Saproxylic beetles in high stumps and residual downed wood on clear-cuts and in forest edges

Abstract

This study evaluates how the placement and the different possible outcomes of a spruce retention tree affected species richness and assemblages of spruce-associated saproxylic beetles. In a field experiment in the boreal zone of central Norway, high stumps were created and compared with residual wood pieces (i.e. top boles with branches), in clear-cuts versus in forest edges. Flight interception traps were mounted close to the substrate. The results were analysed using rarefaction techniques, ordination (DCA) and anova. It was found that the placement of retention trees of spruce does matter: beetle assemblages were significantly different in stumps in the four treatments. For all species pooled, the species richness was higher in stumps in clear-cuts than in stumps or boles in the forest edge. Four red-listed species were more abundant near stumps than boles, and two red-listed species were more abundant in clear-cuts than forest edge. To cater for the variety of habitat preferences among forest beetles in managed forest, managers should leave both standing spruce trees (many of which will end up as windthrown, downed boles) and some high stumps (to secure some upright dead wood), in both exposed clear-cut and semi-shaded forest edge.

Keywords:

• Beetles (Coleoptera)
• boreal forest management
• clear-cut
• forest edge
• high stumps
• Picea abies
• red-listed
• retention
• saproxylic
• sun exposure

Acknowledgements

Thanks are due to Sigmund Hågvar for supervision in the course of K.O.F.'s Master Degree, to Sindre Ligaard who identified the beetles, to Bj⊘rn Arne Rukke for project co-operation, and to Erik Framstad for comments on an earlier version of the manuscript. The study reported is part of a co-operative project between the Norwegian Institute for Nature Research NINA, the Norwegian Forestry Association NORSKOG and the Norwegian Defence Estates Agency Forsvarsbygg, and was supported by a grant from the Norwegian Research Council (NFR-project 163230).