Collaborative Research: How to live on a (carbon and water) budget: Tree investment in chemical defenses across a gradient of physiological drought stress

合作研究：如何依靠（碳和水）预算生活：跨越生理干旱胁迫梯度的化学防御树木投资

• 批准号: 1755362
• 负责人: William Pockman
• 金额: $ 38.72万
• 依托单位: University of New Mexico
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-12-15 至 2024-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1755362&HistoricalAwards=false
• 关键词: Collaborative; Research; How; live; carbon

Drought-induced forest die-off is a global phenomenon with far-reaching ecological and economic impacts. In the western US, tree death from drought, high temperatures, and bark beetle outbreaks now exceeds forest growth. Despite increases in the frequency and severity of drought-related insect outbreaks, factors influencing a tree's susceptibility to insect herbivores, such as the presence of chemical defenses, have received little attention. In particular, it is unclear how drought causes trees to shift resources toward or away from the chemical defenses that deter insect attacks and the subsequent trade-offs that exist with other important plant functions. To address this critical knowledge gap, this study focuses on how pinon pine trees allocate their carbon resources toward defense and other physiological processes under increasing drought stress to avoid death by drought or bark beetle attack. This study uses an isotope labeling approach in both greenhouse and field experiments to track drought-induced changes in carbon allocation to specific chemical compounds that affect bark beetle choice and success. The project increases participation of Native American students through undergraduate recruitment for summer research assistantships as well as other underrepresented minorities in science through the development of two critical thinking modules and support for their adoption in rural middle school classrooms across Montana. The rate of tree mortality has increased across the globe yet the understanding of the mechanisms underlying tree death remains surprisingly limited. Most work to date on drought-related tree death has focused on understanding the coupled roles of carbon starvation and hydraulic failure, but drought is oftentimes accompanied by insect outbreaks that cause or contribute to tree mortality. Research has yet to determine when trees cease investment in effective chemical defenses against biotic attack along the continuum of drought stress, and how these shifts in carbon availability simultaneously impact other plant physiological processes. This study seeks a mechanistic understanding of how drought stress affects the interactions among tree hydraulic function, carbohydrate availability, and chemical defense. Using both greenhouse experiments and field drought manipulations this research will couple enzyme assays with the use of stable isotopes to identify mechanisms responsible for shifts in pinon pine allocation of recently fixed carbon at the level of individual compounds with known impacts on bark beetle behavior. These methods will also allow identification of trade-offs involved in the synthesis of defense compounds at different drought severities while also advancing fundamental understanding of tree physiology and whole tree C budgets. By providing a comprehensive understanding of the effects of drought-induced physiological stress on mechanisms determining defense against bark beetles, a new, more complete framework for assessing mechanisms of tree mortality will be developed. This research was co-funded by the Integrated Ecological Physiology Program in IOS/BIO and by the Established Program to Stimulate Competitive Research (EPSCoR).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.

干旱引起的森林死亡是一种全球现象，具有深远的生态和经济影响。在美国西部，干旱，高温和树皮甲虫暴发的树木死亡现在超过了森林的生长。尽管与干旱相关的昆虫暴发的频率和严重程度增加，但影响一棵树对昆虫食草动物的敏感性的因素（例如化学防御措施的存在）很少受到关注。特别是，目前尚不清楚干旱如何使树木向阻止昆虫攻击的化学防御措施以及其他重要植物功能存在的后续权衡。为了解决这个关键的知识差距，本研究的重点是皮宁松树如何将其碳资源分配给防御和其他生理过程，以避免干旱或树皮甲虫攻击死亡。这项研究在温室和现场实验中使用同位素标记方法，以跟踪干旱诱导的碳分配变化，以影响影响树皮甲虫选择和成功的特定化学化合物。该项目通过夏季研究助理的本科招聘以及其他代表性不足的少数民族在科学方面增加了美国原住民学生的参与，并通过开发两个批判性思维模块，并支持他们在蒙大拿州的农村中学教室中的收养。在全球范围内，树木死亡率的速度增加了，但对树木死亡的机制的理解仍然存在惊人的限制。迄今为止，与干旱相关的树死亡的大多数工作都集中在理解碳饥饿和液压衰竭的耦合作用上，但是干旱通常伴随着导致或导致树木死亡的昆虫暴发。研究尚未确定何时在干旱压力的连续体中停止针对生物攻击的有效化学防御措施的投资，以及这些碳供应性的转变如何同时影响其他植物生理过程。这项研究寻求对干旱应力如何影响树液压功能，碳水化合物可用性和化学防御的相互作用的机械理解。使用温室实验和现场干旱操纵，这项研究将将酶测定与使用稳定的同位素相结合，以识别负责在单个化合物水平上近期固定碳的偏移分配的机制，并对甲壳虫行为产生已知影响。这些方法还将允许在不同干旱严重程度下综合国防化合物涉及的权衡识别，同时还促进了对树木生理学和整个树木预算的基本了解。通过对干旱引起的生理压力对决定防御甲虫的防御的机制的影响有全面的了解，将开发一个新的，更完整的框架，以评估树木死亡的机制。 这项研究是由iOS/BIO的综合生态生理计划和启发竞争性研究的既定计划共同资助的。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛的审查标准通过评估来进行评估的。