Purpose

Reclamation of saline-alkali soils to grow cotton (Gossypium spp.) is very common in the arid Manas River Basin in Northwest China. However, little is known about the degradation potential of soil microbes in reclaimed saline-alkali soils.

Methods

Hence, in this study, the high-throughput metagenomic sequencing was used to assess the degradation potential of soil microbes over seven years after reclamation. Results The results showed that bacteria is the dominant microbial group, and Actinobacteria, Proteobacteria, Chloroflexi, and Firmicutes were dominant phyla in the soil samples collected in each year. Among them, Actinobacteria and Proteobacteria accounted for more than 60% of the total bacteria. Further, soil microbial diversity and abundance of carbohydrate-active enzymes (CAZymes) encoding genes increased after reclamation, as did the abundance of CAZyme encoding genes involved in the decomposition of cellulose, hemicellulose, chitin, and lignin. Deterministic and stochastic processes jointly dominated the succession of microbial communities in reclaimed soils. Redundancy analysis and permutational multivariate analysis of variance showed that soil EC, C/N ratio, and Na⁺ content significantly affected microbial community succession and the abundance of CAZyme encoding genes in reclaimed soils, and soil pH affected soil microbial community diversity.

Conclusions

In conclusion, the degradation potential of soil microbes significantly increased after reclamation. This study deepens our understanding of the degradation potential of soil microbes in the process of reclamation of abandoned saline-alkali soils.