To enhance the utilization of pedunculate oak and sessile oak, it is crucial to identify their seedlings in forest nurseries
One of the most significant threats posed by global climate change is the increasing frequency and duration of dry periods in regions where such conditions have rarely occurred in the past. As a result, the distribution of many tree species is likely to shift toward higher latitudes or higher altitudes. One of the primary strategies for adapting forest ecosystems is to increase the presence of native oak species – specifically, pedunculate oak and sessile oak – in the forests of Central Europe.
Photo: Natural regeneration in oak forest. Author Jan Řezáč
As air temperatures rise and climatic conditions change, oaks are expected to expand into regions where they could not previously thrive. However, their ability to move to higher elevations or more northern areas may be restricted by other ecological factors, such as late frosts or unsuitable soil conditions. Therefore, it is essential to carefully assess individual sources of reproductive material based on their origin. The ecological conditions in which the mother trees (seed sources) grow are especially important.
In the research project NAZV QK24020127, titled “Control of conformity and verification of the origin of reproductive material of forest tree species using DNA analyses” (Kontrola shodnosti a ověřování původu reprodukčního matriálu lesních dřevin pomocí DNA analýz), scientists from the Forestry and Game Management Research Institute, Research Station Opočno, collaborated with researchers from Mendel University in Brno. They investigated this topic and published their findings in the article „Vyhodnocení morfologických znaků sadebního materiálu dubu letního a dubu zimního z různých zdrojů původu“ (Evaluation of the morphological traits of pedunculate oak and sessile oak seedlings from different provenance sources), which appeared in the journal Reports of Forestry Research.
Photo: The natural regeneration of oak, beech and hornbeam forms a good basis for a resistant forest. Author Jan Řezáč
In this paper, scientists assessed morphological parameters of one-year-old seedlings of pedunculate oak and sessile oak, focusing on various sections and origins. They evaluated factors such as the height of the above-ground portion, the thickness of the root collar, and the volume of individual parts of the plants, following the standards outlined in ČSN 48 2115, “Seedling material of forest trees.” The differences in growth dynamics between pedunculate oak and sessile oak are often apparent even during the cultivation of planting material in nurseries, which serves as a useful indicator for distinguishing between the two species.
Both pedunculate oak and sessile oak play crucial roles as deciduous tree species in Central Europe, especially in terms of ecology and forestry. Historically, there has been a notable shift in the species composition of forest stands, with a preference for coniferous trees, particularly Norway spruce and Scots pine, across Europe.
In recent decades, Central Europe has undergone a significant transformation, shifting from coniferous monocultures to mixed or deciduous forests. The primary goal of this transition is to enhance the resilience of these forests in response to changing site and habitat conditions due to ongoing and anticipated climate change.
Promoting the cultivation of sessile oak and pedunculate oak is particularly important because these trees are highly resistant to drought and wind damage. Both types of oaks contribute to the formation of mixed forests, which are more stable and productive than monocultures in the context of changing climate conditions.
Photo: To ensure successful artificial regeneration of clearings, it is essential to use high-quality oak seedlings. Author Jan Řezáč
Currently, the planting of sessile and pedunculate oak is taking place outside their original distribution areas. In the Czech Republic, this primarily involves moving to higher vegetation levels. It is crucial to use the appropriate reproductive material for such planting, ensuring it is well-suited to the specific location where it will be used.
Ignoring the rules for transferring reproductive material can pose genetic risks to the future stability of oak stands, especially when expanding their use beyond the ecological and growth optimals of both sessile oak and pedunculate oak. It is important to note that these two species often overlap in their areas of occurrence and frequently coexist in the same stands.
To significantly increase the representation of both oak species in the forest stands of Central Europe, artificial regeneration is necessary. This method allows for the establishment of young stands even in areas where oaks are not part of the existing mother stands. Artificial regeneration is crucial for changing the species composition of forest stands. However, its success depends not only on the choice of tree species and the cultivation concept but also on combining high-quality planting material with optimal site conditions, particularly adequate light availability and suitable competitive conditions during regeneration.
Successful artificial regeneration requires a comprehensive approach that includes strict adherence to the rules for transferring reproductive material. Additionally, it is essential to use planting material with appropriate morphological characteristics that match the habitat conditions of the locations where it will be utilized. Optimal morphological parameters of planting material are a key prerequisite for promoting receptivity and ensuring successful regrowth after planting.
Photo: Old oaks as home to many organisms are important for biodiversity. Author Jan Řezáč
It is essential to use high-quality planting material that has a well-developed root system, including a strong taproot and a sufficient number of fine roots. The best approach is to select different types of planting material based on the specific planting location.
In the evaluation of the first series of the experiment, scientists found significant differences in various traits between pedunculate oak and sessile oak, as well as within the individual sections of reproductive material origin. The most notable differences were observed in the height of the above-ground parts, which is a crucial factor when selecting planting material for specific site conditions. Taller and more robust plants are better suited for locations with ample water supply and a higher risk of weed competition. Conversely, planting material with a more favourable ratio of roots to above-ground growth is more appropriate for sites that are threatened by drought.
The results of the experiment indicate that the morphological characteristics of pedunculate oak and sessile oak seedlings can vary greatly. Therefore, it is important to consider these differences when selecting seedlings for different site conditions.
Paper „Vyhodnocení morfologických znaků sadebního materiálu dubu letního a dubu zimního z různých zdrojů původu“ (Evaluation of the morphological traits of pedunculate oak and sessile oak seedlings from different provenance sources) can be downloaded here.
Authors: Jan Leugner, VÚLHM, v. v. i, VS Opočno; Eliška Žižková, Mendelova univerzita v Brně; Jakub Černý, VÚLHM, v. v. i, VS Opočno, Mendelova univerzita v Brně; kontakt: e-mail: leugner@vulhmop.cz
Prepared, based on the original work, by Jan Řezáč VÚLHM, v. v. i., e-mail: rezac@vulhm.cz