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

森林对未来全球气候至关重要，北方森林占世界森林的三分之一，其中大部分生长在永久冻土上。然而，由于高纬度地区气候变化速度加快、气温升高、降水制度改变、生长季节延长，以及更重要的是，季节性解冻的土壤更温暖、更深，北方针叶林正在迅速变化。这可能会对全球产生影响，因为这些森林储存了30-40%的陆地碳。在气候变暖、生长季节变长的背景下，快速解冻及其对土壤环境的影响对北方树木生长和生产力的影响途径尚未得到解决，这限制了我们预测高纬度陆地表面-大气相互作用相关变化的能力。为了提高我们对这一关键界面的认识，我的长期目标是确定北方森林对气候变化响应的关键过程，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：1)利用树木年轮研究量化树木生长和补充对气候变暖引起的土壤资源变化的响应，并测量在这些生长期使用的资源（并锁定在树木年轮中）的特征；O2)评估幼树获取永久冻土层深层释放的水分和养分的能力；O3)确定叶片和根系性状对永久冻土条件的响应变异性；(4)在永冻土梯度和有和没有地面冰的地点量化最近的森林动态（生长、补充、死亡）。这些研究将提供深入了解树木获取永久冻土融化期间释放的新资源的潜力，以及这种响应是否具有有限的持续时间，这是预测持续升温和融化下北方森林功能的关键信息。

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.