Reorganization of biotic interactions and distributions of tree species under a warming climate: A biogeochemical perspective

气候变化正在威胁森林提供各种服务的能力，造成前所未有的冰暴、夏季干旱、火灾制度的变化、主要害虫物候的改变等。加拿大致力于维护能够适应当前和即将发生的全球变化的森林。因此，开发更可靠的森林对气候变化反应的模拟模型至关重要，因为它们是确定最佳可能适应战略的关键。为了预测气候变化下的森林死亡事件和树种变化，科学家们最近认识到，不仅需要基于区域气候建立模型，还需要基于树种之间相互作用的重组和可能的反馈。本研究项目主要研究气候变化下糖枫分布的适应与变化。枫树会向北迁移，在北方针叶林中找到它的环境（气候）生态位吗？它会适应当地吗？它会膨胀吗？还是会出现区间收缩？具体而言，我们将研究枫树与加拿大东部其他树种之间的生态/生物地球化学相互作用。我们的目标是评估枫树在土壤养分和水分吸收方面是否比其他物种具有竞争劣势，因为这可能会降低其适应气候变化的能力。我们正在开发一个概念模型，使用枫树作为响应物种，因为它是加拿大的象征性和重要的商业物种，受到许多威胁。这个模型将有助于确定其他物种的分布是否会转移、扩张或收缩。我们已经建立了一个由三个地点组成的实地研究，形成了魁北克枫的最大可能的纬度梯度。在这些地点，枫树的丰度不断增加：(1)在北方针叶林的南缘与枫树相对的针叶树种；(2)在北美东部的落叶林中逐渐取代枫树的美洲山毛榉。该研究包括一系列的野外和室内研究，以测试不同树种组成（冠层类型）对土壤养分有效性、枫树幼苗建立和存活、幼苗/幼树叶片营养、水分利用和生长的影响。我们还将研究不同冠层类型下枫树凋落物分解和菌根真菌与根的关系，以了解影响枫树营养和生长的过程。这项研究将通过增加对复杂森林功能的认识和开发新的工具来更好地预测人类活动对森林的影响，从而改进适应战略。

Climate change is threatening the capacity of forests to provide its various services by causing unprecedented ice-storms, drier summers, changes in fire regimes, modifications in the phenology of key pests, etc. Canada is committed to maintaining forests that are resilient to current and imminent global change. Hence, the development of more robust simulation models of forest response to climate change is crucial as they are key to identifying the best possible adaptation strategies. To forecast forest mortality events and tree species shifts under climate change, scientists have recently recognized the need to develop models not just based on regional climates, but also based on the reorganization of interactions between tree species and possible feedbacks. This research program deals with adaptation and shifts in the distribution of sugar maple under climate change. Will maple migrate North to find its environmental (climatic) niche in the boreal forest? Will it adapt locally? Will it expand? Or will it suffer from range contraction? Specifically, we will study the ecological/biogeochemical interactions between maple and other eastern Canadian tree species. Our objective is to assess whether maple has a competitive disadvantage for soil nutrients and water uptake over other species as this could decrease its capacity to adapt to climate change. We are developing a conceptual model using maple as the response species because it is an emblematic and commercially important species for Canada that is jeopardized by many threats. This model will be instrumental to determine if the distribution of other species will shift, expand or undergo contraction. We have set up a field study consisting of three sites forming the largest possible latitudinal gradient in Quebec for maple. At these sites, maple is found with an increasing abundance of: (1) the conifer species confronting maple at the southern edge of the boreal forest, and (2) American beech which is gradually replacing maple in deciduous forests of eastern North America. The research consists in a series of field and laboratory studies to test the impacts of various tree species composition (canopy types) on soil nutrient availability, maple seedling establishment and survival, and seedling/sapling foliar nutrition, water use and growth. We will also study maple litter decomposition and myccorhizal fungi associations with roots under the various canopy types as a means to understand the processes affecting maple nutrition and growth. This research will lead to improved adaptation strategies by augmenting knowledge on the functioning of complex forests and developing new tools to better predict the impacts of human activities on forests.