Vertical and horizontal distribution of bark and woodboring beetles by feeding guild: is there an optimal trap location for detection?

Bark and woodboring beetles include some of the most economically important forest pests. Understanding how these species are distributed in forests is critical for optimizing detection strategies. We placed traps at three heights above ground level at the edge and in the interior of two forests and focused on two groups: phloem/wood-feeding beetles (Coleoptera: Buprestidae, Cerambycidae, and some Curculionidae: Scolytinae) and ambrosia beetles (Coleoptera: Curculionidae: Scolytinae and Platypodinae). We recorded temperature, humidity, and canopy cover for each trap. Species richness increased with height for phloem-/wood-feeding beetles and decreased with height for ambrosia beetles, even when microclimatic variables were included in the models. Community composition differed greatly among heights but little between horizontal placements. Indicator species analysis found eight species (seven of which were phloem/wood feeders) to be significantly associated with traps at 15 m and eight species (six of which were ambrosia beetles) associated with traps at 0 m. Only one species was significantly associated with the forest edge and one species associated with the interior, but a total of thirteen species were associated with particular combinations of horizontal placement and height. While distance from the forest edge was an important factor for some species, trap height more strongly influenced the species of phloem-/wood-feeding and ambrosia beetles captured and is a more important consideration with respect to optimizing trapping programs.