Natural Resources
Conservation Service
Ecological site R030XC330AZ
Basalt Slopes
10-13" p.z.
Last updated: 2/25/2025
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.
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 30-3 – Upper Mohave Desert
Elevations range from 2800 to 4500 feet and precipitation averages 9 to 12 inches per year. Vegetation includes Joshua tree, blackbrush, creosotebush, ratany, bush muhly, big galleta, black grama, desert needlegrass, and Indian ricegrass. 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 (15%-65%) uplands. Soils are moderately deep to deep. Soil surface is armored with basalt cobble and stone.
Table 1. Dominant plant species
Tree Not specified
Shrub (1) Coleogyne ramosissima
(2) Ephedra nevadensisHerbaceous (1) Muhlenbergia porteri
(2) Pleuraphis rigidaPhysiographic features
This ecological site is found in an upland position on escarpments below basalt flows, often associated with basalt talus slopes and exposed mudstone.
Table 2. Representative physiographic features
Landforms (1) Escarpment
Flooding frequency None Ponding frequency None Elevation 2850 – 4300 ft Slope 10 – 40 % Aspect Aspect is not a significant factor Climatic features
The climate is arid and warm. Annual precipitation ranges from 10 to 13 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 46 to 76 degrees F. The average frost-free period ranges from 121 to 231 days.
Table 3 Representative climatic features
Frost-free period (average) 230 days Freeze-free period (average) 270 days Precipitation total (average) 10 in BarLineFigure 1. Monthly precipitation range
BarLineFigure 2. Monthly average minimum and maximum temperature
">Influencing water features
Soil features
The soil of this ecological site is shallow to very deep with a surface texture of very cobbly fine sandy loam. Subsoil textures are very cobbly loam, cobbly fine sandy loam, gravelly loam, gravelly sandy loam, loam and loamy sand. The soil parent material is colluvium from sedimentary and igneous formations. The geologic formation on which it is found is basalt over Moenkopi. Soil available water capacity is very low to medium. The soil's erosion hazard by water is moderate to very severe and by wind is slight. The soil is non-saline, non-sodic with pH range of 7.6-9.0 (slightly to strongly alkaline). The soil moisture regime is typic aridic and temperature regime is thermic. The soil is calcareous or gypsic throughout the profile.
A typical soil profile is:
A-0 to 2 inches; reddish brown (5YR 5/4) very cobbly fine sandy loam; 15 percent gravel, 25 percent cobbles, and 10 percent stones; slightly effervescent
Bw-2 to 12 inches; reddish brown (5YR 5/4) very cobbly loam; 15 percent gravel, 25 percent cobbles, and 10 percent stones; strongly effervescent
Bk1-12 to 26 inches; yellowish red (5YR 5/6) gravelly loam; 20 percent gravel and 5 percent cobbles; violently effervescent
Bk2-26 to 42 inches; yellowish red (5YR 5/6) gravelly6 sandy loam, 20 percent gravel and 5 percent cobbles; violently effervescent
2Cr-42 inches; mudstone and shale
The taxonomic classification is: coarse-loamy, mixed, thermic Typic Calciorthids
Table 4. Representative soil features
Surface texture (1) Very cobbly loam
(2) Cobbly fine sandy loam
(3) Gravelly loamy sand
Family particle size (1) Loamy
Drainage class Well drained Permeability class Slow to moderately rapid Soil depth 20 – 60 in Surface fragment cover <=3" 25 – 45 % Surface fragment cover >3" 20 – 50 % Available water capacity
(0-40in)1 – 3 in Calcium carbonate equivalent
(0-40in)3 – 22 % Electrical conductivity
(0-40in)2 – 4 mmhos/cm Sodium adsorption ratio
(0-40in)Not specified Soil reaction (1:1 water)
(0-40in)7.9 – 8.4 Subsurface fragment volume <=3"
(Depth not specified)25 – 45 % Subsurface fragment volume >3"
(Depth not specified)20 – 50 % Ecological dynamics
Basalt Slopes, 10"-13" p.z., is a shrub dominated ecological site. Sparse 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), they flourish following wet winters. Dominant shrubs are flattop buckwheat, 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 desert shrub-perennial grass. Major grasses are bush muhly and big galleta. Major shrubs are blackbrush, Nevada mormon tea and creosotebush.
