Occurrence of the bark beetle Ips typographus (L.) in the managed and protected forests in the Gorce Mts.
The research concerning the occurrence of bark beetles was carried out in Norway spruce stands under protection regime and in adjacent managed forests in 1998–2002. The mortality of trees caused by these insects was analyzed on forest complex level (5 complexes) and on the observation plot level (12 plots), in relation to selected parameters characterizing stands as well as particular trees. The population level of bark beetles in the whole Gorce region is high in both protected and managed forests. After the outbreak related to the defoliation by Cephalcia alpina larvae, the population density of bark beetles decreased in 1997–2001, while the area of infested forests increased. The stands in the central part of the Gorce Mts. are actually the most threatened by bark beetles, however the bark beetle populations are increasing also in the eastern, less threatened part. The defoliation level, relatively low in the observed stands, was not significant for the bark beetle related tree mortality nor in the selection of individual trees for infestation. The consequences of the different management procedures, related to the protection regimes (strict reserve – active protection – managed productive forest) in individual parts of the study area, are discussed. The risk of extended Norway spruce mortality in the stands representing high level of bark beetle populations is pointed out. The changes of the nature protection status of threatened stands (incorporation to the strict nature reserves) indicate the need of further studies on the bark beetle population dynamics and applicable protection strategies and tactics.
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