CLIMATIC VARIABILITY AS A TRIGGER FOR RAPID STATE SHIFTS IN KETTLE ECOSYSTEMS: IMPLICATIONS FOR ECOSYSTEM RESPONSES TO CLIMATE CHANGE (Invited Presentation)

Anthropogenic climate change has raised important questions about ecosystem resilience and the likelihood of unexpected ecosystem state shifts in a generally warmer, but more climatically variable future. These questions are especially pressing for ecosystems with high carbon density due to potential climate feedbacks. Northern peatlands are among the most carbon-dense ecosystems on the planet. Despite years of investigation, linkages between peatland development and climatic variability are incompletely understood. Here, we present a series of conceptual models that provide a framework for generating hypotheses about the role of climatic variability in driving long-term peatland development in glacial kettles. Specially, we hypothesize that peatland development in these systems is episodic and driven by climatically induced water-level fluctuations. We are testing this hypothesis through a comparative study of within-basin and regional peatland development in the Laurentian Great Lakes Region. We present a detailed reconstruction of the developmental history of one kettle peatland located in northern Wisconsin, USA based on 21 coring locations and temporally constrained by 68 radiocarbon dates. This record of within-basin peatland development is compared to a regional dataset containing estimated ages of peatland establishment in 75 cores collected from 37 peatlands throughout the region, demonstrating temporal coherence between within-basin and regional peatland establishment, indicating a common climatic driver. Major episodes of peatland establishment occurred around 5000, 3200, 2000, and 1000 cal yr BP. We then employ an empirically based model of peatland development to illustrate the carbon accumulation implications of this episodic developmental history. Finally, we develop a conceptual model that highlights the potential ecological consequences of non-linear patterns of peatland development in kettle ecosystems. Collectively, the results of this study indicate that kettle peatlands likely experienced climate-sensitive and episodic changes during the Holocene, and similar dynamics should be expected in response to ongoing and future climatic change.