Natural forests are complex and intricate communities occupying a place at the very top of the natural ecosystem hierarchy. They are very stable and are able to react relatively quickly to changes in environmental conditions, so-called disturbances. However, it remains unknown how forests will be able to adapt to the effects of rapidly advancing climate change. What we know for sure is that climate change will disrupt the current short-term and long-term dynamics of forests and could seriously jeopardize their ability to provide basic ecosystem functions. In recent years, some important European tree species have already shown their sensitivity to the increasing drought. One of such affected species is Norway spruce, one of the most economically important tree species in the Czech Republic. It is therefore clear that climate change needs to be taken into account in the future and forest management planning needs to be adapted as well. From previous research we know that mixed and richly structured forests are more resistant to the impacts of climate than monocultures. Nevertheless, in the future it is necessary to deepen the knowledge of the dynamics of such stands to successfully combat climate change and effectively manage forests on both regional and European scale.
This paper published by a group of researchers from the Faculty of Forestry and Wood Sciences focuses on the influence of climatic factors on various forest types. The area of ??interest was the Medník National Natural Monument (NNM), which is located in the Sázava River valley in the Central Bohemian Uplands. It gained the status of a protected area due to the northernmost European occurrence of Erythronium-dens canis, a critically endangered species, but also due to the presence of natural forests with many other rare species. The aim of the research was to evaluate the structure, production potential and dynamics of herb-rich beech, spruce and hornbeam-oak stands between 1998 and 2018.
From the results of the study, we will focus mainly on those that indicated the influence of climatic factors on individual target tree species. One of the indicators by which this effect can be measured is the radial growth of the trees, e.g. the width of the growth rings. In the observed period, it was the lowest in sessile oak and Norway spruce, on the contrary the highest in large-leaved lime and European beech. However, lime also showed the highest variability of radial growth, while oak was very stable from this point of view. Climate analyses taking into account radial growth revealed that the most sensitive tree is lime, followed by spruce and beech. The least climate effect was observed for oak.
The main factors that had a negative impact on the growth of lime and spruce were, in particular, the high air temperature and drought during the growing season. Oak and beech were threatened mainly by biotic factors - a vascular disease tracheomycosis for oak, infestation with Cryptococcus fagi for beech. Beech also suffered from late frosts and drought. In general, the radial growth of tree species during the growing season was most significantly influenced by the increased air temperature and in most cases, its effect was negative. An example of this phenomenon is the year 2007, which was the warmest year in the observed period, and during which all target tree species showed the smallest radial growth. Spruce was especially interesting in this study. Despite its otherwise relatively high sensitivity to climatic factors, the spruce stands in NNM Medník were not much affected by climatic fluctuations. It is thanks to the local ecotype of Sázava spruce, the specific microclimate of the habitat and good water availability.
The study's conclusions emphasize that the frequency of unfavourable years for tree growth is currently increasing due to climate change. It is therefore essential that forest planning adapts to this trend, as the consequences of appropriate (but unfortunately also inappropriate) forest management practices can be seen for decades to hundreds of years! Although the negative effects of climate change on tree species are known and often well documented, their actual impact is very unpredictable. The response of the tree species and whether they will be able to adapt to the new conditions remains unknown. Therefore, in the future, climate change will represent a great challenge for both forests and foresters…
Ing. Karel Vančura
In the past, he worked as a secretary in the Czech Forestry Society, the largest professional forestry organization in the Czech Republic. He is currently studying for a doctorate in Forest Cultivation at the FLD CULS in Prague and works at the Czech Hydrometeorological Institute in the position of Head of the Foreign Relations Department.
Prepared by Dagmar Zádrapová