Natural Resources
Conservation Service
Ecological site R030XA104AZ
Granitic Hills 3-6" p.z.
Last updated: 10/21/2024
Accessed: 11/21/2024
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.
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 30-1 – 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 steep slopes. Soils are non-calcareous, very shallow to shallow over hard granite or gneiss bedrock. Soil textures range from gravelly sandy loam to extremely gravelly sandy loam.
Table 1. Dominant plant species
| Tree |
Not specified |
|---|---|
| Shrub |
(1) Encelia farinosa |
| Herbaceous |
Not specified |
Physiographic features
This ecological site occurs as moderately steep to steep granitic hills and mountains. It occurs on all aspects.
Table 2. Representative physiographic features
| Landforms |
(1)
Hill
(2) Mountain |
|---|---|
| Flooding frequency | None |
| Ponding frequency | None |
| Elevation | 152 – 914 m |
| Slope | 20 – 65% |
| 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) | 152 mm |
Figure 2. Monthly average minimum and maximum temperature
Influencing water features
Soil features
Soils are very shallow to shallow. Textures are extremely gravelly sandy loam to very cobbly sandy loam with subsoil textures that are very gravelly sandy loam to extremely gravelly sandy loam. Parent material is granitic alluvium with a geological formation of granite. Available water capacity is very low; permeability is moderately rapid. Water erosion hazard is severe; wind erosion hazard is slight. Runoff is very rapid. Soils are non-saline, non-sodic with pH range of 8.0-8.2 (moderately alkaline). Soil mositure regime is typic aridic; temperature regime is hyperthermic. Landform and position are backslopes, shoulders and summits of hills and mountains. Rock outcrop is associated with this site. Depth to hard granite or gneiss ranges from 4 to 20inches.
A typical soil profile is:
A-0 to 2 inches; extremely gravelly sandy loam
Bw-2 to 13 inches; very gravelly sandy loam
2R-13 inches; unweathered bedrock
This ecological site is correlated to map unit 627048, Goldroad Soil Series, in the Mohave County, AZ, Southern Part SSAand map unit 701103, Lithic Torriorthents, in the Grand Canyon Area, AZ, Parts of Coconino and Mohave County SSA.
Table 4. Representative soil features
| Parent material |
(1)
Alluvium
–
granite
|
|---|---|
| Surface texture |
(1) Very gravelly sandy loam (2) Very cobbly |
| Family particle size |
(1) Loamy |
| Permeability class | Moderate to moderately rapid |
| Soil depth | 10 – 51 cm |
| Surface fragment cover <=3" | 25% |
| Surface fragment cover >3" | 30% |
| Available water capacity (0-101.6cm) |
1.27 – 2.54 cm |
| Calcium carbonate equivalent (0-101.6cm) |
1 – 10% |
| Electrical conductivity (0-101.6cm) |
0 – 2 mmhos/cm |
| Sodium adsorption ratio (0-101.6cm) |
0 |
| Soil reaction (1:1 water) (0-101.6cm) |
7.4 – 8.4 |
| Subsurface fragment volume <=3" (Depth not specified) |
25% |
| Subsurface fragment volume >3" (Depth not specified) |
30% |
Ecological dynamics
The plant community on this site is shrub dominated with a very sparse understory of perennial grasses and perennial forbs. Limited natural disturbance occurs on this site. Steep slopes, rugged terrain, and limited available forage restrict livestock impacts on this site. Annual forbs flourish in springs, particularly following wet winters. The green forage produced during annual forb growth is desired by livestock but this ecological site is largely unused once annuals mature. Non-native annuals are well adapted on this site.
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 the site is a sparse desert-shrub cover with annual grasses and forbs intermixed. Creosotebush, white brittlebush and white bursage are the major shrubs. This site is ephemeral range (annual grasses and forbs with green and growing) for livestock grazing. Because of steep rocky slopes, domestic livestock use is very difficult to achieve.
