Mountain pine beetle is changing the structure of British Columbia's forests, with subsequent impacts on forest hydrology, particularly in snowmelt-dominated hydrological regimes. Previous studies of pine beetle-hydrology interactions have focused on total basin yield rather than specific hydrological processes, and were conducted in regions other than northern British Columbia, which have different hydrological regimes. An understanding of beetle impacts on specific hydrological processes is important for determining future impacts on geomorphology, aquatic ecology, and ecosystem function, as well as the potential impact on surface water supplies, and the implications for forest management (i.e. salvage logging). Snow accumulation, melt and canopy cover were measured in three pine stands (open, dead, alive) near Vanderhoof, B.C. Results indicate that variations in canopy cover are the main driver of between-stand differences in both snow accumulation and melt due to differences in canopy interception of snow. Results are used to predict the potential impacts on runoff at the watershed scale, with the understanding that scaling up from point measurements can be problematic. The study concludes that dead stands constitute a 'transitional' forest canopy type; they accumulate greater snowpack than live stands but less than open stands, and have energy balance characteristics in a linear progression; the progression from dead to open can be mitigated if there is sufficient understory to take over the interception process formerly performed by the pine. Given these results, the report suggests that forest retention during salvage harvesting would be the most effective way to reduce the impacts of beetle infestation on runoffs and peak flows, as it would maintain canopy cover to continue the interception process.
Boon, Sarah. 2006. Determining the impact of MPB-killed forest and elevated harvesting on snow accumulation, and the projected impacts on melt and peak flow. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report. FIA2006MR259