Ips typographus and other bark and wood-boring beetles in girdled spruces :
Abstract: To decrease the number of spruce trees and to create dead wood in some areas several county administration boards have girdled spruces. Girdled spruces have been little studied in terms of the insect fauna. In this study the occurrence of the spruce bark beetle (Ips typographus) and other beetles are investigated in girdled spruce trees (Picea abies) in two provinces in Sweden, Uppland and Jämtland. Girdled trees have been compared with cut trees. The study contains 213 girdled and cut trees. To find out to which extent woodpeckers use girdled spruces as food resource estimation was also done with consideration of how much bark that was picked off each tree. Girdled trees were more long-lived than expected. Most trees with a "normal" girdle was colonised by insects and dead the second season after the treatment while the "lifeline" trees was living even longer. The species composition was much the same in girdled and cut trees and did not seem to differ between below and above the girdle. However, no breeding spruce bark beetle was found below the girdle. Girdled trees were more utilised by spruce bark beetles than cut trees were. Even trees thicker than 25 centimetres in diameter were more utilised while no increase was visible regarding an increased sun exposure. The amount bark picked away by woodpeckers was equal at girdled and cut trees but in one locality there were a correlation between trees colonised by the spruce bark beetle and utilised by woodpeckers. In one another locality the correlation instead was between the larvae of Tetropium sp. and Rhagium sp. and woodpeckers.
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