Fairfield Osborn Preserve - Ecology

Ecology

Principal plant communities within the Preserve include the dominant California oak woodland savanna, and also consist of chaparral, marsh, native Bunch grass, douglas-fir woodland and riparian woodland. Within the oak woodland the main tree species are Coast live oak, Oregon oak, California black oak, Canyon live oak and California bay laurel. The woodland understory exhibits toyon, coffeeberry, poison oak and, in the higher exposed areas with ecotones to chaparral, containing chiefly coyote brush. This community sometimes gradates to small grassland savannas between the oak groves, which are rich with grasses and annual wildflowers. Example plants in this community are the Yellow Hayfield Tarweed, Hemizonia congesta spp. congesta and the Hayfield Tarweed, Hemizonia congesta spp. luzulifolia, which are seen blooming in the late autumn.

The freshwater marsh was formed by massive land movement along the Rodgers Creek Fault. The two ponds on the property are manmade, having been created in the early 20th century. These wetland communities are important habitat for many species including sora and Virginia rails, western pond turtles, and the federally-listed endangered Red-legged Frog. Moreover, natural seeps feed these locations and the outcome is climax vegetation that has stabilized. Turtle Pond has a layer of duckweed on the water surface that is consumed by a variety of fauna. Riparian zones of Copeland Creek have a very high percentage population of California bay laurel, but also provide habitat for a rich variety of amphibians, newts and other fauna. The Pacific Giant Salamander, one of the largest known species of salamander is observed hunting for prey in Copeland Creek. Other amphibians seen in riparian habitats include the Pacific treefrog, Hyla regilla, Rough skinned newt, Taricha granulosa, and California slender salamander, Batrachoseps attenuatus. A number of plants are particular to the deeply shaded riparian zone including snowberry and the uncommon California Ginseng, Aralia californica.