Abstract
<title>Abstract</title> <p> European beech ( <italic>Fagus sylvatica</italic> L.) is a dominant temperate forest species, yet its adaptive potential under changing climates remains uncertain. We evaluated 30 provenances of <italic>F. sylvatica</italic> and <italic>F. orientalis</italic> in the long-term provenance trial Malente (northern Germany), established in 1986, monitoring basal area, survival, phenology, and stem form over four decades. Mixed linear models quantified provenance effects, and best linear unbiased predictors (BLUPs) were integrated into a multi-trait selection framework using the genotype-ideotype distance index (MGIDI). Significant provenance differentiation was observed for basal area (up to 55% of variance), bud burst phenology (up to 75%), and survival (up to 55%), whereas stem form showed comparatively weak genetic control (up to 20%). Multi-trait selection identified six superior provenances (Schmallenberg 1, Ebrach 4, Sovaenger, Reichensachsen, Seesen 1, and Fuerstenberg), combining high productivity, stable survival, and acceptable stem form. Variation in performance was not explained by Euclidean climatic distance to the trial, despite the clear separation of provenance climatic clusters. Climatic variables regressions however, revealed highly significant control of performance. MGIDI was primarily associated with mean coldest month temperature (MCMT, R² = 0.64) and growing degree days above 5°C (GDD5, R² = 0.40), indicating superior multi-trait performance of provenances originating from colder climates with lower heat accumulation. Basal area showed similarly strong associations with MCMT (R² = 0.56) and GDD5 (R² = 0.44), while survival was strongly related to MCMT (R² = 0.63) and climatic continentality (TD, R² = 0.43). Stem form exhibited generally weak climatic associations, with only MCMT showing a significant relationship (R² = 0.18). These results highlight substantial genetic differentiation among beech provenances and demonstrate that combining multi-trait selection with trait and specific climatic variables analyses enables identification of climatically adapted provenances with superior productivity and survival. The findings provide practical guidance for breeding, conservation, and climate-resilient forestry strategies. </p>