Physical Description: The Semitropic Ridge Preserve encompasses approximately 3,700 acres and is located 15 miles northwest of the city of Wasco, Kern County, California. The original "Paine parcel" is found 2.5 miles north of Highway 46 along the east side of Corcoran Road and approximately 5 miles east of Interstate 5. Semitropic Ridge Preserve together with adjacent natural lands forms one of the largest natural remnants of the San Joaquin Valley. The western border of the preserve is contiguous with the Northern Semitropic Ridge Ecological Reserve, owned by the California Department of Fish and Game. The Kern National Wildlife Refuge is approximately 5 miles north of the preserve.

Conservation Purpose: Most of the parcels in the Semitropic Ridge Preserve were acquired to provide habitat for several threatened/endangered species including San Joaquin kit fox, blunt-nosed leopard lizard, Tipton kangaroo rat and the San Joaquin antelope squirrel. However, the first parcel (39 acres) at Semitropic Ridge was acquired in 1968 as a wildflower preserve. This original parcel was purchased with money from the estate of Paul S. Paine, an oil field worker that enjoyed the rich display of wildflowers during his trips across the valley in the spring. Since then more than 3,000 acres have been added to the preserve, acquired mostly through mitigation funds associated with development projects under regulatory authority of the California Energy Commission, U.S. Fish and Wildlife Service and California Department of Fish and Game.

Habitat Types: The major vegetative associations at Semitropic Ridge include valley saltbush scrub and valley sink scrub. Valley saltbush scrub is found within the relatively well-drained soils at slightly higher elevations and dominant shrubs include spiny and common saltbush. Valley sink scrub is found in the heavier clay soils and the dominant shrubs include Iodine bush and seepweed . Common grasses and flowering plants include goldfields, peppergrass, red brome, red-stemmed filaree, and tarweed. After a series of wet years, non-native grasses can become relatively dense and dominate the herbaceous vegetation. Wildfires occur periodically and have converted hundreds of acres of scrub to an open grassland type that is largely devoid of shrubs. Alkali playas and scalds are interspersed throughout much of the preserve and are characterized by bare ground with deposits of white, crusty soil. During wet winters and springs, many of the playas fill with water for several weeks.

Management: The overall management objective at Semitropic Ridge is to maintain a functioning ecosystem that supports the threatened and endangered species for which the preserve was established. Since these species are desert-adapted, special emphasis is placed on maintaining a relatively sparse herbaceous cover. In wet years, the Center enters into grazing agreements with local livestock operators to create a more open habitat structure favored by leopard lizards, kangaroo rats, kit foxes and antelope squirrels. On previously burned lands, methods of re-establishing native shrubs are being evaluated. A suite of trophic levels is monitored annually on the preserve to provide increased understanding of the system and to evaluate the success of management strategies.

Public Access: The preserve is open most of the year to the public with permission from the preserve manager.

Manager: Semitropic Ridge Preserve is managed by Greg Warrick.

For information and inquiries please contact:

Greg Warrick
Preserve Manager
(661) 387-9453 Phone/Fax
e-mail: gwarrick@cnlm.org