Woodfuel harvesting and biodiversity conservation in temperate forests: Effects of logging residue characteristics on saproxylic beetle assemblages

Converting fossil-based energy systems into carbon–neutral systems is an essential strategy to the reach targets set by the Kyoto Protocol. For nations with an active logging industry, salvaging logging residues or slash to produce bioenergy has a huge potential for development. However, removing forest woodfuel may have ecological consequences, notably for saproxylic biodiversity. The consequences of such removals on biotic assemblages in temperate forests remain poorly documented in comparison with boreal forests. In this study, we compared the species richness and composition of saproxylic beetle assemblages among different types of logging residues in several temperate oak-dominated French forests. We showed that residue tree species was the most important factor for saproxylic biodiversity, as it not only influences assemblage composition, but also species number. Oak and hornbeam logging residues were richer than logging residues from beech and spruce. Decay stage also appeared to be an important factor for saproxylic beetles associated to logging residues; richness was lower in fresh than in decayed residues. Moreover canopy closure had a strong and significant effect on beetle assemblages in logging residues. Lastly, residue diameter only partially explained differences in saproxylic beetles assemblages.Comparably to studies in boreal forests (mainly in Scandinavia), our results discuss the role of logging residues retention in maintaining saproxylic biodiversity in temperate forests. It may prove necessary not only to maintain adequate volumes of both fine and mid-size woody debris from varied tree species, but also to let some debris naturally and completely decay.

► Comparison of saproxylic beetle assemblages among different types of logging residues. ► Tree species and decay stage: important factors for saproxylic biodiversity. ► Diameter only partially explained differences. ► Retention or removal of logging residues must still be defined at the landscape scale.