian ricegrass ACHY Achnatherum hymenoides 6–30 – 6 0–12 beautiful rockcress ARPUP Arabis pulchra var. pallens 0–12 – 7 0–6 sixweeks fescue VUOC Vulpia octoflora 0–6 – 8 6–30 Grass, perennial 2GP Grass, perennial 6–30 – Forb9 6–12 desert globemallow SPAM2 Sphaeralcea ambigua 6–12 – 10 6–24 Forb, perennial 2FP Forb, perennial 6–24 – 11 6–24 Forb, annual 2FA Forb, annual 6–24 – Shrub/Vine12 60–120 fourwing saltbush ATCA2 Atriplex canescens 60–120 – 13 6–30 water jacket LYAN Lycium andersonii 6–30 – 14 0–18 western honey mesquite PRGLT Prosopis glandulosa var. torreyana 0–18 – 15 6–30 shadscale saltbush ATCO Atriplex confertifolia 6–30 – 16 6–18 catclaw acacia ACGR Acacia greggii 6–18 – 17 6–30 Shrub, other 2S Shrub, other 6–30 – Table 9. Community 2.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Interpretations
Supporting information
Contributors
Harmon Hodgkinson
Harmon S. Hodgkinson
Larry D. Ellicott
Stephen CassadyApproval
Kendra Moseley, 10/21/2024
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 08/11/2026 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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