Collaborative Research: Integrated Analysis of Late-Glacial Vegetation and Environments in Eastern North America: How Do Novel Plant Associations Arise?

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In the eastern United States, forest plant communities that were present 17,000 to 12,000 years ago are no longer represented on the landscape. This project will determine whether these historic assemblages of vegetation arose from: 1) unusually high temperature seasonality, 2) low atmospheric carbon dioxide concentrations, and/or 3) herbivory by now-extinct ''''megafauna'''' (e.g. mammoths, mastodons). This project integrates paleoecological data and mechanistic vegetation models. Specifically, this project will study lake-sediment cores from seven mid-continental sites from Tennessee to Minnesota and model climatic and carbon dioxide controls on vegetation composition. Sediments will be analyzed to infer ecological histories of vegetation, fire, and megafaunal population density and determine the timing of key ecological events. This study of past environmental change has direct implications for current climate-change concerns. In particular, for planning purposes, there is an urgent need for accurate ecological forecasts, but the robustness of current ecological models, when applied to environmental conditions outside the range of modern observations, is poorly understood. Moreover, climates at the end of the 21st century will likely include combinations of temperature and precipitation unlike any observed today. The well-documented anomalous late-glacial climates and ecological communities are a good testing ground for evaluating the adequacy of current models of ecological response to complex environmental change. This work will support student training and outreach activities for high school teachers and students.