

Natural Resources
Conservation Service
Ecological site R030XB189CA
Shallow Cool Hills
Last updated: 2/25/2025
Accessed: 03/10/2025
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.

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 LRU (designated by ’XB’) 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 to 5000 feet and precipitation ranges from 4 to 9 inches per year, but is generally between 5-6 inches. This LRU is characterized primarily by the summer precipitation it receives, ranging from 18 – 35% but averages 25%. Summer precipitation falls between July and September in the form of rain, and winter precipitation falls starting in November and ends between February and March, also mostly in the form of rain; however it does receive between 0 and 3 inches of snow, with an average of 1 inch. The soil temperature regime is thermic and the soil moisture regime is typic-aridic. Vegetation includes creosote bush, burrobush, Nevada jointfir, ratany, Mojave yucca, Joshua tree, chollas, cactus, big galleta grass and several other warm season grasses. At the upper portions of the LRU, plant production and diversity are greater and blackbrush is a common dominant shrub.
Ecological site concept
This site occurs on steep mountain slopes with shallow soils at elevations between 3300 and 5700 feet. Soils have a cool thermic soil temperature regime. Production reference value (RV) for is 393 pounds per acre, and ranges from 170 to 690 pounds per acre depending on annual precipitation and annual species production. The site is dominated by blackbrush (Coleogyne ramosissima) and California juniper (Juniperus californica). Shallow soils and a cool thermic temperature regime increases soil moisture availability allowing blackbrush and California juniper to dominate. Blackbrush is shallow-rooted, and most competitive on shallow soils. California juniper can thrive in both shallow and deep soils.
Data ranges in the physiographic data, climate data and soil data are based on major components only (15 percent or greater). Information for associated minor components may be included in the narrative section.
This site is part of group concept R030XB151CA.
Associated sites
R030XD003CA |
Hyperthermic Steep South Slopes Hyperthermic steep south facing slopes with brittlebush (Encelia farinosa) and creosote bush (Larrea tridentata) distinguish this site from R030XB189CA. |
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R030XD040CA |
Hyperthermic Steep North Slopes Hyperthermic steep north slopes with burrobush and brittlebush distinguish this site from R030XB189CA. |
R030XB140CA |
Shallow Hill 4-6" P.Z. Side slopes of fan remnants, low hills and mountains on all exposures. Elevations are 1800 to 5000 feet. Slopes range from 4 to 75 percent, but slope gradients of 15 to 50 percent are most typical. Burrobush (Ambrosia dumosa), creosote bush (Larrea tridenta) and desert needlegrass (Achnatherum speciosum) are dominant plant species at this site. The soils at this site generally have a warm thermic soil temperature regime which distinguishes this site from R030XB189CA. |
R030XB164CA |
Steep South Slopes Steep south-facing slopes at elevations of 2300 to 3950 feet. Soils are shallow sands. The southerly aspect, hot temperatures and shallow rocky soils favor brittlebush (Encelia farinosa) which is extremely drought-deciduous and able to effectively use additional run-on moisture when it is available. A warm thermic soil temperature regime distinguishes this site from R030XB189CA. |
R030XB166CA |
Dissected Pediment, Cool Cool thermic dissected pediments with very shallow soils on slopes of 4 to 30% between the elevations of 3280 to 5180 feet. Blackbrush (Coleogyne ramosissima) and California juniper (Juniperus californica) dominate. The pediment landform distinguishes this site from R030XB189CA. |
R030XB168CA |
Cool Deep Sandy Fans This ecological site occurs on cool thermic sandy soils of fan aprons and fan remnants adjacent to mountains. Very deep soils distinguish this ecological site from R030XB189CA. Some minor components may have moderately deep soils over bedrock. Cooler temperatures and water run-off from the nearby mountains allow blackbrush (Coleogyne ramosissima)and California juniper (Juniperus californica) to dominate the site while excluding creosote bush from becoming established at this site. |
R030XB170CA |
