Natural Resources
Conservation Service
Ecological site R030XB202AZ
Basalt Hills
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 ecological site is located on steeply sloping uplands (slopes 15%-65%). Soils are shallow to dark colored basalt bedrock. Dark colored basalt cobbles and gravels armor the soil surface.
Associated sites
R030XB214AZ Limy Upland 6-9" p.z.
Similar sites
R030XB201AZ Andesite Hills 6-9" p.z. Coarse
This ecological site occurs on andesite bedrock.
R030XA101AZ Basalt Hills 3-6" p.z.
This ecological site occurs at lower elevation, higher temperature and lower precipitation.
Table 1. Dominant plant species
Tree Not specified
Shrub (1) Larrea tridentata
Herbaceous Not specified
Physiographic features
This ecological site occurs in an upland position on basalt hills and mountains in associaton with basalt outcrop. It occurs on all aspects.
Table 2. Representative physiographic features
Landforms (1) Hill
(2) Mountain
Flooding frequency None Ponding frequency None Elevation 2000 – 4200 ft Slope 15 – 70 % 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 shallow and is underlaid by basalt bedrock. The soil surface is often covered with basalt stones, cobbles and gravels. The available water capacity of the soil is very low. The soil hazard to wind erosion is slight; water erosion is moderate to severe. Runoff from the site is slow. The soil is non-sodic, non-saline with a pH od 7.4 to 8.4. The moisture regime of the soil is typic aridic and temperature regime is thermic.
A typical soil profile is:
A-0 to 2 inches; extremely cobbly loam
Bk-2 to 15 inches; extremely gravely loam
2R-15 inches; unweathered bedrock
The taxonomic classification of the soil is Loamy-skeletal, mixed, superactive, calcareous, thermic Lithic Torriorthents.
Soils correlated to this ecological site include map units 627092, 627094, 627096, 627104 Razorback soil, Mohave County, AZ, Southern Part SSA.Table 4. Representative soil features
Surface texture (1) Extremely gravelly loam
(2) Extremely stony loam
(3) Extremely cobbly loam
Family particle size (1) Loamy
Drainage class Somewhat excessively drained Permeability class Moderate Soil depth 10 – 20 in Surface fragment cover <=3" 45 – 55 % Surface fragment cover >3" 65 – 75 % Available water capacity
(0-40in)6 – 1 in Calcium carbonate equivalent
(0-40in)2 – 10 % Electrical conductivity
(0-40in)Not specified Sodium adsorption ratio
(0-40in)Not specified Soil reaction (1:1 water)
(0-40in)7.4 – 8.4 Subsurface fragment volume <=3"
(Depth not specified)70 – 80 % Subsurface fragment volume >3"
(Depth not specified)0 – 5 % Ecological dynamics
Basalt Hills, 6"-9" p.z., is a shrub dominated ecological site. Perennial grasses and forbs are occasionally encountered. 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, brittlebush 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 site is a desert shrub with grasses and forbs. Creosotebush is the major shrub. Other shrubs include white bursage, bush encelia, Nevada Mormon tea, range ratany and flattop buckwheat. Big galleta is present in minor amounts. Access by large animals to most of this site is difficult because of loose rock material on the surface and steep slopes.
Grass and grasslike plants make up 10 to 15 percent of the plant community, forbs 10 to 20 percent and shrubs 65 to 75 percent.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)Shrub/Vine 57 145 341 Forb 9 30 91 Grass/Grasslike 9 25 68 Total 75 200 500 Table 6. Ground cover
Tree foliar cover 0% Shrub/vine/liana foliar cover 0-0% Grass/grasslike foliar cover 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 – – – 1-3% >0.5 <= 1 – – 1-3% – >1 <= 2 – 4-6% – – >2 <= 4.5 – – – – >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 Figure 6. Plant community growth curve (percent production by month). AZ3074 , 30.23, 6-9 p.z., Nevada Mormon Tea. Growth primarily in spring and early summer months..
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 15 25 20 15 15 10 0 0 0 0 State 2
Historic Native Plant Community plus Introduced AnnualsCommunity 2.1
Non-native AnnualsThis plant community resembles the historic native plant community, but exotic annuals have been introduced. Non-native species include red brome, Mediterranean grass (Schismus spp.), and filaree. The flourish of non-native annuals that occurs following rainfalls may preclude native annuals.
Transition T1A
State 1 to 2Introduction of non-native annual forb and grass seed.
Restoration pathway R2A
State 2 to 1None known
Additional community tables
Table 8. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 2–10 big galleta PLRI3 Pleuraphis rigida 2–10 – 2 2–10 desert needlegrass ACSP12 Achnatherum speciosum 2–10 – 3 10–20 Grass, annual 2GA Grass, annual 10–20 – 4 0–6 Grass, perennial 2GP Grass, perennial 0–6 – Forb5 0–4 desert globemallow SPAM2 Sphaeralcea ambigua 0–4 – 6 10–30 Forb, annual 2FA Forb, annual 10–30 – 7 2–10 Forb, perennial 2FP Forb, perennial 2–10 – Shrub/Vine8 60–80 creosote bush LATR2 Larrea tridentata 60–80 – 9 2–10 burrobush AMDU2 Ambrosia dumosa 2–10 – 10 2–10 button brittlebush ENFR Encelia frutescens 2–10 – 11 0–10 brittlebush ENFA Encelia farinosa 49–81 – 12 2–10 Nevada jointfir EPNE Ephedra nevadensis 2–10 – 13 2–10 littleleaf ratany KRER Krameria erecta 2–10 – 14 0–10 blackbrush CORA Coleogyne ramosissima 0–10 – 15 2–10 Eastern Mojave buckwheat ERFAP Eriogonum fasciculatum var. polifolium 2–10 – 16 2–4 water jacket LYAN Lycium andersonii 2–4 – 17 0–2 18 2–10 Shrub, other 2S Shrub, other 2–10 – 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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