Leaf Phenological Variability in Fagus sylvatica L. Seedlings from Contrasting European Provenances Across Two Growing Seasons

Abstract

Phenological monitoring plays a critical role in understanding how forest ecosystems respond to climate change, particularly in economically and ecologically important forestry species such as European beech (Fagus sylvatica L., Fagaceae). This study assessed the variability of leafing phenophases in seedlings from 29 European beech provenances originating from Central and Southeastern Europe, grown under common conditions at a trial site on Mt. Goč, Serbia. Observations were conducted during two consecutive growing seasons (2022 and 2023), both warmer than average, with 2022 being notably drier. Significant variation was observed in the timing and duration of leafing phenophases among provenances, especially in 2022. Between-year comparisons revealed a statistically significant difference only for phenophase III (bud cracking), with shorter durations observed in 2022. In general, our results suggest that local climatic parameters and the genetic background influenced phenological variability, although no consistent eco-geographic pattern emerged. These findings represent early-stage results and should be interpreted as a preliminary step toward understanding adaptive potential in juvenile beech populations. Long-term monitoring across multiple years and developmental stages is essential to determine the stability of phenological traits and their relevance for provenance selection. This study contributes to the broader effort of integrating phenological data into climate-resilient forest management and highlights the importance of sustained multi-year research to support future breeding and conservation strategies.