The influence of clear-cut logging and residual leave material on small mammal populations in aspen-dominated boreal mixedwoods

We investigated responses of populations of common small mammals to variation in the amount of standing trees and residual woody material retained during logging in aspen-dominated, boreal mixedwood forest in north-central Alberta. Experimentally manipulated levels of residual material, with two replicates per level, were (i) "zero residual": clear-cut and no woody debris (tree tops and limbs); (ii) "low residual": clearcut and woody debris; (iii) "moderate residual": 10% basal area standing live tree retention, and woody debris; and (iv) "uncut": 100% uncut. Patterns of small mammal abundance were similar throughout the study on uncut and moderate-residual grids, where southern red-backed voles (Clethrionomys gapperi Vigors) and deer mice (Peromyscus maniculatus Wagner) were numerically dominant. In contrast, C. gapperi were virtually absent from the low- and zero-residual grids during the breeding season following logging and occurred at low numbers in the following 2 years. Peromyscus maniculatus were common on low- and zero-residual grids in all years. We found no evidence that rates of reproductive activity and (or) survival in C. gapperi and P. maniculatus were affected by logging treatments. Meadow voles (Microtus pennsylvanicus Ord) were uncommon on uncut and moderate-residual grids throughout the study but were abundant on both low-residual grids and one zero-residual grid, particularly in the second year following logging, when they exhibited irruptive dynamics in midsummer. In sum, relative abundances of common small mammals were most affected by intensive (clear-cut) logging, and our results suggest that the experimental retention of at least 10% basal area on cutovers may reduce some of these effects.