Natural Resources
Conservation Service
Ecological site R018XI163CA
Thermic Low Rolling Hills
Last updated: 4/24/2024
Accessed: 12/22/2024
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 feet 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 low rolling hills composed of dissected erosional surfaces occurring over shallow (occasionally moderately deep) loamy soils of volcanic (tuffaceous) or metasedimentary (slate) origin. This site often occurs in complexes with R018XI164CA (Clayey Dissected Swales), on the upland, or mound positions. Precipitation typically ranges from 26 to 30 inches per year and elevation ranges from 50 and 1550 feet.
Low water balance and acidic, shallow soils prevent the establishment of woody vegetation, particularly at lower elevations of the foothills where precipitation is very low. Pentz, Whiterock and Daulton are among the most common soil components that are correlated to this ecological site. These soils are shallow. Pentz a shallow Ultic Haploxeroll, is a dark, loamy soil formed from andesitic tuffaceous sediments. Whiterock is, as the name implies, a much lighter in color, poorly developed, lithic xerorthent, formed from metasedimentary rock. Daulton is also a lithic xerorthent but Daulton soils are formed from dark colored slates.
This vegetation community consists of annual grasses and forbs. Dominant plants include soft brome (Bromus hordeaceus), wild oat (Avena fatua), and fillaree (Erodium spp.) with 60 to 70% of the annual production made up of these and other grasses.
Associated sites
| R018XI164CA |
Clayey Dissected Swales This site commonly occurs nearby. |
|---|
Similar sites
| R018XI107CA |
Shallow, Undulating Volcanic Hills Site relationships being developed. |
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Table 1. Dominant plant species
| Tree |
Not specified |
|---|---|
| Shrub |
Not specified |
| Herbaceous |
(1) Bromus hordeaceus |
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