Straw and its biochar differently affect soil bacteria community composition, co-occurrence network and function in Cd-contaminated soil

Straw and biochar application can improve soil fertility, but the impacts of straw and its biochar on soil microbial communities in Cd polluted soil remain poorly understood. Herein, a pot study was conducted to explore the differences of straw and its biochar on bacterial structure, network complexity and function in Cd-contaminated soil. Rice straw at 0, 1 %, 2 %w/w rate and biochar produced by the same amount of straw were used. Results indicated that biochar decreases while straw improves soil DTPA-Cd contents and the changes are more obvious at higher rates. In particular, the relative abundance of Gemmatimonadota and Nitrospirota decreased with higher straw return but greatly enhanced in biochar amended treatments. The redundancy analysis (RDA) and Mantel test showed that the alterations of bacteria community structure are closely related to the Cd bioavailability. Biochar application enhanced the network complexity by improving nodes, links, average degree and destabilizing the positive cooperation. Biochar further enhanced the amino acid metabolism, replication and repair and some other functions, making the community more advantageous to adapt to Cd stress. Overall, our results suggested that biochar is more competitive in regulating soil Cd bioavailability and enhancing the network complexity of bacterial community in Cd-contaminated soil.