Section M261E
Sierra Nevada

Geomorphology.  Block mountain range tilted west; accordant crests.  Sierra Nevada Range geomorphic province.

Lithology.  Mesozoic granitic and ultramafic rocks, Paleozoic and Mesozoic strongly metamorphosed sedimentary and volcanic rocks, and Cenozoic volcanic rocks.

Soil Taxa.  Alfisols, Andisols, Aridisols, Entisols, Inceptisols, Mollisols and Ultisols in combination with mesic, frigid or cryic soil temperature regimes and xeric, udic, aridic or aquic soil moisture regimes.

Vegetation.  Predominant potential natural communities include the Mixed conifer series, Ponderosa pine series, Jeffrey pine series, White fir series, Red fir series, Lodgepole pine series, Huckleberry oak series, Western Juniper series, Aspen series, Big sagebrush series, Mixed subalpine forest series, Mountain hemlock series, Whitebark pine series and Giant sequoia series.

The following series are found throughout the section and are not restricted to or extensive in any subsection. Series dominated by exotic plants are not listed under subsections unless they are extensive and stable.

Series dominated by exotic plants: Broom series, California annual grassland series, Cheatgrass series, Introduced perennial grassland series, Kentucky bluegrass series and Tamarisk series.
Series that can occur in all subsections, but are not extensive: Bulrush series, Bulrush - cattail series, Bur-reed series, Common reed series, Cattail series, Creeping ryegrass series, Ditch-grass series, Duckweed series, Holodiscus series, Mosquito fern series, One-sided bluegrass series, Pondweeds with floating leaves series, Pondweeds with submerged leaves series, Quillwort series, Saltgrass series, Sedge series, Spikerush series, Tufted hairgrass series and Yellow pond-lily series.
Series restricted to riparian settings: Black cottonwood series, Mixed willow series, Montane wetland shrub habitat, Mountain alder series, Narrowleaf willow series, Pacific willow series, and Red willow series.

Elevation.  1,000 to 14,495 feet.  Local relief ranges from 500 to 2000 feet.

Precipitation.  10 to 90 inches during fall, winter and spring.  Occurs mostly as snow above 6000 feet.  Rain on snow is common.  Summers are commonly dry with low humidity.

Temperature.  25° to 60°F.

Growing Season.  10 to 200 days.

Surface Water Characteristics.  Many rapid flowing rivers and streams.  Rivers flow west from the crest in deeply incised canyons with bedrock controlled channels to the Great Valley section and Pacific Ocean.  Rivers flow east from the crest in mostly bedrock controlled channels terminating in basins in the Mojave Desert, Mono or Northwestern Basin and Range sections.  There are numerous lakes and wet meadows associated with glaciated areas above 5,000 feet.

Disturbance Regimes.

Fire: At lower and mid-elevations, historic occurrence has changed from frequent, low intensity ground fires to infrequent, high intensity stand replacing fires.  At higher elevations, historic occurrence has changed from infrequent, low and moderate intensity ground fires to infrequent, low, moderate and high intensity surface or stand replacing fires.
Seismic Activity: Seismically active areas along eastern boundary with strong shaking and ground rupture.
Climate: Wide fluctuations in precipitation and temperature for periods of years result in significant or catastrophic changes in biological communities.  Snow avalanches are common at higher elevations.

Cultural Ecology.  Humans have been utilizing the Sierra Nevada for about 10,000 years, and have been an integral part of its ecology for 3,000 to 5,000 years, particularly with documented use of fire to facilitate gathering and to generate species preferred for foodstuffs, basketry materials, and other needs.  Extensive procurement and processing of lithic, acorn, pine nut, basketry fiber, and other resources resulted in innumerable areas of lithic quarry, bedrock mortar, pinyon, Jeffrey pine, sugar pine, oak grove, and other resource alteration.  Contemporary attitudes and beliefs are dichotomized between emphasis on amenity/newcomer and commodity/long-time resident values.  Human environment is characterized by a rural lifestyle of open space and outdoor leisure activity.  Recreation is the primary economic emphasis, trailed by government employment, lumbering, mining, and grazing.  The Sierra is experiencing rapid retiree and commuter resident growth, and large transient recreation populations that provide constant resource pressures.

Subsections.  The Sierra Nevada Section is divided into 21 subsections.