Windthrows and Dead-standing Trees as Bark Beetle Breeding Material at Forest-clearcut Edge
The spatial distribution of windthrows and dead-standing trees as well as the occurrence of two bark beetle species, Ips typographus and Tomicus piniperda, were studied at forest-clearcut edges in southern Finland. More than 80% of the recorded dead trees were situated within the first 15 m from the clearcut border. The number of dead-standing spruces attacked by I. typographus did not depend on the amount of windthrows at the same site. According to logistic regression analysis, the distance from a clearcut border had a negative effect on the likelihood of I. typographus being present in the windthrows. The results indicate that windthrows do not necessarily increase bark beetle-induced tree mortality under endemic wind conditions. The accumulation of dead trees at forest-clearcut edges may support the diversity of saproxylic species, but may also maintain populations of harmful bark beetles under non-epidemic conditions.