Seed Germination Requirements for Four Fire-Recruiter Chaparral Shrubs

Wildfires are a natural part of chaparral ecosystems, as they are essential to vegetative regrowth and plant recruitment. For many chaparral species, fire stimulates germination of dormant seeds in the seed bank. This study explored fire-related cues necessary for seed to break dormancy, germinate, and emerge in four chaparral species (Ceanothus cuneatus, C. jepsonii, Arctostaphylos manzanita, A. viscida). Seed were exposed to various treatments mimicking wildfire conditions, including boiling water and charred wood (charate), as well as physical scarification by concentrated acid, and monitored for germination. Our data indicate that Ceanothus seed require heat cues to germinate, but fire-related chemical cues did not induce germination in any of the species studied. However, pre-treatment with harsh acid was necessary to break physical dormancy in the two Arctostaphylos species, which mimics passage through the mammalian gut. Additionally, all species required two to three months of cold stratification to promote germination. These findings may support restoration and conservation efforts in chaparral areas in which germination from seed is required