Species-specific spatial and temporal variation in foliar nitrogen and phosphorus in mangrove plants

Abstract

Foliar nitrogen (N) and phosphorus (P) concentrations and stoichiometry affect the productivity and functioning of plants, and they play an important role in biogeochemical processes. We investigated spatial and temporal variation in foliar nutrient concentrations and N:P stoichiometry in mangroves of China, and partitioned the relative importance of taxonomic, climatic and edaphic factors in explaining the variations. To assess spatial patterns, we collected mature leaves of 3 broadly distributed mangrove species in China spanning a latitudinal gradient. To assess temporal variation in leaf stoichiometry, we selected 1 site and sampled leaves of 4 species monthly over 12 mo. Positive relationships were found between foliar nutrient concentrations and latitude or soil nutrient concentrations in individual species. Species accounted for 76, 46 and 18% of the spatial variation in foliar N, P and N:P mass ratio, respectively, while soil nutrients and climate accounted for only small portions of the variation (≤8.3%). Different species showed no consistent patterns across temporal variation in foliar nutrient concentrations or stoichiometry, and species accounted for 94, 86 and 26% of the variations in foliar N, P and N:P ratio, respectively, throughout the year, while climatic factors accounted for only a very small portion of the variations (≤0.5%). Our results suggest that species affect foliar nutrient concentrations and stoichiometry in mangroves more strongly than environmental factors, and that stoichiometric homeostasis in mangroves may play an important role in mitigating the effects of environmental changes in coastal areas.