Vulnerability of eastern Canadian forests to climate warming: environmental drivers, plasticity and climatic thresholds

鉴于加拿大森林在固碳、维持生物多样性和木材供应方面的关键作用，我的长期目标是评估加拿大森林对预计的气温和水分压力上升的脆弱性，并提供关于缓解方案的关键知识。在接下来的五年里，我的目标是A)确定当地环境驱动因素对林分易受干旱影响的作用，B)评估当地适应和树种可塑性的重要性，以及C)确定特定物种的气候阈值。为了更好地了解干旱脆弱性的环境驱动因素，我们将在新不伦瑞克建立一个新的树木生长监测网络，这将使我们能够以高分辨率监测树木对缺水反应的林分水平的变异性。这些成果将突出干旱脆弱性的环境驱动因素，从而提供关键知识，以便更好地为管理战略提供信息。作为补充，我们将建立一系列温室实验，以确定干旱时间对林分脆弱性的作用。我们将在受控环境中比较五种升温水平和三种水分亏缺时间下多种植物生长和碳分配的干旱敏感性。在气候变化缓解解决方案中，用相同树种的树木取代原生树木，但在较温暖的气候下生长的种群，可能会提高森林对气候变化的耐受性。我们将从整个物种分布范围来评估成年树木的表现，这些树木是在阿卡迪亚研究森林精心设计的实验中种植的，并将它们的气候敏感度与当地种群进行比较。作为补充，我们将比较50年前沿着5°C温度梯度从魁北克北部到缅因州南部种植的黑云杉种群的气候敏感性。气候敏感性将通过将树轮的树枝解剖特征与季节性气候相匹配来评估。最后，我们将扩大在魁北克省开展的早期工作，将加拿大大西洋和缅因州包括在内，以便更好地评估加拿大东部主要树种当前的气候阈值。我们将使用来自这一大气候梯度上的永久样地的树木生长数据来拟合广义加性模型。这些模型将使我们能够根据替代的气候和管理情景来模拟生长的变化，并帮助检测区域物种的减少。这项工作的影响和应用在于权衡控制气候变暖导致的加拿大东部森林动态未来变化的因素(如竞争、物种)的作用。这一新知识将有助于为减少森林脆弱性的管理解决方案提供信息，并有助于维持最大效益和可持续性。这项研究计划还将有助于获得有关森林生态学和木材生长的生态生理学的新的基础知识。

Given the crucial role of Canada's forest for carbon sequestration, maintenance of biodiversity and wood supply, my long-term objective is to assess the vulnerability of the Canadian forest to projected increases in temperatures and water stress and provide crucial knowledge on mitigation solutions. Over the next five years, I aim to A) determine the role of local environmental drivers on stand vulnerability to drought, B) assess the importance of local adaptation and plasticity in tree species, and C) identify species-specific climatic thresholds. To better understand the environmental drivers of drought vulnerability, we will build a new tree-growth monitoring network by setting up plots in New Brunswick, which will allow us to monitor at high-resolution the stand-level variability in tree responses to water deficits. Such results will highlight environmental drivers of drought vulnerability, thus providing crucial knowledge to better inform management strategies. In complement, we will set up a series of greenhouse experiments to determine the role of drought timing on stand vulnerability. We will compare the drought sensitivity of multiple species growth and carbon allocation under five warming levels and three timings of water deficit in a controlled environment. Amongst climate change mitigation solution, replacing native trees with trees of the same species, but from populations growing under warmer climates may improve forest tolerance to climate change. We will assess the performance of adult trees from the entire species distribution range, planted in well-designed experiments at Acadia Research Forest and compare their climate sensitivity with that of native populations. In complement, we will compare the climate sensitivity of a black spruce population planted fifty years ago along a 5°C temperature gradient from northern Quebec to southern Maine. Climate sensitivity will be assessed by matching dendroanatomical characteristics of tree-rings with seasonal climate. Finally, we will expand earlier work conducted in the province of Québec to include Atlantic Canada and Maine in order to better assess current climatic thresholds of dominant tree species of Eastern Canada. We will fit generalized additive models using tree growth data from permanent sample plots across this large climate gradient. These models will allow us to simulate changes in growth according to alternative climate and management scenarios and help detect regional species declines. The impact and applications of this work consist in weighing the role of the factors (e.g. competition, species) that control future changes in eastern Canada's forest dynamics due to climate warming. This new knowledge will help inform management solutions to reduce forest vulnerability and help maintain maximum benefits and sustainability. This research program will also be instrumental in acquiring new fundamental knowledge on forest ecology and ecophysiology of wood growth.