Grazer Exclusion Enhances Nitrogen Removal in Created Wetlands of the Great Lakes Watershed

Session: Poster session

Kimberly Lodge, Rochester Institute of Technology, [email protected]
Anna Tyler, Rochester Institute of Technology, [email protected]
Carmody McCalley, Rochester Institute of Technology, [email protected]
Nathan Eddingsaas, Rochester Institute of Technology, [email protected]
Andre Hudson, Rochester Institute of Technology, [email protected]

Abstract

Loss of natural wetlands has warranted creation of wetlands to mitigate the reduction of valuable ecosystem functions and services, especially habitat provision and nutrient removal. However, complex interactions between biotic and abiotic factors in wetlands makes creation of fully functional wetlands challenging. In this study, we examined the impact of grazing in two emergent wetlands within the Lake Ontario watershed that differ in land use history and hydrology.  We established paired plots protected from – and open to – large wetland grazers and compared vegetation cover and diversity, soil characteristics, and potential denitrification over a three year period. At the permanently flooded site with high observed grazer densities (predominantly Branta canadensis and other waterfowl) and low nutrient availability (former gravel mine), grazing significantly reduced plant cover and diversity. In contrast, at the seasonally flooded wetland with lower grazer densities and high nutrient availability (former cattle pasture), grazing enhanced plant diversity with no change in total cover.  Soil organic matter and potential denitrification were significantly reduced in grazed plots at both sites.  These results suggest the possibility of long-term grazer-induced shifts in the nutrient removal potential of wetlands in the Great Lakes watershed, especially as migration patterns of herbivorous waterfowl shift.

1. Keyword
wetlands

2. Keyword
nutrients

4. Additional Keyword
grazing

5. Additional Keyword
restoration