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Doctoral thesis, 2002

Dead wood retention and the risk of bark beetle attack

Hedgren, Per Olof

Abstract

Wind-felled Norway spruce trees left for conservation purposes and spruce stems stored as forest fuel may be colonised by the bark beetles Ips typographus and Pityogenes chalcographus (Coleoptera: Scolytidae). The risk of nearby living trees being attacked and killed by these species was experimentally investigated at stand edges bordering fresh clearcuts. Attack by I. typographus was studied at edges of mature spruce with one, five or no cut trees. Attack by P. chalcographus was studied within plots on edges of young spruce. The plots contained piles of cut young trees, or no piles. Number of trees killed by I. typographus did not differ between edges with and without cut trees, or between edges with one and five cut trees. Tree-killing was more frequent close (<20 m) to felled trees than elsewhere on the edges, suggesting that felled trees provide focal points for attacks within edges. The piles increased the risk of P. chalcographus attack, but almost no attacked tree was killed. Attacks were associated with pile colonisation, whereas emergence by the new generation beetles did not increase the risk of attack. Previous studies have shown a high reproductive success of I. typographus in felled trees after storms and a low success in standing trees killed during outbreaks. Here, the success was compared in pairs of colonised cut trees and standing killed trees at a time with no outbreak and relatively few felled trees available in the landscape. The success in killed standing trees was (a) significantly higher than in cut trees, and (b) high enough to suggest that killed standing trees can contribute substantially to the area-wide production of beetles. The ability of P. chalcographus to kill trees and reproduce in them has previously been little studied. Here, attacks on living trees were induced by baiting trees with pheromone dispensers. The tree-killing ability was low. Reproductive success in killed trees was generally low, but was significantly higher in trees also attacked by I. typographus.

Keywords

Ips typographus; Pityogenes chalcographus; Scolytidae; bark beetle; reproductive success; tree killing; Picea abies; Norway spruce; stand edges; windfall; windthrown; wind-felled trees; GROT; dead wood; saproxylic

Published in

Acta Universitatis Agriculturae Sueciae. Silvestria
2002, number: 247
ISBN: 91-576-6331-9
Publisher: Swedish University of Agricultural Sciences

Authors' information

Hedgren, Per Olof
Swedish University of Agricultural Sciences, Department of Entomology

UKÄ Subject classification

Forest Science

URI (permanent link to this page)

https://res.slu.se/id/publ/107580