Can we use domestic thermophilous oaks more effectively?
In certain areas of our country, forest stands are already moving beyond their climatic optimum due to summer drought, rising temperatures, and other environmental changes. The anticipated shift in biodiversity may result in the emergence of new ecological communities. In forestry, critical factors include increasing spring and summer temperatures, reduced summer precipitation, heightened evapotranspiration, the onset of soil drought, and an increase in the frequency and intensity of wildfires. Simultaneously, the demands on forest management are evolving, with a greater emphasis on utilising natural processes and diversifying stand structures.
Photo: Downy oak (Quercus pubescens) in the Lužické šípáky Nature Reserve, České středohoří Protected Landscape Area, Litoměřice Forest Reserve (V. Buriánek, 30. 5. 2023)
In this context, there is an increasing focus on the potential for greater use of thermophilic tree species. This includes thermophilic oaks native to certain regions of the Czech Republic that have previously been economically overlooked. Aside from the Turkey oak (Q. cerris), and the downy oak (Q. pubescens), these species are relatively rare in our area.
Scientists from the VÚLHM, v. v. i., have developed a practical methodological guide as part of their research project TA ČR No. SS06010209, titled Přehled a potenciál využití autochtonních druhů teplomilných dubů v měnících se klimatických podmínkách (Overview and potential of use of autochthonous species of thermophilous oaks in changing climatic conditions). This guide provides an overview of the potential uses of native thermophilic oak species in response to changing climatic conditions. It describes six species of oak: Turkey oak (Q. cerris), downy oak (Q. pubescens), also known in Czech as „šípák“, Virgil’s oak (Q. virgiliana), Dalechamp’s oak (Q. dalechampii), Caucasian oak (Q. polycarpa), and Hungarian oak (also known as Balkan oak) (Q. frainetto).
Photo: Turkey oak (Q. cerris), locality Milíře, Černčice willage, České středohoří Protected Landscape Area (V. Buriánek, 16. 5. 2024)
Some scientists have identified serious issues that will impact the first and second levels of forest vegetation (LVS) in the Czech Republic, specifically in areas up to 300 meters above sea level. These regions are starting to experience conditions similar to those found 500–700 kilometres to the south. Predictions indicate that in the future, LVS 1 may cover a third of the country’s territory, while together with LVS 2, they could encompass as much as half.
The increasing frequency of drought periods is causing stress in trees, which subsequently results in reduced growth and, in severe cases, tree mortality. Evidence of drought stress is most pronounced in the warmest regions of the Czech Republic, where there is significant potential to enhance forestry and landscape management through the use of thermophilic oak species.
The negative effects of summer drought and high temperatures, such as decreased growth and even tree dieback, are particularly pronounced in these warmer areas. These regions also present the greatest opportunity for targeted support of our oak populations.
Certain species, such as the Caucasian oak (Q. polycarpa), exhibit stiffer leaves that enable them to better withstand drought and intense sunlight compared to the leaves of the sessile oak (Q. petraea). As a result, these species experience less premature shedding, or loss of their assimilation apparatus, than the sessile oak (Q. petraea). Additionally, the normal autumn leaf drop in these well-adapted species occurs later in the season. Thermophilic oak species demonstrate greater resilience to both low precipitation and higher temperatures, making them promising candidates for adapting forest stands to climate change.
In the sections devoted to individual thermophilic oak species, the authors examine their production and non-production potential, highlighting the ecosystem services they provide in the context of advancing climate change. Ultimately, they summarise the advantages and disadvantages of all six species based on ten evaluation criteria that are significant for the potential future use of these tree species, along with recommendations for forestry practices.
Photo: Dalechamp’s oak (Q. dalechampii) in the Krásná stráň Nature Reserve, Vonoklasy, Český kras Protected Landscape Area (V. Buriánek, 8. 10. 2024)
Attention is given to the production and usability of wood, its suitability for mixtures, and its resistance to biotic and abiotic factors, with a particular focus on drought. Additionally, other indicators such as the ability for natural renewal and crossability are considered. Basic cultivation aspects for each species are also briefly outlined.
This comprehensive and specifically focused work on our less common oak species, examining their potential for both production and non-production uses, has not previously been available to Petr Novotný, one of the authors, explains: “The increased use of thermophilic oaks in both forested and non-forested landscapes will contribute to the preservation of native tree diversity at the species level. It will also support lower levels of biodiversity, ensuring a diverse trophic base for ecologically connected organisms, such as animals and fungi. This approach will help stabilise slopes at risk of erosion, mitigate climate extremes, and fulfil hydrological, recreational, and other functions that benefit society. For humans, this means maintaining a favourable environment and establishing long-term, stable oak stands capable of continuously producing oak wood as a renewable natural resource.”
Photo: Caucasian oak (Q. polycarpa), Hádecká Planinka Nature Reserve, Moravský kras Protected Landscape Area, ŠLP Křtiny (V. Buriánek, 25. 9. 2024)
In the warmest regions of our country, where there is a realistic threat of local extinction of forest ecosystems, these areas may gradually shift to forest-steppe or steppe formations in the medium to long term. This situation necessitates the use of tree species and provenances that exhibit greater tolerance to the expected long-term high temperatures and periods of soil moisture deficiency. Among these, thermophilic oaks, which are native to a limited area of the Czech Republic, show promising potential to sustain economically viable forests even under extreme conditions predicted by models.
Therefore, expanding the use of thermophilic oaks in the future is economically justifiable. This can be achieved by supporting their natural spread from existing populations or by enhancing artificial regeneration efforts, which may include suitable reproductive material from foreign sources. Beyond the continued production of renewable wood resources in climates that are less favourable, the increased use of thermophilic oaks provides another important, though difficult to quantify, economic benefit: the preservation of biodiversity and the fulfilment of various non-production functions of forests.
In forestry, increased species diversity through the use of thermophilic oaks can help reduce the costs associated with artificial forest regeneration by minimising the need for repeated plantings in dry habitats. From a production standpoint, the most promising species for the future include the Caucasian oak (Q. polycarpa), Dalechamp’s oak (Q. dalechampii), Hungarian oak (also known as Balkan oak) (Q. frainetto), and Turkey oak (Q. cerris), which perform comparably with sessile oak (Q. petraea), under favourable conditions. While these species produce good-quality wood, the Turkey oak’s (Q. cerris) wood is primarily suitable for fuel, limiting its recommendation for broader use. Additionally, the downy oak (Q. pubescens) and Virgil’s oak (Q. virgiliana) are expected to provide protective benefits in extremely sunny and drought-prone environments.
The methodology Přehled a potenciál využití autochtonních druhů teplomilných dubů v měnících se klimatických podmínkách (Overview and potential of use of autochthonous species of thermophilous oaks in changing climatic conditions) can be downloaded here.
Authors: Ing. mult. Bc. Petr Novotný, Ph.D., RNDr. Václav Buriánek, VÚLHM, v. v. i., e-mail: pnovotny@vulhm.cz
Prepared according to the original by Ing. Jan Řezáč, VÚLHM, v. v. i., e-mail: rezac@vulhm.cz