Although　salinization　is　widely　known　to　affect　cycling　of　soil　carbon　(C)　in　tidal　freshwater　wetlands,　the　role　of　the　presence　or　absence　of　plants　in　mediating　the　responses　of　soil　organic　carbon　(SOC)　mineralization　to　salinization　is　poorly　understood.　In　this　study,　we　translocated　soils　collected　from　a　tidal　freshwater　wetland　to　sites　with　varying　salinities　along　a　subtropical　estuarine　gradient　and　established　unplanted　and　planted　(with　the　salt-tolerant　plant　Cyperus　malaccensis　Lam.)　mesocosms　at　each　site.　We　simultaneously　investigated　cumulative　soil　CO2　emissions,　C-acquiring　enzyme　activities,　availability　of　labile　organic　C　(LOC),　and　structures　of　bacterial　and　fungal　communities.　Overall,　in　the　planted　mesocosm,　the　soil　LOC　content　and　the　activities　of　β-1,4-glucosidase,　cellobiohydrolase,　phenol　oxidase,　and　peroxidase　increased　with　salinization.　However,　in　the　unplanted　mesocosm,　soil　LOC　content　decreased　with　increasing　salinity,　whereas　all　the　C-acquiring　enzyme　activities　did　not　change.　In　addition,　salinization　favored　the　dominance　of　bacterial　and　fungal　copiotrophs　(e.g.,　γ-Proteobacteria,　Bacteroidetes,　Firmicutes,　and　Ascomycota)　in　the　planted　mesocosms.　Contrarily,　in　the　unplanted　mesocosms　salinization　favored　bacterial　and　fungal　oligotrophs　(e.g.,　α-Proteobacteria,　Chloroflexi,　Acidobacteria,　and　Basidiomycota).　In　both　planted　and　unplanted　mesocosms,　cumulative　soil　CO2　emissions　were　affected　by　soil　LOC　content,　activities　of　C-acquiring　enzymes,　and　microbial　C-use　trophic　strategies.　Overall,　cumulative　soil　CO2　emissions　increased　by　35%　with　increasing　salinity　in　the　planted　mesocosm　but　decreased　by　37%　as　salinity　increased　in　the　unplanted　mesocosm.　Our　results　demonstrate　that　the　presence　or　absence　of　salt-tolerant　plants　can　moderate　the　effect　of　salinity　on　SOC　mineralization　in　tidal　wetland　soils.　Future　C　prediction　models　should　embed　both　planted　and　unplanted　modules　to　accurately　simulate　cycling　of　soil　C　in　tidal　wetlands　under　sea　level　rise.　©　2022　Elsevier　B.V.