Drought resistance mechanisms and local adaptation of closely related species of Gabon's tropical rainforest | Mécanismes de résistance à la sécheresse et adaptation locale d'espèces étroitement apparentées des forêts tropicales du Gabon

English. Climate change, particularly the increasing frequency and intensity of drought events, poses a major threat to tree populations. In response, trees can adapt through various physiological mechanisms. Investigating xylem embolism resistance (P50) and the turgor loss point (Ψtlp) provides valuable insights into local adaptation and species distribution across environmental gradients. In this study, we examined how P50 and Ψtlp vary with micro-environmental conditions in a tropical rainforest in Gabon, focusing on closely related species of the Berlinia clade (Detarioideae). We measured P50, Ψtlp, soil properties, topographic Index (TPI/TWI) on at least six individuals of nine closely related species from the Berlinia clade, along with their morphological characteristics and life-history traits. By covering 27% of total variation of angiosperm P50 measurements, our findings revealed that embolism resistance is influenced by key soil properties associated with soil fertility, including cation exchange capacity (CEC), sand fraction, TWI and organic matter content. Notably, intraspecific variation exceeded interspecific variation, suggesting a high degree of local plasticity in P50 adaptation, likely driven by environmental heterogeneity. Although well-studied in the Amazonian forest, P50 variation has never been explored in tropical rainforest of Africa until this study. Understanding the mechanisms governing drought resistance in tree species is crucial for predicting and modeling the future floristic composition of African tropical rainforests.

13. Climate action