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Ecology and condition of the ground beetle Scaphinotus angusticollis and distribution of its prey in Pacific Northwest riparian forests Lavallee, Susanne L.


I studied the population ecology of the flightless, forest-dwelling carabid beetle Scaphinotus angusticollis Fischer Von Waldheim (O. Coleoptera F. Carabidae) and several aspects of its body condition for their associations with forest harvesting. Comparison of population estimates revealed that catch-per-unit-effort estimates were not significantly different from more detailed analyses. In two years of trapping, S. angusticollis population densities were found to be significantly lower in clearcuts, as compared to 30 m riparian reserves and uncut forest, suggesting that riparian buffers provide adequate habitat to maintain populations of this terrestrial insect. Movement of S. angusticollis differed in the three habitats studied between years and treatments, with the greatest movement occurring in 30 m buffers in one year and in control sites the next. Clearcuts had the lowest amount of movement in both years. One of the known prey species for S. angusticollis, snails < 2cm in diameter, were more abundant in clearcut habitat, with Ancotrema hybridum the most abundant species. Canonical correspondence analysis suggests that only A. hybridum were positively correlated with plant cover, and that other species abundances may rely on coarse, downed wood as cover. Thus only some species of snails are associated with recently logged areas. The internal body conditions of S. angusticollis living in clearcut, 30 m buffer and uncut sites showed that gut fullness was significantly correlated with energy storage (fat body) and habitat types (clearcut, 30 m buffer and uncut). This study demonstrates how some forest insects, particularly ground beetles, are affected by harvesting and that current management practices on the stand scale can mitigate some of the negative impacts of logging.

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