Impact of fuel wood piles on saproxylic beetles

In Switzerland, a strong increase in the demand for energy wood is expected for the next decades. This is likely to have a strong influence on saproxylic beetles (dependent on dead wood). On the one hand, fewer old trees and less deadwood will remain and decompose in the forest, which directly limits habitat availability for saproxylics. On the other hand, fuel wood exploitation might have indirect ecological consequences. For instance, harvested fuel wood is traditionally stored as large piles beside the nearest forest road and allowed to dry for one summer. These aggregation of fresh deadwood attracts beetles and other insects which lay their eggs on the wood of these piles but cannot complete their development, because the piles are being chipped or removed before the progeny has emerged. Fuel wood piles can therefore act as ecological traps, which may cause population decline and even local extinction.

Goals

We want to

• compare two different survey methods
• verify the attraction of fuel wood piles on saproxylic beetles (ecological trap)
• evaluate the role of the sun-exposition on the attraction of fuel wood piles
• evaluate the effect of sun exposition on the calorific value of fuel wood on shady and sunny piles
• provide basic data for guidelines for sustainable fuel wood management

Methods

The study design consists of shaded and sun-exposed fuel wood piles. On each pile, wood pieces are collected in autumn on the upper layer. The wood samples will be brought to the lab, where the inhabiting beetles are reared for about one year.

To test the attraction of sunny/shady fuel wood piles, flight interception traps will be installed on the piles from May to September. During the same period, interception traps will be installed on sunny and shady control sites in the forest at some distance from wood piles to compare the attraction of fuel piles with the surrounding forest.