Elevation as a Predictor of Marsh Vulnerability to Sea-level Rise along the Eastern Shore of Virginia

To evaluate vulnerability of salt marshes to sea level rise at the Virginia Coast Reserve (VCR) LTER, experiments are under way to identify the optimum elevation for growth of Spartina alterniflora, the dominant plant in the extensive marshes of the VCR. Monthly measurements of plant height, density, and soil pore water characteristics are made along natural elevation gradients in 2 marshes and in experimental “marsh organs” in the tidal creeks adjacent to those marshes. The marshes have different soil organic matter contents (ca. 6-8% vs. > 20% by loss-on-ignition), elevations, and long-term productivity responses to sea level rise. Permanent plots (at 6 elevations) were established along 6 transects in each marsh, oriented to capture the full range of elevations where S. alterniflora grows. Marsh organs simulate different elevations in the marsh (ranging from ca. 40 cm to 100 cm above MSL) and isolate hydroperiod as the key variable. We expect to find differing optimum elevations for above and below ground biomasses within each site, as well as between sites. These optima, coupled with previously established marsh elevations and hypsometry, will then be used to develop vulnerability maps showing which marshes are likely to persist at current and predicted rates of sea-level rise.