United States Department of Agriculture The San Dimas Forest Service Pacific Southwest Experimental Forest: Forest and Range Experiment Station 50 Years of Research General Technical Report PSW-104 Paul H. Dunn Susan C. Barro Wade G. Wells II Mark A. Poth Peter M. Wohlgemuth Charles G. Colver The Authors: at the time the report was prepared were assigned to the Station's ecology of chaparral and associated ecosystems research unit located in Riverside. California. PAUL H. DUNN was project leader at that time and is now project leader of the atmospheric deposition research unit in Riverside. Calif. SUSAN C. BARRO is a botanist, and WADE G. WELLS I1 and PETER M. WOHLGEMUTH are hydrologists assigned to the Station's research unit studying ecology and fire effects in Mediterranean ecosystems located in Riverside, Calif. CHARLES G. COLVER is manager of the San Dimas Experimental Forest. MARK A. POTH is a microbiologist with the Station's research unit studying atmospheric deposition, in Riverside, Calif. Acknowledgments: This report is dedicated to J. Donald Sinclair. His initiative and exemplary leadership through the first 25 years of the San Dimas Experimental Forest are mainly responsible for the eminent position in the scientific community that the Forest occupies today. We especially thank Jerome S. Horton for his valuable suggestions and additions to the manuscript. We also thank the following people for their helpful comments on the manuscript: Leonard F. DeBano, Ted L. Hanes, Raymond M. Rice, William 0. Wirtz, Ronald D. Quinn, Jon E: Keeley, and Herbert C. Storey. Cover: Flume and stilling well gather hydrologic data in the Bell 3 debris reservoir, San Dimas Experimental Forest. (Photo: David R. VanDusen.) Publisher: Pacific Southwest Forest and Range Experiment Station P.O. Box 245, Berkeley, California 94701 May 1988 Years o esearch Paul H. Dunn Susan C. Barro Wade G.Wells II Mark A.Poth Peter M.Wohlgemuth Charles G.Colver CONTENTS Introduction ..........................................................................................1 Physical Description .............................................................................1 Research History ..................................................................................4 Water ............................................................................................. 4 Soils and Slope Stability ..............................................................8 Effects of Fire ............................................................................. 11 Vegetation Management .............................................................11 Chaparral Ecology and Physiology ............................................ 12 Vegetation Classification ............................................................13 Litter Decomposition ..................................................................14 Fauna ...........................................................................................15 On-Going Research ............................................................................15 Appendix .............................................................................................16 A-Flora ..................................................................................... 16 B-Mosses .................................................................................25 C-Vertebrate Fauna .................................................................. 27 Amphibians and Reptiles ....................................................27 Birds .................................................................................... 30 Mammals ............................................................................. 41 References ...........................................................................................44 Additional Reading ............................................................................49 Included in this area is Brown's Flat, a locally unique High Sierra- type meadow supporting a grove of large ponderosa pine. Modem facilities on the Forest are available to researchers throughout the world. Requests for use of the laboratory and e San Dimas Experimental Forest (SDEF) is a field labora housing should be sent to: Forest Manager-San Dimas Experi- ry for studies in the ecology of chaparral and related ecosys- mental Forest, Forest Service, U.S. Department of Agriculture, tems. A broad data base together with unique physical features 110 North Wabash Avenue, Glendora, California 91740 U.S .A. make the SDEF an ideal location for studies of timely topics such The SDEF has been described and its history and research as acid deposition, sediment production, biomass production progress noted in many publications (Hamilton 