Changes in winter habitat use by mammals following commercial thinning of lodgepole pine (Pinus contorta) in west central Alberta

Abstract

In 1996, Millar Western Forest Products initiated an adaptive management experiment to assess the potential benefits of commercial thinning and to monitor its effects on winter habitat use by multiple mammalian species, using indirect evidence (snow tracking). This program was known as the Commercial Thinning Winter Tracking Project (CTWTP). Track surveys are well suited to investigate habitat use, because transects can be restricted to specific habitat types and individual tracks can often indicate behaviour based on gait, movement pattern and other signs associated with the tracks. Differences in the frequency of track occurrence among habitat types can also indicate habitat preference. The CTWTP surveyed mammal track occurrence over 7 years on 30 transects within the 1695 ha Tom Hill study site southwest of Whitecourt, Alberta. Transects were located in one of four forest types: aspen dominated, black spruce dominated, reference lodgepole pine, and treatment (thinned) lodgepole pine. ANOVA and Tukey post-hoc tests were used to identify differences in mammal track occurrence among the three unthinned forest types and between the reference and treatment pine forest types. Moose and weasels were most common in black spruce. Snowshoe hare were most common in reference lodgepole pine. White-tailed deer and marten were more common in aspen. Fisher, rodents, lynx and coyote appear to have no preference for any of the three unthinned forest types. Comparisons between reference and thinned pine forest types identified three groups of species. Fisher and snowshoe hare appear to have decreased after thinning. Weasels, white-tailed deer and marten track occurrence increased after thinning. Species that do not appear to have been affected by the thinning were moose, rodents, squirrels, lynx and coyote. Principal Components Analysis (PCA) was used to identify correlations between track occurrence and habitat variables (i.e. snow depth, temperature).PCA identified positive and negative associations with a variety of habitat characteristics that may underlie the observed differences in track occurrence. Additional investigation focused on the ecology of more specific clades of wildlife and collection of track data at a variety of spatial scales may be a way of taking this broader summary of the CTWTP to a finer investigation ofhabitat use in the Tom Hill study site.