Partial and clear-cut harvesting of high-elevation spruce–fir forests: implications for small mammal communities

Subalpine spruce (Picea) – fir (Abies) forests occur throughout the Cordillera of western North America. A variety of alternative silvicultural systems to clear-cutting are being investigated in these high-elevation forests in terms of their impacts on ecosystem components. We tested the hypotheses that abundance, reproduction, and survival of populations of (i) southern red-backed voles (Clethrionomys gapperi Vigors) will decline, (ii) long-tailed voles (Microtus longicaudus Merriam) and northwestern chipmunks (Tamias amoenus J.A. Allen) will increase, and (iii) deer mice (Peromyscus maniculatus Wagner) will be similar, with respect to decreasing levels of tree retention. Small mammal populations were live-trapped from 1994 to 1998 in replicated sites of uncut forest, single tree selection, 0.1-ha patch cuts, 1.0-ha patch cuts, a 10.0-ha clearcut, and edges in an Engelmann spruce (Picea engelmannii Parry ex Engelm.) – subalpine fir (Abies lasiocarpa (Hook.) Nutt.) forest near Sicamous, British Columbia, Canada. Clethrion omys gapperi dominated the small mammal community, reaching a peak abundance of 80 animals/ha with mean values ranging from 31 to 50 animals/ha. Over the 4 postharvest years, abundance, reproduction, and survival of C. gapperi populations were consistently similar among uncut forest, single tree selection, and patch cut treatments compared with clear-cut sites where this species declined to extirpation. Microtus longicaudus and T. amoenus occurred predominantly in clearcut sites, whereas P. maniculatus was present in low numbers on all sites. With respect to small mammals, partial harvesting systems appear to provide a means for combining timber extraction with maintenance of mature forest habitat in these subalpine ecosystems.