Globally,　a　vast　extent　of　tidal　wetlands　will　be　threatened　by　sea-level-rise-induced　salinization.　Because　ferric　(hydro)oxides　[Fe(III)]　play　a　crucial　role　in　soil　organic　carbon　(SOC)　preservation,　understanding　the　responses　of　the　Fe-bound　C　pool　to　increasing　salinity　could　assist　in　accurate　prediction　of　the　changes　in　C　stocks　in　the　tidal　wetland　soils　facing　imminent　sea-level　rise.　In　this　study,　we　investigated　pools　of　Fe-bound　C　and　SOC,　C-degrading　enzyme　activity,　Fe　species　contents　and　Fe-cycling　bacteria,　and　plant　properties　along　a　salinity　gradient　from　freshwater　(0.0　+/-　0.1　ppt;　part　per　thousand)　to　oligohaline　(2.6　+/-　0.6　ppt)　in　a　subtropical　tidal　wetland.　Overall,　the　belowground　biomass　and　the　content　of　root　Fe(III)　plaque　(a　proxy　of　root　oxygen　loss　potential)　rose　with　the　increasing　salinity.　Along　the　salinity　gradient,　the　abundance　of　Gallionella　(Fe-oxidizing　bacteria)　increased,　but　the　abundance　of　Geobacter　(Fe-reducing　bacteria)　decreased.　The　Fe(II):Fe(III)　ratios　decreased　as　salinity　increased,　implying　that　more　Fe(II)　was　oxidized　and　immobilized　into　Fe(III)　closer　to　the　sea.　Fe　sulfides　contents　also　elevated　close　to　sea.　The　co-existence　of　Fe(III)　and　Fe　sulfides　at　the　oligohaline　sites　implied　a　high　spatial　heterogeneity　of　Fe　distribution.　During　the　growing　season,　the　SOC　pool　generally　decreased　with　increasing　salinity,　probably　due　to　a　reduction　in　aboveground-C　input　and　enhanced　activity　of　the　C-degrading　enzyme.　The　Fe-bound　C　pool　was　positively　affected　by　the　amorphous　Fe(III)　content　and　negatively　related　to　the　activity　of　phenol　oxidase.　The　Fe-bound　C　pool　generally　rose　along　the　salinity　gradient,　with　the　importance　of　Fe-bound　C　to　SOC　increasing　from　18%　to　29%.　Altogether,　our　findings　implied　that　when　the　imminent　sea-level-rise-induced　salinization　occurs,　the　total　soil　C　stock　may　generally　decrease,　but　Fe-bound　C　will　become　increasingly　important　in　protecting　the　rest　of　the　C　stocks　in　tidal　wetland　soils.