No abstract

Nitrogen (N) and phosphorus (P) are essential nutrients for plant metabolism, and their availability often limits primary productivity. Whereas the effects of N availability on photosynthetic capacity are well established, we still know relatively little about the effects of P availability at a foliar level, especially in P‐limited tropical forests. We examined photosynthetic capacity, leaf mass per area (LMA) and foliar P fractions in five woody plant species after 6 years of N and P fertilization in a lowland tropical forest. Foliar N:P ratios indicated P limitation of the unfertilized plants; accordingly, photosynthetic P‐use efficiency (PPUE) and LMA decreased with P addition, and foliar N and P concentrations increased, whereas N addition had little effect on measured foliar traits. However, P addition enhanced photosynthetic capacity only in one species and not in other four species. We then assessed plant acclimation to low P availability by quantifying four fractions of foliar P representing different functional pools: structural P, metabolic P (including inorganic P), nucleic acid P, and residual P. We found that P addition enhanced the concentrations of metabolic, structural, and nucleic acid P fractions in all species, but the magnitude of the effect was species‐specific. Our findings indicate that tropical species acclimate to low P availability by altering allocation of foliar P to meet the demand of P for photosynthesis. Importantly, species typical of lowland tropical forests in East Asia maintained their photosynthetic rate under low P availability. We conclude that P limitation of leaf photosynthetic capacity may not be as common as previously assumed due to plant acclimation mechanisms in low‐P tropical forests. Species‐specific strategies to allocate P to different foliar fractions represent a potentially important adaptive mechanism for plants in P‐limited systems.