Water level of inland saline wetlands with implications for CO2 and CH4 fluxes during the autumn freeze-thaw period in Northeast China.

Abstract

Zhalong wetland is the largest inland saline wetland in Asia and susceptible to imbalance and frequent flooding during the freeze-thaw period. Changes in water level and temperature can alter the rate of greenhouse gas release from wetlands and have the potential to alter Earth's carbon budget. However, there are few reports on how water level, temperature, and their interactions affect greenhouse gas flux in inland saline wetland during the freeze-thaw period. This study revealed the characteristics of CO2 and CH4 fluxes in Zhalong saline wetlands at different water levels during the autumn freeze-thaw period and clarifies the response of CO2 and CH4 fluxes to water levels. The significance analysis of cumulative CO2 fluxes at different water levels showed that water levels did not have a significant effect on cumulative CO2 release fluxes from wetlands. Water levels, temperature, soil moisture content, soil nitrate, and ammonium nitrogen content and organic carbon content could explain 24.5-98.9% of CO2 and CH4 flux variation. There were significant differences in the average and cumulative CH4 fluxes at different water levels. The higher the water levels, the higher the CH4 fluxes. In short, water level had a significant effect on wetland methane fluxes, but not on carbon dioxide fluxes.