Demographic patterns of the shrub Ceanothus megacarpus in an old stand of chaparral in the Santa Monica Mountains

Abstract

Wildfires have had a major influence on the structural and functional adaptations that have evolved in Mediterranean-type ecosystems. Some chaparral shrubs sprout after fires while others produce serotinous cones or seeds refractory to germination until they are cued by a fire. Ceanothus megacarpus is a sclerophylous shrub commonly found in California in either pure of mixed stands which does not survive fires but whose seeds germinate following a fire. Because in recent decades man-made fires have become frequent, few older stands remain, and they have been described as "decadent" or "senescent." Since data on older chaparral stands are scarce, a stand of chaparral in the Santa Monica Mountains of southern California, which last burned in 1929 was studied in an effort to elucidate the survivorship patterns and community structure of Ceanothus megacarpus as it ages. Ceanothus is responsible for 68 percent of the basal coverage at this mixed stand, and one-eighth of the Ceanothus were found to be dead. Over 130 such dead individuals were cut at ground level and aged by ring counts to establish the survivorship curve for this species in this chaparral community in the absence of fires.