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Influence of conifer release treatments on habitat structure and small mammal populations in south-central British Columbia Runciman, James Bruce


I examined the effects of manual cutting and cut-stump applications of glyphosate herbicide on vegetation, woody debris, and small mammal populations in young mixed-conifer plantations of south-central British Columbia, Canada. The experimental design consisted of nine separate and independent plantations: 3 controls, 3 manual treatments, and 3 cut-stump treatments. Treatments were conducted between 21 September and 17 October 1992. Vegetation and woody debris were sampled once within each plantation during the last pre treatment year (1992) and again during the first post-treatment year (1993). Small mammal populations were sampled at three-week intervals within each plantation from September 1991 to October 1993 during snow-free periods. Total volumes of space occupied by herbs, coniferous trees, and woody debris were not affected by manual and cut-stump treatments for conifer release. However, both treatments reduced total volumes of shrubs and deciduous trees. The number of pieces of small diameter woody debris increased following the cutting of competing vegetation and increased the complexity of low ground cover on treated plantations. There were no discernable effects of manual or cut-stump treatments on the population size of deer mice (Peromyscus maniculatus), yellow-pine chipmunks (Tamias amoenus), southern redbacked voles (Clethrionomys gapperi), long-tailed voles (Microtus longicaudus), or meadow voles (M. pennsylvanicus). Sex ratios, body weights, reproduction, recruitment, and survival of deer mice were also similar on treatment and control plantations. Changes in habitat structure during the first post-treatment year did not appear to exceed the tolerance of small mammal populations for early successional change. Continued sampling on these plantations will establish whether there are any long-term treatment effects.

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