[Carbon Stability of Biochar and Its Effects on Soil Organic Carbon Mineralization in Coastal Wetlands]

Biochar has a significant influence of both enhancing carbon sequestration in coastal wetlands and reducing greenhouse gas emissions. However, the carbon sequestration potential of biochar and the pathways that influence soil organic carbon （SOC） mineralization are still unclear. Biochar carbon stability experiments revealed the carbon sequestration potential of biochar prepared using different pyrolysis temperatures. Additionally, the effects and pathways of different biochar additions （0%, 0.1%, 1.5%, and 3%） on the mineralization of SOC were explored through soil mineralization experiments and a path model. The results showed that as the preparation temperature of biochar increased from 300℃ to 600℃, the carbon loss due to chemical oxidation decreased from 46.82% to 14.11%, and the microbial mineralization amount decreased from 3.5% to 0.2%, suggesting that the carbon sequestration potential of biochar at 600℃ was better. Soil mineralization experiments were conducted using 600℃ biochar. The addition of 1.5% biochar resulted in the lowest mineralization rate. The use of biochar increased the SOC content by 1.83 to 3.94 times and decreased the accumulated mineralization amount by 3.43% to 19.1%. The partial least squares path model was used to quantify and reveal the pathways of biochar affecting SOC mineralization in coastal wetlands, as follows： Biochar released a high content of stabilized carbon that is not easily utilized by microorganisms, leading to a low mineralization rate, and biochar increased the content and stability of macroaggregates that physically encapsulated the SOC, promoting carbon sequestration and inhibiting SOC mineralization. This study showed that enhancing the carbon stability of biochar and inhibiting SOC mineralization can enhance the carbon sequestration capacity of coastal wetlands.