Impacts of clearcut harvesting on snow accumulation and melt in a northern hardwood forest

Snow accumulation and melt on north- and south-facing slopes in the Turkey lakes watershed (TLW) in central Ontario were compared for a mature hardwood maple stand and an adjacent clearcut in late winter and spring of 2000 and 2001. Snow accumulation in the clearcut exceeded that in the forest, although the degree of difference varied with slope aspect and year. Melt was significantly larger in the south-facing clearcut and forest relative to corresponding north-facing sites. The south-facing forest sites lost all snowcover 27 days before the north-facing clearcut in 2000, and 4 days before the north-facing clearcut in 2001. Daily melt in the clearcut was slightly greater and more spatially variable than in the adjacent forest, with the exception of the south-facing slope in 2000. Nevertheless, the effect of aspect on spatial variations in melt was larger than that due to clearcutting. There was a slight increase in melt rate with decreased canopy density in the south-facing clearcut and forest; however, variations in canopy density did not explain inter-point differences in daily melt within either the north-facing clearcut or the forest. The hydrological consequences of greater pre-melt snow water equivalent and larger daily melt in clearcuts include quicker delivery of meltwater to the soil surface and promotion of rapid near-surface runoff to receiving waters relative to undisturbed forest stands at TLW.