Jack pine (Pinus banksiana Lamb.) and black spruce (Picea mariana (Mill.) B.S.P.) are both boreal conifer species typical of Quebec’s northern spruce forest. Yet, west of Québec, stands with high ecological and economical value are dominated by those two species take a major place into the mixedwood forest, despite a unfavorable fire regime. However, due to climate warming induced by human activities, growing temperatures promotes, on one and, further northerward the migration of temperate species like red mapple, sugar mapple and yellow birch. On the other hand, climate change is causing a shift in fire regime unfavorable to jack pine and black spruce but favoring boreal broadleaves species (white birch, trembling aspen). The aim of my PhD is to understand the origin and persistence of those boreal conifers into the mixedwood forest in order to asses their futur dynamic.