EFFECTS OF TIMBER HARVEST ON FOREST LEPIDOPTERA: COMMUNITY, GUILD, AND SPECIES RESPONSES

Abstract

Two pressing questions for forestry and conservation biology are whether periodic logging in forest ecosystems significantly changes biodiversity and whether the changes can be mitigated through appropriate harvest methods. Such questions of timber resource management, however, are rarely applied to nonpest insect species, particularly in temperate forest systems. We studied the effects of timber harvest on species richness, abundance, and community composition of forest Lepidoptera (moths). Moths were sampled in 16 forest stands occurring in two watersheds (managed and wilderness) in southeastern Ohio during summer 2000. Stands were chosen from one of four management categories: clear-cut, selectively logged, unlogged, and wilderness. Specifically, we tested the following predictions: (1) shifts in moth community composition would be affected by postharvest changes in stand structure and floristic composition, (2) variation in species richness would be determined by the magnitude of the logging disturbance, and (3) unlogged stands within managed landscapes would contain different species assemblages compared to wilderness stands. Canonical correspondence analysis (CCA) revealed significant compositional differ- ences among moth communities sampled from forest stands differing in harvest regime. Variation among moth communities was mainly attributable to postharvest changes in stand floristic composition rather than stand structure. Postdisturbance shifts in moth community composition were related to the magnitude of displacement of a given forest stand to earlier successional stages. We also found that both species richness of the overall moth community and several feeding guilds were significantly lower in clear-cut stands, but species richness did not differ between selectively logged and unlogged stands. Thus, selective logging appears to be a better strategy for timber harvest when concern is for maintaining species richness of Lepidoptera within stands. Finally, although no differences were detected in overall species richness or abundance of moths sampled from stands in managed or wil- derness watersheds, the CCA suggested that the surrounding landscape influenced the var- iation in community composition within and among forest stands. Therefore, we suggest that the long-term maintenance of lepidopteran species diversity and community compo- sition within temperate deciduous forests managed for timber may ultimately depend on successful regeneration of harvested stands to precut floristic composition as well as the preservation of larger areas of unlogged forests.