Microbial-mediated soil organic carbon sequestration under biochar application in Chinese agricultural soils

Biochar can enhance soil carbon sequestration. However, the role of microbial mechanisms in regulating these gains remains unclear. This study compiled biochar experiments conducted in China, including 392 observations and 2613 effect sizes related to SOC and microbial attributes, to evaluate the effects of biochar application on cropland soil organic carbon stocks from a microbiological perspective. The estimated national mean cumulative SOC sequestration was 128.9 Tg C, corresponding to a national mean SOC sequestration rate of 0.42 Mg C ha⁻¹ yr⁻¹, and the magnitude of the benefits varied among regions. Microbial trophic strategies had a significant influence on these responses. As the biochar application rate and duration increased, community composition shifted from copiotrophic to oligotrophic, which was associated with a decline in biochar use efficiency. These findings suggest that biochar management strategies need to be adjusted in a timely manner to counteract unfavorable microbial succession and to maintain the stable carbon retention capacity of soil ecosystems.