Increasing phosphorus limitation with tree age in tropical forests

Aims Phosphorus (P) availability commonly limits the growth of tropical plants, yet how this limitation changes with tree age remains uncertain. Methods Here we investigated the effect of tree age on P limitation in a tropical forest by examining three functional plant groups: fast-growing, slow-growing, and nitrogen (N)-fixing tree species. We measured leaf N and P resorption efficiency (NRE and PRE), and used the ratio of PRE to NRE (PRE:NRE) as an indicator of plant P limitation. Results Our results revealed a significant increase in both PRE and PRE:NRE with tree age across all functional plant groups, indicating a widespread intensification of P limitation as plants mature. Furthermore, such increase in P limitation was more pronounced in slow-growing and N-fixing species compared to fast-growing species. Conclusions These findings underscore the crucial role of tree age in influencing P limitation in tropical forests, a factor that should be incorporated into terrestrial biogeochemical models, which have traditionally overlooked this effect.