[Response of Black Soil Organic Carbon Pool to Long-term Tillage and Its Evolution Characteristics]

To explore the response of the black soil organic carbon pool to long-term tillage and its evolution characteristics， a field experiment initiated in 1983 was used to study the effects of conventional tillage （CT）， no-tillage （NT）， subsoiling tillage （ST）， and moldboard plowing tillage （MP） on the active organic carbon components and carbon pool in the 0-40 cm soil layer in 2013 and 2022. The results indicated that compared to those under the CT treatment， the NT， ST， and MP treatments significantly increased the organic carbon （SOC）， readily oxidizable organic carbon （ROC） content， and carbon pool management index （CPMI） in the 0-40 cm soil layer in 2013 and 2022， with average increases of 11.92% to 31.89%， 25.64% to 48.72%， and 30.57% to 80.32%， respectively， with the MP treatment showing the highest increase. ST significantly increased the particulate organic carbon （POC） content compared to that in other treatments， with an increase of 13.20% to 52.15%. Compared to those in 2013， all treatments significantly reduced the POC， ROC content， and CPMI in the 0-40 cm soil layer in 2022， with the NT and ST treatments showing the largest and smallest decreases， respectively. The CT and NT treatments also significantly reduced SOC content， while the ST treatment increased SOC content by 10.71%. Redundancy analysis and structural equation modeling indicated that the activities of soil amylase， β-glucosidase， cellulase， and lignin peroxidase were the main factors affecting the changes in POC， ROC content， and CPMI. In summary， long-term MP resulted in the highest SOC content in the 0-40 cm soil layer， with enhanced stability， maintaining the highest carbon pool management index， which is more beneficial for SOC sequestration in black soil farmland. Under the drive of long-term tillage， the black soil organic carbon pool showed a degradation evolution characteristic， with the NT showing the greatest degradation， while ST and MP had better degradation control effects.