Abstract: The stoichiometric characteristics of carbon (C), nitrogen (N), phosphorus (P) and their ratios (C/N, C/P and N/P) are important for understanding organic matter dynamics in wetland ecosystems and ecosystem response to environmental changes. The aim of the study was to reveal the differences of TOC, TN, TP and their ratios among different wetlands in the Liaohe estuary, and to find the factors affecting the stoichiometric characteristics of C, N and P. We selected six types of wetland in Liaohe estuary, including natural Phragmites australis wetland, P. australis wetland of oilfield, degraded P. australis wetland, Suaeda salsa wetland, mudflat, and rice paddy. The results showed that the contents of TOC, TN and TP in soil ranged from 1.612 to 167.832, 0.159 to 4.452 and 0.021 to 0.093 g·kg^-1 at different depths across the six wetland types, respectively. Those values were different among soil depths and wetland types (P<0.05). Higher contents of TOC were found in the natural P. australis wetland and P.australis wetland of oilfield, while higher TN contents were observed in the natural P.australis wetland and rice paddy. Lower TOC and TN were found in the Suaeda salsa wetland and mudflat. The TOC and TN contents in the top soil (0-10 cm) of different wetland types were significantly higher than those in the subsoil (10-40 cm). There were no significant differences in TP contents among different wetland types and among different soil depths (P>0.05). The mean values of C/N, C/P and N/P ratios were 28, 364 and 13 across different wetland types, respectively, which were significantly different among wetlands (P<0.05). Correlation analysis results showed that TOC and TN contents were positively correlated with C/P and N/P, and EC values were weakly negatively correlated with soil TOC, TN, TP, C/N, C/P and N/P. Our results suggest that increasing salinity might weaken the control of N and P on the C accumulation in soil, resulting in carbon loss.

Key words: carbon, nitrogen, phosphorus, stoichiometric characteristics, Liaohe estuarine wetland.