EFFECTS OF LONG-TERM WATER TABLE ALTERATIONS ON PLANT SPECIES, SOIL QUALITY, PORE WATER CHEMISTRY AND CARBON CYCLING IN A GREAT LAKES PEATLAND

Limited knowledge on interactions between peatland soil climate, plant community structure, organic matter quality, and microbial activity has led to uncertainties over peatland responses to climate change. These uncertainties restrict our understanding of carbon (C) cycling in peatlands under current and future climate regimes and reduce our ability to accurately predict and manage future C cycling patterns and trajectories in peat accumulating systems. Our research addresses questions regarding the effects of water table manipulations on peatland carbon cycling and how changes in soil and pore water chemistry and vegetation modify carbon fluxes. In 1935 the Seney National Wildlife Refuge (SNWR) located in the Upper Peninsula of Michigan began constructing an infrastructure of dikes to create waterfowl habitat that resulted in both the inundation and drying of peatlands within the refuge. Peatlands impacted by the dikes provide a unique opportunity to examine how decadal changes in water tables have influenced plant communities, soil and pore water quality, and carbon storage. We chose six sites that represent a gradient of long-term water manipulations (~70 years). The objectives of our research are to investigate how changing water levels influence peatland plant community structure and dynamics, determine whether altered water table levels affect soil and pore water chemical properties, and relate findings of plant, soil, and pore water characteristics to the cycling of greenhouse gases in peatlands. Our study has demonstrated that small changes in the water table level of a peatland have profound effects on the growth and structure of vegetation communities. Soil and pore water chemistry results display long-term changes in soil moisture alter soil chemical constituents. Trends in gas flux data suggest that changes in soil moisture have the potential to significantly influence greenhouse gas cycling in peatlands. This study has enabled us to begin forecasting how global temperature shifts affecting peatland hydrology over decadal time scales potentially alters plant, soil, pore water, and gas cycling processes in northern peatlands and will contribute to improved carbon cycling predictions for peatlands facing shifting moisture regimes resulting from climatic change.