Distribution of a bark beetle, Trypodendron lineatum, in a harvested landscape

Abstract

The response of the striped ambrosia beetle, Trypodendron lineatum (Olivier) (Coleoptera: Curculionidae, Scolytinae), to direct and indirect measures of habitat availability was examined across a heterogeneous forest subjected to various intensities of harvest. The study area was classified into four stand types (conifer-dominated, mixed, deciduous-dominated, and deciduous-dominated with conifer understory) each of which was treated with four harvest intensities (unharvested, and 50%, 80%, and 90% harvested) and replicated three times each. The abundance of T. lineatum was measured using baited funnel traps. In the year prior to harvest, T. lineatum was most abundant in conifer-dominated stands, although the measured abundance of freshly dead conifers (their breeding habitat) did not differ from mixed stands. In the first and second summers after harvest, T. lineatum abundance varied with both stand type (least in deciduous-dominated stands) and harvest level (least in unharvested stands). In particular, abundance increased exponentially with the percent of spruce, Picea spp., in the canopy and the number of spruce stumps in the stand. These results suggest that T. lineatum search more in areas with more actual (stumps) or potential (live spruce) habitat, consistent with the resource concentration hypothesis. Because of the disproportionate response of T. lineatum to habitat cues, managers should minimize the concentration of freshly dead boles, particular in conifer stands.