Author
Vanessa J. CRAIG, Walt KLENNER, Michael C. FELLER, Thomas P. SULLIVAN
Correspondence: Thomas P. Sullivan, Department of Forest and Conservation Sciences, Faculty of Forestry, 2424 Main Mall, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada. Email: tom.sullivan@ubc.ca
Submitted 15 May 2014 – Accepted 28 August 2014
Abstract
Downed wood has long been identified as an important habitat component for many small mammals, particularly for late seral forest species such as the Red-backed Vole (Myodes gapperi). We report on the relationship between manipulated volumes of downed wood and Red-backed Vole population dynamics, in both forested and clearcut habitats, and in two distinct ecosystems. We tested the hypotheses (H) for Red-backed Voles that: (H1) abundance and reproduction would be lower on forested sites with less downed wood; (H2) a positive relationship between Redbacked Vole population parameters and downed wood will not depend on the presence of alternate forms of cover; and (H3) retention of downed wood on clearcuts would mitigate the negative effects of harvesting. There were two study areas: a dry Douglas-fir (Pseudotsuga menziesii) – Lodgepole Pine (Pinus contorta) forest (Opax), and a highelevation Engelmann Spruce (Picea engelmannii) – Subalpine Fir (Abies lasiocarpa) forest (Sicamous) in southern British Columbia, Canada. We monitored the responses of Red-backed Voles to three levels of downed wood over a 4-year period in replicated forest and clearcut sites at each area. There were no changes in abundance or reproduction of Red-Backed Voles in response to removal of downed wood on forested sites at either study area, thereby not supporting H1. Clearcutting negatively affected Red-backed Voles at both study areas; but at Opax, the immediate impact of clearcutting was partially mitigated, at least in the short term, by maintaining >75 m3/ha of downed wood on site, a result that partially supported H2 and H3. Downed wood on Sicamous clearcut sites did not prevent immediate declines of voles after harvest. It is important to retain downed wood in dry ecosystems, where it might act as a moisture reservoir, particularly for Red-backed Voles. For downed wood to be maintained through time, larger pieces should be left on site after harvesting as they provide greater amounts of cover and decay more slowly.
Key Words: Abundance, Clearcuts, Douglas-fir Forest, Downed Wood, Myodes gapperi, Population Dynamics, Red-backed Voles, Spruce-Fir Forest.
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