Natural Resources
Conservation Service
Ecological site R030XA114AZ
Sandy Loam Upland 3-6" p.z.
Last updated: 2/18/2025
Accessed: 05/10/2025
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 30-1 – Lower Mohave Desert
Elevations range from 400 to 2500 feet and precipitation averages 3 to 6 inches per year. Vegetation includes creosotebush, white bursage, Mormon tea, and brittlebush. The soil temperature regime is hyperthermic and the soil moisture regime is typic aridic.
Ecological site concept
This ecological site is located on relatively flat plains and alluvial fans. Soils are deep, non-calcareous with sandy loam to loam textures.
Table 1. Dominant plant species
| Tree |
Not specified |
|---|---|
| Shrub |
(1) Ambrosia dumosa |
| Herbaceous |
(1) Pleuraphis rigida |
Physiographic features
This site occurs in a upland position. The plant community neither benefits significantly from run-in or runoff moisture. It can occur on all exposures, and usually occurs in recent alluvium on flood plains and low terraces.
Table 2. Representative physiographic features
| Landforms |
(1)
Plain
(2) Alluvial fan |
|---|---|
| Flooding frequency | None |
| Ponding frequency | None |
| Elevation | 600 – 2,500 ft |
| Slope | 3% |
| Aspect | Aspect is not a significant factor |
Climatic features
The 30-1AZ Lower Mohave Desert Shrub land resource unit is characterized by a hot, dry climate. The average annual rainfall is 3 to 6 inches, but it can be extremely variable (e.g. from 0 to 11 inches). There can be long periods when little or no precipitation is received. Most of the precipitation for the year could arrive in just a couple of storms. The soil moisture regime is typic aridic and the soil temperature regime is hyperthermic. Winter precipitation from November through April occurs as gentle rains from storms coming out of the Pacific Ocean. Snow is very rare and only falls in the highest mountains. A seasonal drought occurs in May and June. Summer/fall precipitation from July through October comes from spotty, unreliable, and sometimes violent thunderstorms. The moisture originates in the Gulf of Mexico (and the Pacific Ocean in the fall) and flows into the state on the north end of the Mexican monsoon. Strong winds are common, especially during the spring.
Table 3. Representative climatic features
| Frost-free period (average) | 325 days |
|---|---|
| Freeze-free period (average) | 365 days |
| Precipitation total (average) | 6 in |
Figure 1. Monthly average minimum and maximum temperature
Influencing water features
Soil features
Soils are deep. Soils can absorb and hold all moisture the climate provides. Soluble salt accumulations are low; pH range is 7.9-8.4. With good vegetative cover, infiltration rates are high. Erosion is average; plant-soil moisture relationships are good. Gravel may occur throughout the soil, but is generally less than 35% of total soil volume.
Table 4. Representative soil features
| Surface texture |
(1) Gravelly fine sandy loam (2) Sandy loam |
|---|---|
| Family particle size |
(1) Loamy |
| Drainage class | Well drained |
| Permeability class | Moderately rapid to rapid |
| Soil depth | 60 in |
| Surface fragment cover <=3" | 35% |
| Surface fragment cover >3" | Not specified |
| Soil reaction (1:1 water) (0-40in) |
7.9 – 8.4 |
| Subsurface fragment volume <=3" (Depth not specified) |
35% |
| Subsurface fragment volume >3" (Depth not specified) |
Not specified |
Ecological dynamics
Sandy Loam Upland, 3"-6" p.z., ecological site is co-dominated by shrubs and perennial grasses. Trees are widely scattered. This site is favored by livestock and wildlife for it's gentle terrain and relative abundance of forage. Continuous heavy grazing will remove perennial grasses. Once introduced, non-native forbs and grasses flourish after rainfall.
This site is easily traversed by cows, calves and stocker cattle. It will be one of the first upland sites to respond to grazing management. Extra care must be taken to maintain a good vegetative cover for erosion control. Fencing and water developments are important on these areas to permit grazing management.
While this site doesn't provide all the elements for good wildlife habitat, the site is usually near the bottom sites or cultivated areas that provide feed, cover and water.
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 text
State 1 submodel, plant communities
State 2 submodel, plant communities
State 3 submodel, plant communities
State 1
Historic Climax Plant Community
Community 1.1
Historic Climax Plant Community
The plant community on this site is a mixture of desert shrubs and trees with an understory of perennial grasses. Winter and summer annual grasses are abundant in years with above average moisture in the respective season.
Figure 2. 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 | 120 | 180 | 220 |
| Shrub/Vine | 120 | 170 | 200 |
| Forb | 40 | 50 | 60 |
| Total | 280 | 400 | 480 |
Figure 3. Plant community growth curve (percent production by month). AZ3011, 30.1 3-6" p.z. all sites. Growth begins in 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 | 7 | 30 | 32 | 13 | 7 | 3 | 5 | 2 | 1 | 0 | 0 |
State 2
Historic Native Plant Community plus Introduced Annuals
Community 2.1
Non-native Annual Understory
This 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.
