The next step: Capitalizing on long-term experimental manipulations to understand and predict arctic terrestrial ecosystem responses to climate warming

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The Arctic is undoubtedly experiencing rapid recent warming that is very likely to substantially affect the structure and functioning of its ecosystems. As a terrestrial ecosystem ecologist and biogeochemist, the long-term goal of my research over the next 15 years is to substantially advance our biological understanding of how Canadian arctic tundra ecosystems function, and therefore how they may be affected by climate change. This next 5 year research period is the time for me to fully investigate the mechanisms and implications of our recent discoveries, so as to significantly improve our understanding of the biological controls and interactions that govern arctic terrestrial ecosystem functioning. My proposal describes multiple specific hypotheses that are centered on the following three major interconnecting objectives which have arisen from my previous research:1. To determine the biogeochemical and ecological significance of our discovery that mesic tundra plant growth can be co-limited by nitrogen (N) and phosphorus (P).2. To predict the likely impacts of not just climate change, but also declining caribou and other mammalian herbivory, on tundra deciduous and evergreen shrub abundances. 3. To evaluate the biogeochemical significance of the stoichiometric differences among plants, soils, and soil microbes in understanding tundra ecosystem responses to climate change.My lab group will test innovative research hypotheses using the experimental infrastructure that I initiated at our Daring Lake research site in central low arctic Canada in 2004. These fully replicated (n = 5-10) experimental manipulations include both high and low-level factorial NxP annual additions, summer plastic greenhouses, snowfences, and caribou exclosures. In addition, I have a long-term observational study of vegetation change across the full range of habitat-types in the Daring Lake landscape, a second experimental fertilization research site in Northern Quebec, ongoing active research collaborations at Toolik, Alaska and Abisko, Sweden, and I am leading several pan-Arctic investigations based on colleagues' leaf and soil samples from 52 high latitude tundra sites. Undertaking these investigations will provide cutting-edge HQP training in emerging concepts such as ecological stoichiometry and herbivore-plant-soil nutrient interactions, and in the development and use of novel/recent techniques such as ion exchange membrane for measuring plant available nutrients in tundra, phosphate P 18Op and 15N isotope use for determining P fluxes and N fixation respectively, and soil enzymology. Ultimately, I hope that this research will lead to adaptive land management in the North, as well as greater public appreciation of the ecological value of the Arctic, and therefore serve as a wake-up call' to more effective and sustainable environmental policies and practices for Canada as a whole.