Germination and Predation of Quercus geminata and Quercus myrtifolia Acorns on Santa Rosa Island, Florida

摘要

Scrub oak species are an important component of barrier island and xeric mainland scrub ecosystems. Limited recruitment of scrub oaks has been noted on barrier islands. This study evaluated several factors believed to alter germination of the scrub oak species Quercus geminata (sand live oak) and Quercus myrtifolia (myrtle oak) along interior dune fields and swales of Santa Rosa Island in the western panhandle of Florida. Influences of dune-field microrelief (interdunal swale or low-lying dune), vegetation cover (vegetated and unvegetated), and seed placement (buried and surface) on germination of acorns were analyzed. Predation of acorns with and without protection from nonburrowing herbivores (open-bottom cage and no cage) was also evaluated. Acorn predation was high. Less than 1% of Q. myrtifolia acorns were recovered outside cages. Only 33% of Q. geminata acorns were recovered outside of cages, with acorn loss reduced only by burial. Burrowing beach mice were able to access acorns within cages. Recovery inside cages was also greater when acorns were buried. Germination of Q. geminata acorns was 15% and was greatest when acorns were buried but was not influenced by microsite or vegetation cover. Germination of Q. myrtifolia was 74% and greater when buried but similar regardless of microsite and vegetation cover. Scrub restoration strategies to increase germination of these two scrub oak species would benefit from an approach that implements direct seeding (burial) in mesic microsites, while sites with strong predator pressure would further benefit from addition of physical protection from seed predators.