Role of fire in restoration of a ponderosa pine forest, Washington

Ponderosa pine forests in the Eastern Cascades of Washington support dense, overstocked stands in which crown fires are probable, owing to postsettlement sheep grazing, logging, and fire exclusion. In 1991, the Okanogan-Wenatchee National Forests began to apply long-term management techniques to reverse postsettlement changes in ponderosa pine forests. For 9 years, the effects of thinning and burning in a ponderosa pine/pinegrass forest were evaluated, using prescribed fire in fall 1997 in forest stands that had been thinned in 1996. Thinning and burning had little effect on the canopy layer of ponderosa pine, western larch, and Douglas-fir, but small grand fir trees, and nearly half of the saplings of all species, were killed. Shrubs in the middle forest layer were top-killed, but resprouted during the first postfire growing season, and increased dramatically after 3 years and 9 years. Frequency and cover maintained or increased for species in the lower forest layer in postfire years 1, 3, and 9. The thinning and fire treatments reduced the middle layer of small trees and shrubs in the first postfire year, but by the third and ninth postfire years tree seedlings, especially grand fir and ponderosa pine, and small shrubs were abundant in the understory. Thinning trees and removing excess fuels, coupled with low intensity late season prescribed burns, offers a promising management strategy for restoring the presettlement structure of the ponderosa pine/pinegrass community in Beehive Forest.