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)Shrub/Vine 165 245 319 Grass/Grasslike 109 175 240 Forb 18 35 54 Tree 8 20 37 Total 300 475 650 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 – – – – >0.5 <= 1 – – 1-3% – >1 <= 2 – – – – >2 <= 4.5 – 5-7% – – >4.5 <= 13 0-2% – – – >13 <= 40 – – – – >40 <= 80 – – – – >80 <= 120 – – – – >120 – – – – Figure 4. Plant community growth curve (percent production by month). AZ3024 , 30.3 10-13" p.z. upland 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 8 18 18 11 14 20 8 2 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 wild oat, 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.
Additional community tables
Table 8. Community 1.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Grass/Grasslike1 24–71 bush muhly MUPO2 Muhlenbergia porteri 24–71 – 2 24–48 big galleta PLRI3 Pleuraphis rigida 24–48 – 3 10–48 threeawn ARIST Aristida 10–48 – 4 10–19 desert needlegrass ACSP12 Achnatherum speciosum 10–19 – 5 6–14 sand dropseed SPCR Sporobolus cryptandrus 0–14 – mesa dropseed SPFL2 Sporobolus flexuosus 0–14 – 6 0–10 Indian ricegrass ACHY Achnatherum hymenoides 0–10 – 7 0–10 slim tridens TRMU Tridens muticus 0–10 – 8 0–10 low woollygrass DAPU7 Dasyochloa pulchella 0–10 – 9 5–14 Grass, annual 2GA Grass, annual 0–14 – sixweeks fescue VUOC Vulpia octoflora 0–14 – Forb10 5–24 desert trumpet ERIN4 Eriogonum inflatum 5–24 – desert globemallow SPAM2 Sphaeralcea ambigua 5–24 – 11 5–24 Forb, perennial 2FP Forb, perennial 0–14 – winding mariposa lily CAFL Calochortus flexuosus 0–14 – bluedicks DICA14 Dichelostemma capitatum 0–14 – princesplume STANL Stanleya 0–14 – 12 5–14 Forb, annual 2FA Forb, annual 0–14 – Shrub/Vine13 24–71 blackbrush CORA Coleogyne ramosissima 24–71 – 14 14–48 Nevada jointfir EPNE Ephedra nevadensis 14–48 – 15 5–24 creosote bush LATR2 Larrea tridentata 5–24 – 16 5–24 button brittlebush ENFR Encelia frutescens 5–24 – 17 5–14 rayless goldenhead ACSP Acamptopappus sphaerocephalus 5–14 – 18 5–14 water jacket LYAN Lycium andersonii 5–14 – 19 0–24 littleleaf ratany KRER Krameria erecta 0–24 – white ratany KRGR Krameria grayi 0–24 – 20 57–119 Shrub, other 2S Shrub, other 0–40 – broom snakeweed GUSA2 Gutierrezia sarothrae 0–40 – burrobrush HYSA Hymenoclea salsola 0–40 – winterfat KRLA2 Krascheninnikovia lanata 0–40 – Fremont's dalea PSFR Psorothamnus fremontii 0–40 – banana yucca YUBA Yucca baccata 0–40 – Tree21 10–33 Joshua tree YUBR Yucca brevifolia 10–33 – Table 9. Community 2.1 plant community composition
Group Common name Symbol Scientific name Annual production () Foliar cover (%) Interpretations
Animal community
Wildlife found on this ecological site include jackrabbit, coyote, desert cottontail, pocket gopher, antelope squirrel, kangaroo rat, gambel quail, raven, gopher snake, Mohave rattlesnake, western rattlesnake and pocket mouse.
Supporting information
Type locality
Location 1: Mohave County, AZ Township/Range/Section T35N R16W S1 General legal description Pakoon Springs Quad. about 3 miles north of Pakoon Springs Ranch. Contributors
Larry D. Ellicott
Stephen Cassady
Steve BarkerApproval
Sarah Quistberg, 2/25/2025
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 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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