Assessing the lifeboat effect of retention forestry using flying beetle assemblages

Abstract

Retention forestry is a silvicultural approach used to retain structural and compositional components of the harvested area, maintain some connectivity throughout the landscape and provide a “lifeboat” area for species as part of a conservation effort. However, no manipulative field experiment has assessed the lifeboat functioning of retention forestry more than a decade post-harvest. In this study, we documented the effects of retention plots 20 years after their establishment on flying Coleoptera assemblages using flight intercept traps. 3414 beetles from 160 different species or genera were recovered during the study. Results demonstrated that beetle abundance and species richness were comparable between retention patches and continuous forests in the vicinity. However, beetle assemblages differed between the treatments because closed-habitat species and fungivorous beetles declined in retention patches and open-habitat species considered as tourists were associated with retention patches. Yet, beetle assemblages varied more in response to interannual effects than treatment effects. With respect to the lifeboat effect of retention forestry, we conclude that retention patches do not host the same species assemblage than continuous stands but are nevertheless effective for the conservation of species abundance and richness within a harvested area.