Retention or salvage logging of standing trees killed by the spruce bark beetle Ips typographus: Consequences for dead wood dynamics and biodiversity

Standing Norway spruce (Picea abies) trees attacked by the spruce bark beetle are often logged to reduce the risk of future bark beetle attacks. This study focuses on the potential ecological value of such trees. The study was conducted in six reserves in Sweden that were hit by a storm in 1995 and suffered from tree mortality caused by the spruce bark beetle, Ips typographus (L.) (Col.; Curculionidae). The volumes of storm-felled trees and of standing trees killed by the spruce bark beetle were recorded during 5 years after the storm. In the present study five of the six reserves were revisited in 2006. Of the dead standing wood, 81% was created by the spruce bark beetle, while 19% constituted of stumps from trees broken by the storm. Thirty-seven per cent of the beetle-killed trees remained standing in 2006, 8-9 years after tree death. A significantly higher frequency of fruiting bodies of Fomitopsis pinicola on broken snags compared with on intact snags indicates that the rot caused by this fungus contributed to tree fall. Almost 30% of the bark remained on both intact and fallen snags. The ecological value of snags created by the spruce bark beetle is discussed.