Calibration and Holocene reconstruction of vegetation, fire and climate in the boreal forest of Eastern Canada

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Boreal forests of Canada shelter rich biological communities, are of great cultural importance and provide many ecosystem services such as carbon storage and forest resources production. In the boreal biome, vegetation distribution is driven by the climate and by the occurrence of large-scale natural disturbances such as fires and insect outbreaks. A sustainable management of these ecosystems thus represents many challenges. One of the most ambitious consists in reducing the differences between managed and natural forest ecosystems. This reduction would ensure the provision of forest ecosystem services and would likely promote the resilience of these ecosystems in the face of current climatic changes and the associated disturbance modifications. However, long-term data are required for understanding and characterizing those natural forests and their associated ecological processes. To fulfill these challenges, understanding the historic baselines of boreal ecosystems (productivity, biodiversity, structure, etc.) and understanding how disturbances and climate interacted in the long-term to shape them is highly crucial. Future conditions of climate and disturbances will probably have no analogues in the present. As a consequence, long-term reconstructions using paleoecological tools are needed to explore the response of ecosystems under an extensive range of conditions that observation alone cannot provide. Currently, one of the greatest challenge of paleoecology is the calibration of sedimentary biological proxies in order to quantify past changes in units that are consistent with climatic and vegetation models outputs, and with current observation variables. Therefore, I propose in this research program an original approach to calibrate fire regime and vegetation reconstructions for Canada's boreal forests combining different sources of information (paleoecological series, modern data and models). Applying these calibration functions to long-term data will help to better understand the mechanisms that linked disturbances, climate, vegetation productivity and diversity in the past. The knowledge that will be acquired during this research program is fundamental to the field of paleoecology and will also be useful for research in related disciplines such as ecosystem modeling, modern ecology and ecosystem management. Moreover, forest industry and government agencies will benefit these recent advances in the understanding of long-term ecosystem dynamics. Indeed, implementing paleoecological data and knowledge for forecasting and managing future ecosystems is crucial for Canadian forestry in order to achieve sustainability goals in ecosystem management and to adapt forests and practices to future climate.