Variations on the diazotrophic community in the rhizosphere soil of three dominant plant species in a lead-zinc mine area

AimsThe aims of the current study were to understand the variation in the abundance, diversity and structure of the diazotrophic communities in the rhizosphere soil of these three dominant plant species around Siding Pb-Zn mine.MethodsThree dominant plant species (Pteris vittata, Miscanthus floridulus and Phragmites australis) were randomly selected, and rhizosphere soils were sampled from the rhizosphere of the plants.ResultsThe nifH gene abundance in the rhizosphere soil of Pteris vittata was the highest among the three plant species. Variations in rhizosphere soil diazotrophic communities were mainly due to the changes in soil nutrient contents through plant-soil system interactions. Diversity and structure of soil diazotrophic communities, including Alphaproteobacteria, Deltaproteobacteria and Cyanobacteria, were strongly influenced by soil heavy metals, ammonium nitrogen, soil moisture and available phosphorus contents. In addition, soil enzymes, especially urease, protease and alkaline phosphatase activities, also contributed to the structure of the diazotrophic communities. Alphaproteobacteria and Cyanobacteria play vital roles in the soil biological nitrogen fixation process. Heavy metal enrichment in mines provides electron donors for diazotrophs to support their activities in harsh environments. Diazotrophs can provide N to support plant growth in mines to help restore heavy metal-containing soil by dominant plants.ConclusionsOur results showed the variations in diazotrophic community compositions in rhizosphere soil of three dominant plants and their impact on heavy metal accumulation. This study will help to determine the role and importance of soil properties and plant species in the soil biological nitrogen fixation process in highly contaminated mine areas.