Snow accumulation and ablation under fire-altered lodgepole pine forest canopies

Clearcut, burned, and undisturbed lodgepole pine forests in southwestern Montana were studied to determine if forest fire increased snow accumulation and ablation rates on the forest floor. Snow depth, snow density, and snow water equivalence data were collected at each plot throughout the ablation period during the 1992 snow season and the accumulation and ablation periods during the 1993 snow season. Forest variables including percent canopy cover, basal area, and tree height were measured during the 1992 summer season to assess the effects of forest cover on snow variables. The burned forest canopy produced a 9 percent increase in snow water equivalence accumulation as compared to that produced by the mature forest stand. Canopy reduction in the burned forest stand resulted in an ablation rate up to 57 percent greater than that in the mature forest stand. The forest structures of the burn and of the clearcut produced similar snow accumulation and ablation responses.