Have you ever wondered how it is possible to find out which woody plants should naturally predominate without human influence? How is it possible to assess the historical representation of tree species? Due to the ongoing calamities, today's forestry policy aims to reduce the share of spruce. In altitudes between 400 and 900 m above sea level, there is an effort to increase the proportion of forest beech and white fir so that Norway spruce occurs only as a secondary tree. The beech is considered to be the dominant tree species in the natural composition temperate forests. However, management plans with the aim of returning to the natural representation of tree species are probably based mainly on the Geobotanical Map and the Map of Potential Natural Vegetation.
So how can we estimate how the vegetation developed in any area? A possible solution now offers increasingly developing methods of palynology, which are used to study pollen contained in soil sediments. With the help of probes, soil profiles are taken mainly from wetlands, peat bogs or the bottom of lakes, where pollen is easily deposited. The amount of pollen grains at different depths is monitored and their age is determined, often using the radiocarbon method (estimation of the change in the number of atoms during the decay of a radioactive isotope of carbon). The results are then plotted using pollen diagrams as a percentage of pollen grains over time or to profile depth.
One of the first such diagrams from the early 20th century comes from the Šumava region and the Bohemian and Bavarian Forest, where even now scientists, including experts from the Faculty of Forestry and Wood Technology, deal with the analysis of pollen deposits. In this study, they tried to create a more accurate reconstruction of the long-term development of vegetation and to describe in more detail the changes in the composition of the predominant tree species. They focused on the areas around Lake Prášil and Rachelsee in Germany to use the results of previous studies to gain an image in the context of the wider region. They found that, in fact, the percentage of beech did not exceed about 25% over 10,000 years. On the other hand, spruce was most of the time represented by an average of 50%, and even at the time of the greatest distribution of beech and fir about 4000 years ago, it accounted for about 40% of the vegetation cover in the area. About 1000 years ago the proportion of beech and fir began to decline significantly. Increasing human use of the landscape may have been a likely factor, but the impact of colder climates due to the small ice age may not have been negligible.
National parks in particular are striving to return to the original wood composition. In the case of the Šumava National Park, according to the proposal based on relatively outdated data of the mentioned maps and previous research, the goal is to reduce the proportion of spruce from the current 80% to 30-40%. However, based on current research, the authors believe that spruce removal should not be so drastic, given that spruce has dominated here throughout the Holocene (~ 12,000 years ago to the present). They argue for the long-term presence of spruce, which suggests that forest management, including spruce planting, has not caused the beech to recede. On the contrary, the Šumava and Bavarian National Parks should be used to preserve mountain spruces, which are beginning to be threatened by global warming. According to the scientists' proposal, the target proportion of spruce should be around 45%, which is within the limits of natural distribution. In addition, they emphasize the importance of mixed forests composed of several tree species, which provide a high ecosystem function and guarantee stability against potential climate change. The authors therefore recommend considering the use of palynological research in further planning.
Advanced research in the field of palynology gives us a chance to rework the view of the state of forests in the past and their long-term development. Being able to more accurately assess the abundance of different tree species is important not only for creating proper restoration plans in protected areas, but also to choose global warming management practices based on knowledge of how trees have responded to past climate change.
Carter V. A., Chiverrell R. C., Clear J. L., Kuosmanen N., Moravcová A., Svoboda M., Svobodová-Svitavská H., van Leeuwen J. F. N., van der Knaap W. O., Kuneš P. Quantitative Palynology Informing Conservation Ecology in the Bohemian/Bavarian Forests of Central Europe. Frontiers in Plant Science. 8, 2018.
Prof. Ing. Miroslav Svoboda,
Ph.D.Mr. Svoboda is focused on ecology and forest cultivation, management of specially protected areas and biodiversity. In particular, he focuses on the dynamics of natural European forests, the impact of disturbances, the importance of rotting wood in the forest and dendrochronology and its use for research on forest ecosystems.
Prepared by: František Viktorin