Evaluation of strip‐cutting to conserve carabid beetle diversity in a conifer plantation

Abstract To mitigate the impact of clear‐cutting, the use of strip‐cutting has increased in Japan. Strip‐cutting creates uncut strips and extends forest edges compared to clear‐cutting. To evaluate the impacts of strip‐cutting on insect diversity, we captured carabid beetles using pitfall traps with or without fish meat bait in a conifer plantation that had undergone partial harvesting through 40‐m‐wide strip‐cuttings and 60–120‐m‐wide clear‐cuttings immediately before the study. The presence of bait had a negligible effect on carabid beetles. Species richness and Simpson's diversity index (1/D) were significantly higher in strip‐cut areas than in clear‐cut areas due to the increased presence of newly colonizing open‐land species in the strip‐cuts. Beetle assemblages were similar, with no significant differences observed between uncut forests and uncut strips. Species richness and diversity index were significantly higher at forest edges than in uncut areas, attributed to the presence of open‐land species and the reduced abundance of the dominant forest species, Synuchus cycloderus , at forest edges. The diversity index was also significantly higher at forest edges than in harvested areas due to the presence of forest species and the low abundances of open‐land species at forest edges. These findings suggest that strip‐cutting is a more favorable harvesting method than clear‐cutting to mitigate the impact on carabid diversity. Harpalus tridens , Harpalus jureceki , and Dolichus halensis exhibited significant positive relationships with understory cover degree in logged areas, whereas Colpodes buchanani showed a negative relationship. Carabus japonicus was abundant in both uncut areas and forest edges.