Tolerance of salt spray from the ocean may influence species distributions on coastal dunes. I tested the effects of salt spray on growth and survival of seedlings of common species from a barrier dune at Waquoit Bay National Estuarine Research Reserve, Falmouth, MA. Five species were tested: Rosa rugosa, the dominant shrub on the back slope of the dune; Myrica pensylvanica, the dominant shrub in the flat zone behind the dune; Solidago sempervirens, a subordinate species present on the dune front, back, and flat; Artemisia campestris ssp. caudata, a common herb on the dune back and flat; and Oenothera parviflora, a subordinate species found only on the dune flat. Seedlings were grown in the greenhouse from field-collected seeds, and exposed to daily salt spray equivalent to average levels on the dune front, average levels on the dune flat, or a control of distilled water.

Results/Conclusions

High levels of salt spray (levels found on the dune front) decreased survival of Myrica and Oenothera, and decreased growth of Rosa and Myrica. These results are consistent with the absence of these three species on the dune front. Further tests with a wider range of salt spray levels are needed to determine whether salt tolerance can explain why Rosa, but not Myrica or Oenothera, can survive on the dune back slope. Solidago growth and survival was not affected by any level of salt spray, consistent with its presence in all dune zones. However, Artemisia, which is not found on the dune front, was not affected by salt spray. Ongoing work is investigating factors that may limit the distribution of Artemisia. In conclusion, tolerance of salt spray can at least partially explain the distribution of these five species across the coastal sand dune habitat.