CO₂ Emission And Salinity Impacts In Wetland Of The Liaohe Estuary

Liaohe estuary wetland is the largest estuary wetland in China's middle and high latitudes,the wetland types are Phragmites australis wetland,Suaeda salsa wetland and mudfalt wetland.In recent years,with the decline of precipitation and river water,the expansion of seawater intrusion,the increase of soil salinity in wetland,the difference of water and salt environment characteristics of different wetland types is obvious,which leads to Liaohe estuary wetland CO₂ emissions have undergone significant changes.In this study,Three types of wetland?Phragmites australis,Suaeda salsa,mudflat?in Liaohe estuary were selected to measure CO₂ emission,using static box-gas chromatography and indoor simulated culture method,and CO₂ Emission and Salinity Impacts in Wetland of the Liaohe estuary,the biochemical mechanism of CO₂ emission from Liaohe estuary wetland was revealed.The results are as follows:?1?There were significant differences in CO₂ emission rate among the three types of wetland,Both the Phragmites australis wetland and Suaeda salsa wetland reached the peak value of CO₂ emission in August,with an order as Phragmites australis>Suaeda salsa>mudflat,during June 5th to November 1st in 2016;There was a significant negative correlation between the CO₂ emission and EC value among the three wetlands Liaohe Estuary,indicating that salinity is the key environmental factor impacting the CO₂ emission from wetlands of the Liaohe estuary.?2?The CO₂ emission rate of Phragmites australis wetland with different salinity input in Liaohe estuary is obviously different,CO₂ emission rate in the order of standard seawater dilution 45 times treatment>standard seawater dilution 20 times treatment>standard seawater dilution 10 times treatment>standard seawater diluted 5 times treatment,The increase of salt content inhibits the decrease of CO₂ emission rate by inhibiting the content of soil microbial biomass carbon and plant growth in Phragmites australis wetland.?3?The CO₂ production rate of 0-10 cm depth soil in Phragmites australis wetland was significantly higher than that in 10-20 cm depth soil,while there was no significant difference in CO₂ production rate between different soil depths of Suaeda salsa wetland.Under anaerobic conditions,the high concentration of Cl^-input significantly inhibited the CO₂ production rate of 0-10cm soil in Phragmites australis wetland,The high concentration of SO₄^2-input promoted the CO₂ production rate at 10-20 cm depth of Phragmites australis and Suaeda salsa wetland,The high concentration of SO4^2-input relative to the Cl^-input can significantly promote the CO₂ production rate in the 10-20 cm depth soil of the Phragmites australis wetland.The results showed that the CO₂ production rate of Cl^-and SO₄^2-input in seawater was different from that in Liaohe estuary wetland.The above results show that the CO₂ emission rate between different wetland types in Liaohe estuary is obviously affected by salt,the salinity increase caused by seawater intrusion can reduce the CO₂ emission rate in Liaohe estuary wetland.The effect of salt on CO₂ emissions from Liaohe estuary wetland is due to the effect of salt on soil ion type,intensity,microbial biomass carbon and plant growth.