California Foothill Blue Oak Woodland

This ecological system is primarily found in the valley margins and foothills of the Sierra Nevada and Coast Ranges of California from approximately 120-1200 m (360-3600 feet) in elevation on rolling plains or dry slopes. Over a century of anthropogenic changes (especially cutting of oak) have altered the density and distribution of woody vegetation. A high-quality occurrence often consists of open park-like stands of Pinus sabiniana, with oaks and other various broadleaf tree and shrub species, including Quercus douglasii, Quercus wislizeni, Quercus agrifolia (primarily central and southern Coast Ranges), Quercus lobata, Aesculus californica, Arctostaphylos spp., Cercis canadensis var. texensis, Ceanothus cuneatus, Frangula californica, Ribes quercetorum, Juniperus californica, and Pinus coulteri (central and southern Coast Ranges). Pinus sabiniana tends to drop out all together in the driest and more southerly sites, which are often dominated by Quercus douglasii. The California central coast region may have open stands of just Juniperus californica, with a grassy understory. These stands belong here due to proximity to other blue oak and gray pine stands or chaparral, and due to the heavy native or non-native grass cover. This is distinguished from Great Basin pinyon-juniper stands, which have little herbaceous understory, and Pinus monophylla rather than Pinus sabiniana. These stands of only juniper are caused by repeated removal of the oaks by humans and feral pig populations. Northern extensions of this system include Quercus garryana as the dominant oak, where it becomes successional to Mediterranean California Lower Montane Black Oak-Conifer Forest and Woodland (CES206.923). Pinus sabiniana density also varies based on intensity or frequency of fire, being less abundant in areas of higher intensity or frequency, hence it is often more abundant on steep, rocky or more mesic north-facing slope exposures. Historically, understory vegetation included mixed chaparral to perennial bunchgrass. Currently, most occurrences have understories dominated by dense cover of annual species, both native and non-native. Variable canopy densities in existing occurrences are likely due to variation in soil moisture regime, natural patch dynamics of fire, and land use (fire suppression, livestock grazing, herbivory, etc.).

A high-quality occurrence often consists of open park-like stands of Pinus sabiniana, with oaks and other various broadleaf tree and shrub species, including Quercus douglasii, Quercus wislizeni, Quercus agrifolia (primarily central and southern Coast Ranges), Quercus lobata, Aesculus californica, Arctostaphylos spp., Cercis canadensis var. texensis (= Cercis occidentalis), Ceanothus cuneatus, Frangula californica (= Rhamnus californica), Ribes quercetorum, Juniperus californica, and Pinus coulteri (central and southern Coast Ranges). Pinus sabiniana tends to drop out all together in the driest and more southerly sites, which are often dominated by Quercus douglasii.

Soils are shallow, low in fertility, and moderately to excessively drained with extensive rock fragments. It occurs on valley margins and foothills, rolling plains or dry slopes, and generally steeper and drier slopes than pure blue oak woodlands without foothill pine. Mediterranean climate with mild winter rain (not snow) and very hot summers. This system is extremely drought-tolerant. The upper elevational limit is 150 m in the north and 900 m in the south.

This system occurs primarily in the valley margins and foothills of the Sierra Nevada and Coast Ranges from approximately 120-1200 m (360-3600 feet) elevation, from Shasta County to Kern and northern Los Angeles counties, California. It is unlikely to occur in the southern portion of zone 7 (Modoc Plateau), but this needs to be confirmed with California ecologists.