Drought as a Trigger for Rapid State Shifts in Kettle Ecosystems: Implications for Ecosystem Responses to Climate Change
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Global climate change has raised important questions about ecosystem resilience and the likelihood of unexpected and potentially irreversible ecosystem state shifts. Conceptual models provide a framework for generating hypotheses about long-term ecosystem processes and their responses to external perturbations. In this article, we review the classic model of autogenic peatland encroachment into closed-basin kettle lakes (terrestrialization) as well as studies that document patterns of terrestrialization that are inconsistent with this hypothesis. We then present a new conceptual model of episodic, drought-triggered terrestrialization, which is consistent with existing data and provides a mechanism by which climatic variability could cause non-linear patterns of peatland development in these ecosystems. Next, we review data from comparative studies of kettle lakes along a peatland-development gradient to explore potential ecological and biogeochemical consequences of non-linear patterns of terrestrialization. Finally, we identify research approaches that could be used to test conceptual models of terrestrialization, investigate the ecological implications of non-linear patterns of peatland development, and improve our ability to predict responses of kettle systems to climate changes of the coming decades and century.