The role of altered resource availability in determining taiga forest response to permafrost thaw

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Forests are critical to future global climate and boreal forests represent a third of world's forests, much of which occurs on permafrost (perennially frozen ground). However, boreal forests are changing rapidly due to faster rates of climate change at high latitudes and associated warmer air temperatures, altered precipitation regimes, longer growing seasons and, importantly, warmer and deeper seasonally-thawed soils. This could have global implications as these forests store 30-40% of terrestrial carbon. The pathways through which rapid thaw and its impacts on the soil environment affect boreal tree growth and productivity in the context of warmer, longer growing seasons are unresolved limiting our ability to predict changes relevant to high latitude land surface-atmosphere interactions. To advance our knowledge at this critical interface, my long-term goal is to identify key processes underlying the response of boreal trees to climate change thereby enhancing our ability to predict future boreal forest function. This will be achieved by: O1) Quantifying tree growth and recruitment responses to warming-induced changes in soil resources using tree ring studies and measuring signatures of the resources used (and locked into the tree rings) during those growth periods; O2) Evaluating the ability of young trees to access water and nutrients released deeper in the soil profile where permafrost thaw occurs; O3) Determining variability in leaf and root traits in response to permafrost conditions; and O4) Quantifying recent forest dynamics (growth, recruitment, death) across the permafrost gradient and in sites with and without ground ice. These studies will provide insights into the potential for trees to access novel resources released during permafrost thaw and whether this response has a limited duration, key information for predicting boreal forest function under ongoing warming and thaw.