Natural Resources
Conservation Service
Ecological site R018XC103CA
Lithic Thermic Foothills
Last updated: 4/24/2024
Accessed: 11/23/2024
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.
MLRA notes
Major Land Resource Area (MLRA): 018X–Sierra Nevada Foothills
Major Land Resource Area (MLRA) 18, Sierra Nevada Foothills is located entirely in California and runs north to south adjacent to and down-slope of the west side of the Sierra Nevada Mountains (MLRA 22A). MLRA 18 includes rolling to steep dissected hills and low mountains, with several very steep river valleys. Climate is distinctively Mediterranean (xeric soil moisture regime) with hot, dry summers, and relatively cool, wet winters. Most of the precipitation comes as rain; average annual precipitation ranges from 15 to 55 inches in most of the area (precipitation generally increases with elevation and from south to north). Soil temperature regime is thermic; mean annual air temperature generally ranges between 52 and 64 degrees F. Geology is rather complex in this region; there were several volcanic flow and ashfall events, as well as tectonic uplift, during the past 25 million years that contributed to the current landscape.
LRU notes
LRU 18XC is located on moderate to steep mountains and hills in the Sierra Nevada Foothills east of Fresno, CA. The major differences between the southern and northern foothills are the dryer climate (12 to 37 inches of annual precipitation), greater summer/winter temperature variation, and steeper topography of the southern foothills. The geology of this region is predominately granitoid. The elevation ranges between 300 and 4100 feet above sea level. Warmer temperatures and lower precipitation (than at higher latititudes) allow for blue oak grasslands to exist at higher elevations. The soil temperature regime is primarily thermic, however some mesic soils are found at higher elevations of 18XC. At these upper elevations, the break in soil temperature regime (between thermic and mesic) is highly aspect dependent. Southern and western aspects at the steep, high elevations promote chamise-yucca plant assemblages. Buckeye is common in the concave positions. Riparian trees that are generally absent from the northern LRU’s include California Sycamore (Plantanus racemosa) and lemon scented gum (Eucalyptus citriodora).
Classification relationships
CLASSIFICATION RELATIONSHIPS
This site is located within M261F, the Sierra Nevada Foothills Section, (McNab et al., 2007) of the National Hierarchical Framework of Ecological Units (Cleland et al., 1997), M261Fc, the Lower Granitic Foothills and M261Fd, Southern Granitic Foothills Subsections.
Level III and Level IV ecoregions systems (Omernik, 1987, and EPA, 2011) are: Level III, Central California Foothills and Coastal Mountains and Level IV, Ecoregion 6c, Southern Sierran Foothills.
Ecological site concept
This site is characterized by lithic to moderately deep soils occurring on backslopes, shoulders, and summits of low hills on metamorphic geologies. Some rock outcrop can occur, but usually less than 25%. Slopes typically range from 5 to 60%. Precipitation typically ranges from 17 to 24 inches per year, and elevation ranges from 900 feet to 2800 feet.
Shallow soil depth and low available water capacity, coupled with lower foothill elevations where higher evapotranspiration demands exist (relative to the entire elevation profile of 18XC), are the main limits to woody production. Representative soil components include Millerton, Fallbrook and Vista. Millerton soils are shallow over schist, with weakly developed argillic horizons. Fallbrook soils are deep to grus with more pronounced argillic horizons. Both soils are well drained and are classified as ultic haploxeralfs. Vista soils are moderately deep to grus and are also well drained. Vista soils are less developed than both Millerton and Fallbrook and are classified as coarse-loamy, mixed, superactive, thermic Typic Haploxerepts.
This ecological site consists of annual forbs and grasses. Fillaree (Erodium spp.), ripgut brome (Bromus diandrus), soft chess (Bromus hordeaceus), and foxtail fescue (Festuca megalura) are some of the main species. Shrubs in this site are uncommon or make up a very low percentage of the site.
Associated sites
| F018XC203CA |
Cool Thermic Slopes This site commonly occurs nearby. |
|---|---|
| R018XC104CA |
Thermic Free Face Foothills This site commonly occurs nearby. |
Similar sites
| R018XC102CA |
Steep Thermic Clayey Shallow Site relationships being developed. |
|---|
Table 1. Dominant plant species
| Tree |
Not specified |
|---|---|
| Shrub |
Not specified |
| Herbaceous |
(1) Erodium |
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