The study investigates the impact of soil acidification on soil carbon sequestration in highly acidic subtropical forests in southern China. The researchers conducted a 11-year field experiment to assess how elevated acid deposition affects the accumulation of soil organic carbon (SOC) and its two components: particulate organic carbon (POC) and mineral-associated organic carbon (MAOC). Key findings include: 1. ** increased POC and MAOC**: Both POC (0–20 cm) and MAOC (10–20 cm) significantly increased with acid addition. 2. **Microbial Contributions**: Acid addition reduced the contributions of fungal, bacterial, or total microbial residue carbon to SOC but increased plant-derived soil carbon in both soil depths. 3. **Lignin Phenols and Soil Microbes**: The increase in lignin phenol levels and the suppression of soil organic matter decomposition by soil microbes suggest that soil POC increased with acid addition. 4. **Mineral Protection**: Soil acidification strongly enhanced MAOC accumulation through increased lignin and mineral protection by iron–aluminum oxides and cations. The study concludes that increased mineral protection of plant-derived carbon is the dominant driver of increased SOC sequestration under acid addition. This finding provides new insights into the mechanisms of SOC accumulation in highly acidic subtropical forests and the interactions between plants, soil, and minerals under increasing acid deposition.The study investigates the impact of soil acidification on soil carbon sequestration in highly acidic subtropical forests in southern China. The researchers conducted a 11-year field experiment to assess how elevated acid deposition affects the accumulation of soil organic carbon (SOC) and its two components: particulate organic carbon (POC) and mineral-associated organic carbon (MAOC). Key findings include: 1. ** increased POC and MAOC**: Both POC (0–20 cm) and MAOC (10–20 cm) significantly increased with acid addition. 2. **Microbial Contributions**: Acid addition reduced the contributions of fungal, bacterial, or total microbial residue carbon to SOC but increased plant-derived soil carbon in both soil depths. 3. **Lignin Phenols and Soil Microbes**: The increase in lignin phenol levels and the suppression of soil organic matter decomposition by soil microbes suggest that soil POC increased with acid addition. 4. **Mineral Protection**: Soil acidification strongly enhanced MAOC accumulation through increased lignin and mineral protection by iron–aluminum oxides and cations. The study concludes that increased mineral protection of plant-derived carbon is the dominant driver of increased SOC sequestration under acid addition. This finding provides new insights into the mechanisms of SOC accumulation in highly acidic subtropical forests and the interactions between plants, soil, and minerals under increasing acid deposition.