Short-term effects of prescribed fire in grand fir-white pine-western hemlock slash fuels

Experimental burns were conducted on 36 plots in mixed conifer logging slash in northern Idaho, under varying fuel loadings and moisture conditions. This paper reports the immediate effects of these burns on the forest floor, the woody fuel complex, and the plant community, and includes recommendations to managers for using prescribed fire in this forest type. Much of the shallow layer of duff was consumed exposing mineral soil under the full range of burn conditions; however, the deep pockets of rotten wood in the forest floor retained moisture throughout the burning season, and were largely intact after fire. Most (70%, or an average of 31 tons/acre) of the large woody fuel was retained. Planted Douglas-fir, western larch and white pine had greater average height growth on burned units than on unburned. Natural regeneration of grand fir and western hemlock was taller with greater average annual increment on unburned units than on burned units. There were more grand fir seedlings on unburned units, but more hemlock seedlings on burned units.