Biochar improves soil organic carbon stability by shaping the microbial community structures at different soil depths four years after an incorporation in a farmland soil

Soil organic carbon (SOC), mineralization and microbial community structures were investigated at different depths of farmland soils 4 years after a single biochar amendment. Biochar increased SOC at 0-20cm (10.7%) and 20-40cm (24.9%). Mineralization decreased with depth and further decreased 12.3% (0-20cm), 8.5% (20-40cm) and 30.5% (40-60cm) with biochar amendment. Subsoils selected for oligotrophs (e.g., Chloroflexi, Acidobacteria) associated with lower mineralization rates and limited copiotrophs (e.g., Proteobacteria, Ascomycota) which exhibit higher respiration rates. Biochar enhanced oligotrophs in topsoil and restricted copiotrophs at all depths. This demonstrates how biochar increases SOC stability by changing microbial community structures at different depths.