DISSERTATION RESEARCH: Physiological mechanisms in climate-induced forest mortality

在美国西部，最近在许多树种中发生了大规模的死亡事件，通常与严重的干旱和温度有关，预计下个世纪的气候变化会增加。颤抖的白杨林最近经历了严重而迅速的干旱，导致西部几个州的白杨林死亡，影响了多达五分之一的白杨林。尽管这些事件普遍存在并产生了影响，但人们对森林究竟是如何死于干旱和温度压力的知之甚少。这项拟议的研究将有助于阐明白杨林多年来如何屈服于干旱压力的生理机制。了解严重干旱对树木吸收和利用水分的长期影响，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，这是目前一个很大的不确定性。树木死亡可以改变区域景观，并对森林的功能及其为人类提供的服务（如木材、旅游和野生动物栖息地）产生严重影响。此外，森林枯死可导致森林对碳的吸收急剧减少，从而对气候变暖产生正反馈。因此，了解未来森林如何以及在哪里死亡将极大地有利于美国西部的当地利益相关者。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，该研究将让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者和利益相关者，从而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.