State 3
Desert Shrub
Community 3.1
Creosote and White Bursage
This plant community is dominated by creosote and white bursage with mixed shrubs throughout. Annual forbs and grasses flourish after wet winters. Non-native annuals are present. Remnant perennial grasses may be found within the protection of shrub bases.
Transition T1A
State 1 to 2
Wind and mechanical transport of non-native seed and propagules.
Transition T1B
State 1 to 3
Long term yearlong livestock or burro grazing. Introduction of non-native annuals.
Restoration pathway R2A
State 2 to 1
None known.
Transition T2A
State 2 to 3
Long-term, yearlong grazing by livestock or burros.
Restoration pathway R3A
State 3 to 1
None known.
Restoration pathway R3B
State 3 to 2
Prescribed grazing/no grazing. Targeted range planting if perennial grass seed source depleted.
Additional community tables
Table 6. Community 1.1 plant community composition
| Group | Common name | Symbol | Scientific name | Annual production (lb/acre) | Foliar cover (%) | |
|---|---|---|---|---|---|---|
|
Grass/Grasslike
|
||||||
| 1 | 60–120 | |||||
| big galleta | PLRI3 | Pleuraphis rigida | 60–120 | – | ||
| 2 | 20–40 | |||||
| bush muhly | MUPO2 | Muhlenbergia porteri | 20–40 | – | ||
| 3 | 20–40 | |||||
| sixweeks threeawn | ARAD | Aristida adscensionis | 0–20 | – | ||
| needle grama | BOAR | Bouteloua aristidoides | 0–20 | – | ||
| sixweeks grama | BOBA2 | Bouteloua barbata | 0–20 | – | ||
| Rothrock's grama | BORO2 | Bouteloua rothrockii | 0–20 | – | ||
| sixweeks fescue | VUOC | Vulpia octoflora | 0–20 | – | ||
| 4 | 4–20 | |||||
| Santa Rita threeawn | ARCAG | Aristida californica var. glabrata | 0–10 | – | ||
| purple threeawn | ARPU9 | Aristida purpurea | 0–10 | – | ||
| blue threeawn | ARPUN | Aristida purpurea var. nealleyi | 0–10 | – | ||
| Parish's threeawn | ARPUP5 | Aristida purpurea var. parishii | 0–10 | – | ||
|
Forb
|
||||||
| 5 | 20–40 | |||||
| pepperweed | LEPID | Lepidium | 0–20 | – | ||
| evening primrose | OENOT | Oenothera | 0–20 | – | ||
| desert Indianwheat | PLOV | Plantago ovata | 0–20 | – | ||
| Coulter's globemallow | SPCO2 | Sphaeralcea coulteri | 0–20 | – | ||
| 6 | 4–20 | |||||
| scarlet spiderling | BOCO | Boerhavia coccinea | 4–10 | – | ||
| cryptantha | CRYPT | Cryptantha | 4–10 | – | ||
| Gordon's bladderpod | LEGO | Lesquerella gordonii | 4–10 | – | ||
| desert globemallow | SPAM2 | Sphaeralcea ambigua | 4–10 | – | ||
| Emory's globemallow | SPEM | Sphaeralcea emoryi | 4–10 | – | ||
| woolly tidestromia | TILA2 | Tidestromia lanuginosa | 4–10 | – | ||
|
Shrub/Vine
|
||||||
| 7 | 20–60 | |||||
| burrobush | AMDU2 | Ambrosia dumosa | 20–60 | – | ||
| 8 | 20–40 | |||||
| button brittlebush | ENFR | Encelia frutescens | 20–40 | – | ||
| 9 | 4–20 | |||||
| creosote bush | LATR2 | Larrea tridentata | 4–20 | – | ||
| 10 | 20–40 | |||||
| whitethorn acacia | ACCO2 | Acacia constricta | 0–10 | – | ||
| catclaw acacia | ACGR | Acacia greggii | 0–10 | – | ||
| fourwing saltbush | ATCA2 | Atriplex canescens | 0–10 | – | ||
| singlewhorl burrobrush | HYMO | Hymenoclea monogyra | 0–10 | – | ||
| white ratany | KRGR | Krameria grayi | 0–10 | – | ||
| desert-thorn | LYCIU | Lycium | 0–10 | – | ||
| Mexican bladdersage | SAME | Salazaria mexicana | 0–10 | – | ||
| lotebush | ZIOB | Ziziphus obtusifolia | 0–10 | – | ||
| 11 | 4–20 | |||||
| Engelmann's hedgehog cactus | ECEN | Echinocereus engelmannii | 0–5 | – | ||
| candy barrelcactus | FEWI | Ferocactus wislizeni | 0–5 | – | ||
| ocotillo | FOSP2 | Fouquieria splendens | 0–5 | – | ||
|
Tree
|
||||||
| 12 | 0–5 | |||||
| desert ironwood | OLTE | Olneya tesota | 0–5 | – | ||
| yellow paloverde | PAMI5 | Parkinsonia microphylla | 0–5 | – | ||
Interpretations
Supporting information
Contributors
Larry D. Ellicott
Unknown
Approval
Kendra Moseley, 2/18/2025
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 | 02/20/2025 |
| Approved by | Kendra Moseley |
| 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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