subsection comprises the higher elevations of the western slope of the
Sierra Nevada from the Grand Canyon of the Tuolumne River south-southwest
to Slate Mountain, which is on the drainage divide west of the Kern River.
It has a cold and humid climate. MLRA 22e.
Lithology and Stratigraphy. Mesozoic granitic rocks
predominate in this subsection; pre-batholith metamorphic rocks are common,
but post-batholith volcanic rocks are sparse. Pleistocene glacial
till and outwash are common in the northern part to sparse in the southern
part of the subsection. There are small areas of Quaternary alluvial
and lacustrine deposits.
This subsection is on a gently sloping to moderately steep plateau with
some steep mountains on it. Glacial erosion has modified most of
the valleys. Several large rivers between the Tuolumne and Tule Rivers
head in or cross the subsection. Some of these rivers flow
in the bottoms of very steep sided canyons. The elevation ranges
about 6000 to 10000 feet. Mass wasting and fluvial erosion are the
main geomorphic processes.
The soils are mostly Dystric Xeropsamments; Dystric Xerorthents; Dystric
Xerochrepts; and Entic, Typic, and Pachic Xerumbrepts, plus Aquic Cryumbrepts
in wet areas. There are some Cryumbrepts at the highest elevations.
The soils are mostly well drained. Soil temperature regimes are mostly
frigid, but some are 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.
The predominant natural plant communities, from lower to higher elevations,
are Mixed conifer series, White fir series, and Red fir series. Jeffrey
pine series is common on shallow and rocky soils. 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, but they are not extensive. Some groves
of Giant sequoia series occur at lower elevations in this subsection.
Characteristic series by lifeform include:
Climate. The mean annual precipitation is about 40 to 60 inches;
most of it falls as snow. Mean annual temperature is about 35°
to 50° F. The mean freeze-free period is about 25 to 100 days.
Grasslands: Ashy ryegrass series, California oatgrass series,
Montane meadow habitat, Needle-and-thread series.
Shrublands: Brewer oak series, Chamise series, Deerbrush series,
Greenleaf manzanita series, Interior live oak series, Tobacco brush series,
Wedgeleaf ceanothus series.
Forests and woodlands: Giant sequoia series, Incense-cedar series,
Jeffrey pine series, Lodgepole pine series, Mixed conifer series, Red fir
series, White fir series.
Surface Water. Runoff is rapid from most of the area.
Most of the runoff flows to the Tuolumne, Merced, San Joaquin, Kings, Kaweah,
Tule, or Kern Rivers or tributaries of them. Maximum flow in these
rivers is during spring when snow is melting rapidly. There are many
small natural lakes or ponds in glaciated terrain, and some reservoirs.