Thursday, August 7, 2008: 10:30 AM
201 A, Midwest Airlines Center
Sheri A. Shiflett, Biology, Virginia Commonwealth University, Richmond and Donald R. Young, Alaska Department of Fish and Game
Background/Question/Methods Seed arrival is an ecological flux that when quantified provides an understanding of patch dynamics and variations in community structure across the landscape. On barrier islands, microsites favorable for germination are continually being created and destroyed via physical disturbances, but also by biotic interactions. Thus, it is advantageous for plants to have seeds dispersed to a multitude of patches in order to increase chances of survival and growth. We hypothesized that avian species play key roles as agents of seed dispersal and may influence vegetation community structure and patch dynamics across the barrier island landscape. This study focused on three central questions: does patch type influence the favorability of seed deposition, is there latitudinal spatial variation in seed deposition among the islands, and what is the species composition of seeds deposited relative to the current vegetation of the surrounding landscape. This study was conducted on three barrier islands of the Virginia Coast Reserve, which represent a range of size, topographic complexity and species richness. For each of the three islands, a transect was positioned at a woody site and a graminoid site. Artificial perches were set-up at each transect with an attached fecal seed trap. Deposited seeds were collected at four times throughout the year, including both the autumn and spring passerine migrations.
Results/Conclusions Overall woody species composition for any given site was low with n=6 being the most species with seeds deposited at a site. Field observations indicate that collector usage is highest at woody sites. Collectors positioned near woody species also have a higher concentration of woody species deposition. However, there is no correlation between island location (i.e. north vs. south) and number of species deposited. Seed composition generally reflects local species composition (i.e. species located within a 10 m radius of each collector); but some collectors have received species outside of the local range of collectors. Local dispersal appears to be the main mechanism by which avian-mediated seed dispersal on Virginia barrier islands occurs. Thus, any structure that attracts passerines may influence species arrival and presumably, future community composition. Coastal restoration projects may be enhanced by providing perches for natural recolonization.
