The Effects Of The First Thinning On Stand Structure In Oak and Hornbeam Mixed Stands

This study, conducted in Istanbul's Belgrad Forest, examines the effects of thinning on stand dynamics. In 2017, a moderate to heavy thinning intervention was implemented in a mixed stand of sessile oak (Quercus petraea) and common hornbeam (Carpinus betulus). Changes in diameter and basal area increments, stand stratification, and vitality (health condition) were analyzed over a two-year period following the intervention. The study employed a randomized design with control and treatment groups. During thinning, 0% (control) and 15–20% (moderate) of the basal area were removed from the stand. The two-year results revealed that thinning significantly increased diameter and basal area increments in both species. The diameter increment was statistically significant, whereas the basal area increment was not. Sessile oak, positioned in the dominant canopy layer, exhibited greater diameter and basal area increments compared to common hornbeam. Compared to the control plots, the treated plots displayed a 57% higher diameter increment in sessile oak and a 14% higher increment in common hornbeam. Similarly, the basal area increment was 12% higher in sessile oak and 15% higher in common hornbeam. Analyses of stratification and vitality changes indicated that moderate thinning interventions enhanced the potential for high-quality stem development in sessile oak individuals. While further long-term data are necessary to fully evaluate the effects of thinning, moderate to heavy thinning is recommended for sessile oak stands mixed with shade-tolerant species.