Stoichiometry patterns of leaf carbon, nitrogen and phosphorous in aquatic macrophytes in eastern China

Ecological stoichiometry focuses on the balance of chemical elements and can enhance our understanding of the adaptive strategies of plants. However, few studies concerning the stoichiometry patterns of leaf carbon (C), nitrogen (N) and phosphorous (P) concentrations in aquatic macrophytes across latitudinal gradients have been reported. We collected 681 samples from 213 sites in eastern China, including 122 species from 55 genera and 35 families, to analyse variations in leaf C, N and P and their relationships with latitude, mean annual temperature and mean annual precipitation. The leaf C, N and P concentrations were significantly different among the four investigated life forms, but no significant differences were detected between seed plants and ferns. The N:P ratios were well constrained in different functional groups. The C:P and N:P ratios found in aquatic macrophytes in the present study were lower than previous findings, likely due to higher concentration of P in the surrounding environments. As the temperature increased, the leaf N concentration and leaf N:P ratio increased, whereas the leaf P concentration decreased. Furthermore, temperature was the key factor which can affect the stoichiometry patterns observed in widely distributed species directly and also indirectly at the community level. The slope of the regression line of the log 10-transformed N concentrations against the log 10-transformed P concentrations found in the seed plants of aquatic macrophytes was conserved and was greater than the slope of 2/3 reported for terrestrial plants, suggesting that the leaf N concentration increases faster relative to leaf P in aquatic than terrestrial plants.