Effects of biochar addition on aeolian soil microbial community assembly and structure

The effects of biochar on soil improvement have been widely confirmed, but its influence on soil microorganisms is still unclear. Elucidating the complex relationship and the community assembly processes of microorganisms under biochar addition is important to understand the ecological effects of this substance. We performed a one-time addition of biochar on aeolian soils and planted maize (Zea mays L.) continuously for 7 years. Afterwards, soil samples were collected, and the 16S/ITS rRNA gene sequencing technology was used to study changes in microbial community structure, network characteristics, and community assembly processes in the aeolian soils. We found that biochar addition significantly increased the maize yield and changed the soil microbial community composition (β-diversity), but had no significant effect on the microbial α-diversity. The addition of 31.5-126.0 Mg ha^-1 of biochar led to a reduction of the rhizosphere bacterial network's edge number, average degree, and robustness, but had no significant effect on the fungal network properties. The bacterial community was controlled by deterministic processes, while fungi were mainly controlled by stochastic processes. The addition of 126.0 Mg ha^-1 of biochar led to a transformation of the bacterial community's assembly processes from deterministic to stochastic. These results indicate that the stability of the rhizosphere bacterial community's complex network in aeolian soils diminishes under biochar addition, together changed the bacterial community's assembly processes. Fungi can instead effectively resist the environmental changes brought by biochar addition, and their network remains unchanged. These findings help clarify the effect of biochar addition on microbial interaction and assembly processes in aeolian soils characteristic of arid regions. KEY POINTS: • Biochar addition led to changes in the microbial community composition • Biochar addition reduced the network's stability of rhizosphere bacteria • Biochar addition changed the processes of the bacterial community assembly.