Use of long term vegetation census data to inform restoration methods and processes of community ecology on a barrier island

Background/Question/Methods

Barrier islands are a dominant feature of coastlines worldwide and absorb the wind and wave action from both regular climate patterns and storms. In particular, large storms can disrupt the normal pattern of dunes and swale development and dramatically affect the vegetation through sand movement and saltwater flooding. Understanding changes in vegetation on dunes in response to climatic events can help to elucidate mechanisms of ecological processes occurring in these areas as well as predict future effects of global change for management of sensitive coastal areas. A ten-year census documenting the dynamics of dune vegetation on St. George Island, FL, has provided the opportunity to correlate vegetation and climate patterns. St. George is composed of the three dune habitats found on most barrier islands: high foredunes facing the ocean, flat overwash interdunes, and relatively stable backdunes facing the bay. Total number of species found within plots increased from the foredune to the backdune habitat. However, species in each habitat showed a similar range of response to storms, with about a quarter of total dune vegetation species demonstrating positive growth in responses to hurricanes. Six species that responded particularly well following storms were identified: Fimbristylis spp. and Uniola paniculata from the foredune habitat, Centella asiatica and Sporobolus virginicus from the interdune habitat and Muhlenbergia capillaries and Schizachyrium maritimum from the backdune habitat. A transplant experiment across dune microhabitats was conducted to test the prediction that these species may be useful for restoring damaged coastal areas. I quantified (1) the success of the transplants across the three dune habitats (2) how transplants encourage the growth of proximate individuals to accelerate habitat rehabilitation and (3) how mechanisms of facilitation and succession differ between dune areas, considering major differences in environmental characteristics between habitats.

Results/Conclusions

Results suggest that the habitat from which a transplant originates is not a good indicator of its success in different habitats. Further, it appears that transplants encourage succession across degraded habitat by increasing soil moisture and stabilizing substrate, but facilitation operates differentially across the dune habitats. Lastly, a succession model developed from the long term census data suggests that the rate of dune species assemblage and composition of vegetation communities following damaging events will be affected by the increase in storm frequency predicted to occur in future climate change scenarios.