Debarking harvesters simultaneously combat the European spruce bark beetle (Ips typographus) and conserve non‐target beetle diversity

Abstract

In the face of climate change, the European Spruce Bark Beetle (Ips typographus) breeding predominantly in Norway spruce (Picea abies) led to exceptional amounts of damaged timber in European forests. Up to now, if pest control is applied, damaged or weakened P. abies trees are either extracted by salvage logging or, when quantities are low, made unsuitable for breeding by manual debarking techniques. Both pest control interventions are costly, are often limited by the short timeframe of effectiveness and come with negative impacts on the non‐target biodiversity. As alternatives for timely removal, a debarking head for harvesters for large scale disturbances and a bark gouging device for motor‐manual treatment have been developed in recent years to make breeding material unsuitable for bark beetles and reduce existing larvae. Based on data from an experimental design with infested Norway spruce logs, we show that the harvester debarking head and the motor‐manual bark gouging regulate I. typographus populations efficiently, whereas a conventional harvester did not reduce the emerging bark beetles. Species assemblages of non‐target beetles living in the infested Norway spruce logs were altered from the natural species assemblages in control logs by processing logs with the debarking head or the bark gouging device but not by the conventional harvester. None of the bark treatments reduced non‐target beetle species richness in this experiment. Practical implication. We endorse the debarking head and bark gouging as alternatives to salvage logging and manual debarking. This uncouples pest control from in‐time dependencies on the availability of transport capacities. The debarking head and bark gouging open up the opportunity to retain dead wood biomass in the forest, supporting ecological benefits and conservation goals. Particularly for protected areas these two new management options better balance requirements of pest control and biodiversity conservation.