| In recent decades mountain pine beetle (MPB) has become an important natural disturbance agent in western Canada, thus the impact of this disturbance will likely be an important component affecting water resources in this region. Despite the widespread recognition of the potential changes, there has been limited research focused on how MPB affects key hydrological processes in lodgepole pine forests throughout west central Alberta.;To better understand how water inputs and outputs are modified at stand scales after the MPB attack I investigated: 1) the initial effects of simulated MPB on individual components of the stand water balance, including forest evapotranspiration (rainfall interception, transpiration and forest floor evaporation) and soil moisture as these components along with precipitation regulate water production from forested regions; and 2) the likely integrated effect of these components on the water balance of Alberta's lodgepole pine forests.;My research indicated that rainfall interception dominates the evaporative losses from mature lodgepole pine stands, and while the impact of MPB on water balance increases in proportion to the intensity of the attack, lower intensities of attack (affecting <1/3 of the stand) may not result in increased drainage or runoff because of increased water use by surviving trees. MPB impacts on forest water balance is likely greatest in the regions of Alberta where growing season precipitation is greatest. Thus, interactions among water balance components such as forest floor rainfall interception, and highly variable changes in transpiration can moderate the impacts of MPB on water balance across a gradient of increasing intensity of MPB attack.;I also found that intensively MPB attacked forests can exhibit strong seasonal variations in drainage that parallels the distribution of summer rain. Thus, soil moisture during the growing season in attacked stands may not be as reliant on strong snowmelt recharge as in healthy forests.;These findings are novel because impacts of MPB attack on the components regulating stand water balance have not been previously documented. Thus the combined effect of MPB on the processes that govern water cycling in MPB affected pine forests have been speculative prior to this study. |
