Plant Communities of Mount Diablo State Park
Glenn Keator, Ph. D.
(Excerpted from MDIA's book Plants of the East Bay Parks)
Hard chaparral replaces soft chaparral in hotter, drier inland areas, usually on steep, rocky slopes. (Shrubs favor the summer heat of south facing slopes.) From a distance the dense, tall shrubberies of hard chaparral look like a uniform dark green velvet draped over the mountainsides.
Hard chaparral is so named because its component species have stiff, tough, durable leaves that are seldom shed even at the peak of summer's heat. In fact, the main attribute of such leaves is their long tenancy; shrubs do not have to expend valuable water to create a new set of leaves each year should rains be sparse.
Leaf design varies as much as the several families and general represented. Manzanitas make stiff ovate leaves that are turned edgewise or vertically to avoid the full brunt of sun -- and some kinds, like big-berry manzanita (Arctostaphylos glauca), have whitish leaves that reflect away excess light and heat. Chamise (Adenostoma fasiculatum) uses narrow, needle-like leaves clustered together to conserve water by minimizing surface area exposed to sun. Wild lilacs (ceanothuses) cover their leaves with a thick, waxy covering that makes them shiny. Bush poppy (Dendromecan rigida) has bluish green leaves held obliquely to reflect away heat and minimize the impact of the fierce summer sun.
In addition to their ingeniously designed leaves, chaparral shrubs have deeply probing roots that serve to hold shrubs in place and find sources of deeply hidden water. Roots may also carry on chemical warfare with neighboring shrubs to prevent invasion into their own root zone. Chaparral pea (Pickeringia montana) and ceanothuses have tiny knobs on their roots that house nitrogen-fixing bacteria. As a result, such shrubs can move onto nutrient-poor soils; when they die they may pave the way for other shrubs to move in by releasing these nitrogenous compounds into the soil.
Chaparral shrubs grow into nearly impenetrable canopies -- from head high to well over ten feet. The best way to pass through is to crawl beneath the branch canopy as small mammals do. Chaparral has been called the elfin forest in allusion to this dense but short forest-like growth pattern.
Link to California Chaparral Field Institute website.
Link to Belorussian Translation website