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

加拿大的北方森林庇护着丰富的生物群落，具有重要的文化意义，并提供许多生态系统服务，如碳储存和森林资源生产。在北方生物群落中，植被分布受气候和大规模自然干扰（如火灾和虫害暴发）的影响。因此，这些生态系统的可持续管理面临着许多挑战。其中最雄心勃勃的目标之一是缩小管理森林生态系统与自然森林生态系统之间的差异。这种减少将确保森林生态系统服务的提供，并可能促进这些生态系统在面对当前气候变化和相关干扰变化时的复原力。但是，了解和描述这些天然林及其相关生态过程需要长期数据。为了应对这些挑战，了解北方生态系统的历史基线（生产力，生物多样性，结构等）以及了解干扰和气候如何在长期内相互作用以塑造它们是至关重要的。未来的气候条件和扰动很可能在现在没有类似的情况。因此，需要利用古生态工具进行长期重建，以探索生态系统在广泛条件下的响应，而这些条件仅靠观测是无法提供的。目前，古生态学面临的最大挑战之一是沉积物生物代用物的校准，以便量化与气候和植被模型输出以及当前观测变量一致的单位过去的变化。因此，我在这个研究项目中提出了一种结合不同信息来源（古生态序列、现代数据和模型）的原始方法来校准加拿大北方森林的火灾状态和植被重建。将这些校准函数应用于长期数据将有助于更好地理解过去将扰动、气候、植被生产力和多样性联系起来的机制。在这个研究项目中获得的知识是古生态学领域的基础，也将对生态系统建模、现代生态学和生态系统管理等相关学科的研究有用。此外，森林工业和政府机构将受益于了解长期生态系统动态的这些最新进展。事实上，为了实现生态系统管理的可持续性目标，并使森林和实践适应未来气候，将古生态数据和知识用于预测和管理未来生态系统对加拿大林业至关重要。

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.