RAPID: Seed caches as a fire survival mechanism in Arctostaphylos (Ericaceae)

San Francisco State University, San Francisco CA

Investigators

Abstract

The seeds of several plant species in California chaparral require fires to germinate. In the genus Arctostaphylos (Ericaceae), a group of woody shrubs and small trees found in chaparral, seeds are initially dispersed locally. As seeds are slowly incorporated into the soil, they create dormant, persistent soil seed banks where they remain until conditions are right for germination following fire. Critically, seeds must reach a sufficient depth to survive the heat of fire but still be shallow enough to emerge after germinating. After seedlings establish following fire, survivors generally take several to nearly 10 years before they begin producing seeds. Fires during Summer 2008 have revealed an intriguing pattern suggesting that rodents cache Arctostaphylos seeds by burying collections of seeds below 5 cm enabling higher rates of survival during fires. This project focuses on documenting survival rates of seedlings emerging from seed banks as individuals versus from caches following the 2008 fires in several California field sites that differ in plant species composition and past fire intensity. Sampling must occur quickly before seedlings experience the usual late-summer drought and die-off. Secondary dispersal of seeds by mammals as suggested here has rarely been investigated thus results will have implications for relevant theory and for other ecosystems. Two-thirds of the taxa of Arctostaphylos are of limited distribution, and many are listed or being considered for listing (state and federal) as threatened or endangered. These species often occur in habitats that may be encroached upon with development. Results of this project will have conservation implications because managing these plant species may require effective management of associated animal communities. Undergraduates and a research technician will be mentored and trained in this project, and several public outreach efforts are planned.