Diversity Comparisons Between Diked and Undiked Coastal Freshwater Marshes on Lake Erie During a High-water Year

Abstract

The effect of high water on floristic composition and diversity was compared at a diked, managed marsh, and an undiked, unmanaged marsh. Species richness and alpha diversity were determined for Cells A through D at Pipe Creek Wetland (PCW), a restored, managed marsh, and MHD Wetland, an undiked, unmanaged marsh. Both wetlands are located on Sandusky Bay in the western basin in Lake Erie, Ohio. Water levels were unusually high during 1997 when this study was conducted. Thus, the flora of Cells C and D at PCW in 1997 were compared to results from a vegetation survey of these cells conducted in 1994, a low-water year. Values for species richness in 1997 ranged from 25 (Cell A) to 42 (Cell D). Pipe Creek Wetland, and Cell D in particular, had higher species richness than MHD Wetland. Average alpha diversity values in 1997 ranged from 0.95 to 1.34; Cell D had significantly higher alpha diversity than Cell C at PCW and MHD Wetland. Species richness of Cells C and D at PCW declined substantially between 1994 and 1997 and species composition changed considerably. These findings reflect the combined effects of the very different marsh surfaces, hydrologic regimes, and human influences at Pipe Creek and MHD Wetlands. It is suggested that species richness and alpha diversity at Pipe Creek Wetland would be even higher in a low-water year. However, MHD Wetland would not become more diverse if water levels dropped due to the extreme dominance of stress-tolerant, aggressive plant species at MHD.