Dyke Marsh Preserve - Feasibility of Restoration
Hog Island Gut in Dyke Marsh Preserve. Dyke Marsh is an important, large tract of freshwater tidal marsh along the Potomac River in the Washington, D.C. area and has existed for at least 5,000 years. Located just south of the city of Alexandria, VA, Dyke Marsh is viewed as a national treasure because of its proximity to the nation's capital and a large urban/suburban population, its history, and its current potential for provision of ecological services, recreational values, and educational opportunities. In addition, its location along a major travel corridor (George Washington Memorial Parkway) to one of the most popular tourist destinations in the D.C. area (Mount Vernon) provides Dyke Marsh Preserve (DMP) with opportunities to enhance the economic productivity and environmental education in the region.
Downloading data from the tide gage at Dyke Marsh.Since 1973 the National Park Service (NPS) has managed the Dyke Marsh Preserve (DMP) just south of Alexandria, VA, as the last major remnant of formerly extensive freshwater tidal marshes along the Potomac. Previous to NPS supervision, portions of the emergent marsh at DMP were dredged for sand and gravel with resultant loss of approximately half the emergent wetlands. Restoration of emergent marsh to the dredged areas would enhance the ecosystem and economic services provided by the marsh, expand the extent and quality of a relatively rare wildlife habitat, and extend the aesthetic appeal of this urban/suburban wetland. However, ecological feasibility and logistical problems of such a restoration effort cannot be taken lightly. This project reviewed the available data on both the physical and biological components of the marsh and supplemented that information with new data on standing vegetation and seed banks, hydrochory, marsh elevation, water and soil chemistry, and tidal fluxes to describe current conditions and evaluate the potential for success and sustainability of a marsh restoration effort.
Aerial views of Dyke Marsh in 1937, 1954, and 1994. By 1940, the marsh was being dredged for sand and gravel. As a result, almost 200 acres of marshland were lost.Our overall goal was to determine the feasibility of restoring those portions of Dyke Marsh Preserve that were dredged to productive emergent wetlands, while maintaining the integrity and health of the existing marsh. If feasible, restoration could return much of the Preserve to historical conditions, enhancing wildlife habitat, recreation opportunities, and ecosystem services.
Samples were collected along the driftline and returned to AL for germination to help identify which seeds are washing up on shore.Dyke Marsh Plant Community:
Understanding the vegetation community dynamics (i.e., annual vs.
perennial), as well as the environmental factors that affect vegetation
composition are very important when considering ecosystem restoration.
Extensive surveys have been conducted in DMP to assess the plant
community. In addition to above-ground vegetation surveys, researchers
have also sampled the seed bank, driftline, and Potomac River for seed
sources. As conditions in the marsh continue to change,
recovery of the natural plant community could occur. For example,
water inundation has been found to play a role in which species of
seed germinate. In addition, elevation may affect which seedlings
survive to maturity.
Future Work:
AL researchers plan to continue examining the relationships between
elevation, water inundation, and vegetation distribution. Using modeling,
they will map projected sea level changes and create maps of potential
scenarios that could occur if climate change does results in sea level
changes. The result of these scenarios will be useful for NPS management. AL scientists also plan to develop a model that relates physical
environmental factors (e.g., elevation, light), chemical factors
(e.g., nutrient levels), and biological factors (e.g., vegetation community).
These relationships will be used in assessing climatic or chemical changes
to DMP.
NPS is also investigating the potential for restoration. Restoring
Dyke Marsh could require filling in portions of the marsh that were
previously dredged. The first step in this process is an Environmental
Assessment.
To Learn More:
Project PI:
Dr. Katia Engelhardt
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