Spatial and temporal dynamics of floating and drift-line seeds at a tidal freshwater marsh on the Potomac River, USA

The dispersal of seeds through hydrochory can be an important driver of community dynamics and play an integral role in the colonization of restored wetlands. We assessed sources of seeds on the shoreline and in adjacent waters of the Potomac River to Dyke Marsh in Virginia. Drift-line samples were taken at 40 random points four times during 2005–2006, and water surface net trawling took place on the Potomac River from 2003–2005 using six, 200-m transects around the perimeter of the marsh. Seed supply through hydrochory and species richness was low at Dyke Marsh when compared to other regional tidal freshwater marshes. We discovered distinct temporal patterns, where high species richness and seed density were found in the fall for the water trawl samples but in the spring for the drift-line samples. High fall dispersal in the water trawls may exist owing to peak plant senescence and seed release, while high seed germination in the spring along shorelines may arise due to sufficient cold stratification of marsh seeds.