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

森林对未来的全球气候至关重要，北方森林占世界森林的三分之一，其中大部分位于永久冻土层（常年冻土）上。然而，由于高纬度地区气候变化速度加快，气温升高，降水状况改变，生长季节延长，重要的是，季节性解冻的土壤温度更高、深度更深，北方森林正在迅速变化。这可能具有全球影响，因为这些森林储存了30 - 40%的陆地碳。快速解冻的途径及其对土壤环境的影响，影响北方树木的生长和生产力的背景下，温暖，较长的生长季节是未解决的限制我们的能力，以预测高纬度陆地表面-大气相互作用的变化。为了提高我们在这一关键界面的知识，我的长期目标是确定北方树木对气候变化的反应的关键过程，从而提高我们预测未来北方森林功能的能力。这将通过以下方式实现：O1）利用树木年轮研究量化树木生长和补充对变暖引起的土壤资源变化的反应，并测量所用资源的特征O2）评估幼树获取永久冻土融化发生的土壤剖面深处释放的水分和养分的能力; O3）确定响应于冻土条件的叶和根性状的变异性;和O4）量化最近的森林动态（生长，招聘，死亡）在整个冻土梯度和在有和没有地面冰的网站。这些研究将深入了解树木在冻土融化过程中获得新资源的潜力，以及这种反应是否具有有限的持续时间，这是预测北方森林在持续变暖和融化下功能的关键信息。

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.