Soil salinization alters biogeochemical cycles in agricultural ecosystems by reducing carbon-cycling microorganisms

Salinity stress can decline crop yield in agricultural systems. Beyond the environmental conditions that drive agricultural plant growth, the diverse roles of microbes represent a critical, often overlooked factor in shaping crop health and productivity. Salinization exerts a profound effect on soil microbial communities, with consequences for biogeochemical cycles. However, the salinity adaptation mechanisms of microorganisms participating in biogeochemical cycles remain incompletely understood, which hold considerable promise for microbial solutions in saline agriculture. In this study, metagenomics-based technology was employed to analyze agricultural soils within a region-scale irrigation area characterized by varying degrees of salinization. According to the results of generalized linear models, bell-shaped trends were observed for the diversity and abundance of biogeochemical cycling genes along the soil salinity gradient, all of which peaked at a salinity of approximately 7.5 ‰. Further comparisons indicated reduced total abundance of all biogeochemical cycling genes in high salinity soils (>7.5 ‰) compared to those in low salinity soils (