Extensive disturbances have a significant effect on the dynamics of forest ecosystems. Due to the limited awareness of this issue, similar events bring a great deal of uncertainty to the subsequent management measures in such affected forests. The current situation of extensive gradations of bark beetles across coniferous forests throughout the northern hemisphere has raised a wave of interest in the topic of disturbances, which leads, among other things, to trying to determine whether and how the forest will naturally regenerate after its decay.
German, American and Czech scientists, including experts from the Faculty of Forestry and Wood Technology at the CULS, followed a series of extensive and serious disturbances of the stand (99% mortality of the upper tree layer) caused by the spruce bark beetle (Ips typographus) on the Czech and German side of Šumava. Their basic goal was to assess the dynamics of restoration of mountain forest ecosystems, where Norway spruce (Picea abies) predominates. In particular, they wondered whether the competitive effects (in the case of species predominance of spruce rejuvenation) would support direct restoration back to pure spruce forest, or whether a significant effect of such severe and extensive disturbance would override these effects and lead to the promotion of pioneer and deciduous trees. The researchers had at their disposal an extensive data set from the forest inventory, covering an area of ??over 7,000 ha. Every year for fifteen years from the beginning of disturbance, the dynamics of rejuvenation was evaluated in the form of species representation, density and height in all tree species.
The density of rejuvenation has increased fivefold in the ten years since the disturbance, from four hundred trees per hectare at the time of disturbance to two thousand trees per hectare ten years after the decay of the forest. From the beginning of the disturbance, the spruce, which arose from the rejuvenation that awaited in reserve before the disintegration of the forest, led in the percentage, and gradually occupied all height classes. The only other tree species that significantly increased its abundance for some time was the mountain-ash (Sorbus aucuparia). Despite the overall dominance of spruce, in addition to pure spruce, mixed stands were also recorded. Both types of stands were variable in height and density, so they were exactly those that contribute to the diversified early succession structure.
"Contrary to current expectations, the gradation of the spruce bark beetle in Central Europe effectively supports the growth and regeneration of Norway spruce even in the long term. Forests crumbling under the influence of the bark beetle will naturally be restored despite the great severity and extent of the disturbance. Therefore, natural regeneration can be considered as one of the most effective ways of afforestation of ecosystems affected by bark beetles, "adds prof. Svoboda from the Department of Forest Ecology.
Prof. Ing. Miroslav Svoboda, Ph.D. (* 1977)
He studied forestry at the Faculty of Forestry and Wood Sciences, CULS in Prague. He became an associate professor of ecology in 2009 at the Faculty of the Environment at the CULS and obtained a professorship at the Faculty of Forestry and Wood Sciences at the CULS this spring. He currently works as the head of the youngest department – forest ecology.
Prepared by: Hana Mrhalová