The San Dimas Biosphere Reserve and Experimental Forest is an experimental forest located in the front range of the

San Gabriel Mountains The San Gabriel Mountains ( es, Sierra de San Gabriel) are a mountain range located in northern Los Angeles County, California, Los Angeles County and western San Bernardino County, California, United States. The mountain range is part of the Tr ...

of southern California. San Dimas constitutes a protected field laboratory jointly managed by the Angeles National Forest and the Pacific Southwest Research Station of the United States Forest Service under the designation San Dimas Experimental Forest. It was designated as a UNESCO Biosphere Reserve in 1976 and withdrawn from the programme in July 2018. It encompasses the upper Big Dalton and San Dimas watersheds. The experimental forest was originally established in 1933 and was designated as a biosphere reserve in 1976. San Dimas is a

chaparral Chaparral ( ) is a shrubland plant community and geographical feature found primarily in the U.S. state of California, in southern Oregon, and in the northern portion of the Baja California Peninsula in Mexico. It is shaped by a Mediterranean c ...

-dominated

Mediterranean ecosystem Mediterranean forests, woodlands, and scrub is a biome defined by the World Wide Fund for Nature. The biome is generally characterized by dry summers and rainy winters, although in some areas rainfall may be uniform. Summers are typically hot i ...

. In addition to the chaparral vegetation (including chamise), riparian woodland, sage- buckwheat and barren areas, oak woodland and open yellow pine woodlands are represented. The Fern Canyon Research Natural Area is in the remote eastern part the San Dimas reserve. This Research Natural Area includes Brown's Flat, a locally unique mountain meadow that supports a relict grove of ponderosa pine (''Pinus ponderosa'' Douglas ex C. Lawson). In addition to Fern Canyon, the reserve's research facilities include over 50 gauged watersheds, a lysimeter complex, two major dams and reservoirs—

San Dimas Dam San Dimas Dam is a concrete gravity dam in Los Angeles County, California. The dam and its flood control basin/reservoir are in the San Gabriel Mountains and within the Angeles National Forest. The dam is currently operated by the Los Angeles Cou ...

and

Big Dalton Dam Big Dalton Dam is a multiple arch concrete dam in Los Angeles County, California, built for the Los Angeles County Flood Control District and completed in August 1929. The dam is one of the earliest of the multiple arch "double-wall" buttress des ...

—and three plantations of domestic and introduced trees. Studies at San Dimas have provided valuable information on air pollution, fire effects, erosion, hydrology, and plants and animals in southern California watersheds. The area also provides opportunities for ecological research to many nearby colleges, universities and governmental agencies. Wildfires have frequently burned through the San Dimas area, most recently when the Williams Fire burned much of the forest in September 2002. The forest is currently closed for the general public, except under special written permit. No hunting or other recreational activities are currently allowed.

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{{coord, 34, 12, N, 117, 46, W, type:landmark_region:US-CA, display=title Former biosphere reserves of the United States San Gabriel Mountains Protected areas of California Angeles National Forest Research forests