Leaf nitrogen and phosphorus stoichiometry of plant communities in geochemically phosphorus-enriched soils in a subtropical mountainous region, SW China

Leaf nitrogen (N) and phosphorus (P) stoichiometry might reflect the biogeochemical features of ecosystems, yet the potential range of stoichiometric flexibility under geochemically P-enriched soils (GPES) is still unclear. Leaf N and P of 126 plant species in 70 vegetation plots in GPES were investigated in central Yunnan, southwestern China, and leaf P fractions (i.e., inorganic vs. organic P) of the dominant species were examined. Our objectives were to improve the understanding of the role of soil N and P variability in controlling leaf N and P stoichiometry of plant communities in GPES. We found that plants in GPES had higher mean leaf P (4.07 mg/g) and lower N:P ratios (4.94) than average plant values that have been recorded in other parts of the world so far. Some fast-growing plants had extremely high leaf P (> 10 mg/g). Community leaf N and P contents increased as soil N availability increased, but soil N variability was unrelated to community leaf N:P. Instead, community leaf P and N:P ratios were primarily determined by soil P; as soil P availability increased, leaf P increased and leaf N:P significantly decreased. Greater accumulation of inorganic P relative to organic P in leaf was the direct driving factor for community leaf P and N:P ratio patterns in GPES. Although soil P availability was the main controlling factor of leaf N:P patterns, community composition could be manipulated to restore the balance of N and P stoichiometry based on the different responses across species and plant types.