This project will use the sediment record of kettlehole ecosystems to study ecological responses to prolonged or extreme drought. These ecosystems are widespread in previously glaciated landscapes. Relationships among drought, peatland establishment and expansion, and lake-ecosystem dynamics will be examined using paleoecological techniques along a landscape gradient in northern Wisconsin. Research will test the hypotheses that 1) peatland development occurs suddenly rather than gradually, triggered by drought variability, 2) basin morphology and landscape position determine whether peatlands develop, and 3) the rapid development of peatland leads to abrupt changes in remnant lakes, producing changes in rates of carbon storage within kettle systems.
Warming temperatures associated with global climate change are expected to lead to more frequent and intense droughts in many mid-latitude regions. These predictions present a challenge to ecologists and resource managers; yet few datasets exist to provide a basis for understanding ecosystem responses to these anticipated changes. This research will provide critical, long-term perspectives on the role of hydroclimate variability in triggering abrupt and permanent state shifts in ecosystems. Such threshold responses are difficult to anticipate or predict, and the research will provide a foundation for evaluating the relative sensitivity and vulnerability of ecological systems.