Natural Resources
Conservation Service
Ecological site R030XD041CA
Channeled Warm Alluvial Fans
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
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 (primarily hyperthermic and thermic; however at higher elevations, generally above 5000 feet, mesic, cryic and frigid) and dry (aridic). Elevations range from below sea level to over 12,000 feet in the higher mountain areas found within the MLRA. Due to the extreme elevational range found within this MLRA, Land Resource Units (LRUs) were designated to group the MLRA into similar land units.
LRU notes
This Land Resource Unit (designated by ‘XD’) is found on the eastern side of California. Elevations range from 400 to 2200 feet on average, but may be found up to 3600 feet on southern exposures. Precipitation ranges from 1 to 6 inches per year, but averages between 2-4 inches. This LRU is characterized primarily by the extreme aridity, hot temperatures, hyperthermic soil temperatures and low stature of widely spaced vegetation. Temperatures can reach over 110 degrees Fahrenheit for several weeks in July and August. Summer precipitation falls between July and September, ranging from 20-33% in the form of rain, and winter precipitation falls starting in November and ends between February and March, ranging from 56-70%, also mostly in the form of rain. Vegetation is primarily small, widely-spaced, low-producing creosote bush (Larrea tridentata), burrobush (Ambrosia dumosa), and brittlebush (Encelia farinosa).
Classification relationships
Mojave Creosote Bush (Holland 1986).
Larrea tridentata Shrubland Alliance (Sawyer et al. 2009).
Ecological site concept
This ecological site occurs on gently sloping channeled fan aprons and fan remnants, typically on the upper portion of the fan piedmont, at elevations of 950 to 2390 feet. Soils are typically very deep with sandy textures. This site typically has a rare surface flooding regime, but may have none to occasional flooding.
Production reference value (RV) is 242 pounds per acre, and ranges from 160 to 390 pounds per acre depending on annual precipitation and annual forb production. The site is dominated by creosote bush (Larrea tridentata), and burrobush (Ambrosia dumosa) and brittlebush (Encelia farinosa) are important secondary species. A hyperthermic climate, landform positions near the base of mountains, a channeled alluvial topography with additional run-on from the adjacent mountains, and a rare to occasional surface flooding regime drives the vegetation community of this ecological site. This site is more productive and diverse than landforms at the same elevation with less additional moisture.
Data in the following sections is based on Pintobasin components (all minor) associated with this ecological site.
Associated sites
R030XD004CA |
Low-Production Hyperthermic Hills This ecological site occurs on steep sideslopes of fan remnants. Sparse vegetation is dominated by creosote bush (Larrea tridentata). |
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R030XD015CA |
Hyper-Arid Fans This ecological site occurs on adjacent fan aprons receiving less additional moisture. Creosote bush (Larrea tridentata) and burrobush (Ambrosia dumosa) dominate. |
R030XD025CA |
Hyperthermic Sandsheets This ecological site is found on adjacent sandsheets. Creosote bush (Larrea tridentata) and big galleta (Pleuraphis rigida) dominate. |
R030XD042CA |
Hyperthermic Shallow To Moderately Deep Fan Remnants This ecological site is found on adjacent stable fan remnants. Sparse vegetation is dominated by creosote bush (Larrea tridentata). |
Similar sites
R030XD015CA |
Hyper-Arid Fans This ecological site occurs on fan aprons receiving less additional moisture. Channeling is not as prevalent. The plant community is less productive and less diverse, and brittlebush (Encelia farinosa) is not an important species. |
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R030XD039CA |
Coarse Gravelly Fans This ecological site occurs on soils with a higher percentage of rock fragments on the surface and in the soil profile. Brittlebush (Encelia farinosa) and creosote bush (Larrea tridentata) dominate. |
R030XD006CA |
Abandoned Fan This ecological site occurs on fan aprons receiving much less additional moisture. The plant community is much less productive and diverse. Creosote bush (Larrea tridenta) is the only dominant shrub. |
Table 1. Dominant plant species
Tree |
Not specified |
---|---|
Shrub |
(1) Larrea tridentata |
Herbaceous |
Not specified |
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