Natural Resources
Conservation Service
Ecological site R018XI125CA
Very Steep Skeletal 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, 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 occurs on skeletal soils on very steep hills (55 to 70% slope), generally on south-facing backslopes in metasedimentary or metavolcanic parent material. Mean annual precipitation typically ranges from 27 to 34 inches, and elevation ranges from 800-1600 feet.
Steep terrain coupled with rocky soils and often south-facing aspects limits woody production. Most of the acres where this ecological site is found belong to Mocassinhill or Gopheridge components, both of which are moderately deep and loamy-skeletal. Mocassinhill is a Humic Haploxerept originating from colluvium formed from metasedimentary parent material. Gopheridge weathered from greenstone or other metavolcanic rocks and is an Ultic Haploxeralf. A minor component correlated to this site is the Jasperpeak soil. Jasperpeak is also loamy-skeletal but is shallow and found on metavolcanic parent material and classifies as a Lithic Haploxeralf.
The dominant vegetation in this ecological site consists of annual grasses and forbs and occasional shrubs or stunted trees. Common species include wild oat (Avena fatua), soft brome (Bromus hordeaceus), California poppy (Eschscholzia sp.), fiddleneck (Amsinkia spp.), and various clover (Trifolium spp.) species. Annual grasses make up between 70% and 85% of the annual production, while forbs generally make up between 15% and 30%. Woody vegetation of any type is < 1% of the annual production.
Associated sites
| F018XI201CA |
Moderately Deep Thermic Foothills This site commonly occurs nearby. |
|---|
Similar sites
| R018XI107CA |
Shallow, Undulating Volcanic Hills Site relationships being developed. |
|---|
Table 1. Dominant plant species
| Tree |
Not specified |
|---|---|
| Shrub |
Not specified |
| Herbaceous |
(1) Avena fatua |
Click on box and path labels to scroll to the respective text.