Seed Banks, Seed Germination, and Implications for Conservation of the Endangered, Fire-Dependent Shrub, Arctostaphylos morroensis

Conservation of obligate-seeding shrubs from Mediterranean-climate regions is an international conservation priority. Morro manzanita (Arctostaphylos morroensis) is one such shrub whose persistence may depend on germination and establishment from soil-stored seeds following fire. However, fire has been virtually eliminated from its remaining habitat. Thus, conservation of A. morroensis may depend on actions that stimulate germination to establish new populations. We characterized seed banks in different-aged stands and examined viability and germination of A. morroensis seeds in response to various cues, including heat and charred wood. We found that seed density varied greatly among sites, although not increasing with stand age as predicted. Rather, the oldest stand had especially low seed densities and viability. Viability of A. morroensis seeds was low—on average ∼4%—limiting germination. Surprisingly, ∼40% of viable seeds germinated with no fire treatments. Neither heat nor charred wood alone enhanced germination; however, when combined the two resulted in highest germination. Seeds soaked in water prior to heat-and-charred-wood treatments had significantly reduced germination, suggesting that prescribed burns conducted in the wet season would result in a poor germination response. Characterization of the seed bank and determination of the cues stimulating germination can provide information vital to the maintenance of this and similar obligate-seeding species.