THE ASPEN PARKLAND IN WESTERN CANADA - A DRY-CLIMATE ANALOG FOR THE FUTURE BOREAL FOREST

Predicted future changes in regional climate under a doubling of atmos pheric CO2 concentrations were applied to the 1951-80 normals of 254 c limate stations to examine future impacts on the boreal forest of west ern Canada. Previous analyses have indicated that in this region, the southern boreal forest is presently restricted to areas where annual p recipitation (P) exceeds potential evapotranspiration (PET). The prese nt analysis suggests that a predicted 11% increase in P would be insuf ficient to offset the increases in PET resulting from a predicted warm ing of 4-5 degrees C. As a result, half of the western Canadian boreal forest could be exposed to a drier climate similar to the present asp en parkland zone (P < PET), where conifers are generally absent and as pen is restricted to patches of stunted trees interspersed with grassl and. Future changes could result in permanent losses of forest cover f ollowing disturbance and an increase in the proportion of exposed edge habitat in remaining stands, where environmental conditions might ind uce additional stresses on tree growth. Thus if the predicted warming and drying occurs, productivity of aspen and other commercial species in the southern boreal forest would be greatly reduced.