Distribution pattern and influencing factors of nitrogen-fixing microbial community in the rhizosphere of Pueraria lobata

Abstract:

[Objective] The aims of this study were to clarify the spatial pattern of the nitrogen-fixing microbial community in the rhizosphere of Kudzu (Pueraria lobata), and to explore the relationship between environmental factors and the spatial pattern. [Methods] A total of 17 rhizosphere soil samples were collected from Hunan, Jiangxi, and Guangxi province, where Kudzu was widely distributed. The physical and chemical parameters of the samples were measured by routine methods, and the composition and diversity of nitrogen-fixing microbial community was performed by high-throughput sequencing of nifH gene. Multivariate statistical analysis was used to explore the relationship between the composition of the nitrogen-fixing microbial community and environmental factors. [Results] The α diversity of nitrogen-fixing microorganisms were not significantly different among three sampling regions. The composition of nitrogen-fixing microbial communities were similar in the same sampling region, while were quite different among three sampling regions. It indicated that biogeographical pattern of nitrogen-fixing microbial community was existed. The predominant phylum of nitrogen fixing microorganisms was Proteobacteria, whose relative abundance accounted for more than 60%. At the order level, the species that could be annotated mainly belonged to Rhizobiales and Burkholderiales. The relative abundance of Rhizobiales was highest in Jiangxi, while the relative abundance of Burkholderiales was highest in Hunan. pH, exchangeable calcium, total potassium, elevation and annual mean temperature were the main factors that influenced the composition of nitrogen fixing community. Burkholderiales was positively correlated with pH, exchangeable calcium and total potassium; while was negatively correlated with the ratio of carbon to nitrogen. Rhizobiales was positively correlated with total potassium and the content of sand, while was negatively correlated with pH, exchangeable calcium, elevation and annual mean temperature. [Conclusion] There was no significant difference in the α diversity of nitrogen-fixing microorganisms in the Kudzu rhizosphere soil across different geographical regions; while a clear biogeographical pattern of nitrogen-fixing microorganisms was existed. The spatial pattern of the community was jointly affected by the geographic and soil factors; in addition, the effects of the same environmental factor were distinct for different nitrogen-fixing microbial populations.