Natural Resources
Conservation Service
Ecological site F018XI200CA
Low Elevation Foothills
Last updated: 4/24/2024
Accessed: 11/13/2024
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 on 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
This LRU (designated XI) is located on moderate to steep hills in the Sierra Nevada Foothills east of Sacramento and Stockton, CA. Various geologies occur in this region: metavolcanics, granodiorite, slate, marble, argillite, schist and quartzite, as well as ultramafic bands to a limited and localized extent. It includes mesa formations from volcanic flows, where vernal pool habitats occur. Soil temperature regime is thermic and soil moisture regime is xeric. Elevation ranges between 300 and 3400 ft above sea level. Precipitation ranges from 14 to 42 inches annually. Most precipitation falls between the months of November and March in the form of rain. Dominant vegetation includes annual grasslands, blue oak (Quercus douglasii), interior live oak (Quercus wislizeni), chamise (Adenostoma fasciculatum), buckbrush (Ceanothus cuneatus), and foothill pine (Pinus sabiniana).
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), M261Fb, the Lower Foothills Metamorphic Belt Subsection.
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 6b, Northern Sierran Foothills, Ecoregion 6c, Comanche Terraces.
Ecological site concept
This site is characterized by shallow or coarser-textured moderately deep soils occurring on low hills (relief 100 to 300 feet). This site occurs on all hillslope positions, except toeslopes, on metamorphic and granitic hills. Slopes typically range from 1 to 50%. Precipitation typically ranges from 25 to 29 inches per year, and elevation ranges from 150 feet to 2100 feet.
Soil depth and low available water capacity, typical of the lower foothill elevations where higher evapotranspiration demands exist, are the main limits to woody production. Representative soil components include Auburn, Andregg, and Whiterock soils. Generally these are shallow, weakly developed soils. Auburn and Whiterock soils are loamy Lithic Haploxerepts or Xerorthents. Andregg soils are moderately deep, coarse-loamy Ultic Haploxerolls occurring in granite parent material.
This ecological site consists of open blue oak (Quercus douglasii) stands (5 to 20% canopy cover) with smaller trees that rarely exceed 30 feet in height with high cover of annual forbs and grasses. Shrubs in this site are uncommon or make up a very low percentage of the site. Annual forbs and grasses together make up more than 80% of the annual production.
Associated sites
F018XI201CA |
Moderately Deep Thermic Foothills This site commonly occurs nearby. |
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F018XI202CA |
Deep Thermic Steep Hillslopes This site commonly occurs nearby. |
F018XI205CA |
Thermic Granitic Foothills This site commonly occurs nearby. |
Similar sites
F018XI201CA |
Moderately Deep Thermic Foothills Site relationships being developed. |
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R018XI107CA |
Shallow, Undulating Volcanic Hills Site relationships being developed. |
Table 1. Dominant plant species
Tree |
(1) Quercus douglasii |
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Shrub |
Not specified |
Herbaceous |
(1) Bromus hordeaceus |
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