Salt Marsh Plant Community Structure on Horse Island, South Carolina

Sea level rise is causing an increase in salt water encroachment and flooding in many coastal habitats, and increasing salinity can have negative impacts on plant communities. The objective of our research was to determine the impact of salinity on salt marsh plant community structure on Horse Island, South Carolina. We investigated variation in plant cover and height with distance from a tidal creek and the effect of increasing salinity on seedling emergence from the seed bank. We established three transects in the salt marsh habitat and recorded plant species presence, percent cover of each species, and height of the tallest individual of each species in 11 plots along each transect. Total plant cover was consistent from 0 to 24 m and increased from 24 to 40 m from the tidal creek; several species only occurred 36-40 m from the tidal creek. Percent cover of Spartina alterniflora, the dominant species, increased from 24 to 36 m from the tidal creek. The height of S. alterniflora was negatively correlated with percent cover of S. alterniflora and distance from the tidal creek. To assess the seed bank, we established 12 plots in the salt marsh-maritime forest ecotone, and soils collected from plots were assigned to each of four salinity treatments (0, 6, 12, and 26 ppt). Across all treatments, only one seedling emerged from the soil. The cover, height, and distribution of salt marsh species on Horse Island are likely to change as sea level continues to rise, but the role of the seed bank in affecting plant community structure remains unclear