Climate change and water use: can increase diversity help protect forests?

我们的合作伙伴和森林管理者表示需要预测气候变化对森林的影响，并提出缓解战略，以限制因水资源紧张造成的预期死亡率及其对加拿大森林生产力的影响。事实上，在这个项目中开展的研究将大大有助于减轻加拿大森林面临的一些最重要威胁的影响：由于迁移失败而导致的多样性减少和树种适应不良，以及由于气候变化而导致的干旱期增加。该项目的主要科学目标是评价经常被引用但缺乏证明的假设，即森林多样性将缓冲水压力对生产力，特别是死亡率的负面影响。考虑到加拿大预计的气候变化对降水的预期变化和不确定性，这是一个极具战略意义的假设。它还可以很容易地转化为管理天然林和人工林的适应战略。此外，我们将评估气候变化后树木不适应造成的死亡率上升对森林生产力的影响程度，这在目前基本上是未知的，管理人员和政府目前也没有考虑到这一点。为此，我们使用了实验方法，得益于我们的树木多样性实验网络（IDENT），以及使用来自永久森林地块的数据的观测方法。实验方法将利用稳定同位素（氘）来追踪树木的水分吸收，以及叶片温度（热像仪）和空间冠层组织的遥感（无人机），以跟踪水分利用和蒸发蒸腾，在高度控制的树木多样性实验中，包括水分胁迫处理。观测分析将受益于我们在qusamubec的大型永久地块网络，以及全球森林生物多样性倡议，该倡议涵盖了世界上所有森林生物群系的100多万个森林地块。

This research project is strongly grounded on the needs expressed by our partners and by forest managers for predictions on the impacts of climate change on forests, and mitigation strategies to limit the expected mortality due to water stress and its effect of the productivity of Canadian forests. Indeed, the research developed in this project will contribute significantly to mitigating the impacts of some of the most important threats to Canadian forests: decreasing diversity and maladaptation of tree species from failure to migrate, combined with increasing periods of drought due to changes in climate. The main scientific objective of the project is to evaluate the often cited but poorly demonstrated hypothesis that forest diversity will buffer the negative impacts of water stress on productivity, especially mortality. This is a highly strategic hypothesis given the expected changes, and uncertainty, in precipitation from projected climate change in Canada. It will also be easily translated into adaptation strategies for both managed natural forests and tree plantations.Furthermore, we will evaluate the size of the impact that increased mortality caused by the maladaptation of trees following climate change will have on forest productivity, which is largely unknown at this time, and not accounted for at present by managers and governments.To do so, we use both an experimental approach, benefiting from our network of tree diversity experiments (IDENT), as well as an observational approach using data from permanent forest plots. The experimental approach will make use of a stable isotope (deuterium) to trace water uptake in trees, as well as remote sensing (drones) of leaf temperatures (thermal cameras) and canopy organization in space, to track water use and evapo-transpiration, in highly controlled tree diversity experiments that include water stress treatments. Observational analyses will benefit from our network of large permanent plots in Québec, as well as the Global Forest Biodiversity initiative, encompassing over 1 million forest plots across all forested biomes of the world.