Although　increasing　studies　have　reported　that　microorganisms　play　an　important　role　in　carbon　(C)-degrading　enzyme　activities　under　salinization,　there　is　little　experimental　evidence　for　the　associations　between　C-degrading　enzyme　activities　and　microbial　community　structure.　Here,　we　examined　the　C-degrading　enzyme　activities,　bacterial　and　fungal　community　abundance　and　composition　(16S　and　ITS　rRNA　gene　sequencing),　soil　organic　carbon　(SOC)　storage,　carbon/nitrogen　(C/N)　ratios,　labile　organic　carbon　(LOC)　levels,　and　LOC/SOC　ratios　along　an　estuarine　salinity　gradient　[range:　0.1–2.2　part　per　thousand　(ppt)]　of　a　subtropical　tidal　wetland.　To　help　isolate　salinity　effects,　sampling　sites　were　selected　to　be　similar　in　plant　community　composition,　soil　texture,　and　tidal　influence.　Our　results　indicated　that　the　SOC　storage,　LOC　levels,　and　LOC/SOC　ratios　decreased,　whereas　C/N　ratios　increased　with　salinization.　The　activities　of　β-1,4-glucosidase,　cellobiohydrolase,　phenol　oxidase,　and　peroxidase　increased　by　485%,　147%,　699%,　and　868%,　respectively,　with　increasing　salinity.　The　α-diversities　of　bacterial　and　fungal　communities　did　not　change,　whereas　the　abundances　of　bacterial　and　fungal　communities　decreased　with　increasing　salinity.　Both　bacterial　and　fungal　oligotrophs/copiotrophs　ratios　were　positively　associated　with　salinity,　suggesting　that　bacterial　and　fungal　communities　shifted　from　being　copiotroph-dominated　to　oligotroph-dominated　as　salinity　increased.　All　C-degrading　enzyme　activities　were　correlated　with　the　relative　abundance　of　typical　bacterial　and　fungal　oligotrophs,　e.g.,　α-Proteobacteria,　δ-Proteobacteria,　Chloroflexi,　Acidobacteria,　and　Basidiomycota.　Overall,　the　C-degrading　enzyme　activities　were　co-determined　by　the　C/N　and　LOC/SOC　ratios　and　the　fungal　and　bacterial　oligotrophs/copiotrophs　ratios.　Our　observations　indicated　that　salinization　influenced　C-degrading　enzyme　activities　via　modulating　substrate　quality　and　lability　and　causing　shifts　in　microbial　C-use　trophic　strategies.　Our　proposed　oligotrophic–copiotrophic　scheme　could　be　a　novel　method　for　incorporating　vast　taxonomic　data　of　microbial　communities　into　enzyme　activity　prediction　in　an　ecologically　meaningful　manner.　©　2022　Elsevier　B.V.