Ecological Sections: Sierra Nevada - (MAP)
subsection is a mountain range east and northeast of lake Tahoe.
It has a cold to very cold and semi-arid to subhumid climate. MLRAs
22e and 22f.
Lithology and Stratigraphy. Mesozoic granitic rocks
and, in the northern part of the subsection, Tertiary andesite and lahar
predominate in this subsection. There are some pre-batholith metamorphic
rocks, too. Pleistocene glacial till and outwash are common on both
sides of the Carson Range. There is little Holocene alluvium.
Geomorphology. Steep mountain slopes predominate
in this subsection. The Carson Range is elongated parallel to high-angle,
or normal, faults and is aligned north-south. There is small area of gently
to moderately sloping subsummit plateau at the north end of the Carson
Range. Also, there are small areas of gently sloping to moderately
steep glacial moraines and nearly level to moderately sloping outwash plain,
floodplain, and alluvial fans. The elevation ranges from 5500 or
6000 feet at the northern end of the Carson range, or 6230 feet along the
shore of Lake Tahoe, up to 10,776 feet on Mt. Rose and 10,881 feet on Freel
Peak. Faulting, mass wasting, and fluvial erosion and deposition
are the main geomorphic processes.
Soils. The soils are mostly shallow Typic and Dystric Xeropsamments;
shallow Typic Cryopsamments; Typic Cryorthents; Typic, Entic, and Andic
Xerumbrepts; Lithic, Typic, and Entic Cryumbrepts; and, around the north
end of the Carson Range, Aridic Pachic Haploxerolls and Aridic Argixerolls.
Mollic Cryoboralfs are common on the subsummit plateau, with Humic Cryaquepts
in swales. Soils on moraines are mostly Entic and Pachic Xerumbrepts.
The soils are mostly well drained; poorly drained soils are not extensive.
Soil temperature regimes are mostly frigid and cryic. Soil moisture
regimes are mostly xeric, but aridic at lower elevations at the north end
of the Carson Range.
Vegetation. The predominant natural plant communities
are Jeffrey pine series and White fir series at lower elevations.
At higher elevations, there is Red fir series and, on north-facing slopes,
small areas of Mountain hemlock series. Whitebark pine series is
common at the highest elevations. Sedge meadow communities
and Willow thickets predominate in wet areas, with Lodgepole pine series
around the margins of wet areas.
Characteristic series by lifeform include:
Climate. The mean annual precipitation is about 15 to 40 inches;
most it falls as snow. Mean annual temperature is about 35° to
45° F. The mean freeze-free period is about 25 to 100 days.
Grasslands: Alpine habitat, Ashy ryegrass series, Montane meadow
habitat, Nebraska sedge series, Needle-and-thread series, Rocky Mountain
Shrublands: Big sagebrush series, Bitterbush series, Greenleaf
manzanita series, Low sagebrush series, Parry rabbitbrush series, Rubber
rabbitbrush series, Tobacco brush series.
Forests and woodlands: Jeffrey pine series, Lodgepole pine series,
Mountain hemlock series, Red fir series, Washoe pine series, Western white
pine series, White fir series, Whitebark pine series.
Surface Water. Runoff is rapid from most of the area.
The runoff flows to the Carson River, Truckee River, or Lake Tahoe, which
is drained by the Truckee River.