Santa Margarita Ecological Reserve

Map Satellite

Included in this Reserve are 4 kilometers (2.5 miles) of the Santa Margarita River, the only permanent un-dammed river in Southern California.

Four plant associations are represented on the Reserve: chaparral, riparian forest, open and closed oak woodland.

A fire in 1969 burned over 90% of the area, including virtually all the chaparral; most of the unburned areas lie in canyon bottoms. The chaparral has been invaded by foreign species in most areas but the chamise, Adenostoma fasciculatum, is still the dominant plant. Other resprouters doing well include scrub oak, Quercus sp., Eastwood manzanita, Arctostaphylos glandulosa, hard tack, Cercocarpus betuloides, and red berry, Rhamnus crocea. Ceanothus tomentosus seedlings are profuse in some areas. Many annual grasses and other invasive species are growing in the chaparral at present.

Riparian vegetation occurs along the canyon bottom and some washes. Willows, Salix spp., reeds, Scirpus spp., and cattail, Typha latifolia, are common here. Trees other than Quercus and Salix that grow along the river include elderberry, Sambucus mexicana, Arizona ash, Fraxinus velutina, sycamore, Platanus racemosa, and the cottonwoods, Populus trichocarpa and Populus fremontii. Besides the scrub oak, the coast live oak, Quercus agrifolia and mesa oak, Quercus engelmannii, are found here. In the southern valley the oaks have a much denser understory than those on the northern boundary. The association of Quercus agrifolia and Quercus engelmannii with coastal sage undergrowth is a rarity in the State. The rare Dudleya viscida occurs in the gorge.

Animal populations here are rich and varied; however, no rare or endangered species are found on the Reserve. The rare Stephen's kangaroo rat, Dipodomys stephensi, occurs in the vicinity. Several uncommon animals are present, including mountain lion, Felis concolor, ringtailed cat, Bassariscus astutus, gray shrew, Notiosorex crawfordi, golden eagle, Aquila chrysaetos, San Diego horned lizard, Phrynosoma coronatum blainvillei, orange-throated whiptail lizard, Cnemidophorus hyperythrus beldingi, and two-striped garter snake, Thamnophis couchi hammondi. Beaver, Castor canadensis, have been introduced into the area.

Geologically, the outstanding feature of the area is the Temecula Canyon (Santa Margarita Gorge). Here the Santa Margarita River cuts through what would otherwise be continuous mountainous terrain. The method of formation of the gorge, whether through down-cutting or back-cutting, is at present undetermined. There is evidence that the current has been strong in the past, and the distribution of Quarternary stream gravels suggests that the canyon could have been cut in during the Pleistocene.

Integrity: Much of the area has been burned at various times, the latest in 1969. In the past, portions were used for ranching, including grazing, and buildings, orchards, etc., are present. An aqueduct crosses the Reserve. It has been a Reserve since 1962.

Use: Research, education.

Ref: Cooper, C. F., H. N. Coulombe, R. L. Hays, P. H. Zedler (eds.), 1973. The Santa Margarita Ecological Reserve, a Resource Inventory. Center for Regional Environmental Studies, San Diego State University.

May 1975