Collaborative Research: Shrub Impacts on Nitrogen Inputs and Turnover in the Arctic, and the Potential Feedbacks to Vegetation and Climate Change

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Ecosystems develop and change through interactions between living organisms and their physical environment. A shift in vegetation is one of the most important changes an ecosystem can experience, because it can alter exchanges of energy (originating from sunlight), water, and elements such as carbon and nitrogen, among air, plants, and soil. In the Arctic, a widespread shift from tundra to shrub-dominated vegetation appears to be occurring. This research project will discern whether, through complex interactions, this transition to shrublands in the Arctic is likely to result in the release of more carbon into the air (as either carbon dioxide or methane, which are both greenhouse gases). Vast amounts of carbon are stored in Arctic and northern soils, so reduced carbon storage in the Arctic may affect weather and climate in other parts of the world. This project will assess the contributions of different shrub feedbacks to carbon (C) and nitrogen (N) cycling. Snow depth will be manipulated with existing snow fences across a natural gradient of shrub density and height, and a new snowfence experiment will be established in alders. Shrub-induced changes in soil C over the longer term in one ecosystem will be examined in an 18-year-old species removal experiment. Shrub growth, primary production, and biomass will be measured. Long-term effects of added snow on ecosystem N partitioning and shrub N uptake will be measured in a 15N tracer experiment. N fixation will be measured in alder populations and moss communities associated with shrubs. The relative strengths of different shrub feedbacks to N availability and uptake by vegetation will be evaluated. This project will improve prediction of the consequences of shrub expansion in the Arctic, and its potential impacts on regional and global climate. Results will contribute to training of graduate and undergraduate students, to public outreach and training of K-12 teachers and students, and to development of a web-based resource for education.