Consequences of climate changes on fire frequency and forest composition in the southwestern boreal forest of Quebec.

Consequences of climate changes on fire frequency and forest composition in the southwestern boreal forest of Quebec. We present a synthesis of the research made on fire frequency and forest composition in relation to climate change in the southwestern boreal forest of Quebec. Dendrochronological studies, for the last 300 years, showed a decrease of fire frequency since the end of the Little Ice Age (similar to 1850). Simulations using the Canadian General Atmospheric Circulation Model predict a decrease in forest fire activity with future warming. The decrease in fire frequency is responsible for an increase in balsam fir (Abies balsamea L.) and white cedar (Thuja occidentalis L.) abundance during the twentieth century. A low fire frequency could also explain the high abundance of white cedar during the warmest period of the Holocene (similar to 6000 BP) while its subsequent decrease, together with a significant increase in jack pine (Pinus banksiana Lamb.), may be explained by an increase in fire frequency following the cooling of the climate that has occurred through the Neoglacial period. The agreements between studies and at different time scales suggest that warming leads to an important decrease in fire activity in the southern boreal forest. These results may apply to a large part of the boreal forest.