Resilience of western Canadian forests to climatic extremes

背景气候变暖和极端气候是全球森林面临的主要问题。干旱在成熟的森林中造成毁灭性的枯死，并通过死亡损害了重新造林。在另一个极端，严寒事件仍然是一个令人担忧的问题：早春变暖会刺激树木过早生长，使它们在气温恢复正常时容易受到随后霜冻的影响。这可能导致人工林失败并损害老树，也使它们容易受到其他死亡因素的影响。加拿大有3.5亿公顷的森林覆盖率，每年种植5亿棵树，后果可能是广泛的。我们今天种植的植物以及我们如何管理这些摊位将在未来几十年产生巨大影响-但我们受到基础知识的限制。我们迫切需要对干旱和霜冻如何与森林结构、竞争和资源可用性相互作用进行合理的预测。 从长远来看，该计划将增加对森林生产力和健康如何与耐旱性和抗冻性联系在一起的理解，以及它们与生态关系的相互作用。这项工作将改进预测，有助于减少气候变化的影响。在未来五年内，4名研究生和5名本科生HQP将有助于实现以下短期目标：1）量化导致干旱和霜冻损害的树间竞争和树木大小效应; 2）调查营养物质的可用性如何与竞争相互作用，以影响对极端事件的反应; 3）整合混合物种的生态位分区，以预测对极端气候的恢复力。这项研究将受益于一个多元化和包容性的团队，以及积极的工作环境。每个人都能公平地获得培训、资源和机会。通过与多元化的合作伙伴合作，HQP将接触到世界级的森林科学专家，不同的思维方式以及技术和技术。方法本研究将年轮观测方法与长期田间试验相结合。几十年的老树将在控制营养、竞争、树木大小和物种组成的试验中进行测量。通过非破坏性取样获得的树芯提供了对过去干旱或霜冻事件反应的档案。功能木材解剖技术将这些生长反应的生理机制。 数百万美元的实地试验投资现在可以重新用于大规模气候变化实验。了解森林对极端气候事件的反应将改善对气候变化的预测。这些知识可以指导减少森林死亡率的方法，帮助维持依赖健康森林的社区，并减少碳反馈。与最终用户的合作确保了成果的吸收，在高级别期刊上发表的文章将导致广泛的读者群，以最大限度地扩大影响。

Background Climate warming and extremes are major issues facing forests worldwide. Droughts have caused devastating dieback in mature forests and have compromised reforestation through mortality. At the opposite extreme, severe cold events remain a concern: Early spring warming can stimulate trees to grow too early, making them vulnerable to subsequent frosts when temperatures return to normal. This can cause planted forests to fail and damage older trees, also making them susceptible to other mortality agents. With 350 million ha of forest cover across Canada, and 500 million trees planted every year, consequences can be extensive. What we plant today, and how we manage these stands, will have a large impact for decades - yet we are limited by fundamental knowledge. We urgently need sound predictions as to how drought and frost interact with forest structure, competition and resource availability. Objectives & HQP Long-term, this program will increase understanding on how forest productivity and health are linked to drought and frost tolerance, and their interplay with ecological relationships. This work will result in improved predictions that help reduce impacts of climate change. Within the next five years, 4 graduate and 5 undergraduate HQP will contribute to the following short-term objectives: 1) quantifying inter-tree competition and tree size effects that contribute to drought and frost damage; 2) investigating how nutrient availability interacts with competition to affect response to extremes; and 3) integrating niche partitioning in mixed species stands to predict resilience to climate extremes. This research will benefit from a diverse and inclusive team, and a positive work environment. Individuals will have equitable access to training, resources and opportunities. By working with diversified collaborators, HQP will be exposed to world-class experts in forest sciences, different ways of thinking as well as techniques and technology. Methods This research combines observational tree-ring methodologies with experimental manipulations in long-term field trials. Decades-old trees will be measured in trials controlling nutrients, competition, tree size, and species composition. Tree cores obtained through non-destructive sampling provide archives of responses to past drought or frost events. Functional wood anatomical techniques will link these growth responses to physiological mechanisms. Impact Million-dollar investments in establishing field trials can now be re-purposed as large-scale climate change experiments. Understanding forest responses to extreme climatic events will improve predictions under climate change. This knowledge can guide approaches to mitigating forest mortality, helping sustain communities relying on healthy forests and reducing carbon feedbacks. Collaboration with end-users ensures results uptake and publications in high-ranking journals will lead to broad readership to maximize impact.