This study investigates the impact of decadal biochar amendment on soil organic carbon (SOC) accrual and carbon dynamics in upland soils. The researchers introduced fresh organic matter (FOM) to soils with and without a decade-long history of biochar amendment and performed microcosm incubations to evaluate carbon and iron cycling, as well as microbial properties. Key findings include: 1. **SOC Accrual**: Biochar amendment resulted in a 2-fold increase in SOC over a decade, and it reduced FOM-induced CO₂ emissions by approximately 11% during a 56-day incubation. 2. **Iron Cycling**: Biochar facilitated microbially driven iron reduction and subsequent Fenton-like reactions, potentially enhancing microbial extracellular electron transfer and carbon utilization efficiency. 3. **Biotic and Abiotic Processes**: Mineral protection contributed to both microbial carbon accumulation and plant debris preservation, while direct adsorption and occlusion of SOC by biochar particles also played a role. 4. **Microbial Community**: Decadal biochar amendments influenced soil microbial community composition and underlying carbon turnover, with biochar soils showing lower bacterial diversity but higher fungal diversity compared to control soils. 5. **Fenton(-like) Reactions**: The presence of FOM and biochar synergistically boosted hydroxyl radical (OH) generation, indicating a significant role of microbially driven Fenton(-like) reactions in upland soils. 6. **Environmental Implications**: The study highlights the importance of considering soil Fenton-like reactions in uplands, emphasizing the need to reassess microbially extracellular ROS formation pathways in soils. Overall, the research provides insights into the intricate biotic and abiotic mechanisms governing carbon dynamics in long-term biochar-amended upland soils, with potential implications for carbon sequestration and climate change mitigation.This study investigates the impact of decadal biochar amendment on soil organic carbon (SOC) accrual and carbon dynamics in upland soils. The researchers introduced fresh organic matter (FOM) to soils with and without a decade-long history of biochar amendment and performed microcosm incubations to evaluate carbon and iron cycling, as well as microbial properties. Key findings include: 1. **SOC Accrual**: Biochar amendment resulted in a 2-fold increase in SOC over a decade, and it reduced FOM-induced CO₂ emissions by approximately 11% during a 56-day incubation. 2. **Iron Cycling**: Biochar facilitated microbially driven iron reduction and subsequent Fenton-like reactions, potentially enhancing microbial extracellular electron transfer and carbon utilization efficiency. 3. **Biotic and Abiotic Processes**: Mineral protection contributed to both microbial carbon accumulation and plant debris preservation, while direct adsorption and occlusion of SOC by biochar particles also played a role. 4. **Microbial Community**: Decadal biochar amendments influenced soil microbial community composition and underlying carbon turnover, with biochar soils showing lower bacterial diversity but higher fungal diversity compared to control soils. 5. **Fenton(-like) Reactions**: The presence of FOM and biochar synergistically boosted hydroxyl radical (OH) generation, indicating a significant role of microbially driven Fenton(-like) reactions in upland soils. 6. **Environmental Implications**: The study highlights the importance of considering soil Fenton-like reactions in uplands, emphasizing the need to reassess microbially extracellular ROS formation pathways in soils. Overall, the research provides insights into the intricate biotic and abiotic mechanisms governing carbon dynamics in long-term biochar-amended upland soils, with potential implications for carbon sequestration and climate change mitigation.