Stoichiometric characteristics of nitrogen and phosphorus in major wetland vegetation of China

Abstract

Aims Little is known on the stoichiometric characteristics of nitrogen (N) and phosphorus (P) in wetland vegetation across China. This work is aimed to study the stoichiometric characteristics of wetland vegetation in China, which are of great significance for revealing the coupling relationship between vegetation and habitats. Methods Based on previous studies, a data set comprising N and P contents and N:P of wetland vegetation attained from 649 observations in 52 study sites, was classified and analyzed, which concerned vegetation organs, growth periods, plant life forms, climate zones and wetland types. Important findings The geometric mean of N, P and the N:P of different organs occurred in descending order as follows: leaf (N, 16.07 mg·g; P, 1.85 mg·g; N:P, 8.67) > aboveground organ (N, 13.54 mg·g; P, 1.72 mg·g; N:P, 7.96) > stem (N, 7.86 mg·g; P, 1.71 mg·g; N:P, 4.58). Leaf N showed a three-peak seasonal distribution, with the peaks occurring in May, July and September, whilst stem N exhibited a bimodal distribution with peaks in May and September. Leaf N:P fluctuated in conformity to N before maturity, but changed corresponding to P in senescence phase. The type of wetlands was found to be the key factor significantly impacted the stoichiometric characteristics of wetland vegetation in China. Specifically, the highest and lowest leaf N and P contents were found in the bottom lands and marshes, respectively, while the N:P displayed a reversed trend. The geometric mean of leaf N, P contents and the N:P followed the order of: tropics > temperate zone > subtropics, albeit no significant differences (p > 0.05) among them. In addition, most of the leaf N:P were less than 14, indicating that the wetland vegetation in China was under the conditions of N limitation.