Natural Resources
Conservation Service
Ecological site R030XC330AZ
Basalt Slopes 10-13" p.z.
Last updated: 2/25/2025
Accessed: 05/11/2025
General information
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 |
| Herbaceous |
(1) Muhlenbergia porteri |
Physiographic 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 | 2,850 – 4,300 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) | 231 days |
|---|---|
| Freeze-free period (average) | 269 days |
| Precipitation total (average) | 13 in |
Figure 1. Monthly precipitation range
Figure 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
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State 1 submodel, plant communities
State 2 submodel, plant communities
State 1
Historic Climax Plant Community
Community 1.1
Historic Climax Plant Community
The 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 | 1-3% |
| Grass/grasslike foliar cover | 0-2% |
| 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/ Grasslike |
Forb |
|---|---|---|---|---|
| <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 Annuals
Community 2.1
Non-native Annuals
This 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 2
Introduction 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 (lb/acre) | Foliar cover (%) | |
|---|---|---|---|---|---|---|
|
Grass/Grasslike
|
||||||
| 1 | 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 | – | ||
|
Forb
|
||||||
| 10 | 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/Vine
|
||||||
| 13 | 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 | – | ||
|
Tree
|
||||||
| 21 | 10–33 | |||||
| Joshua tree | YUBR | Yucca brevifolia | 10–33 | – | ||
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 Barker
Approval
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 | 02/26/2025 |
| Approved by | Sarah Quistberg |
| Approval date | |
| Composition (Indicators 10 and 12) based on | Annual Production |
Indicators
-
Number and extent of rills:
-
Presence of water flow patterns:
-
Number and height of erosional pedestals or terracettes:
-
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
-
Number of gullies and erosion associated with gullies:
-
Extent of wind scoured, blowouts and/or depositional areas:
-
Amount of litter movement (describe size and distance expected to travel):
-
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
-
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
-
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
-
Presence and thickness of compaction layer (usually none; describe soil profile features which may be mistaken for compaction on this site):
-
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:
-
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
-
Average percent litter cover (%) and depth ( in):
-
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
-
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:
-
Perennial plant reproductive capability:
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