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Subsection M261Es
Tehachapi - Piute Mountains

This subsection is the southern end of the Sierra Nevada.  It includes most of the Tehachapi and Piute Mountains.  It has a hot to cold and semi-arid to subhumid climate.  MLRAs 18e and 22d.

Lithology and Stratigraphy.   Mesozoic granitic rocks predominate in this subsection, but there are some areas of pre-batholith metamorphic rocks.  There is a large area post-batholith volcanic rocks, mostly Miocene and Pliocene, on and around Emerald Mountain.  Quaternary alluvium is extensive in Walker, Tehachapi, Cummings, and Bear Valleys.

Geomorphology.   This subsection is characterized by steep mountains.  Many ridges are slightly elongated with many different orientations, but those in the Piute Mountains are generally aligned near north-south and those in the Tehachapi Mountains are generally aligned near east-west.  There is a small area of rolling plateau surface above 6000 feet in the Piute Mountains.  Slopes are gently sloping to moderately steep on Quaternary volcanic rocks, which are not extensive, and nearly level to moderately sloping on Quaternary alluvial fans and basin floors.  The elevation ranges from about 3500 up to 7981 feet on Double Mountain in the Tehachapi Mountains and 8318 feet in the Piute Mountains.  Mass wasting and fluvial erosion are the main geomorphic processes.

Soils.  The soils are mostly Typic and Pachic Haploxerolls and Lithic and Typic Argixerolls.  There are Umbrepts at higher elevations in the Piute Mountains, but they are not extensive.  Soils are mostly Xeric Torripsamments and Xeralfic Haplargids in Walker Basin and Mollic Xerofluvents and Typic and Pachic Argixerolls in the other large valleys.  The soils are well drained.  Soil temperature regimes are mostly thermic and  mesic, but frigid at the highest elevations.  Soil moisture regimes are mostly xeric, but aridic in Walker Basin.

Vegetation.   The predominant natural plant communities are Blue oak series, and Singleleaf pinyon series on the southeast edge of the subsection and north of Walker Basin.  Canyon live oak series is common on very steep rocky slopes and Mixed chaparral shrublands are common on shallow soils.  There is some Ponderosa pine series on Breckenridge Mountain and some Jeffrey pine series and White fir series in the higher parts of the Piute and Tehachapi Mountains.  Black oak series and Valley oak series are common on mountain footslopes and in valleys.

Climate.  The mean annual precipitation is about 12 to 30 inches.  Most of the precipitation is snow at higher elevations.  Mean annual temperature is about 42° to 56° F.  The mean freeze-free period is in the range from  75 to 175 days.

Surface Water.  Runoff is rapid from most of the area.  It flows to the Kern River or to closed basins in the southern end of the Great Valley or in the Mojave Desert.  All streams are dry through the summer. There are no natural lakes or ponds in the subsection. 

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