1940; Hill 1963b; control, and chaparral management systems. Located in the San Hopkins andothers 1958,1961; Kraebel and Sinclair 1940; Millett Gabriel Mountains northeast of Los Angeles, the Forest is a valu- 1974; Mooney and Parsons 1973; Robinson 1980; SDEF Staff able research site because it is close to urban universities, is 1935-1938,1951;Sinclair and Kraebel 1934; Sinclair and others protected from public disturbance, and because little public land is 1958; Storey 1982). currently available for field research as a result of pressure for This report describes the physiography of the San Dimas recreation sites. Experimental Forest and summarizes its research history for The SDEF is under the jurisdiction of the Pacific Southwest amateur biologists, graduate students, and other scientists inter- Forest and Range Experiment Station, Forest Service, U.S. De- ested in using its research facilities. Also included is a comprehen- partment of Agriculture, and has been recognized by national and sive listing of publications related to the Forest or the research con- international organizations. The Man and the Biosphere Program ducted there. of the United Nations recognizes SDEF as a "Biosphere Preserve." The National Science Foundation and The Institute of Ecology recognize the SDEF as an "Experimental Ecological Reserve." PHYSICAL IPTIO Fern Canyon, a 555-ha (1370 acres) tributary of San Dimas Canyon, was selected as a research natural area in 1972; only The San Dimas Experimental Forest covers an area of 6945 ha nondestructive observational research may be conducted there. (17,153 acres) near Glendora, California (fl. 1). It is 45 km (28 Lat + Climatic station Stream gaging station - Streams control dam Buildings Recording raingage 451 Elevation Figure 1-The San Dimas Experimental Forest is in a front range of the shows the 2 major watersheds and 10 minor watersheds in the Forest San Gabriel Mountains in southern California. This general map also (Source: Hill 1963b). Elevations are in meters. USDA Forest Service Gen. Tech. Rep. PSW-104.1988 1 Figure 2-Extensive steep canyons dissect the San Dimas Experimental Forest. Contour lines are at 1004 (30.5-m) intervals. mi) northeast of Los Angeles on the northern edge of the Los vegetation management to obtain maximum water yields with Angeles basin. The headquarters and laboratory are at Tanbark minimum erosion (SDEF Staff 1935). To proceed with this Flats (latitude 34¡12'Nlongitude 117¡46'W) The Experimental research an understanding of the factors influencing the hydro- Forest area is within the San Gabriel Mountain fault block, and is logic budget was necessary. Such environmental factors as the extensively dissected by steep canyons. The elevation on the Ex- temperature of air and soil, precipitation, evaporation, relative perimentalForestranges from 457 to 1677 m (1500 to 5500 ft) (fig. humidity, windspeed and direction, and even solar radiation were 2). The average slope is 68 percent. monitored in this endeavor. Soon after the Forest was established The two major watersheds within the boundaries of theExperi- in 1935, complete climatological stations were established at San mental Forest are Big Dalton (1 155 ha or 2853 acres) and San Dimas Canyon, 442 m (1450 ft); Tanbark Flats, 831 m (2725 ft); Dimas (4079 ha or 10,075acres). These watersheds form an ideal San Gabriel Divide, 1326 m (4350 ft); and Fern Canyon, 1540 m experimental area as they have vegetation patterns typical of (5050 ft). These were equipped with air hygrothermographs, soil southern California; they are separated from the main mass of the hygrothermographs, air and soil thermometers, psychrometers, San Gabriel Mountains by deep canyons (Cow Canyon on the anemometers, wind direction transmitters, evaporation pans, and north, San Antonio Canyon on the east, and Little Dalton on the atmometers (SDEF Staff 1935). Today the only complete weather west); the two major drainages have small tributaries suitable for station on the Forest is located at Tanbark Flats. Past records of study; and both San Dimas and Big Dalton Canyons are harnessed temperature (Reimann 1959a),evaporation (Reimann 1959b),and by County Flood Control Dams (Robinson 1980). climate (Hamilton 1951) have been reported, but a large amount of Tnere are also 10 intermediate size watersheds in the Forest: this data is still unpublished.' seven in the San Dimas watershed (Wolfskill, Fern, Upper East The San Dimas Experimental Forest has a typical Mediterra- Fork, East Fork, North Fork, Main Fork, and West Fork); and three nean-type climate, with mild winters and summer droughts. Most in Big Dalton (Bell, Volfe, and Monroe). The two sets of small of the precipitation falls from December to March in less than 20 watersheds on the Forest