Ecological Sections: Sierra Nevada - (MAP)
subsection is along the crest of the Sierra Nevada from Granite Dome just
south of Sonora Pass southeast to Mt. Whitney. It has a cold to very
cold and humid climate. MLRA 22d.
Lithology and Stratigraphy. Mesozoic granitic rocks
predominate in this subsection. There are areas of pre-batholith
rocks, too. The Mesozoic plutonic rocks are mostly adamellite, or
quartz monzonite, and granodiorite, but they range from granite to gabbro.
The pre-batholith rocks are mostly metamorphosed Jurassic and earlier marine
sedimentary and volcanic rocks. There are a few small basalt flows.
Pleistocene glacial till is common and there are small areas of Quaternary
This subsection is characterized by steep mountains at the northeastern
edge of a plateau that is extensive west of the crest; some of the rolling
plateau west of the crest is included in this subsection. The plateau
surface is interrupted by the Cathedral and Ritter Ranges west and southwest
of Mammoth Pass. Glacial erosion has modified most of the landforms.
Cirques, aretes, cols, horns, and smooth, striated bedrock are common.
The moraines have been modified by fluvial erosion. Some of the rivers
flow in the bottoms of very steep sided canyons. The elevation ranges
from about 6000 or 7000 feet up to 14495 feet on Mt. Whitney. Many
peaks are higher than 12000 feet. Mass wasting and fluvial erosion
are the main geomorphic processes.
The soils are mostly Lithic and Andic Cryumbrepts; Dystric Xeropsamments;
Typic Cryorthents; and Andic Haplumbrepts, plus Aquic Cryumbrepts in wet
areas. Soils on glacial moraines are mostly Pachic and Typic Xerumbrepts.
Much of the granitic rock is barren, lacking soil. The soils are
mostly well drained, but those in wet meadows are somewhat poorly to poorly
drained. Soil temperature regimes are mostly frigid and cryic.
Soil moisture regimes are mostly xeric. Soils have udic moisture
regimes where snow persists through spring, melting to keep soils moist
through much of the summer. Soils with aquic moisture regimes
are present in glaciated terrain and small valleys, but they are
Vegetation. Most of this subsection is sparsely vegetated.
The predominant natural plant communities are Mixed subalpine forest series
and Red fir series, and communities of Subalpine meadow habitat.
Jeffrey pine series are common on shallow and rocky soils at lower elevations.
There is some Foxtail pine series at high elevations near the southwestern
end of the subsection. Lodgepole pine series prevails on many
wet soils and on drier soils where cold air drainage and frost limit the
regeneration of other conifers. Sedge meadow communities are common.
Characteristic series by lifeform include:
Climate. The mean annual precipitation is about 20 inches
on the southeast to 60 inches on the northwest. Most of the precipitation
is snow. Mean annual temperature is about 25° to 45° F.
The mean freeze-free period is ranges from less than 10 to about 50 days.
Grasslands: Alpine habitat, Ashy ryegrass series, Fen habitat,
Montane meadow habitat, Mountain heather - bilberry series, Nebraska sedge
series, Needle-and-thread series, Rocky Mountain sedge series, Rothrock
sagebrush series, Shorthair reedgrass series, Shorthair sedge series, Subalpine
Shrublands: Bush chinquapin series, Greenleaf manzanita series,
Huckleberry oak series, Mountain whitethorn series, Subalpine upland shrub
habitat, Subalpine wetland shrub habitat, Tobacco brush series.
Forests and woodlands: Aspen series, Foxtail pine series, Jeffrey
pine series, Limber pine series, Lodgepole pine series, Mixed subalpine
forest series, Mountain hemlock series, Red fir series, Western white pine
series, White fir series, Whitebark pine series.
Surface Water. Runoff is rapid from most of the area.
Most of the runoff flows to the Stanislaus Rivers, Tuolumne, Merced, San
Joaquin, Kings, or Kaweah on the west; to the Walker River, Mono Lake,
or Owens Valley on the east; or to the Kern River on the south. Maximum
flow in these rivers is during spring when snow is melting rapidly.
There are many small natural lakes or ponds in glaciated terrain.