Natural Resources
Conservation Service
Ecological site R030XA116AZ
Cobbly Limy Upland 3-6" p.z. Deep
Accessed: 03/28/2024
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
AZ CRA 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. 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.
Associated sites
R030XA109AZ |
Limy Upland 3-6" p.z. Deep Limy Upland, Deep, 3 to 6" P.Z. |
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Similar sites
R030XA109AZ |
Limy Upland 3-6" p.z. Deep Limy Upland, Deep, 3 to 6" P.Z. |
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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 summits and shoulders of fan terraces. The site is identifiable by the numerous stones and cobbles on the soil surface.
Table 2. Representative physiographic features
Landforms |
(1)
Fan
(2) Terrace |
---|---|
Flooding frequency | None |
Ponding frequency | None |
Elevation | 500 – 2,000 ft |
Slope | 2 – 15% |
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 2. Monthly average minimum and maximum temperature
Influencing water features
Soil features
The soil of this ecological site is deep to very deep and is very cobbly throughout the soil profile. The soil surface ranges from very cobbly sandy loam to extremely cobbly sandy loam. The subsurface textures range from very gravelly sandy loam to very gravelly sand. The soil is derived from parent material of mixed igneous and metamorphic alluvium. The available water holding capacity is low to moderate. The permeability of the soil is moderately rapid to rapid. Hazard of erosion by water: slight to moderate; wind: slight.
A typical soil profile is:
A-0 to 2 inches; extremely cobbly sandy loam
Bk-2 to 12 inches; gravelly sandy loam
Bkq-12 to 60 inches; extremely gravelly sany loam
This ecological site has been correlated to map unit 697060, Huevi very gravelly sandy loam, Mohave County, AZ, Central Part SSA.
Table 4. Representative soil features
Surface texture |
(1) Very cobbly sandy loam (2) Extremely cobbly sandy loam |
---|---|
Family particle size |
(1) Sandy |
Drainage class | Well drained |
Permeability class | Moderately rapid |
Soil depth | 60 in |
Surface fragment cover <=3" | 50 – 60% |
Surface fragment cover >3" | 65 – 95% |
Available water capacity (0-40in) |
5 – 10 in |
Calcium carbonate equivalent (0-40in) |
10 – 30% |
Electrical conductivity (0-40in) |
2 mmhos/cm |
Sodium adsorption ratio (0-40in) |
2 |
Soil reaction (1:1 water) (0-40in) |
7.9 – 8.4 |
Subsurface fragment volume <=3" (Depth not specified) |
70 – 80% |
Subsurface fragment volume >3" (Depth not specified) |
15% |
Ecological dynamics
The plant communities found on an ecological site are naturally variable. Composition and production will vary with yearly conditions, location, aspect, and the natural variability of the soils. The historical climax plant community represents the natural potential plant communities found on relict or relatively undisturbed sites. Other plant communities described here represent plant communities that are known to occur when the site is disturbed by factors such as grazing, fire, or drought.
Production data provided in this site description is standardized to air-dry weight at the end of the summer growing season. The plant communities described in this site description are based on near normal rainfall years.
NRCS uses a Similarity Index to compare existing plant communities to the plant communities described here. Similarity Index is determined by comparing the production and composition of a plant community to the production and composition of a plant community described in this site description. To determine Similarity Index, compare the production (air-dry weight) of each species to that shown in the plant community description. For each species, count no more than the maximum amount shown for the species, and for each group, count no more than the maximum shown for the group. Divide the resulting total by the total normal year production shown in the plant community description. If rainfall has been significantly above or below normal, use the total production shown for above or below normal years. If field data is not collected at the end of the summer growing season, then the field data must be corrected to the end of the year production before comparing it to the site description. The growth curve can be used as a guide for estimating production at the end of the summer growing season.
State and transition model
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Ecosystem states
State 1 submodel, plant communities
State 1
Historic Climax Plant Community
Community 1.1
Historic Climax Plant Community
The dominant aspect of this ecological site is a sparse stand of desert shrubs such as creosotebush, white brittlebush and white ratany. In years of above average annual precipitation annual grasses and forbs are abundant and showy. With severe disturbance plants that will increase include annual forbs and grasses and plants that will invade include exotic annual grasses and forbs. Change in the plant community is limited by low moisture and high temperatures. Fire is not a common occurance on this site due to the limited amount of biomass to serve as fuel generated on the site.
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 | 245 | 265 | 280 |
Forb | 52 | 72 | 88 |
Grass/Grasslike | 4 | 13 | 18 |
Total | 301 | 350 | 386 |
Table 6. Ground cover
Tree foliar cover | 0% |
---|---|
Shrub/vine/liana foliar cover | 0-2% |
Grass/grasslike foliar cover | 0% |
Forb foliar cover | 0-2% |
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 | – | – | – | 4-6% |
>0.5 <= 1 | – | – | 0-2% | – |
>1 <= 2 | – | 4-6% | – | – |
>2 <= 4.5 | – | – | – | – |
>4.5 <= 13 | – | – | – | – |
>13 <= 40 | – | – | – | – |
>40 <= 80 | – | – | – | – |
>80 <= 120 | – | – | – | – |
>120 | – | – | – | – |
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). AZ3070, 30.23 6-9" p.z. big galleta. Growth begins in the spring, 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 | 0 | 10 | 15 | 5 | 0 | 10 | 45 | 15 | 0 | 0 | 0 |
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 | 0–7 | |||||
big galleta | PLRI3 | Pleuraphis rigida | 0–7 | – | ||
2 | 4–7 | |||||
sixweeks fescue | VUOC | Vulpia octoflora | 4–7 | – | ||
3 | 4–7 | |||||
Grass, annual | 2GA | Grass, annual | 4–7 | – | ||
Forb
|
||||||
4 | 4–18 | |||||
desert Indianwheat | PLOV | Plantago ovata | 4–18 | – | ||
5 | 35–70 | |||||
Forb, annual | 2FA | Forb, annual | 35–70 | – | ||
6 | 4–7 | |||||
devil's spineflower | CHRI | Chorizanthe rigida | 4–7 | – | ||
Shrub/Vine
|
||||||
7 | 140–175 | |||||
creosote bush | LATR2 | Larrea tridentata | 140–170 | – | ||
8 | 18–35 | |||||
white ratany | KRGR | Krameria grayi | 18–35 | – | ||
9 | 35–70 | |||||
brittlebush | ENFA | Encelia farinosa | 35–70 | – | ||
10 | 0–7 | |||||
burrobush | AMDU2 | Ambrosia dumosa | 0–7 | – | ||
11 | 0–10 | |||||
Shrub, other | 2S | Shrub, other | 0–10 | – |
Interpretations
Animal community
Wildlife species common to this ecological site include lizards, snaked, burros, blacktail jackrabbit, and ants.
Supporting information
Type locality
Location 1: Mohave County, AZ | |
---|---|
Township/Range/Section | T22 N. R21 W. S32 |
General legal description | Davis Dam Quad. - 2 miles NE of Katherine; Sec. 32, T 22 N., R 21 W., Mohave County, Arizona. |
Contributors
Harmon Hodgkinson
Larry D. Ellicott
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 | |
Approved by | |
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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