Understory

The Blacks Mountain Research Natural Area, which total 521 acres, was selected because it contains some of the best old-growth stands of interior ponderosa pine in California's National Forests. It is located in Blacks Mountain Experimental Forest, about 45 miles northwest of Susanville, California.

Higher elevation north slopes of the Fern Canyon Research Natural Area are covered with southern California woodland type vegetation. Predominant types are canyon live oak (Quercus chrysolepis) and bigcone Douglas-fir (Pseudo-tsuga macrocarpa). South facing slopes have California shrub oak (Q. dumosa), buckthorn (Ceanothus sp.), and chamise (Adenostoma fasciculatum) chaparral. Vegetation density varies from very dense to fairly open, depending upon soil depth and steepness of slope.

The southeast slopes of Mt. Shasta are characterized by a series of mudflows of volcanic materials that descended in creek channels and on slopes over a period of thousands of years. While such mudflows are found throughout the Cascade Volcanic Province of Oregon and northern California, the Mt. Shasta mudflow has the advantage of great diversity in number of flows, extent, pattern of spread, vegetative mantle, and sequence of buried but well-preserved soil profiles.

The San Joaquin Experimental Range Research Natural Area is located near the center of the state in the granite-soil section of the Sierra Nevada foothills. Located in Madera County, 28 miles north of Fresno, this experimental range was established in 1934 as a branch station of what was then called the California Forest and Range Experiment Station.The range lies in the annual grass/oak woodland type and is characterized by grassy rolling hills with sparse covering of trees and occasional dense stands of brush. It is in the lower part of the woodland zone between the agricultural lands of the...

The Backbone Creek Research Natural Area covers 430 acres (174 ha), and the elevations range from 1250 to 2400 ft (381-731 m). With the San Joaquin River as the northern boundary, the RNA consists mainly of north-facing slopes. Three intermittent streams dissect the area. The surface soil is grayish brown, slightly acid, coarse sandy loam; the subsoil is brown, strongly acid, sandy clay loam, overlying on weathered acid igneous bedrock. The annual precipitation is approximately 25 inches (6361 mm).

The Frenzel Creek Research Natural Area is at the extreme northern limit of the range of Sargent cypress (Cupressus sargentii Jeps.). Significant stands of this species are present as well as stands of MacNab cypress (Cupressus macnabiana A. Murr.). The interrelationships between these two cypresses are of scientific interest. Other rare herbaceous species are present.

The area is located on the eastern exposure of the White Mountain range. It is deeply cut by the Poison Creek and Cottonwood Creek drainages, to such an extent that every conceivable topographic aspect is found. Elevations very from 9,900 feet to ll,419 feet above sea level. The soil is thin - and very rocky, the parent material being frequently exposed.

The area covers 800 acres (324 ha). Elevations range from 5100 ft to 5190 ft (1555- 1582 m). Topography is very gradual and gently-rolling, with one shallow, vernally flooded depression located in the south-central portion. A small area of fault-raised rimrock escarpment occurs on the northeast corner. Patterned ground related to frost heaving occurs in portions of the area.