Multiresource effects of a stand-replacement prescribed fire in the Pinus contorta-Abies lasiocarpa vegetation zone of central Washington.

Abstract

A stand-replacement prescribed fire in an over-mature lodgepole pine (Pinus contorta Dougl. ex Loud.)-subalpine fir (Abies lasiocarpa (Hook.) Nutt.) stand (snag area) and in a mature lodgepole pine thicket (thicket area) resulted in lower plant diversity within the first year after burning, and as fire energy outputs increased, postburn plant cover and diversity decreased. There was no reestablishment of the original plant cover where total heat output exceeded 100 000 kcal/m². Apparently, most plants in this habitat were not fire resistant. Postfire recovery appears to depend on immigration of seeds from adjacent unburned areas or on seeds and rhizomes that survive on unburned microsites (refugia) within the burn. After fire, temperatures increased in the forest floor fermentative layer (FL) (10 to 19 °C) and upper 10 cm of the soil layer (SL) (3 to 7 °C) on several dates in summer 1976. Increased pH levels in FL (about 2 units) and SL (about 0.5 unit) after burning provided an improved environment for bacterial development, and counts of total bacteria and proteolytic bacteria both increased. Both nitrogen fixation and nitrification were increased after burning. Despite the apparent increase in microbiological activity, microbial respiration declined after burning—apparently because of reduced forest floor organic carbon energy reservoir. Diversity of birds increased the year after burning. New species of birds included hairy woodpecker (Picoides villosus), black-backed woodpecker (Picoides arcticus), three-toed woodpecker (Picoides tridactylus), common flicker (Colaptes auratus), and mountain bluebird (Sialia currucoides). Numbers of needle-foraging species, such as Townsend’s warbler (Dendroica townsendi), hermit thrush (Catharus guttatus), golden-crowned kinglet (Regulus satrapa), and western tanager (Piranga ludoviciana), declined or were absent after fire. Responses of small mammals to fire were not definitive, but there was a marked decline in Townsend’s chipmunk (Tamias townsendii) after burning. In the first year after burning, forage for elk (Cervus elaphus) in the burned area was higher in crude protein than in unburned areas, but low productivity and distance from water diminished the value of the burned area for elk.

Keywords

Forest succession, forest floor, understory vegetation, fuels, soil physical properties, wildlife, snags, downed wood, microbial populations, nitrification, nitrogen fixation, small mammals, birds, elk

Citation

Tiedemann, Arthur R.; Woodard, Paul M. 2002. Multiresource effects of a stand-replacement prescribed fire in the Pinus contorta-Abies lasiocarpa vegetation zone of central Washington. Gen. Tech. Rep. PNW-GTR-535. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 26 p