Canadian Forest Service Publications
Impact of Horizontal Edge-Interior and Vertical Canopy-Understory Gradients on the Abundance and Diversity of Bark and Wood boring Beetles in Survey Traps. 2020. Sweeney, J.; Hughes, C.; Webster, V.; Kostanowicz, C.; Webster, R.; Mayo, P.; Allison, J.D. Insects 11 (9).
Issued by: Atlantic Forestry Centre
Catalog ID: 40544
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Semiochemical-baited intercept traps are important tools used to collect information about the presence/absence and population dynamics of forest insects. The performance of these tools is influenced by trap location along both horizontal edge–interior and vertical understory–canopy gradients. Consequently, the development of survey and detection programs requires both the development of effective traps and semiochemical lures but also deployment protocols to guide their use. We used field trapping experiments to examine the impact of both horizontal edge–interior and vertical understory–canopy gradients and their interactions with the species richness and abundance of Buprestidae, Cerambycidae and Curculionidae. Both gradients had significant effects on the diversity and abundance of all three families collected in traps and the pattern of gradient effects differed between the two experiments. In the first experiment, traps were deployed along transects involving large (>100 m) forest gaps and in the second experiment traps transected small (ca. 15 m) forest gaps. These results were consistent with the idea that gradient effects on the abundance and diversity of these three families of forest Coleoptera are context dependent. The results of this study suggest that monitoring programs for bark and woodboring beetles should deploy traps at multiple locations along both vertical understory–canopy and horizontal edge–interior gradients.
Plain Language Summary
Traps baited with sex attractants and plant odors are used extensively by regulatory agencies to survey for alien invasive forest insects in urban forests near ports and industrial parks that receive goods from overseas. The performance of these surveys perform may be affected not only by the type of traps and attractants used, but also by where the traps are placed at the survey sites. This study tested the effect of horizontal trap position (placed inside the forest vs. on the edge of the forest vs. outside the forest in the open) and vertical trap position (upper tree canopy vs. understory) on the number or species and specimens of bark- and wood boring beetles captured in traps. Both horizontal and vertical trap position affected trap performance. For example, jewel beetles were caught almost entirely in canopy traps regardless of horizontal position, longhorn beetles were caught mainly in canopy traps placed inside the forest, and most bark beetle species were caught in understory traps placed along the forest edge. The authors concluded that for optimal early detection of all “target” species of bark beetles and wood borers, trapping surveys should place traps at multiple locations, that is, in the canopy and the understory, inside the forest as well as along the forest edge. The study also found that the effects of forest edge on trap catch varied with the size of the forest gap. Traps placed in the middle of a narrow opening in the forest performed about the same as traps placed on the forest edge, whereas traps placed 30 m from the forest edge in an open field detected far fewer target species.