RII Track-4: NSF: Does warming-driven root damage lead to drought stress in declining yellow-cedar trees?

在北美西北部的温带雨林中，黄雪松（Callitropsis nootkatensis）正在经历大范围的枯死。大量证据支持这样一种观点，即全球变暖造成的绝缘积雪损失使黄杉（YC）的根部受到霜冻的损害，最终导致树木死亡。该项目的目的是更好地了解气候变化如何影响黄雪松（YC），这是一种正在广泛衰退的标志性树种。迄今为止，超过3,000平方公里的YC森林经历了重大的枯死，这对阿拉斯加东南部和不列颠哥伦比亚省的经济、生态和文化产生了深远的影响。黄杉现在被认为是全球森林健康下降趋势的“海报儿童”，以应对人为变暖，成功的YC保护工作将取决于确定气候变化和树木死亡之间的所有联系。干旱胁迫后，霜冻损害YC根在异常期间，冬末天气是一个未经测试的，但潜在的关键环节，在顶梢枯死过程中。通过阿拉斯加大学费尔班克斯（UAF）和亚利桑那大学之间的合作，该项目将通过应用新开发的方法分析雪松木材解剖来测试衰退的YC树木是否表现出干旱胁迫的症状。除了同行评审的出版物和由早期职业研究人员领导的会议演讲外，该项目还将与Kake阿拉斯加土著社区的K-12学生和森林管理人员举行为期一周的研讨会。这个项目的主要目标是测试一个重要的推论的“霜冻损坏的根”假说，即YC根损伤的结果在干旱胁迫和最终的树木死亡率。为了避免空洞化，干旱胁迫下的针叶树在年轮内形成了直径更薄、壁更厚的管胞细胞，这些解剖学变化可以用木材定量解剖学（QWA）的新方法来记录。该项目将使用这些方法来测试预测，即相对于附近健康YC树中生长的相同年轮，衰退和死亡YC树的外环中的管胞细胞具有显着较低的管腔面积和较厚的壁。为了实现这一目标，来自UAF的研究人员将与亚利桑那大学树木年轮研究实验室的合作者合作，将QWA方法应用于从阿拉斯加东南部收集的长期死亡，积极衰退和目前健康的YC树木。这些结果将为气候变化和森林枯梢病提供新的见解，并使利益相关者能够更准确地预测霜冻和干旱对这一重要树种的影响。此外，该项目将通过获得新的分析方法来扩大UAF的研究基础设施，这将有利于阿拉斯加的一系列环境研究。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Yellow-cedar (Callitropsis nootkatensis) is now experiencing widespread dieback in the temperate rainforests of northwestern North America. Significant evidence supports the idea that a loss of insulating snow cover caused by global warming exposes yellow-cedar (YC) roots to frost damage, which eventually leads to tree death. The purpose of this project is to better understand how climate change is affecting yellow-cedar (YC), an iconic tree species in widespread decline. To date, over 3,000 km2 of YC forests have experienced significant dieback, which has had far-reaching economic, ecological, and cultural effects in Southeast Alaska and British Columbia. Yellow-cedar is now considered a “poster child” of the global trend of declining forest health in response to anthropogenic warming, and successful YC conservation efforts will hinge on identifying all the links between climate change and tree death. Drought stress in the aftermath of frost damage to YC roots during periods of anomalous, late-winter weather is an untested yet potentially critical link in the dieback process. Through a collaboration between the University of Alaska Fairbanks (UAF) and the University of Arizona, this project will test whether declining YC trees exhibit symptoms of drought stress by applying newly developed methods to analyze cedar wood anatomy. In addition to peer-reviewed publications and conference presentations led by an early-career researcher, this project will involve a week-long workshop with K-12 students and forest managers in the Alaska Native community of Kake. The primary goal of this project is to test an important corollary of the “frost-damaged root” hypothesis; namely, that YC root injury results in drought stress and eventual tree mortality. To avoid cavitation, drought-stressed conifer trees lay down thinner-diameter and thicker-walled tracheid cells within their annual rings, and these anatomical changes can be documented using new methods in quantitative wood anatomy (QWA). This project will use these methods to test the prediction that tracheid cells in the outer rings of declining and dead YC trees have significantly lower lumen areas and thicker walls relative to the same annual rings grown in nearby healthy YC trees. To accomplish this, the investigator from UAF will work with a collaborator at the Laboratory of Tree-Ring Research at the University of Arizona to apply QWA methods on long dead, actively declining, and currently healthy YC trees collected from Southeast Alaska. These results will provide new insight about climate change and forest dieback and will allow stakeholders to predict the impacts of frost damage and drought more accurately on this important tree species. In addition, this project will expand research infrastructure at UAF by acquiring new analytical methods that will benefit an array of environmental research in Alaska.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.