Linking a Large-Watershed Hydrogeochemical Model to a Wetland Community-Ecosystem Model to Estimate Plant Invasion Risk in the Coastal Great Lakes Region, USA

Friday, 19 December 2014: 8:40 AM
William S. Currie1, Laura L Bourgeau-Chavez2, Kenneth J. Elgersma3, Nancy H F French4, Deborah E. Goldberg5, Stephanie Hart1, David W Hyndman6, Anthony D Kendall6, Sherry L Martin6 and Jason Philip Martina1,5, (1)University of Michigan, School of Natural Resources and Environment, Ann Arbor, MI, United States, (2)Michigan Technological University, Michigan Tech Research Institute, Ann Arbor, MI, United States, (3)University of Northern Iowa, Department of Biology, Cedar Falls, IA, United States, (4)Michigan Technological University, Michigan Tech Research Institute, Houghton, MI, United States, (5)University of Michigan Ann Arbor, Ecology and Evolutionary Biology, Ann Arbor, MI, United States, (6)Michigan State University, Department of Geological Sciences, East Lansing, MI, United States
In the Laurentian Great Lakes region of the Upper Midwest, USA, agricultural and urban land uses together with high N deposition are contributing to elevated flows of N in rivers and groundwater to coastal wetlands. The functioning of coastal wetlands, which provide a vital link between land and water, are imperative to maintaining the health of the entire Great Lakes Basin. Elevated N inflows are believed to facilitate the spread of large-stature invasive plants (cattails and Phragmites) that reduce biodiversity and have complex effects on other ecosystem services including wetland N retention and C accretion. We enhanced the ILHM (Integrated Landscape Hydrology Model) to simulate the effects of land use on N flows in streams, rivers, and groundwater throughout the Lower Peninsula of Michigan. We used the hydroperiods and N loading rates simulated by ILHM as inputs to the Mondrian model of wetland community-ecosystem processes to estimate invasion risk and other ecosystem services in coastal wetlands around the Michigan coast. Our linked models produced threshold behavior in the success of invasive plants in response to N loading, with the threshold ranging from ca. 8 to 12 g N/m2 y, depending on hydroperiod. Plant invasions increased wetland productivity 3-fold over historically oligotrophic native communities, decreased biodiversity but slightly increased wetland N retention. Regardless of invasion, elevated N loading resulted in significantly enhanced rates of C accretion, providing an important region-wide mechanism of C storage. The linked models predicted a general pattern of greater invasion risk in the southern basins of lakes Michigan and Huron relative to northern areas. The basic mechanisms of invasion have been partially validated in our field mesocosms constructed for this project. The general regional patterns of increased invasion risk have been validated through our field campaigns and remote sensing conducted for this project.