Arctostaphylos Occurence and Historical Fires table

Ecological factors favoring either resprouting or obligate seeding in plants have received considerable attention recently. Three ecological models have been proposed to explain patterns of these two life history types. In this study we test these three models using data from California chaparral. We take an innovative approach to testing these models by not testing community or landscape patterns, but instead, investigating environmental patterns characteristic of pairs of either resprouting or obligate seeding subspecies of Arctostaphylos (Ericaceae), a dominant and diverse shrub genus in chaparral. Four species were investigated that contain both a resprouting and an obligate seeding subspecies. Data were analyzed for % bare ground, elevation, annual precipitation, number of fires, and time between fires and were compared independently for each subspecies pair. Results were consistently supportive of the gap-dependent model suggesting that obligate seeders are favored when post-disturbance gaps are large. Results for other aspects were inconclusive or contrary to expectations for either of the other models.