Global meta-analysis reveals positive effects of biochar on soil microbial diversity

Biochar has gained global attention due to its potential for climate change mitigation and soil quality improvement. Yet, the consequences of biochar additions for soil microbes-the major biotic drivers of soil function-remain unknown across global environmental gradients. We aimed to explore the responses of soil bacterial communities to biochar addition, and further investigate how biochar and soil properties impact these responses. We conducted a global meta-analysis and found that, in general, biochar has a limited impact on the proportion of major bacterial phyla, with only Acidobacteria and Gemmatimonadetes being largely impacted: the relative abundance of Acidobacteria decreased by 14.6%, while that of Gemmatimonadetes increased by 19.8%. Also, the experimental type played a role in shaping the response of microbial community to biochar application. In addition, biochar significantly promoted the diversity of soil bacteria, i.e., genetic richness and diversity. These changes were significantly associated with biochar load, C/N ratio, pyrolysis temperature, biochar pH, as well as soil C/N ratio and pH. We further found that the impacts of biochar on functional diversity, i.e., C substrate richness consumed by soil microbes increased with the biochar load, which might relate to increased genetic richness. Our work suggests that selecting key biochar properties can improve soil quality, microbial function, and climate change mitigation while maintaining the positive impacts of biochar on soil microbial diversity. Further research is needed to link the response of soil microbial composition at the genus level to biochar addition, with microbial functions.

Automated summary

Biochar has limited impact on the proportion of major bacterial phyla, but it significantly promotes the diversity of soil bacteria. The impacts of biochar on soil microbial community are influenced by biochar properties, experimental type, and soil properties such as C/N ratio and pH. Additionally, biochar load affects functional diversity by increasing the genetic richness consumed by soil microbes. Our work highlights the importance of selecting key biochar properties for improving soil quality, microbial function, and climate change mitigation while maintaining microbial diversity.