The management of pedunculate oak (Quercus robur L.), one of Croatia’s most important tree species from both socio-economic and ecological perspective, is facing increasing challenges. Various biotic and abiotic threats are affecting overall forest stability. Given the significant variability in the morphological and physiological properties of this tree species, research into provenance productivity plays an important role for the forestry sector. Therefore, this study analyses the productivity of 16 pedunculate oak provenances on two sites in Croatia's lowlands: Gajno in Central Croatia and Slavir in Eastern Croatia. Both trials were established in 1988 in a randomised block design in four repetitions by the Croatian Forest Research Institute. Data were collected from 2017 to 2025 (diameter at breast height (DBH) and tree height (h)). Tree volume (v) was calculated, and descriptive statistics, RM-ANOVA, MANOVA, and Tukey post hoc tests were used for data analysis. The results revealed statistically significant differences in volume in the Gajno site, with Velika Gorica provenances exhibiting the highest productivity across the studied years. Provenances Gunja (in 2017), Motovun (in 2021), and Morović (in 2023) displayed the lowest values. In the Slavir site, the highest productivity was recorded in the Guševac provenance, while the lowest was observed in the Velika Gorica provenance across the studied years, even though a statistically significant difference was not proven. Analysis between the two sites confirmed statistically significant differences, with Slavir showing higher productivity. Since the local provenances showed the highest volume, it is recommended to use them for forest restoration programs in the Croatian lowlands. Attention should also be given to the Vrbanja provenance, which displayed above-average volume at both sites, indicating good adaptability to a wider range of site conditions. The findings highlight the importance of scientifically based provenance selection for forest restoration programs, particularly in the context of climate change adaptation. Continuous monitoring and silvicultural measures are imperative for enhancing resilience and ensuring the long-term sustainability of achieving optimal provenance productivity for a given site.
Đodan et al. (Tue,) studied this question.