Geographic factors explain soil nitrogen and phosphorus stoichiometry in the Chinese wetlands

Abstract

Generally, the contents of nitrogen (N) and phosphorus (P), and their stoichiometry, in the soil of terrestrial ecosystems exhibit certain geographic patterns. However, it remains poorly understood whether these patterns also exist for wetland soils. Here, we compiled a dataset of 731 observations among 468 sites from both published reports and field investigations, to examine the continental-scale geographic patterns in soil N and P stoichiometry of the Chinese wetlands. The results showed that the averaged soil N contents, P contents and N:P ratio were 1.98 mg g−1, 0.70 mg g−1, and 3.59, respectively, which were also dependent on wetland types and vegetation. Moreover, soil N and P contents and N:P ratio concurrently exhibited clear latitudinal, longitudinal and altitudinal patterns, more diversified patterns than those in terrestrial ecosystem. The observed patterns were explained primarily based on geographic factors, particularly the altitude, rather than vegetation and climate conditions. These findings advance our understanding of biogeographical nutrient cycles in wetlands and highlight the critical role of geographic factors in regulating soil N and P stoichiometry under global climate change.