Relationship of small mammal populations to uniform even-aged shelterwood systems

This study was designed to test the hypothesis that a shelterwood silvicultural system would reduce small mammal population levels in 30% and 50% basal area removal stands. The benefit of an overstory canopy, or shelterwood, may help reduce the frequent frost problems observed in interior Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. glauca) plantations, and improve the success of natural regeneration, if seed predation does not threaten the survival of the seed supply. Small mammal population levels, seed fall, seed germination, and seed predation were monitored in order to determine the small mammal population dynamics associated with seed predation in the central interior of British Columbia, Canada. Deer mice (Peromyscus maniculatus) and red-backed voles (Clethrionomys gapperi) were the most common small mammal species sampled prior to harvesting, and both species continued to be dominant in the first and second year post-harvest. There was no negative effect on small mammal populations due to the different intensities of basal area removal. Seed fall crops were recorded the first and second year post-harvest; the seed crop in the second year post-harvest was substantially larger than the first year post-harvest on treatments and controls. Seed predation varied between l5.4x10 and 35.0x10 seeds/ha/month, and seemed to fluctuate with the seasonal small mammal population levels (lower in spring and higher in fall) but not with the amount of seed crop available. Germination occurred in 62% to 63 % of the seeds that survived overwinter, on the seedbeds created during harvesting. Thus, the regeneration success of the stands, with regard to seed survival and establishment, in 30% and 50% basal area removal stands did not seem to be inhibited by the small mammal communities observed on the sites.Forestry, Faculty ofGraduat