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

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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.