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Ecological Sections: Sierra Nevada - (MAP)

Subsection M261Eo
Glaciated Batholith

This 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 alluvium.

Geomorphology.  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.

Soils.  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 not extensive.

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:
    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 meadow habitat.
    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.
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.

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. 

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