The boreal forest is one of the most important global carbon sinks but its carbon fluxes and total amount of sequestered carbon depend on the regional climate variability. Because of this sensitivity to climate, boreal trees are also important natural archives of current and past climate change. During this project, we will use a data-model approach to improve our understanding of the links between forests and climate in a Canadian boreal region over the last millennium. More specifically, we will adapt the process-based ecophysiological model MAIDENiso to investigate factors influencing the growth and underlying biogeochemical processes of black spruce (Picea mariana (Mill.) B.S.P.), the most representative species of the North American boreal biome. This will give an insight into carbon storage in the taiga and will provide the first multiproxy (ring widths and δ18O and δ13C in tree-ring cellulose) regional climate reconstruction in Eastern North America over the last millennium. MAIDENiso will be calibrated on a recently developed network of tree-ring data from the taiga of Quebec. This project will have important implications. First, we will get information on the capacity of black spruce forests to adapt to climate change and to act as carbon sink using an innovative approach that can be transferred to study European boreal ecosystems as well. Second, we will reduce the uncertainties on the estimates of the climate variability of the last millennium in a region that has historically been under-represented in the Northern Hemisphere network of climate reconstructions (see IPCC AR5). Finally, we will be able to analyze the impact of each climate forcing (volcanism, solar activity, CO2 concentration) on the regional climate and carbon sink variability. An important aspect of this project is its multidisciplinarity. Climatology, geochemistry, dendrochronology, tree physiology and numerical modelling will be used linking together European and Canadian scientists.