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

我们的合作伙伴和森林管理人员表示需要对气候变化对森林的影响进行预测，并制定缓解战略，以限制因水压力造成的预期死亡率及其对加拿大森林生产力的影响，因此，这一研究项目具有很强的基础。**事实上，该项目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：由于不能迁徙而导致的树种多样性减少和适应不良，以及气候变化导致的干旱周期增加。**该项目的主要科学目标是评估经常被引用但缺乏证据的假设，即森林多样性将缓冲水分胁迫对生产力，特别是死亡率的负面影响。考虑到加拿大预测的气候变化对降水的预期变化和不确定性，这是一个高度战略性的假设。我们还将很容易地将其转化为管理的天然林和树木种植园的适应战略。**此外，我们将评估气候变化后树木适应不良导致的死亡率增加对森林生产力的影响的大小，目前尚不清楚，管理者和政府目前也没有考虑到这一影响。**为此，我们既使用实验方法，受益于我们的树木多样性实验网络(IDENT)，又使用来自永久林地的数据进行观察。在包括水分胁迫处理在内的高度受控的树木多样性实验中，该实验方法将利用稳定的同位素(氚)来跟踪树木的水分吸收，以及空间中叶温(热像仪)和树冠组织的遥感(无人机)，以跟踪水分利用和蒸散。观测分析将受益于我们在魁北克的大型永久地块网络以及全球森林生物多样性倡议，该倡议涵盖了世界所有森林生物群的100多万块林地。

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.******