Increases in heat-induced tree mortality could drive reductions of biomass resources in Canada’s managed boreal forest

Abstract

The Canadian boreal forest provides valuable ecosystem services that are regionally and globally significant. Despite its importance, the future of the Canadian boreal forest is highly uncertain because potential impacts of future climate change on ecosystem processes and biomass stocks are poorly understood. We investigate how anticipated climatic changes in coming decades could trigger abrupt changes in the biomass of dominant species in Canada’s boreal forests. Using the dynamic global vegetation model LPJ-LMfire, which was parameterized for the dominant tree genera in Canada’s boreal forests (Picea, Abies, Pinus, Populus) and driven by a large range of climate scenarios grouped by two forcing scenarios (RCP 4.5/8.5), we simulated forest composition, biomass, and the frequency of disturbance, including wildfire, from Manitoba to Newfoundland. Results suggest that responses of this region to a warmer future climate will be very important, especially in southern boreal areas and under the RCP 8.5 forcing scenario. In these areas, reductions of total aboveground biomass incurred by fire and heat-induced tree mortality events are projected; the fertilizing effect of increasing atmospheric CO2 on forest productivity is unlikely to compensate for these losses. Decreases in total forest stocks would likely be associated with forest cover loss and a shift in composition in particular from needleleaf evergreen (softwood) to broadleaf deciduous (hardwood) taxa. The simulated future reduction in softwood biomass suggests that forest management strategies will have to be adapted to maintain a sustainable level of forest harvest and tree density that meets demands for wood products, while maintaining other ecosystem services.