RELATIONS OF SMALL MAMMAL POPULATIONS TO EVEN-AGED SHELTERWOOD SYSTEMS IN SUB-BOREAL SPRUCE FOREST

Natural regeneration of cutover forest lands and integration of nontim ber resources into forest management have generated investigation of a lternative silvicultural systems to clearcutting. An overstory canopy or shelterwood, may reduce the frequent frost problems observed in int erior Douglas-fir (Pseudotsuga menziesii var glauca) plantations and i mprove the success of natural regeneration, if seed predation by small mammals does not threaten the survival of the seed supply: We tested the hypothesis that a shelterwood silvicultural system would adversely affect dynamics of small mammal populations in 30% and 50% basal area (BA) removal stands. and we evaluated natural seed production, predat ion, and germination under a shelter-wood canopy in the southcentral i nterior of British Columbia. Deer mice (Peromyscus maniculatus) and so uthern red-backed voles (Clethrionomys gapperi) were the most common s mall mammal species prior to harvest, and both species continued to be dominant in the first and second lear postharvest. Abundance (P = 0.0 07) and recruitment (P = 0.015) of red-backed voles was 50% higher in shelterwood (treatment) than unharvested (control) stands. The shelter wood han est did not affect abundance (P = 0.42) or recruitment (P = 0 .47) of deer mice. There were no differences in average survival of de er mice and red-backed voles between control and treatment stands (P > 0.05). Mean body mass of adult male deer mice was similar in control and treatment stands (P = 0.27) but was lower for red-backed voles in the 50% BA removal than control stands (P = 0.05). Seedfall crops in t he second year postharvest were 7.4-29.6 times larger than in the firs t year on treatment and control units, but there was no difference bet ween units in either year (1992: P = 0.24; 1993: P = 0.93). Seed preda tion seemed to fluctuate with seasonal levels of small mammal populati ons (lower in spring and higher in fall) but not with the amount of se ed crop available. Germination occurred in 62% of the seeds that survi ved overwinter on the seedbeds created during harvesting. Thus, regene ration success, as measured by seed survival and establishment, did no t seem affected by the small mammal communities in 30% and 50% BA remo val stands.