Changes in soil bacterial abundance and diversity in response to drip irrigation to Establish plant communities on highly saline Lands in north China

Soil salinization represents a significant challenge to agricultural production and ecosystem establishment in arid areas. Water–salt regulation by drip irrigation has emerged as a promising approach to significantly reducing soil salinity and rapidly allowing the formation of plant communities. Although one of the most important indicators of soil quality, soil bacteria have been less extensively investigated in such studies. Therefore, the objective of this study was to investigate the effect on soil bacterial abundance and diversity of water–salt regulation by drip irrigation. To this end, the study employed a spatiotemporal iterative method through plate culture and high-throughput sequencing to examine soil bacterial changes in response to drip irrigation over a four-year period (4a), a three-year period (3a), a two-year period (2a), and a period without water–salt regulation (0a). The results demonstrated that drip irrigation significantly reduced soil salinity and increased bacterial abundance in highly saline soils. After four years of drip irrigation, the abundance of soil bacteria and actinobacteria had increased 900-fold and 1,325-fold, respectively, compared with untreated saline soils. The Actinobacteriota and Proteobacteria were the dominant bacterial phyla during testing of saline soils, and the percentage abundance of Actinobacteriota, Proteobacteria, and Chloroflexi in the topsoil increased with the increasing years of drip irrigation. The functions of the bacterial communities in response to drip irrigation changed in terms of RNA processing and modification, chromatin structure and dynamics, etc. Structural equation modeling demonstrated that the number of years of drip irrigation significantly affected soil bacterial abundance and diversity, with correlation coefficients of 95% and 43% with time, respectively. Additionally, soil bacterial abundance exhibits a more pronounced response to the duration of drip irrigation, whereas soil bacterial diversity responds more strongly to sudden shifts in soil environment. It is important to recognize that the bacterial diversity index should not be relied upon in isolation in evaluating the overall soil environment; rather, it should be combined with the abundance of soil bacteria for a comprehensive evaluation. The current study provided a scientific basis for the changes in the biological characteristics of highly saline soils in arid zones using drip irrigation and consequent water–salt regulation.