Abstract
Background and Aims Plant resilience to drought is strongly modulated by nutrient availability, which triggers complex physiological and metabolic reprogramming. In European forests, native species with high resource demands may be disadvantaged under abiotic stress compared to more efficient alien species. This study investigates how drought and phosphorous (P) availability affect the responses of Quercus robur (EO) and Quercus rubra (RO), focusing on root metabolism and nutrient allocation between leaves and roots. Methods A greenhouse mesocosm experiment was conducted with EO and RO subjected to two water regimes (well-watered and drought) and two P levels (− P and + P). Stem water potential, biomass, elemental composition, FTIR spectra, and root metabolomic profiles (UHPLC/QTOF-MS) were analyzed. Univariate and multivariate statistics were used to evaluate treatment effects. Results EO showed greater responsiveness to P, with increased root biomass and limited metabolic suppression during drought conditions. RO displayed a more stable biomass and elemental profile, but its metabolism was more strongly repressed under drought with P input. Under P deficiency, RO accumulated phenylpropanoids and alkaloids, indicating adaptation to low-resource stress. Conclusions EO exhibits higher metabolic plasticity and benefits from P supply under drought, while RO adopts a conservative strategy suited to nutrient-poor environments. These contrasting responses suggest that P availability may shift the competitive balance between native and alien oak species under climate-induced drought, favoring EO under P-rich conditions and RO under P-limited conditions.