C. Vontrebra et al., RELATIONS OF SMALL MAMMAL POPULATIONS TO EVEN-AGED SHELTERWOOD SYSTEMS IN SUB-BOREAL SPRUCE FOREST, The Journal of wildlife management, 62(2), 1998, pp. 630-642
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.