VEGETATION AND GEOMORPHIC CHANGES IN A NEW ENGLAND SALT MARSH IN THE LAST 1,000 YEARS

Headquarters marsh is one of several marshes in the Barn Island Wildlife Management Area in Stonington, CT near the Connecticut-Rhode Island border. Modern coastal marshes in Connecticut generally began forming after the period of rapid post-glacial seal level rise, which ended 3,000 y ago. Headquarters marsh peat records approximately the last 1,000 y of relative sea level rise and subsequent coastal change. We compare peat accumulation rates from Cs-137 derived 1954 horizons, excess Pb-210 dating, and C-14 dating with nearby tide gauge records to trace the growth and landward encroachment of Headquarters marsh. With sea level rise, succession of marsh grasses is preserved in peat as roots or rhizomes. In recent decades, there is a particularly striking reduction in the mid to high marsh species Juncus gerardi and Distichlis spicata. There is also a gradual increase in Spartina spp. on the upper slope of the high marsh. Marsh flora follow a general pattern from low marsh to high marsh to upland, but microtopography, drainage, and other factors such as human modifications influence the mosaic of vegetation visible today. Using data from thirty new cores (up to 7 m in length), we present geomorphic and vegetation changes to the area since the marsh first formed, with some dramatic changes since early studies of this location in the 1940s.