Unstable and changing natural conditions pose new challenges for forestry science
Fortunately, the year 2025 proved to be relatively favourable for both foresters and researchers. The weather lacked significant extremes, with a cold May and early June contributing to a further decline in the bark beetle population. A notable dry spell occurred only towards the end of the growing season, which helped improve the overall health of the forests.
Photo: A mixed and more resilient forest is gradually regenerating in areas that were clear-cut due to pest outbreaks. Author Jan Řezáč
Changing climatic conditions, especially prolonged droughts and rising temperatures, along with the need to restore forests damaged by the bark beetle outbreak, present significant challenges for everyone involved. In 2025, staff at the Forestry and Game Management Research Institute (FGMRI) worked on ten projects funded by the National Agency for Agricultural Research, ten projects supported by the Technology Agency of the Czech Republic, six projects from the LČR Grant Service, and five international projects. A notable new development is the inclusion of European Innovation Partnership projects, which aim to directly deliver research activities to specific forest owners.
The research revealed several important findings. Notably, the current extent of clear-cut areas caused by forest disasters in the monitored watersheds does not significantly affect runoff patterns, both in terms of quantity and stream water quality. Additionally, the carbon stocks stored in forest soils are not experiencing dramatic changes. However, it is essential for forests to survive in order to sequester carbon effectively.
Photo: Scientists monitored the occurrence of nests and the activity of „wood ant workers“ outside of the growing season, in relation to forest management practices. Author Jan Řezáč
Scientists view the widespread practice of large-scale clear-cutting as a significant risk and recommend prompt forest regeneration. This should involve a combination of natural and artificial methods, as well as the use of species that can tolerate the open area’s microclimate. The long-term objective should be to cultivate forest stands with greater diversity in terms of species, age, and spatial structure, enhancing their resilience to both biological and environmental stressors.
To prevent future bark beetle outbreaks, researchers are focusing on developing a predictive model for the spruce bark beetle’s swarming period and exploring new methods for forest protection. They have established experimental plots to evaluate the protection of fir and horse chestnut tree species against harmful agents through injections of various synthetic and natural insecticides and fungicides. Additionally, they are studying the reproductive strategies of bark beetles in Europe. They have also investigated the impact of predators on the presence of economically undesirable species, specifically examining the relationship between wood ants and oak lace bug (Corythucha arcuata). This research involves monitoring nest occurrences and worker ant activity outside the growing season in connection with forest management practices.
To reforest large clearings caused by natural disasters, it is essential to produce enough planting stock. Researchers are expanding the network of research plots where they measure diverse types of planting stock and monitor ecological parameters across various site conditions. Additionally, they assess growth dynamics on long-term research plots dedicated to testing various silvicultural practices for reforesting disaster-stricken areas, afforesting agricultural land, and establishing agroforestry systems. Simultaneously, they are developing methods to enhance conditions for forest regeneration.
Photo: Fir seedlings thriving in the shade of preparatory tree species. Author Jan Řezáč
Evaluations of morphological parameters in cultivated pedunculate and sessile oak seedlings have consistently shown significant differences (particularly in height and the root-to-shoot ratio) between one-year-old seedlings of the two species. Therefore, it is important to consider these differences during planting.
Measurements of the growth response of fir tree species growing beneath a birch preparatory stand revealed that thinning the birch population, by reducing the number of birch stems by half, significantly impacted both DBH and height growth two years later. The height and DBH growth of the released dominant firs was nearly double that of the unreleased trees, while the protective canopy function of the birch stand was effectively maintained.
Research indicates that European beech is more sensitive to temperature and precipitation than Oriental beech. Over the past two decades, a decline in radial growth of 13–19% has been recorded in lowland areas, whereas an increase of 6–10% has been observed in mountainous regions. Insufficient precipitation is the primary limiting factor in lowlands, while low temperatures are the limiting factor in the mountains.
In a structurally diverse forest stand, spruce demonstrates more than 40% higher productivity compared to a monoculture. For beech tree species, fostering a mixed-species composition and encouraging spatial differentiation contribute to increased productivity and stability.
Photo: A forest retains water over the long term in various wetlands, pools, and streams. Author Jan Řezáč
An assessment of the impact of afforestation and tree species on soil carbon stocks in former agricultural lands indicates that eighty years of afforestation has led to notable differences in soil properties. Specifically, afforestation has significantly increased oxidizable carbon (Cox) stocks, particularly in the organic surface horizons (O-horizons). In various sites, the Cox values under tree stands ranged from 11 to 89 times higher than those found in adjacent meadow areas. Norway spruce and common alder showed statistically significant higher accumulation of Cox in the O-horizon compared to sycamore maple and the meadow, suggesting that litter decomposition occurs more quickly under sycamore maple.
In response to ongoing climate change, it is essential to explore new methods for maintaining healthy forest stands. One approach is to modify species composition and increase the use of native tree species that have been underutilised, such as thermophilic oak species. As a result, scientists are currently identifying and mapping sites where these oaks naturally occur, primarily in southern Moravia. They are also classifying these species and selecting high-quality trees to serve as sources of reproductive material. By 2025, researchers had processed data from 300 Turkey oak, 80 downy oak, and 320 sessile oak individuals.
Scientists studied the genetic differences among various oak species, including downy oak, Turkey oak, pedunculate oak, sessile oak, Quercus polycarpa, and Quercus dalechampii, with a sufficient number of individuals analysed for each. They found very low levels of genetic differentiation among sessile oak, Quercus dalechampii, and Quercus polycarpa. In contrast, high levels of differentiation were observed between Turkey oak and the other species studied, while moderate differentiation was noted between pedunculate oak and sessile oak. Additionally, genetic analysis of five downy oak populations revealed a sufficient level of genetic diversity.
Photo: In a separate study, extreme concentrations of cadmium (15.12 mg/kg dry weight) were detected in Xerocomellus boletes from the Orlické hory Mountains, along with an unusually high mercury level (12.75 mg/kg) found in the Manětín region. Author Jan Řezáč
One of the long-term activities involves monitoring forest ecosystems, specifically within the context of the food chain. In 2025, the focus of the monitoring program expanded to analyse the levels of cadmium (Cd) and mercury (Hg) in the fruiting bodies of edible mushrooms. The scope of the work was significantly broadened compared to the previous year, with 45 samples collected from 32 different forest areas. This collection included 13 species of mushrooms, such as Boletus edulis, Neoboletus erythropus, and Macrolepiota procera.
The results indicated stable contamination levels, with values exceeding safety limits found in 4.4% of samples for cadmium and 8.9% for mercury. Notable findings included an extremely high concentration of cadmium (15.12 mg/kg dry weight) in Xerocomellus boletes from the Orlické hory Mountains, as well as an unusually high mercury level (12.75 mg/kg) detected in the Manětín region.
Details regarding the activities of VÚLHM, v. v. i., can be found in the 2025 Annual Report, available for download here.
Prepared by Jan Řezáč, VÚLHM, v. v. i., e-mail: rezac@vulhm.cz