DISSERTATION RESEARCH: Physiological mechanisms in climate-induced forest mortality

在美国西部，许多树种最近发生了大规模死亡事件，通常与严重干旱和温度有关，预计在下个世纪随着气候变化而增加。颤抖的白杨森林最近在西部几个州经历了严重而迅速的干旱导致的死亡，影响了多达五分之一的白杨森林。尽管这些事件的普遍性和影响，人们对森林如何死于干旱和温度压力的确切情况知之甚少。这项拟议中的研究将有助于阐明白杨森林多年来如何屈服于干旱胁迫的生理机制。了解严重干旱对树木水分吸收和利用的长期影响，对于了解此类死亡事件的途径和阈值至关重要。这项研究将揭示森林对气候变化的反应，目前是一个很大的不确定性。树木死亡可以改变区域景观，并对森林的功能以及它们为人类提供的服务产生严重影响，如木材，旅游业和野生动物栖息地。此外，森林枯梢病可导致森林碳吸收量急剧减少，对气候变暖产生积极的反馈作用。因此，了解未来森林死亡的方式和地点将使美国西部的当地利益攸关方受益匪浅。这项研究将有助于预测哪些地区、树种和森林最容易受到干旱和气候的影响。此外，这项研究将使当地社区的学生参与实地研究，并将结果传达给广泛的土地管理人员和利益攸关方，大大增加研究结果的影响。

In western United States, massive mortality events have occurred recently across many tree species, often linked to severe drought and temperature, and are expected to increase with climate change in the next century. Trembling aspen forests recently experienced a severe and rapid drought-driven mortality across several western states, affecting up to a fifth of aspen forests. Despite the prevalence and impact of these events, there is relatively little known about exactly how forests die from drought and temperature stress. The proposed research would help illuminate the physiological mechanisms of how aspen forests succumb to drought stress over multiple years. Understanding the long term effects of severe drought on water uptake and use by trees is critical to informing pathways and thresholds of such mortality events. This research will shed light on the response of forests to climate change, currently a large uncertainty.Tree death can transform regional landscapes and have severe effects on how forests function and on the services they provide to humans, such as timber, tourism, and wildlife habitat. Furthermore, forest diebacks can lead to dramatic decreases in forest uptake of carbon, resulting in an positive feedback to climate warming. Thus, understanding how and where forests could die in the future would greatly benefit local stakeholders in the western United States. This research will aid in projecting which regions, tree species, and forests could be most vulnerable to drought and climate. Additionally, the research will involve students from local communities in field research and will communicate the results to a broad array of land managers and stakeholders, greatly increasing the impact of the findings.