INTERACTION BETWEEN GEOGRAPHIC POSITION, MARSH TYPE, HERBIVORY AND HYDROLOGY ON THE HYPSOMETRY OF CAPE COD NATIONAL SEASHORE SALT MARSHES

With accelerated sea level rise rates and increasing storm intensities, the capacity of salt marshes to accrete sediments and grow vertically is crucial to maintain their protective ecosystem services such as buffering storm surge and reducing flood impacts. Cape Cod National Seashore (CCNS) has back-barrier and riverine salt marshes on the ocean and bay sides of the peninsula. Using Real-Time Kinematic surveying to collect elevation data at regular intervals along the entirety of the marsh surface, DEMs (digital elevation models) were created for five CCNS salt marshes. By comparing the differences in marsh elevations and hypsometry (extent of those elevations), tidal ranges and inundation, geographic position, herbivory stress and marsh type, we can assess the relative importance of each of these factors in influencing marsh capital and relative vulnerability to climate change effects such as SLR and increased storms. Additionally, an intensive study area that has been dramatically affected by crab herbivory was surveyed for the third year using a very high concentration of survey points. In addition to the higher sampling density, a data dictionary was used which included parameters such as vegetation type and percent cover, sediment type, evidence of crab burrows, etc. By comparing results from three years’ worth of high-density, ground survey data, realistic comparisons of elevation loss and shifting plant communities can be made. Recommendations for marsh elevation survey methods will be made.