Salt marsh communities are sensitive to disturbance and perturbations from natural causes such as storms and geomorphic processes, as well as human induced impacts associated with nutrient loading, watershed development, tidal restrictions, and ditching. There is a long history of alteration of salt marshes along the Northeast coast, including extensive ditching for mosquito control, salt hay farming, and restriction of tidal exchange by roads, causeways, bridges, and dikes. As the coastal corridor becomes more urbanized, watersheds become increasingly developed, and salt marsh acreage declines and become fragmented. Urbanization leads to nutrient-laden runoff.
By monitoring Salt Marsh vegetation, the Network will be able to provide information to park managers on how park salt marsh communities are changing over time. Detection of species composition change, including the presence of invasive species can provide early warning to park managers that changes in pollution levels, salinity levels, tidal flow and groundwater levels may be occurring within or around the park.
Identify temporal patterns in salt marsh vegetation communities as determined by species composition and abundance (measured by percent cover) within NCBN parks.
Two to three study marshes of approximately 10ha in size will be randomly selected from the population of all potential study marshes so that statistical inference can be extended to all salt marshes within each park unit. Vegetation will be sampled within 35, 1m2 plots aligned along a minimum of 7 transects. Once selected, each study marsh site will remain permanent and will be re-sampled in future years; however transects and plots will be randomly re-located within each study marsh each year.
The percent cover of salt marsh vegetation and other covers (e.g., water, bare ground, wrack and litter) within the 1m2 plots will be visually estimated using the Braun-Blanquet scale. Additional data will also be collected using the point intercept method in short canopied (<1m height) vegetation at a subset of selected plots. Other metrics, such as height of species of interest (e.g., Phragmites australis) can also be measured when they occur within the vegetation plots. Salt marsh vegetation is sampled once per year, near the end of growing season.