Arctic LTER: Climate Change and Changing Disturbance Regimes in Arctic Landscapes

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This award supports the fifth phase of the Long Term Ecological Research Site (ARC LTER) at Toolik Lake, AK. The arctic region has warmed significantly over the past 30 years and arctic lands and freshwaters are already changing in response. The changes include a general "greening" of the arctic landscape, changes in species distributions and abundance, and changes in geophysical and biogeochemical processes and cycles at local and regional scales. Since 1975, the ARC LTER project and its predecessors have studied these changes by long-term monitoring of tundra and freshwater ecosystems in relation to climate change, by experimental manipulations of whole tundra, lake, and stream ecosystems, and by comparisons among climatically different sites in northern Alaska and throughout the Arctic. Increasingly, however, it is apparent that climatic warming in the Arctic is accompanied by dramatic changes in disturbance regime, including disturbances related to thawing of permafrost, a surprising increase in wildfire, and changes in the seasonality and synchrony of ecosystem processes. These disturbances, in addition to having major impacts on biogeochemistry, populations, and communities, also lead to major changes in surface energy balance, surface temperatures, water balance, and heat transfer into the permafrost that lies beneath the tundra, lakes, and streams. The result is much more dramatic and rapid change in biota and element cycles than is predicted in response to warming alone. In the long term, warming-related changes in disturbance regime may be more important than the direct effects of warming on arctic tundra and freshwater ecosystems, and on the entire Arctic. Over the next six years the ARC LTER project will address these issues in an integrated landscape framework, viewing the Arctic landscape as a spatially linked system including tundra, streams, and lakes and leading to long-term predictions of change at hillslope, watershed, and regional scales. The long-term goal, to develop a predictive understanding of the landscape of Northern Alaska including tundra, streams, lakes, and their interactions, remains the same but efforts for the next six years will include a new emphasis on changing disturbance regimes and their interactions with climate change. This refocusing will involve some shifts in effort, away from long-term experiments manipulating individual climatic, biotic, and biogeochemical drivers, and toward increased effort on characterizing disturbances including thermokarst, fire, and changing seasonality, and on new research focused on landscape linkages and physical disturbance. New areas of research will include changes in surface energy exchange and heat flux into permafrost, and a program on climate change impacts and responses by local Native Alaskan communities.The scientific impacts of this research are much broader than improvement of the ability to predict ecosystem structure, function, and change in Northern Alaska. The role of disturbance in long-term change is of broad theoretical and empirical interest in ecology and is closely related to controls on resilience, tipping points, and thresholds in populations, communities, ecosystems, and complex landscapes. The landscape near Toolik Lake, Alaska is an excellent model system for analysis of these issues at multiple spatial and temporal scales. Work at Toolik Lake will provide a multidimensional view of how responses of tundra and freshwater ecosystems to environmental change can feed back, both positively and negatively, on the factors driving the change. This is of broad importance both theoretically and from the perspective of global climatic change. A multifaceted education program will include: a Schoolyard project of lectures and inquiry in the largely Native Alaskan town of Barrow, Alaska; field courses in Arctic Ecology and in Polar Science for Journalists; and undergraduate and graduate research and degree programs. Research at the ARC LTER will benefit society as a case study of a landscape where local, subsistence land use is still common and important, and where climate change and its impacts are felt directly in the delivery of key ecosystem services.