Natural Resources
Conservation Service
-
Search
Major Land Resource Area or ecological site by name and/or ID.
General information
Draft. A draft ecological site description is either incomplete or has not undergone quality control and quality assurance review.
MLRA notes
Major Land Resource Area (MLRA): 022A–Sierra Nevada and Tehachapi Mountains
MLRA 22A
Major Land Resource Area 22A, Sierra Nevada Mountains, is located predominantly in California and a small section of western Nevada. The area lies completely within the Sierra Nevada Section of the Cascade-Sierra Mountains Province. The Sierra Nevada range has s gentle western slope, and a very abrupt eastern slope. The Sierra Nevada consists of hilly to steep mountains and occasional flatter mountain valleys. Elevation ranges between 1,500 and 9,000 ft throughout most of the range, but peaks often exceed 12,000 ft. The highest point in the continental US occurs in this MLRA (Mount Whitney, 14,494 ft). Most of the Sierra Nevada is dominated by granitic rock of the Mesozoic age, known as the Sierra Nevada Batholith. The northern half is flanked on the west by a metamorphic belt, which consists of highly metamorphosed sedimentary and volcanic rocks. Additionally, glacial activity of the Pleistocene has played a major role in shaping Sierra Nevada features, including cirques, arĂȘtes, and glacial deposits and moraines. Average annual precipitation ranges from 20 to 80 inches in most of the area, with increases along elevational and south-north gradients. Soil temperature regime ranges from mesic, frigid, and cryic. Due to the extreme elevational range found within this MLRA, Land Resource Units (LRUs) were designated to group the MLRA into similar land units.
LRU XI Central Sierra Lower Montane
This LRU comprises the lower elevations of the western, central, Sierra Nevada Mountains. Elevations are typically between 2,000 and 4,700 feet, with higher elevations in the south. The frost free season ranges from 150 to 240 days, MAAT ranges from 50 to 62 degrees F, and MAP ranges from 32 to 57 inches. Soil temperature regime is generally mesic, although warmer pockets of thermic exist within this LRU.
Ecological site concept
This ecological site differs from other similar ecological sites by virtue of its dry landscape positions that generally shed water. These are steep side slopes or convex nose slopes. Soils are generally deep to very deep and parent material is made of metasedimentary rock. A secondary controlling factor is the precipitation which ranges from 33 to 45 annual inches, among the lowest within the LRU. Soil temperature regime is mesic, although post-fire plant community phase may have significantly higher soil temperatures.
Plant communities consist of oak montane mid-canopy dominating the site (canyon live oak/ occasionally interior live oak), toyon, manzanita, poison oak, deer brush and scattered to dense ponderosa pine and foothill pine (rarely sugar pine). In these shrub dominated areas, little herbaceous production occurs.
Table 1. Dominant plant species
Tree (1) Quercus chrysolepis
(2) Pinus ponderosaShrub (1) Heteromeles arbutifolia
(2) Toxicodendron diversilobumHerbaceous Not specified