Bouldery Very Shallow To Shallow Gravelly Slopes Cool hills and mountains with very shallow to shallow soils over bedrock. Blackbrush (Coleogyne ramosissima), singleleaf pinyon (Pinus monophylla) and Muller oak (Quercus cornelius-mulleri) are the dominant species at this site. The presence of singleleaf pinyon suggests this site is a bit cooler and moister than R030XB189CA. A high percentage of rock outcrops also distinguishes this site from R030XB189CA. |
R030XB172CA |
Warm Gravelly Shallow Hills This site is found on steep stony mountain and hill slopes with shallow to moderately deep soils. Slopes are generally greater than 40% with more than 10% surface stone cover. A warm thermic soil temperature regime allows creosote bush (Larrea tridentata) and Parish’s goldeneye (Viguiera parishii) to dominate the site, distinguishing this site from R030XB189CA. |
R030XB193CA |
Very Shallow To Moderately Deep Gravelly Slopes This site occurs on warm thermic steep hill and mountain slopes with very shallow to moderately deep soils which typically have an argillic horizon within 2 to 7 cm of the soil surface. Both a warm thermic soil temperature regime and an argillic horizon distinguish this site from R030XB189CA. The site is characterized by a diverse shrub assemblage, comprised of Jojoba (Simmondsia chinensis), burrobush (Ambrosia dumosa), Parish’s goldeneye (Viguiera parishii), Nevada jointfir (Ephedra nevadensis), and water jacket (Lycium andersonii), and is not strongly dominated by any one species. |
R030XE200CA |
Xeric Very Deep Sandy Fan Aprons On Pediments This site occurs on hills with 4-8% slopes. Very deep soils, lower slopes and a xeric-aridic soil moisture regime distinguish this site from R030XB189CA. |
R030XB213CA |
Moderately Deep Gravelly Mountain Slopes This site is found on very steep, very shallow to moderately deep, warm thermic hill and mountain slopes. California juniper (Juniperus californica) and Eastern Mojave buckwheat (Eriogonum fasciculatum) are the dominant species. The warm thermic temperature regime distinguishes this site from R030XB189CA. |
R030XY202CA |
Very Rarely To Rarely Flooded Thermic Ephemeral Stream This is a very rarely to rarely flooded ephemeral stream with Nevada jointfir (Ephedra nevadensis), water jacket (Lycium andersonii) and desert almond (Prunus fasciculata). |
R030XE196CA |
Sandy Xeric-Intergrade Slopes Shallow soils on steep hill and mountain slopes. A xeric-aridic soil moisture regime distinguishes this site from R030XB189CA. Muller oak (Quercus cornelius-mulleri) and singleleaf pinyon (Pinus monophylla) are the dominant species on R030XE196CA. |
R030XE191CA |
Dry Sandy Mountain Slopes This site is found on steep hill and mountain slopes. Soils are shallow to weathered bedrock. A xeric-aridic soil moisture regime distinguishes this site from R030XB189CA. Muller oak (Quercus cornelius-mulleri) and singleleaf pinyon (Pinus monophylla) are the dominant species on R030XE191CA. |
Similar sites
R030XB170CA |
Bouldery Very Shallow To Shallow Gravelly Slopes Cool hills and mountains with very shallow to shallow soils over bedrock. Blackbrush (Coleogyne ramosissima), singleleaf pinyon (Pinus monophylla) and Muller oak (Quercus cornelius-mulleri) are the dominant species at this site. The presence of singleleaf pinyon suggests this site is a bit cooler and moister than R030XB189CA. A high percentage of rock outcrops also distinguishes this site from R030XB189CA. |
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R030XB168CA |
Cool Deep Sandy Fans This ecological site occurs on cool thermic sandy soils of fan aprons and fan remnants adjacent to mountains. Very deep soils distinguish this ecological site from R030XB189CA. Some minor components may have moderately deep soils over bedrock. Cooler temperatures and water run-off from the nearby mountains allow blackbrush (Coleogyne ramosissima)and California juniper (Juniperus californica) to dominate the site while excluding creosote bush from becoming established at this site. |
R030XB166CA |
Dissected Pediment, Cool Cool thermic dissected pediments with very shallow soils on slopes of 4 to 30% between the elevations of 3280 to 5180 feet. Blackbrush (Coleogyne ramosissima) and California juniper (Juniperus californica) dominate. The pediment landform distinguishes this site from R030XB189CA. |
Table 1. Dominant plant species
Tree |
Not specified |
---|---|
Shrub |
(1) Coleogyne ramosissima |
Herbaceous |
Not specified |
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