Conservation-oriented manipulations of coarse woody debris affect its value as habitat for spruce-infesting bark and ambrosia beetles (Coleoptera: Scolytinae) in northern Sweden

Abstract

Many species of Scolytinae are pests in boreal forests, so factors that affect their abundance are of great interest to forestry. Using emergence and window traps we examined the effects of stand type and substrate characteristics on the abundance of spruce-infesting Scolytinae in northern Sweden. Several species of Scolytinae (Crypturgus subcribrosus, Hylastes cunicularius, Hylurgops palliatus, Pityogenes chalcographus, Polygraphus punctifrons) were captured in greater numbers on snags than on untreated logs. Log exposure also had a significant effect on some species, H. palliatus and Trypodendron lineatum were more abundant in window traps on artificially shaded logs than on naturally shaded or untreated logs. Significantly fewer Dryocoetes autographus, H. palliatus,Hylurgops glabratus, andH. cunicularius were captured on burned logs than on untreated logs. Stand type clearly affected several species, P. chalcographus emerged in greater numbers on clearcuts than in mature managed and old-growth stands, and D. autographus,H. glabratus, and T. lineatum showed the opposite pattern. Historical records suggest that pest outbreaks are rare in northern Sweden; however, improved knowledge of the habitat preferences of potential pest species in this region will allow us to take the necessary precautions against outbreaks, whilst leaving sufficient dead wood to support intact saproxylic assemblages.