A synergistic system based on N-doped biochar mitigates soil greenhouse gas emissions through microbial functional remodeling

The synergistic application of N-doped biochar, arbuscular mycorrhizal fungi, and wood vinegar (WMUMB) represents a promising strategy for mitigating soil greenhouse gas emissions. However, the mechanisms by which this treatment regulates soil microbial communities and modulates CO 2 , CH 4 , and N 2 O emissions remain poorly understood. Here, high-throughput sequencing and multiple biochemical analyses were employed to compare soil microbial community structure, functional gene profiles, and greenhouse gas fluxes between modified biochar alone (UMB) and the WMUMB treatment. The results showed that biochar derived from Chinese fir branches exhibited a well-developed microporous structure and abundant nitrogen- and oxygen-containing functional groups. Lignin/CRAM-like compounds dominated soil dissolved organic matter across all treatments. Relative to UMB treatment, the WMUMB treatment significantly reduced global warming potential by 46.53%. This treatment increased nosZ abundance while decreasing the ( nirK + nirS )/ nosZ ratio, suggesting a microbial functional shift toward enhanced N₂O reduction and reduced net N₂O emissions. A two-year pot experiment demonstrated the sustained reduction efficiency of WMUMB treatment on soil CO₂ emissions, with only a 5.2% decrease in mitigation efficiency during the second year compared with the first year. Collectively, this study provides insights into the multiple pathway-mediated synergistic mechanisms of WMUMB through microbial functional remodeling and highlights its potential for low-carbon biomass residue utilization and sustainable soil management.