Document: STE-3-45-2

Coastal dune perennials facilitate seed accumulation: Results of a seedbank study.

FRANKS, S.J.* and C.J.PETERSON

The University of Georgia, Athens, GA, USA ¹

Abstract:
To investigate the role of adult plants in facilitating the accumulation of seeds in coastal dunes, we sampled the seedbank at 25 locations along each of three transects on Key Island, Florida and Sapelo Island, Georgia in September 1999. At each point, we collected five cubic centimeters of soil from the nearest vegetated (>75% cover) and nearest open (<25% cover) location, for a total of 300 samples. The samples were placed in a greenhouse and scored for numbers of germinants. 1,218 seedlings were observed by January 18, 2000. On Key Island, the vegetated areas had significantly more viable seeds than the open areas (1.05 vs. 0.22 seeds per cubic centimeter soil, p<0.0001 based on a Mann-Whitney rank sum test). The vegetated areas also contained more seeds than the open areas on Sapelo, but the difference was not significant (1.62 vs. 0.33 seeds per cubic centimeter soil, p=0.0637 based on a Mann-Whitney rank sum test). Species diversity was higher in the vegetated than in the open areas, and both seed density and diversity tended to increase with increasing distance from the shoreline, probably due to proximity to more seed sources. The composition of the seedbank differed from the dominant standing vegetation and included many weedy species. In the vegetated plots, the seed species were often different from the adults, indicating that the adults were accumulating dispersed seeds rather than simply having a small seed shadow. The results indicate that adult plants accumulate seeds in the coastal dune habitats studied. Perennial adult species such as Uniola paniculata and Iva imbricata may thus be necessary for the establishment of "pioneer" annual species and for the maintenance of species diversity.

Keywords: dune plants, seedbank, facilitation, species diversity

This abstract is being presented at: 4:00 PM in session:
Oral Session #68: Dispersal of Seeds and Fruits.