If we build habitat, will they come? Woody debris structures and conservation of forest mammals

Abstract

Coarse woody debris (CWD) from forest harvesting and salvage wood from wildfire and insect outbreaks provide habitat for an array of forest-floor small mammal species and some of their mammalian predators. Because forest clear-cutting reduces abundance of many mammal species, strategic management of postharvest debris could help maintain abundance and diversity of forest mammals on harvested sites. We tested hypotheses that abundance and species diversity of forest-floor small mammals would be lower on conventional clear-cuts than in uncut forest; abundance and species diversity of forest-floor small mammals and relative activity and species richness of winter mammals would be higher on clear-cut sites with woody debris arranged in large piles or windrows than a dispersed treatment of debris. Small mammals were intensively livetrapped, and winter mammals snow-tracked, from 2007 to 2009 in replicated (n¼ 3) woody debris treatments of dispersed, piles, windrows, and uncut mature forest at 3 study areas in south-central British Columbia, Canada. We captured all 9 species of forest-floor small mammals. Compared with uncut forest, clear-cutting had no effect on mean total abundance of the small-mammal community, and species richness and diversity were either similar or higher. With respect to habitat preference, generalist species increased while specialist species declined. Habitat structures of large piles and windrows of woody debris on clear-cuts dramatically ameliorated these responses. On the basis of track counts, relative activity and species richness of winter mammals were enhanced by these structures, but the response was species specific. This is the 1st investigation showing significant increases in abundance and species diversity of forest-floor small mammals associated with constructed piles and windrows of postharvest woody debris on clear-cuts. Large-scale CWD structures as piles or windrows have clear conservation implications for mammals in commercial forest landscapes.