Relations of small mammal populations to even-aged shelterwood systems: A reply

The comment by Smith (1999) suggested the field experiment reported by Von Trebra et al. (1998) failed to meet its research objectives. Shelterwood sy stems are suitable for those forest sites which experience regeneration pro blems because of frost or drought, and as a harvesting system to integrate nontimber resources into forest management. As such, this silvicultural sys tem, 1 of many different forestry practices, would not be generally prescri bed across landscapes. Each of the 3 experimental blocks was located within a similar landscape matrix of coniferous tree species and successional sta ges. Size of blocks corresponded with conventional prescriptions for shelte rwoods of 20-30 ha. Contrary to the prediction of Smith (1990), effective t rapping area (ETA) was similar among all grids for both southern red-backed voles (Clethrionomys gapperi; preharvest: P = 0.26; postharvest: P = 0.61) and deer mice (Peromyscus maniculatus; preharvest: P = 0.13; postharvest: P = 0.10). Overall mean (+/- SE) ETA was 1.70 +/- 0.06 ha for red-backed vo les and 1.71 +/- 0.06 ha for deer mice. Population estimates calculated ove r ETA for red-backed voles and deer mice showed an identical pattern of res ponse to the shelterwood treatments as that reported by Von Trebra et al. ( 1998). The initial shelterwood harvest resulted in an increase in red-backe d vole populations but had no effect on deer mice, up to 2 years postharves t. In addition, mean length of movement of red-backed voles declined from 3 4.2 +/- 2.7 m preharvest to 14.1 +/- 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 our data indicate quite clearly that animals were responding to treatments rather than to a mosaic of habitat p atches in a given experimental block. We welcome researchers to challenge o ur results based on data from field studies, conducted within the context o f realistic forest management scenarios.