Relationship of Bacterial Microdiversity of Rhizosphere and Bulk Soil with Soil Organic Carbon Mineralization in Maize Fields

Abstract

[Objective] The bacterial community microdiversity in the maize rhizosphere and bulk soil was determined to study the relationship between microdiversity and soil organic carbon mineralization through the use of high-resolution taxonomy in order to provide a theoretical foundation for microbially driven carbon cycling in the maize rhizosphere. [Methods] The rhizosphere and bulk soil samples were collected in maize fields on the experimental farm of Cao Xinzhuang, Northwest A&F University. High-throughput sequencing technology was used to detect the bacterial community structure in the rhizosphere and bulk soil. Thereafter, distinct taxonomic resolution levels (OTUs vs ASVs) were used to reveal the microdiversity of bacterial communities. Incubation experiments were conducted to examine organic carbon mineralization characteristics of the rhizosphere and bulk soil of maize. [Results] The distinct taxonomic resolution levels revealed similar bacterial community structure in the rhizosphere and bulk soil. ASVs depicted bacterial community composition at a fine scale taxonomic resolution level, and revealed different strains or ecotypes prevalent within the same OTU. Furthermore, differences in the relative abundance of bacterial species from distinct growth strategies (r-and K-strategies) were the main factors contributing to the different bacterial community structures in the rhizosphere and bulk soil. Incubation experiments showed that organic carbon mineralization was significantly higher in the rhizosphere than in bulk soil. The results of three years of continuous sampling revealed that roots were the main factor causing differences between the rhizosphere and bulk soil physicochemical properties of mature maize in the field, and that time had little influence (from 2019 to 2021). Cumulative mineralization of soil organic carbon was associated with bacterial microdiversity between the rhizosphere and bulk soil. [Conclusion] ASV-level exhibited significant differences in bacterial microdiversity between the rhizosphere and bulk soil in a maize field, and bacterial microdiversity was associated with cumulative mineralization of soil organic carbon.

Keywords

• rhizosphere
• bulk soil
• bacteria
• microdiversity
• soil organic carbon