Effect Of Salinity On Soil Organic Carbon Mineralization In Liaohe Estuary Wetland

Estuary wetlands are a special kind of ecosystem, which are located at the junction of ocean and river ecosystem. Estuary wetlands have become important soil carbon pools because of their unique environmental characteristics, biological structure and giant storage of organic carbon. As an important part of the carbon cycles, soil organic carbon mineralization plays a key role for the carbon balance of estuary wetlands. The soil salinity in estuary wetlands has increased due to the seawater intrusion and human disturbance. The increasing salinization in soil of estuary wetlands may change the carbon biogeochemical processes. However, the effect of salinity on carbon mineralization and its mechanism are still unclear. In order to explore the response of soil organic carbon mineralization to salinity change and its mechanisms, laboratory closed culture and soil column simulation methods were used to to study the effect of salinity on soil organic carbon mineralization and also to discuss the biochemistry mechanism of carbon mineralization in Liaohe estuary wetland. The main results were listed as follows:i. The electrical conductivity(EC1:5), content of ion and nitrogen in the Liaohe estuary wetland surface soil were increased with salinity increasing along a sanility gradient. The potential mineralization of soil organic carbon in different salinity was significantly correlated with the EC1:5, Mg2+, Cl-, Ca2+, organic carbon and nitrogen contents. The synergistic effect of salt and soil organic matter properties is important to soil organic carbon mineralization in Liaohe estuary wetland.ii. Increase of soil salinity decreased the DOC concentration in soil water and increased the proportion of aromatic components(SUVA) in DOC. High soil salinity decreased the release of CO2 from soil columns. The release of CO2 was positively correlated with DOC concentration and negatively correlated with SUVA.iii. In the higher Cl- and SO42- treatments, the mineralization of soil organic carbon was significantly inhibited and the inhibition effect of Cl- on carbon mineralization was stronger than that of SO42-. The result of 16 sDNA showed that an increase of soilsalinity had changed the structure of the bacterial community and increased the microbial diversity.The results showed that the soil organic carbon mineralization in the Liaohe estuary wetland was significantly affected by salt and the increase of salinity could decrease the carbon loss in the form of DOC and CO2 release. The results suggest that the mechanisms of soil organic carbon mineralization responsing to salinity may be the changes of the soil matrix properties, ionic strength and type and also microbial community.