Natural Resources
Conservation Service
Ecological site R018XI111CA
Low Gradient, Concave Depressions
Last updated: 4/24/2024
Accessed: 11/14/2024
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
This LRU (designated XI) is located on moderate to steep hills in the Sierra Nevada Foothills east of Sacramento, Stockton, and Modesto, 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 found in drainageways, depressions or otherwise concave positions on nearly level to strongly sloping hills where water tends to accumulate. Soils are moderately deep to deep and formed from alluvium or residuum from granitic, metavolcanic, and metasedimentary origin. Soils generally tend to have redox depletions or some evidence of aquic conditions for part of the year during normal years. Mean annual precipitation typically ranges from 27 to 34 inches. Elevation ranges from 1000 to 2000 feet.
Ephemeral channels may be associated with this site, containing water during the winter, spring, and early summer months. However, obligate wetland species are generally absent because the soils generally dry out during years of normal precipitation during the dry season (May through October). Most of the soils correlated to this site are at the family level (Aquic or Aeric subgroups). Shenandoah is one series commonly correlated to this site. Shenandoah soils are fine, smectitic, thermic Aquic Palexeralfs occurring on granitic parent material.
Vegetation consists of annual grasses, especially bulbous bluegrass (Poa bulbosa), rushes (Juncus spp.), sedges (Carex spp.), and forbs, such as western buttercup (Ranunculus occidentalis) and clover (Trifolium spp.). Sparse blue oak (Quercus douglasii) cover is sometimes found, but usually is limited to the drier upland surfaces.
Associated sites
| F018XI200CA |
Low Elevation Foothills This site commonly occurs nearby. |
|---|---|
| F018XI205CA |
Thermic Granitic Foothills This site commonly occurs nearby. |
| F018XI208CA |
Deep Low Rolling Hills and Terraces This site commonly occurs nearby. |
Table 1. Dominant plant species
| Tree |
(1) Quercus douglasii |
|---|---|
| Shrub |
Not specified |
| Herbaceous |
(1) Juncus |
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