Effects of climatic conditions on growth and wood anatomical traits of European beech (Fagus sylvatica L.) at the edges of its range

The effects of climate change, particularly extreme temperatures and drought conditions, pose significant challenges to forest ecosystems. This study aims to assess the ability of beech trees (Fagus sylvatica L.) to cope with climate stressors by examining the relationship between growth and wood anatomical traits in the context of environmental adaptation. By investigating beech trees at the rear edges of their habitat range—where climatic responses are more pronounced—it becomes possible to explore how these trees respond to varying climatic conditions, particularly temperature and precipitation patterns that influence annual growth, such as those occurring in spring and autumn. These diverse locations serve as models for both current and future climate scenarios, offering insight into how beech trees may adapt to or shift their distribution in response to changing environmental conditions. Accordingly, this study examines the factors influencing beech tree growth in Etna, Italy, and Slătioara, Romania, which represent the southern and eastern limits of the species’ natural distribution, respectively. Using a retrospective methodological approach that combines dendrochronology and quantitative wood anatomy, the obtained data were correlated with a 120-year climate series (1901–2022) to determine the impact of climate on growth and xylem anatomical traits. Specifically, both inter- and intra-annual analyses were conducted between the standardized mean chronologies of anatomical parameters—mean ring width (RWL), cell number (CNo), cell density (CD), mean lumen area (MLA), maximum lumen area (MAXLA), theoretical hydraulic conductivity (Kh), mean hydraulic diameter per ring (Dh), and ring-level vessel grouping index (RVGI)—and climatic variables such as maximum and minimum temperature, precipitation, the Standardized Precipitation-Evapotranspiration Index (SPEI03), nitrogen oxides (NOx), sulfur dioxide (SO₂), and carbon dioxide (CO₂).