Abstract: While tree species in phosphorus (P) impoverished subtropical forests exhibit divergent foliar P allocation strategies to maximize phosphorus-use efficiency, how these strategies integrate with the leaf economics spectrum (LES) and are modulated by leaf habit (deciduous vs. evergreen) remains unclear. Five foliar P fractions involving inorganic, metabolite, nucleic acid, lipid, and residual were quantified alongside LES traits across 10 deciduous and 22 evergreen woody species grown in standardized monocultures under uniform conditions. Deciduous species had 30% higher total foliar P than evergreens due to 50% and 35% greater metabolite P and nucleic acid P fractions, respectively. Evergreens allocated more P to residual fractions associated with higher leaf mass per area and conservative traits, whereas deciduous species linked lower residual P to rapid photosynthetic turnover. Evergreen species reduced allocation to inorganic P and residual P, together with increased nucleic acid P allocation, corresponding closely with their LES positioning. In deciduous species, however, LES variation was largely independent of foliar P allocation patterns. Importantly, deciduous species exhibited 31% higher photosynthetic P-use efficiency (PPUE) than evergreens. Overall, PPUE was shaped by the combined effects of leaf habit and LES, with foliar P fractions the primary proximate driver and LES functioning as the central mediator. These findings demonstrate that leaf habit governs the physiological coupling of regional LES trade-offs with foliar P biochemistry, underpinning niche differentiation in P-limited soils and enhancing trait-based predictions of nutrient utilization across tree functional types.

Key words: Leaf functional traits, Deciduous species, Evergreen species, Phosphorus (P) fractions, Photosynthetic P-use efficiency (PPUE)