Ecological Sections: Sierra Nevada - (MAP)
This subsection extends from the northern edge of the Sierra Nevada, which
is along the Susan River, south to Grizzly Peak. It has a temperate
to cold, subhumid to humid climate. MLRA 22e.
Fredonyer Butte - Grizzly Peak
Lithology and Stratigraphy. Strongly folded basement
rocks predominate in this subsection. They include metamorphosed Jurassic
marine sedimentary, Jurassic-Triassic volcanic, and Paleozoic marine
sedimentary and volcanic rocks. There are a few small Mesozoic granitic
bodies. Tertiary volcanic rocks, largely dacitic lahar, and
nonmarine sedimentary rocks are moderately extensive in the northern
part of the subsection. Quaternary alluvium has accumulated in Mountain
Meadows and a few smaller valleys.
Geomorphology. Steep mountain and moderately steep
hill slopes predominate in this subsection. Alluvial fans, floodplains,
terraces, and basin floors are present but not extensive. Keddie
Ridge, one of the few mountains that is distinctly elongated, is aligned
toward the west-northwest. The elevation ranges from about 4000 feet
along Lights Creek up to 7387 feet on Hamilton Mountain, 7472 on Dyer Mountain
on Keddie Ridge, and 8197 feet on Grizzly Peak. Faulting, mass wasting,
and fluvial erosion are the main geomorphic processes. The
north sides of Grizzly Peak and Keddie Ridge were glaciated during the
Soils. The soils are mostly Ultic Argixerolls, Ultic Haploxeralfs,
Ultic Palexeralfs, Andic Xerumbrepts; Pachic Haploxerolls; and a diverse
group of shallow soils. There are Aquolls in Mountain Meadows.
The soils are mostly well drained, some soils in meadows are poorly drained.
Soil temperature regimes are mesic and frigid. Soil moisture regimes
are mostly xeric, but aquic in Mountain Meadows.
Vegetation. The predominant natural plant communities
are Jeffrey pine series, Mixed conifer series, and White fir series.
Small areas of Red fir series occur at the highest elevations. Western
juniper series is present on some shallow soils. The most common
streamside riparian communities are Black cottonwood at lower elevations
and Mountain alder series at higher elevations. Sedge meadow communities
occur in wet areas.
Characteristic series by lifeform include:
Climate. The mean annual precipitation is about 20 to 40 inches;
much of it falls as snow. Mean annual temperature is about 40°
to 50° F. The mean freeze-free period is about 50 to 125 days.
Grasslands: Ashy ryegrass series, Green fescue series, Idaho
fescue series, Montane meadow habitat, Nebraska sedge series, Needle-and-thread
series, Rocky Mountain sedge series.
Shrublands: Bitterbush series, Greenleaf manzanita series, Parry
rabbitbrush series, Rubber rabbitbrush series, Tobacco brush series.
Forests and Woodlands: Aspen series, Incense-cedar series, Jeffrey
pine series, Jeffrey pine - Ponderosa pine series, Mixed conifer series,
Mountain juniper series, Ponderosa pine series, Red fir series, Western
white pine series, White fir series.
Surface Water. Runoff is rapid from most of the area, but
slow on the basin floor in Mountain Meadows. Most of the runoff flows
to tributaries of the Feather River. In the northern part of the
subsection it flows to the Susan River, which runs to Honey Lake.
There is a reservoir on Mountain Meadows.