| dc.description.abstract | The European spruce bark beetle Ips typographus is a severe pest in mature spruce forests, with the potential to cause widespread tree mortality. Managed forests are suggested to be particularly susceptible to I. typographus infestations compared to more diverse, unmanaged forests, partly because they are thought to support less natural enemies and competitors of the beetle. This study explores whether forest management practices that enhance forest diversity and populations of natural enemies and interspecific competitors can suppress I. typographus reproductive success and thus mitigate outbreak risks. Experimental pheromone-baited logs were placed in near-natural and previously clear-cut forest stands across 10 paired sites in SE-Norway. Analysis of bark occupation by interspecific competitors and I. typographus reproductive success was conducted on the bark, and data on I. typographus predatory beetle assemblages was collected via window traps. Results revealed a tendency for higher reproductive success of I. typographus in managed forests. Occurrence of predatory beetles and interspecific competitors was similar between management types and did not affect I. typographus reproductive success. Intraspecific competition, estimated by attack density, tended to be higher in unmanaged forests and had a significant negative effect on I. typographus reproductive success. Results indicate that forest management that promotes forest diversity does not increase predatory beetle or interspecific competitor populations and thus might not mitigate bark beetle outbreak risks. Instead, it appears that decreased reproductive success of I. typographus in unmanaged forests can be explained by increased intraspecific competition for resources, underscoring intraspecific competition as one of the main drivers of I. typographus population dynamics. | |
