The CAZyme family regulates soil organic carbon accumulation under amendments application in saline-alkali soil

The application of amendments can alter soil properties and hold great potential for soil organic carbon (SOC) sequestration. However, the impacts of amendments application on soil microbial carbohydrate-active enzyme (CAZyme) genes and their roles in regulating SOC in saline-alkali soils remain incompletely understood. Here, we employed a metagenomics sequencing to explore the effects of amendments application on CAZyme encoding genes. Four treatments were included: no amendment control (CK); desulfurization gypsum (DE); cattle manure(CM); and desulfurization gypsum plus cattle manure (DC). Our findings showed that amendments application notably reduced soil pH, electrical conductivity (EC), improved soil nutrients and promoted SOC accumulation. Compared to CK treatment, DC treatment raised the abundance of Proteobacteria and Acidobacteria, while reduced Chloroflexi. Moreover, the abundance of CAZyme genes and families were higher in DC treatment relative to CK treatment. Networks showed that families of CAZyme genes belonging to glycoside hydrolase (GHs) and glycosyl transferase (GTs) had more links. Key genes including GH5 and GH20 were centrally positioned in the network and mainly influenced by soil chemical properties and bacterial diversity. Moreover, soil chemical properties played a much greater role in explaining variation of plant- and microbial-derived carbon decomposition genes than soil bacterial diversity and physical properties. Overall, our study provides deep insights into the degradation potentials of microbial CAZyme genes and role of microbial functions in regulating SOC in saline-alkali soils. • Manure plus desulfurization gypsum increased plant and microbial-derived SOM decomposition genes. • GHs and GTs families had more links within the network. • Genes in decomposing fungi-derived SOM were linked to soil pH and electric conductivity.