Relations of small mammal populations to even-aged shelterwood systems: a reply.
Sullivan, T. P.; Sullivan, D. S.; Kurta, C.;
Journal of Wildlife Management Year: 1999 Vol: 63 Issue: 4 Pages: 1381-1389 Ref: 43 ref.
1999
บทคัดย่อ
The comment by Smith (1999) [Smith, W. P. Journal of Wildlife Management (1999) 63, 1376-1380] suggested the field experiment reported by Von Trebra et al. (1998) [Trebra, C. von; Lavender, D. P.; Sullivan, T. P. Journal of Wildlife Management (1998) 62, 630-642] failed to meet its research objectives. Shelterwood systems are suitable for those forest sites which experience regeneration problems because of frost or drought, and as a harvesting system to integrate nontimber resources into forest management. As such, this silvicultural system, 1 of many different forestry practices, would not be generally prescribed across landscapes. Each of the 3 experimental blocks was located within a similar landscape matrix of coniferous tree species and successional stages. Size of blocks corresponded with conventional prescriptions for shelterwoods of 20-30 ha. Contrary to the prediction of Smith (1999), effective trapping area (ETA) was similar among all grids for both southern red-backed voles (Clethrion
omys gapperi; preharvest: P = 0.26; postharvest: P = 0.61) and deer mice (Peromyscus maniculatus; preharvest: P = 0.13; postharvest: P = 0.10). Overall mean ( plus or minus SE) ETA was 1.70 plus or minus 0.06 ha for red-backed voles and 1.71 plus or minus 0.06 ha for deer mice. Population estimates calculated over ETA for red-backed voles and deer mice showed an identical pattern of response to the shelterwood treatments as that reported by Von Trebra et al. (1998). The initial shelterwood harvest resulted in an increase in red-backed vole populations but had no effect on deer mice, up to 2 years postharvest. In addition, mean length of movement of red-backed voles declined from 34.2 plus or minus 2.7 m preharvest to 14.1 plus or minus 0.9 m postharvest in 1991, again, the opposite trend predicted by Smith (1999). Configuration of treatments was a limitation in the overall design, but the data indicate quite clearly that animals were responding to treatments rather than to a mosaic of habitat patches in a gi
ven experimental block. Researchers are welcome to challenge the results based on data from field studies, conducted within the context of realistic forest management scenarios.