Change of soil microorganism communities under saline-sodic land degradation on the Songnen Plain in northeast China

Background The Songnen Plain in northeast China was one of three major grasslands in China and has now become one of the most concentrated areas of sodic-saline soil worldwide due to soil parent material characteristics, hydrological conditions, and overgrazing. Aims The aim of this study was to evaluate the direct effects of environmental factors in shaping prokaryotic communities under three natural contiguous areas (severe saline-alkaline field with no vegetation, moderate saline-alkaline field with Suaeda glauca, and mildly saline-alkaline field with natural grass vegetation) on the Songnen Plain in northeast China. Methods Physicochemical properties of the soil pH, electric conductivity (EC), and soil organic carbon (SOC) were determined in three soil types with or without vegetation, while the metabarcoding analysis of the prokaryotic diversity and composition were analyzed by Illumina Miseq sequencing. Results Our study revealed that the moderate and mildly saline-alkaline soil exhibited lower pH by 0.614% and 10.17%, and significantly lower EC by 47.96% and 89.22%, respectively, in comparison to severe saline-alkaline field soil. Prokaryotic 16S rRNA gene amplicon analysis revealed that mildly saline-alkaline soil with native grasses had significantly higher alpha-diversity. The composition of the prokaryotic community was highly correlated with the soil physicochemical properties, but the SOC was the most important driving forces for the prokaryotic composition. Random matrix theory (RMT) network analysis revealed the keystone operational taxonomic unit (OTU) (OTU3096, OTU137, OTU3198 and OTU2210) that was significantly affected by the soil physicochemical properties in the three contiguous areas. Conclusions Collectively, these findings demonstrate that the mildly saline-alkaline soil with natural grass vegetation has a beneficial impact on the soil physical properties and prokaryotic community relative to severe saline areas in the Songnen Plain of northeast China.