Mount Diablo
Map SatelliteMount Diablo, one of the highest peaks in the northern portion of the south Coast Ranges, is of considerable botanical interest. Some 525 of the 650 plants found here are natives.
Among the plant communities is chaparral, which occurs in patches on much of the mountain. In the inner Black Hills there is an Adenostoma fasciculatum-Arctostaphylos spp. association, with the endemic and rare Arctostaphylos auriculata the dominant and with Arctostaphylos manzanita ssp. laevigata equally abundant but less conspicuous.
There are several other chaparral associations. In the valleys and lower slopes the foothill woodland includes various oaks, Quercus spp., gray pine, Pinus sabiniana, and an occasional buckeye, Aesculus californica. A well-developed coastal sage scrub community with California sage brush, Artemisia californica, black sage, Salvia mellifera, and scattered toyon, Heteromeles arbutifolia, occurs here. The latter normally is found nearer the coast; its presence here is due to the frequent fog.
There is a closed-cone pine forest, with knobcone pine, Pinus attenuata, in association with Arctostaphylos auriculata and Arctostaphylos manzanita ssp. laevigata in the Cave Point region. This is one of the two localities of the knobcone pine in the Bay Area. (See Flicker Ridge)
There is also some grassland, with a Stipa-Sitanion association. On some of the creek there is a riparian Alnus-Platanus association. On the north slope there is a stand of Coulter pine, Pinus coulteri, which reaches its northern limit 5 kilometers (3 miles) northeast. (See Nortonville Coulter Pine Groves). The north side of the mountain is particularly rich in the diversity and integrading of plant communities.
Some 38 species of plants reach their northern limit at Mount Diablo, including Arctostaphylos glauca which becomes a virtual tree in lower Donner Canyon. Nine species of oak, exploiting different habitats, are found here and include Quercus douglasii, Quercus lobata, Quercus agrifolia, Quercus garryana, Quercus kelloggii, Quercus durata, Quercus chrysolepis, Quercus wislizenii and Quercus berberidifolia. Twelve rare plants occur here. They are, in addition to the Arctostaphylos, Arabis blepharophylla, Calochortus pulchellus, Cordylanthus nidularius, Eriogonum truncatum, Helianthella castanea, Hesperolinon bicarpellatum, Juglans hindsii, Malacothamnus fasciculatus (= hallii), Phacelia phacelioides, Sanicula saxatilis and Streptanthus hispidus.
Animal life is rich and varied and may include the rare Alameda striped racer, Masticophis lateralis euryxanthus. Several fossil localities, where both plant and animal remains have been found, occur on the mountain. (See Black Hawk Ranch Fossil Site).
The mountain offers an excellent example of a diapir, the piercement of the overlying igneous and sedimentary strata by Franciscan rocks and serpentine thrust up during the Plio-Pleistocene Coast Range orogeny. The strata range from Jurassic to Upper Miocene in age.
Integrity: While the area has been developed as a State Park, with all the associated facilities, much of it, particularly the north side, is virtually undisturbed. Portions have been grazed.
Use: Educational, research, observational, light recreational.
Ref: Bowerman, Mary, 1944. The Flowering Plants and Ferns of Mount Diablo, California; Their Distribution and Association into Plant Communities. Berkeley Gillick Press, 290 pp.
Colburn, I. 1961. Tectonic History of Mount Diablo. Unpub. Ph.D. Thesis, Stanford University. Clark, B. L. and A. S. Campbell, 1942. Eocene Radiolarian Faunas from the Mount Diablo Area, California. Geol. Soc. Am. Spec. Paper 39, pp. 1-112.
October 1975
Inventory of California Natural Areas
Revision © 2009 Steven Louis Hartman
