Past and projected future changes in moisture conditions in the Canadian boreal forest

Spatial data for the Climate Moisture Index and the Palmer Drought Severity Index were generated from gridded temperature and precipitation data for the Canadian boreal zone over the period 1951-2010. Annual values for the indices for 2011-2100 were generated from projections of future climate derived from four general circulation models forced by three greenhouse gas emissions scenarios. Linear regression models between the indices and time were fitted to examine long-term trends. Results indicated that several large regions of the Canadian boreal forest experienced substantial drying during 1951-2010. Future projections indicated a general trend toward drier conditions during the 21st century. Overall, the analysis indicated more frequent and/or more severe droughts across managed western and central portions of the boreal forest in coming decades. These projections of indices are relevant to forest management because soil moisture availability is an important determinant of forest distribution, tree health, and regeneration success. Knowledge of the range of potential future changes in drought occurrence and intensity will aid forest managers and decision-makers in incorporating climate change considerations into forest management planning and practices.