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Marshes on the Move: Testing effects of seawater intrusion on vegetation communities of the salt marsh-upland ecotone
Citation:
Baughn, C., R. Martin, Rick Mckinney, AND C. Wigand. Marshes on the Move: Testing effects of seawater intrusion on vegetation communities of the salt marsh-upland ecotone. New England Estuarine Research Society (NEERS) Fall Meeting, Block Island, Rhode Island, October 20 - 22, 2016.
Impact/Purpose:
This research tests the response of salt marsh-upland ecotone vegetation to seawater intrusion using a transplant experiment.
Description:
The Northeastern United States is a hotspot for sea level rise (SLR), subjecting coastal salt marshes to erosive loss, shifts in vegetation communities, and altered biogeochemistry due to seawater intrusion. Salt marsh plant community zonation is driven by tradeoffs in stress tolerance and interspecific interactions. As seawater inundates progressively higher marsh elevations, shifts in marsh vegetation communities landward may herald salt marsh “migration”, which could allow continuity of marsh function and ecosystem service provision. To elucidate possible effects of seawater intrusion on marsh-upland edge plant communities, a space-for-time approach was replicated at two Rhode Island salt marshes. At each site, peat blocks (0.5 m x 0.5 m x 0.5 m, n=6) with intact upland-marsh edge vegetation were transplanted downslope into the regularly-inundated mid-marsh. Procedural controls (n=3) were established at each elevation by removing and replacing peat blocks, and natural controls (n=3) consisted of undisturbed plots. During peak productivity, each plot was assessed for species composition, percent cover and average height. Results demonstrate stunting of marsh-upland edge vegetation in response to increased inundation, and the beginnings of colonization of the transplanted plots by salt marsh species. The extent of colonization differed between the two sites, suggesting that site-specific factors govern vegetation responses to increased inundation. Though this experiment is ongoing and in its early stages, results suggest the potential for seawater intrusion to drive shifts in marsh-upland edge plant community composition. These findings have implications for the ability of marshes to migrate in the face of sea level rise.