Researchers from the Faculty of Forestry and Wood Sciences at the CULS published probable scenarios for the further development of Šumava stands, where the upper tree layer died. Since similar events took place in the past and thus entered the "memory" of trees as chroniclers of the landscape, we can read from them today how the forest developed after the disturbances.
Disturbance is any event that disrupts the structure of an ecosystem, community or population. However, it creates – either directly or indirectly – space for colonization and development of new individuals. We also call this phenomenon succession. In the formation of forest stands, disturbances play an important role both in terms of structure (storey size and age of the stand) and in species composition. However, their effects on the forest ecosystem are little studied in Central Europe and are not given sufficient importance in terms of forest development dynamics.
The mountain ecotype of Norway spruce (Picea abies) in the Šumava (Šumava Protected Landscape Area) was selected to analyse the course of forest development. For this research, a method of dating the age of wood was used – dendrochronology, the principle of which is to measure the widths of annual rings. In this way, it is possible to determine not only the age of the trees, but also the influence of the environment. It is possible to analyse healing tissues, scars, traumatic resin channels and changes in the structure of tissues on annual rings. These changes can be caused, for example, by fire or mechanical damage, such as wind, frost, game browse or cyclic damage by insect. The analysis can be used to determine exactly when these events occurred.
Ing. Chad and his colleagues established several experimental areas with an area of ??0.25 ha, where they took samples from all trees and stumps thicker than 10 cm. The samples were then evaluated in the laboratory of the Faculty of Forestry and Wood Sciences in Prague using the computer system Past4 software.
In terms of historical development, the results are as follows: the greatest disturbances occurred in the 1920s and 1960s. However, less serious ones occurred every 10 to 50 years. The data also coincide with other areas where some previous research has already taken place. Most of the disturbances were probably caused by historically known storms (some also by bark beetle gradations). Regarding growth strategies, several types of behaviour of individual trees after the greatest disturbance were distinguished based on cluster analysis (statistical method used to classify objects): spruces with fast growth after disturbance and spruces whose growth was slow after disturbance. The research showed that the most common identified spruce strategy was rapid growth from the beginning of the stand, which later slowed to an average value. In contrast, only 2 % of the trees were included in the group, which grew slower than usual all the time.
In conclusion, it is necessary to emphasize that disturbances contribute to a wide variability of mountain forests. Many organisms are also dependent on these changes. Data from recent studies suggest that similar disturbances known in recent years have been common in the past. Moreover, thanks to these findings, we can anticipate further development of currently disturbed stands in the future.
Čada V., Svoboda M., Janda P., 2013: Dendrochronological reconstruction of the disturbance history and past development of the mountain Norway spruce in the Bohemian Forest, central Europe. Forest Ecology and Management 295: 59–68.
Ing. Vojtěch Čada, PhD.
Ing. Vojtěch Čada, PhD., (* 1985) graduated from the Faculty of Environment of the Czech University of Life Sciences in Prague, majoring in Engineering Ecology. Since 2009 he has worked as a doctoral student at the Faculty of Forestry and Wood Sciences, CULS in Prague, Department of Forest Cultivation.
Prepared by: Michaela Veselá