LTER: The Role of Biogeochemical and Community Openness in Governing Ecological Change in Arctic Ecosystems

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The Arctic is one of the fastest warming regions on Earth and as such may well provide an idea of the future changes likely to occur further south. This warming has increased disturbances such as wildfire as well as thawing of permafrost in ecosystems of Northern Alaska. As a result of this warming and increased disturbance, animal and plant communities on land and in streams and lakes are changing. Underlying these community changes are changes in the availability and cycling of nutrients, in the amount of carbon stored in soils and vegetation, and in the exchange of carbon dioxide and nutrients between arctic landscapes and the atmosphere and downstream rivers and oceans. Collectively, these changes may have profound effects, not just on the arctic ecosystems, but globally, with implications for humans. A better understanding of these changes can lead to better predictions of the future, and those predictions could provide the basis for better planning. To understand these changes, scientists with the Arctic Long-Term Ecological Research (ARC-LTER) Project monitor long-term changes in terrestrial, stream, and lake ecosystems in the vicinity of Toolik Lake, Alaska. They make observations of the recovery of these ecosystems from natural and experimentally imposed disturbances, and initiate and maintain long-term experiments designed to understand interactions among arctic species, nutrient cycles, and the connections among terrestrial and aquatic ecosystems on the arctic landscape. Scientists working at the ARC-LTER site will engage students from Barrow, Alaska, run a program for journalists, and participate in short courses for Alaskan Natives in three communities, all designed to increase the public understanding of Arctic Ecology. Briefings to national and state land managers and resource managers will help provide scientific knowledge that can inform policy.The research is organized around the concepts of ecosystem openness and landscape connectivity. Biogeochemical openness is the degree to which ecosystems depend on external sources of nutrients and organic carbon versus nutrients recycled within the ecosystem and organic carbon produced locally by photosynthesis. Community openness is the degree to which the movement of organisms in and out of the ecosystem determines community and food-web structure. Finally, landscape connectivity describes the nature and strength of interactions among ecosystems on the landscape and the resultant propagation of responses to disturbances across the landscape. Components of the arctic landscape differ widely in biogeochemical and community openness. Research at the ARC-LTER will compare key ecosystems of the Arctic to determine how their degree of openness governs their responses to climate variation and to acute disturbance such as fire and surface slumping associated with permafrost thaw. The proposed research will also determine how the responses to climate and disturbance are mediated by landscape connectivity and the movement of nutrients, carbon, and organisms across arctic landscapes. To accomplish these goals, ARC-LTER research will include continued long-term fertilizer and warming experiments; monitoring of chemical budgets, community changes, and species movements; monitoring recovery of tundra, rivers, and lakes that were previously fertilized; establishing new larger greenhouses in different aged landscapes; blocking fish movement into a lake connected to migratory streams and adding fish to a lake currently isolated from a stream network; and searching for correlations between terrestrial production and aquatic metabolism and nutrient concentrations. This research will support two undergraduate student researchers per year and provide opportunities for students working on other projects to work on Arctic LTER sites and experiments.