Biochar application increases soil organic carbon sequestration in grassland

Global climate change and human activities have exacerbated the degradation of grassland ecosystems, which has involved substantial losses of soil organic carbon (SOC). Biochar is a material that may be used to enhance SOC sequestration and mitigate the effects of climate change. This review systematically synthesizes the research from 2014 to 2024, integrating a literature analysis, meta-analysis, and representative field experiments to explore the mechanisms through which biochar application influences SOC sequestration in grasslands from multiple dimensions. Specifically, this study covers the following aspects: 1) the effects of biochar on regulating the physicochemical properties of the soil, such as bulk density, pH, porosity, and aggregate structure; 2) the biological effects of biochar application on grassland vegetation (plant productivity, litter decomposition, and root exudation) and soil biota (microbial community structure, enzyme activity, and soil fauna diversity); 3) the influence of biochar on the SOC pool (particulate and mineral-associated organic carbon), priming effects, and soil respiration through altering the dynamic balance between carbon inputs (plant-derived carbon) and outputs (microbial decomposition). The findings indicate that biochar application improves the soil structure, enhances nutrient cycling, shapes the rhizosphere microenvironment, promotes plant growth, regulates microbial metabolism, and influences soil fauna activity in grassland environments, ultimately contributing to SOC stabilization and accumulation. However, the effects of biochar use vary depending on the biochar feedstock, pyrolysis temperature, application rate, and soil type; and the long-term effects require further validation. This review clarifies the critical role of biochar in grassland SOC management and provides a theoretical basis for optimizing biochar production processes and scientifically developing application strategies. Such insights are essential for restoring degraded grasslands and achieving global carbon reduction goals. Future studies should integrate long-term multiscale field observations, molecular biology techniques, and modeling approaches to identify the dynamic interactions within the biochar-soil-biota system, thereby expanding the application of biochar in grassland ecosystems.