Plant "communities" are useful constructs for describing the wild environments around us; defining a set of community types makes the every-varying world seem a little more manageable and understandable. Although scientists continue to argue over the specifics of how communities are defined, we will use simple general categories.
Communities each have personalities of their own determined by their place and time, and the personalities in turn determine what specific plants and animals you find there. The dominant plants (whether they be shrubs, grasses, wildflowers, or trees) give the community its unique character and name. The communities fall into these categories:
Plants of Mount Diablo State Park & Vicinity
Open places, without woody plants. Grasslands may represent natural places as well as disturbed, unnatural habitats, such as pastures and grazed areas. Long called hog wallows as well as other degrading names, vernal pools are specialized habitats within our grasslands. Wherever clay soils form small depressions underlain by cement-like hardpans, vernal pools appear.
Most of our shrublands are called chaparral, but that name actually covers several kinds of shrublands. Generally speaking, chaparral is typical of our hottest, steepest, rockiest slopes -- often south-facing -- where the summer sun is strong and winter rains run off (rather than being retained as they are on gentle slopes and flats). Here shrubs occur in dense stands, overshadowing all else. The Spanish term "chaparral" -- a grove of scrub oaks -- has been adapted for many of our shrublands. Also called coastal scrub or coastal sage scrub, soft chaparral is dominated by small shrubs with "soft leaves" (leaves with a pliable, thin texture). Hard chaparral replaces soft chaparral in hotter, drier inland areas, usually on steep, rocky slopes. (Shrubs favor the summer head of south-facing slopes).
Trees dominate all such places. There are two general categories: forests (where tree canopies overlap, creating dense shade) and woodlands (where trees are scattered with openings between). Riparian woodland is found only along permanent streams and rivers, where the water table remains at or just below the surface all year. The most characteristic type of tree land in our part of California is the oak woodlands, as they occur in the large areas of low foothills in both the Coast Ranges and the Sierra Nevada. Where oak canopies overlap, conditions favor a variety of other evergreen trees such as the California bay laurel, madrone, Douglas fir, tanbark oak, and California nutmeg.
Redwood forests are represented in our area by isolated fragments found in the deepest, most protected canyon bottoms within the reach of summer fogs.
Excerpted from MDIA's book Plants of the East Bay Parks by Glenn Keator, PhD
Chaparral - Chamise
Mount Diablo Buckwheat Rediscovered by Robert Sanders
New Perspective on the Flora of Mount Diablo by Kevin Hintsa
Poison Oak from Mountain News, January 1999
Rugged Plants Struggle to Survive on Barren Serpentine Soil contributed by Dan Day, NCGS Newsletter