Effects of Hydrology, Herbivory and Sediment Disturbance on Plant Recruitment in a Lake Erie Coastal Wetland

Abstract

Coastal wetlands of the Laurentian Great Lakes provide many valuable ecological functions and, currently, there are extensive efforts to preserve and manage remaining habitats. We examined plant recruitment in a Lake Erie coastal marsh on bare mudflats exposed during 2 y of below average water levels. In 2000 mudflat vegetation was sampled in shallow, medium and deep water transects and compared to germinable seeds found in sediments from 0–15 cm below the surface. Effects of sediment disturbance and herbivory on plant recruitment were tested in 1 m2 quadrats in 2000 and vegetation was sampled in 2001 to assess how well the disturbance/herbivory experiment predicted plant communities that became established on the mudflats. In 2000, 18 species were found on mudflats and 19 species were reared from the seedbanks. Seed densities (∼3000 seedlings/m2) were comparable to other freshwater wetlands and did not differ by sediment depth. Taxa richness was highest in sediments 0–5 cm below the surface. Most plants on the mudflats were found in the shallow transect, but seed abundance and richness were highest in deep transects. Sediment disturbance decreased taxa richness and herbivory decreased both plant cover and richness; however, responses varied among plant taxa. Our results indicate that abundant seedbanks exist in this wetland, but plant recruitment will be restricted to shallow areas due to turbidity. Communities in 2001 were more diverse (40 species) than predicted from vegetation in 2000 probably because propagules were introduced from nearby habitats. Communities in 2001 were most similar to ungrazed and undisturbed quadrats in 2000 because these had the most species.