Effect Of Salinity Changes On Soil Organic Carbon Mineralization And Carbon Gases Effluxes From Tidal Wetland In The Min River Estuary,China

To explore the impact of saltwater intrusion on soil carbon(C)accumulation in the tidal wetlands,we translocated the vegetated and unvegetated soil cores from freshwater wetlands to brackish wetlands,and also translocated the soil cores from brackish wetlands to freshwater wetlands.We measured soil properties,different C species,microbial abundance and extracellular enzyme activities,C minerlization rates and C gases emission.(1)When soil was translocated from freshwater wetlands to brackish wetlands,the concentrations of DON,PO₄^3-,NH₄⁺,NO₃^-,SO₄^2-and Cl^-increased in either vegetated or unvegetated soil cores.However,all these variables decreased,when soil was translocated from brackish wetlands to freshwater wetlands.(2)When soil was translocated from freshwater wetlands to brackish wetlands,the contents of EOC,MBC,DOC increased by 16%,47%and 29%respectively and the content of SOC decreased by 17%in vegetated soil cores.However,all these variables showed opposite results,when soil was translocated from brackish wetlands to freshwater wetlands.The change of SOC content was same as the vegetated soil cores and the contents of EOC and DOC didn't change after transplantation in unvegetated soil cores.When soil was translocated from freshwater wetlands to brackish wetlands,the content of MBC increased.However,MBC content remained constant when soil was translocated from brackish wetlands to freshwater wetlands.(3)When soil was translocated from freshwater wetlands to brackish wetlands,the abundance of bacteria,fungi increased,and Acidobacteria and Proteobacteria increased by 16%and 21%respectively.However,all these variables decreased except Acidobacteria kept constant,when soil was translocated from brackish wetlands to freshwater wetlands.(4)When soil was translocated from freshwater wetlands to brackish wetlands,the activities of?G,CBH,PHO and PEO increased in either vegetated or unvegetated soil cores.However,all these variables decreased,when soil was translocated from brackish wetlands to freshwater wetlands.When soil was translocated from freshwater wetlands to brackish wetlands,the production rate of CH₄decreased while the total mineralization rate of soil increased by 49%in either vegetated or unvegetated soil cores.However,all these variables showed opposite results,when soil was translocated from brackish wetlands to freshwater wetlands.The total mineralization rate of soil decreased by 30%.(5)When soil was translocated from freshwater wetlands to brackish wetlands,the CH₄effluxes and the concentration of dissolved CH₄decreased and the CO₂effluxes and the concentration of DIC increased in either vegetated or unvegetated soil cores.However,all these variables showed opposite results,when soil was translocated from brackish wetlands to freshwater wetlands.According to the above results,the increased salinity in the future will change the structure of soil microbial community,increase the microbial activities and decomposable carbon contents,increase the mineralization rate of soil organic carbon and CO₂effluxes,and decrease the content of SOC.