Effects of biochar on bacterial genetic diversity in soil contaminated with cadmium

Abstract

AbstractBiochar has various ecological effects on heavy metal‐contaminated soils. Biochar can be used to passivate the activity of heavy metals and improve environmental conditions for microbial growth. A greenhouse pot experiment was conducted to explore the diversity of microbes in red soil under cadmium (Cd) stress following the application of wheat straw biochar. The contaminant Cd was prepared at 2.5 mg kg‒1 with deionized water to simulate the heavy metal pollution of red soil under natural conditions, and the proportions of wheat straw biochar used were 2.5% and 10%. The complete genetic diversity of red soil bacteria in this study was evaluated using high‐throughput sequencing. The results showed that the bacterial genetic diversity of Cd‐contaminated red soils was restored with biochar treatment, and recovery with 2.5% biochar was significant. Biochar significantly affected the richness of soil bacteria by 6.79%–21.04%. Forty‐three phyla of bacteria, including Proteobacteria, Acidobacteria and Gemmatimonadetes, constituted the bacterial community in the red soils. Further principal component analysis showed that Cd pollution and biochar application collectively affected the bacterial genetic diversity. Hydrogenophaga, Rubrivivax, Haliscomenobacter, Citrobacter, Methylibium and Azospirillum were indicator strains for Cd‐contaminated red soils, while Steroidobacter, Bradyrhizobium, Anaerolinea, Chloronema Dubinina and Gorlenko were key strains for the biochar remediation of Cd contamination. In conclusion, for soil polluted with 2.5 mg kg Cd‒1, the application of 2.5% wheat straw biochar significantly increases soil microbial abundance and genetic diversity and plays an active role in improving the soil micro‐ecosystem.