Effects Of Simulated Sea-level Rise And Nitrogen Loading On Rates And Pathways Of Soil Organic Carbon Mineralization In The Tidal Wetland Of The Min River Estuary,China

To exlore the impact of sea level rise and nitrogen enhancement on rates and pathways of soil carbon(C)accumulation in tidal wetlands,we established four treatments(control,+flooding,+N loading,+flooding+N loading).We examined carbon mineralization rates(CMR),microbial iron reduction(Fe RR),microbial sulfate reduction(SRR),nitrate reduction(NRR)and methanogenesis(MPR)in the 240,420 and 630 days in the Min River Estuary,southeastern China.Our results showed that:(1)Relative to control,N loading treatment elevated the concentrations of SOC,TN,DOC,DON,NO₃^–and Fe(III).N loading also improved the microbial biomass C(MBC)and N(MBN),activities of and,abudance of bacteria,Geobacter and dsr A.Flooding treatment and the interaction of N loading and flooding treatment strikingly increased the concentrations of DOC,while did not significantly change the abudance of total bacteria.(2)Proteobacteria,Bacteroidetes and Chloroflexi were the dominant species of control.N loading treatment and flooding treatment both reduced the proportion of Bacteroidetes,but increased the proportion of Acidobacteria and Firmicutes,respectively.There was no difference between the dominant species in the interaction of N loading and flooding treatment and control.(3)In control,Fe RR and SRR are the main pathways for carbon mineralization,followed by MPR,and NRR contributes the least.N loading treatment increased Fe RR,s SRR,NRR and CMR.Flooding treatment can promote MPR.The interaction of N loading and flooding treatment inhibited CMR,but did not affect the proportion of each mineralization pathway to organic carbon mineralization rate.(4)CMR and four mineralization pathways in the growing period(240 days and630 days)were higher than those in the non-growing period(420 days).Fe RR was dominant in the growing period,while SRRwas dominant in the non-growing period.According to the above research results,N loading treatment can increase SOC content and CMR of estuarine wetland in the future.Sea level rise can increase MPR,but its influence on SOC and organic carbon mineralization is limited.When nitrogen loading and sea level rise in estuarine wetland occur simultaneously in the future,organic carbon mineralization rate and pathway will not change significantly,indicating that the interaction of these two global changes has a mutual subtraction effect on organic carbon mineralization in estuarine wetland.