Figure 3. Annual production by plant type (representative values) or group (midpoint values)
Table 5. Annual production by plant type
| Plant type | Low (kg/hectare) |
Representative value (kg/hectare) |
High (kg/hectare) |
|---|---|---|---|
| Shrub/Vine | 182 | 196 | 211 |
| Grass/Grasslike | 43 | 35 | 56 |
| Forb | 28 | 49 | 43 |
| Total | 253 | 280 | 310 |
Figure 4. 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 |
Figure 5. Plant community growth curve (percent production by month). AZ3082, 30.27 3-6" p.z. creosotebush. Growth occurs mostly in the spring using stored winter moisture. Flowers and sets seed by July..
| 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 | 20 | 40 | 20 | 20 | 0 | 0 | 0 | 0 | 0 | 0 |
Figure 6. Plant community growth curve (percent production by month). AZ3083, 30.27 3-6" p.z. white bursage. Growth begins in early spring. Dormancy occurs during the hot summer months. With sufficient summer/fall precipitation, some plants may break dormancy and produce a flush of growth. Flowers and sets seed by July..
| 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 | 5 | 20 | 40 | 20 | 15 | 0 | 0 | 0 | 0 | 0 | 0 |
Figure 7. Plant community growth curve (percent production by month). AZ3084, 30.27 3-6" p.z. white brittlebush. Growth begins in the late winter and continues through mid spring, goes dormant during the summer heat. Flowers and sets seed by July..
| 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 | 5 | 30 | 45 | 20 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Figure 8. Plant community growth curve (percent production by month). AZ3086, 30.27 3-6" p.z. big galleta. Growth begins in the late winter and early spring, goes dormant in May through June, most growth occurs during the summer rainy season..
| 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 | 10 | 20 | 10 | 0 | 0 | 15 | 40 | 5 | 0 | 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 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 and grass seed.
Restoration pathway R2A
State 2 to 1
None known
Additional community tables
Table 6. Community 1.1 plant community composition
| Group | Common name | Symbol | Scientific name | Annual production (kg/hectare) | Foliar cover (%) | |
|---|---|---|---|---|---|---|
|
Grass/Grasslike
|
||||||
| 1 | 0–9 | |||||
| Parish's threeawn | ARPUP5 | Aristida purpurea var. parishii | 0–9 | – | ||
| 2 | 2–13 | |||||
| big galleta | PLRI3 | Pleuraphis rigida | 2–13 | – | ||
| 3 | 0–6 | |||||
| bush muhly | MUPO2 | Muhlenbergia porteri | 0–6 | – | ||
| 4 | 0–6 | |||||
| black grama | BOER4 | Bouteloua eriopoda | 0–6 | – | ||
| 5 | 0–6 | |||||
| sixweeks fescue | VUOC | Vulpia octoflora | 0–6 | – | ||
| 6 | 2–6 | |||||
| sixweeks grama | BOBA2 | Bouteloua barbata | 2–6 | – | ||
| 7 | 2–13 | |||||
| Grass, annual | 2GA | Grass, annual | 2–13 | – | ||
|
Forb
|
||||||
| 8 | 2–13 | |||||
| desert globemallow | SPAM2 | Sphaeralcea ambigua | 2–13 | – | ||
| 9 | 2–9 | |||||
| desert Indianwheat | PLOV | Plantago ovata | 2–9 | – | ||
| 10 | 2–13 | |||||
| Forb, perennial | 2FP | Forb, perennial | 2–13 | – | ||
| 11 | 2–13 | |||||
| Forb, annual | 2FA | Forb, annual | 2–13 | – | ||
|
Shrub/Vine
|
||||||
| 12 | 43–56 | |||||
| brittlebush | ENFA | Encelia farinosa | 43–56 | – | ||
| 13 | 56–84 | |||||
| creosote bush | LATR2 | Larrea tridentata | 56–84 | – | ||
| 14 | 43–56 | |||||
| burrobush | AMDU2 | Ambrosia dumosa | 43–56 | – | ||
| 15 | 0–9 | |||||
| Nevada jointfir | EPNE | Ephedra nevadensis | 0–9 | – | ||
| 16 | 0–6 | |||||
| white ratany | KRGR | Krameria grayi | 0–6 | – | ||
| 17 | 0–6 | |||||
| sweetbush | BEJU | Bebbia juncea | 0–6 | – | ||
| 18 | 0–2 | |||||
| 19 | 2–13 | |||||
| Shrub, other | 2S | Shrub, other | 2–13 | – | ||
Interpretations
Supporting information
Contributors
Harmon Hodgkinson
Larry D. Ellicott
Approval
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 | 11/21/2024 |
| 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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