Natural Resources
Conservation Service
Ecological site F018XI202CA
Deep Thermic Steep Hillslopes
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 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 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.
Ecological site concept
This site occurs on steep sideslopes and backslopes (often north-facing) in soils derived from metasedimentary or metavolcanic parent material. Slopes typically range from 4-70%. Mean annual precipitation typically ranges from 32 to 49 inches, and elevation typically ranges from 600 feet to 2000 feet. Soil temperature regime is thermic, albeit on the cool side of thermic.
Soil depth and the slope aspect result in higher available water capacity which allow for closed woodlands (mean canopy cover of trees 38%) to dominate the site. Representative soil components include Sanguinetti, Motherlode, and Wardsferry soils. These soils are shallow to moderately deep and well drained. They have thermic soil temperature regimes and are classified as Typic Haploxerepts (Sanguinetti) and Ultic Haploxeralfs (Motherlode & Wardsferry).
The dominant vegetation in this ecological site consists of dense interior live oak (Quercus wislizeni), toyon (Heteromeles arbutifolia), manzanita (Arctostaphylos spp.), poison oak (Toxicodendron diversilobum), and sparse to moderate herbaceous annual forbs and grasses (comprising 10% or less of total annual production). Shrubs contribute an additional 15%, and annual production of the tree component ranges up to 75% of total production.
Associated sites
F018XI205CA |
Thermic Granitic Foothills This site commonly occurs nearby. |
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F022AW007CA |
Deep Mesic Mountains >40"ppt This site commonly occurs nearby. |
F018XI201CA |
Moderately Deep Thermic Foothills This site commonly occurs nearby. |
Table 1. Dominant plant species
Tree |
(1) Quercus wislizeni |
---|---|
Shrub |
(1) Arctostaphylos |
Herbaceous |
(1) Bromus hordeaceus |
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