

Natural Resources
Conservation Service
Ecological site R030XB009CA
Loamy Cool Aridic Fans 6-8
Last updated: 2/18/2025
Accessed: 03/16/2025
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
MLRA Description:
Major Land Resource Area (MLRA) 30, Mojave Desert, is found in southern California, southern Nevada, the extreme southwest corner of Utah and northwestern Arizona within the Basin and Range Province of the Intermontane Plateaus. The climate of the area is hot and dry with mostly hyperthermic and thermic soil temperature regimes and typic-aridic soil moisture regimes. Mean annual air temperatures are between 59-68 degrees F (15-20 C) with average summer maximum temperatures between 100-115 degrees F (38-46 C) and average winter minimum temperatures between 32-59 degrees F (0-15 C). This MLRA is within the arid climate zone however steep elevational gradients contribute to microclimates where semi-arid [mean annual precipitation is greater than 8 inches (200mm)] and hyper-arid [mean annual precipitation is less than 4 inches (100mm)] islands exist. Elevations range from below sea level to over 12,000 feet (3650 meters) in the higher mountain areas. Generally above 5,000 feet, soil temperature regimes can be mesic, cryic and frigid with soil moisture regimes being xeric or ustic. Orographic effects and low elevations can create hyper-arid conditions where the soil moisture regime is aridic-aridic. Due to the extreme elevational range found within this MLRA, land resource units (LRUs) were designated to group areas within the MLRA into similar land units.
LRU Description:
The arid climate zone (XB in ESD ID) LRU is found across the eastern half of California, much of the mid-elevations of Nevada, the southernmost portions of western Utah, and the mid-elevations of northwestern Arizona. Elevations range from 1800-5000 feet and precipitation ranges from 4-8 inches/year. Precipitation is bi-modal for most of the Mojave with precipitation occurring in winter and summer. Areas west of the 117 degree W meridian near Barstow, CA receive precipitation mainly during the winter months (Hereford et al. 2004). The soil temperature regimes are hyperthermic and thermic with a typic-aridic soil moisture regime. Vegetation includes creosote bush (Larrea tridentata), burrobush (Ambrosia dumosa), Mojave yucca (Yucca schidigera) Joshua tree (Yucca brevifolia), chollas, cactus, big galleta grass (Pleuraphis rigida) and several other warm season grasses. At the upper portions of the LRU, where the mean annual precipitation is between 6 to 8 inches (150-200 mm), plant production and diversity are greater and blackbrush (Coleogyne ramosissima) is a common dominant shrub.
Classification relationships
Class - 3 Xeromorphic Woodland, Scrub & Herb Vegetation Class
Subclass - 3.B Cool Semi-Desert Scrub & Grassland Subclass
Formation - 3.B.1 Cool Semi-Desert Scrub & Grassland Formation
Division - 3.B.1.Ne Western North American Cool Semi-Desert Scrub & Grassland Division
Macrogroup - 3.B.1.Ne.1 Chrysothamnus viscidiflorus - Coleogyne ramosissima / Achnatherum hymenoides Great Basin & Intermountain Dry Shrubland & Grassland Macrogroup
Group - 3.B.1.Ne.1.a Yucca brevifolia - Eriogonum fasciculatum - Ephedra fasciculata Mixed Desert Scrub Group
Alliance - 3.B.1.Ne.1.a Coleogyne ramosissima Mojave Desert Shrubland Alliance
(Schulz 2014)
Ecological site concept
This ecological site is linked to group concept R030XB188CA.
This ecological site occurs on fan remnants within the lower fan piedmont. Soils have a typic-aridic soil moisture regime, and a cool thermic soil temperature regime. Soils are moderately deep to very deep, with a fine-loamy particle size control section. The upper boundary of an argillic or calcic horizon is present within the top 25cm of the soil profile. In rare instances a root restrictive horizon such as a duripan or petrocalcic horizon may be present. The representative plant community is dominated by blackbrush (Coleogyne ramosissima). Creosote bush (Larrea tridentate) and Mojave yucca (Yucca schidigera)are subdominants. Joshua Tree (Yucca brevifolia var. jaegeriana) is often an emergent canopy species at 0 to 3 percent cover.
Associated sites
R030XC047CA |
Bi-Modal Semi-Arid Order 3 Ephemeral Wash Occurs in stream order 3 size washes which drain the semi-arid zones (greater than 8 inches of mean annual precipitation). |
---|---|
R030XB039NV |
LIMY FAN 5-7 P.Z. Occurs on nearby alluvial fans with moderately deep or deeper soils [soil profile depth is greater than 40 inches (100 cm)] with no shallow diagnostic horizons. |
R030XB172CA |
Warm Gravelly Shallow Hills Occurs on nearby warm hills with a thermic and/or hyperthermic soil temperature regime. Mean annual air temperature is generally greater than 17 degrees C. |
Similar sites
R030XB173CA |
Coarse Loamy Very Deep Fan Remnants The same ecological site concept. Plant Community Phase 2.4. |
---|---|
R030XB043NV |
CLAYPAN 5-7 P.Z. The same ecological site concept. Plant Community Phase 3.2. |
R030XB137CA |
Granitic Loam This ecological site occurs at lower elevations, has lower production, and is co-dominated by white bursage. |
R030XB107NV |
COARSE GRAVELLY LOAM 5-7 P.Z. The same ecological site concept. Plant Community Phase 2.4. |
R030XB039NV |
LIMY FAN 5-7 P.Z. This ecological site has higher production and a greater diversity of native perennial grasses. |
R030XB143CA |
Shallow Granitic Loam 5-7" P.Z. The same ecological site concept. Plant Community Phase 2.2. |
R030XB183CA |
Loamy Very Deep Fan Remnants The same ecological site concept. Plant Community Phase 2.3. |
Table 1. Dominant plant species
Tree |
Not specified |
---|---|
Shrub |
(1) Coleogyne ramosissima |
Herbaceous |
Not specified |
Click on box and path labels to scroll to the respective text.