New research on the impacts of postfire logging and wildlife

By adamswitalski

February 5, 2009

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There is great debate over postfire logging.  While some argue timber should be “salvaged” following a fire, an increasing amount of scientific literature has documented the ecological consequences of postfire logging (for review see Conservation Biology journal volume 18 issue 4).  One such study recently published in Forest Ecology and Management and conducted in Alberta examined the impact of post fire logging on elk, deer, and moose.   Hebblewhite et al. (2009) found that elk avoided pre and postfire logged areas even though there was greater forage.  Wolves on the other hand preferred roaded landscapes that were recently burned and logged.  They concluded that “ungulates avoided postfire logged areas because of human alteration of top-down predation risk despite enhancements to bottom-up forage biomass.”  So although logging did increase food resources for ungulates (hoofed mammals), they avoided them because of predation risk from wolves.  They recommend ways to mitigate these impacts through “use of existing roads, minimizing the construction of new roads, and managing road removal following postfire logging.”

Here is the citation and abstract:

Hebblewhite, M., R.H. Munro, and E.H Merrill.  2009.  Trophic consequences of postfire logging in a wolf-ungulate system.  Forest Ecology and Management 257(3): 1053-1062.

Abstract: Controversy surrounds postfire logging, often because of negative effects on snag-dependent wildlife species. Few studies, however, have examined effects on early-seral species that may benefit from postfire logging, nor effects on trophic relationships. We studied the effects of postfire logging on trophic dynamics between wolves (Canis lupus), three ungulate species and ungulate forage biomass during the first 3 years in a large burn in the Canadian Rockies, Alberta, Canada. We examined plant biomass and ungulate responses to two treatments (post- and prefire logging) compared to a burned but unlogged area (control). We evaluated resource selection for the three treatments by elk (Cervus elaphus) using radiotelemetry and for deer (Odocoileus spp.), moose (Alces alces), and, secondarily, elk using pellet counts. Elk resource selection was modeled as a function of the trade-off between wolf predation risk and herbaceous forage biomass to test for trophic impacts of postfire treatments. Postfire logging had transient effects on total herbaceous biomass; while forb biomass was reduced, increases in graminoid biomass more than compensated by the third year. Prefire logging areas were dominated by a few species, but had generally higher forage biomass by the third year. Ungulates avoided postfire and prefire logged areas despite greater herbaceous biomass. Only when we considered elk resource selection as a function of both forage and wolf predation risk was the extent to which trophic interactions affected by postfire logging revealed. Wolves selected proximity to roads and the higher forage biomass associated with postfire logging in open logged areas. This translated to the highest predation risk for elk in postfire logged areas. Thus, ungulates avoided postfire logged areas because of human alteration of top-down predation risk despite enhancements to bottom-up forage biomass. Managers should consider trophic consequences of postfire logging on the interactions among species when gauging logging effects on terrestrial ecosystems. Making use of existing roads, minimizing the construction of new roads, and managing road removal following postfire logging will help mitigate the negative effects of postfire logging on terrestrial ecosystems.

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