Salt spray effects on forest succession in rare coastal sandplain heathlands: evidence from field surveys and Pinus rigida transplant experiments'

GRIFFITHS M. E. AND C. M. ORIANS (Department of Biology, Tufts University, Medford, MA 02155). Salt spray effects on forest succession in rare coastal sandplain heathlands: evidence from field surveys and Pinus rigida transplant experiments. J. Torrey Bot. Soc. 131: 23-31. 2004.-Coastal sandplain heathland is a rare ecosystem maintained by recurrent disturbances and chronic abiotic stress. In areas with low disturbance or stress, heathland communities are succeeded by tree species, such as Pinus rigida, that outcompete native heathland plants. We propose that salt spray is an important natural abiotic stress factor that helps to maintain heathlands near the coast by slowing tree succession. We investigated whether salt spray inhibits succession in heathlands on Martha's Vineyard, Massachusetts, by surveying natural field distributions of species and by quantifying the survival and growth of P rigida seedlings transplanted at different distances from the ocean. Tree species did not grow in areas with high salt spray and multivariate analyses identified salt spray as an important ecological factor influencing species distributions in coastal heathlands. Although transplanted P. rigida seedlings exhibited low mortality close to the ocean, they exhibited higher water stress and needle necrosis as well as inhibition of growth, suggesting that salt spray may be important in suppressing trees close to the