Original scientific paper
https://doi.org/10.31298/sl.150.9-10.1
An Early Proactive Approach to the Development of Pedunculate Oak Seed Stands – Effects of Thinning Intensity on Stand Structural Elements
Vladimir Novotny
; Croatian Forest Research Institute, Jastrebarsko, Croatia
Saša Bogdan
; University of Zagreb Faculty of Forestry and Wood Technology, Zagreb, Croatia
*
Mladen Ivanković
; Croatian Forest Research Institute, Jastrebarsko, Croatia
Luka Novotny
; CROATEL Ltd., Zagreb, Croatia
Stjepan Dekanić
; Croatian Forest Research Institute, Jastrebarsko, Croatia
* Corresponding author.
Abstract
The aim of this study was to assess the applicability of an early and proactive approach to the development of future seed stands of pedunculate oak (Quercus robur L.) and to determine the effects of different intensities of individualized thinning on the development of selected structural characteristics of target trees. Unlike the traditional approach of designating already established seed stands, the approach used in this study is based on the early phenotypic selection of high-quality target trees and their gradual release from competition, with thinning intensity determined according to the initial crown development and the potential growing space required for further crown development. The study was conducted on three permanent sample plots in young and middle-aged pedunculate oak stands in Bjelovar and Sisak Management Units. Four treatment variants were applied on each plot: control, and low, medium and high thinning intensity. Treatment effects were assessed based on changes in tree circumference, mean crown radius and total tree height over an eight-year period, from 2016 to 2024, using analysis of covariance and comparison of estimated marginal means. Thinning intensity had a statistically significant effect on the development of tree circumference on all study plots. The strongest response was observed in the youngest stand, where the estimated circumference increased from 18.7 cm in the control treatment to 22.1 cm under high-intensity thinning, with statistically significant differences among all treatments. In the stand of the third age class, the estimated circumference was 27.8 cm in the control treatment and 29.7 cm under high-intensity thinning, while in the oldest stand it increased from 36.0 cm in the control treatment to 37.2 cm under high-intensity thinning. Crown development also showed a positive response to thinning, particularly in the stand of the third age class, where the mean crown radius under high-intensity thinning was 5.18 m, compared with 3.32 m in the control treatment. In the youngest stand, a significant interaction between initial crown development and thinning intensity was found, indicating the importance of timely selection of target trees. In contrast, increasing thinning intensity did not result in greater final tree height; the highest estimated tree heights were generally recorded in the control treatments. The results indicate that the early phenotypic selection of target trees and individualized thinning can direct the development of tree circumference and crown dimensions and create more favourable structural conditions for future seed stands of pedunculate oak. However, since flowering, acorn yield and the quality of forest reproductive material were not directly monitored during the study, the results do not allow a direct conclusion to be drawn regarding an increase in reproductive potential. Longer-term monitoring is required to determine whether this proactive approach can also produce a measurable effect on future seed production and the reproductive function of seed stands.
Keywords
phenotypic selection; pedunculate oak (Quercus robur L.); individualized thinning; target trees; crown development; stand structure; seed stands
Hrčak ID:
351707
URI
Publication date:
30.9.2026.
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