Effect of the Duration of Abandonment Management on Soil Organic Carbon and Its Fractions of Phyllostachys edulis Forests

To investigate the effect of the duration of abandonment on soil organic carbon (SOC) content and its fractions in Phyllostachys edulis forests, this study selected typical P. edulis forests in Zhejiang Province, using plots with abandonment durations of 0 years (CK), 2～5 years (U-I), 7～10 years (U-II), and 11～14 years (U-III). The total SOC, mineral-associated organic carbon (MOC), non-easily oxidizable organic carbon (NEOC), recalcitrant organic carbon (ROC), easily oxidizable organic carbon (EOC), dissolved organic carbon (DOC), and microbial biomass carbon (MBC) contents in the 0～15 cm soil layer were determined, and the driving factors were analyzed in combination with soil physicochemical properties. The results showed that with the increasing years of abandonment, SOC content exhibited an upward trend. Among the six carbon fractions, NEOC showed the greatest increase, while changes in MOC, ROC, and other fractions were not significant or fluctuated only slightly. In terms of the proportions of fractions, the proportions of MOC and EOC decreased while the proportion of NEOC increased after abandonment, indicating that abandonment promoted the transformation of soil organic carbon toward more stable forms. Stepwise regression analysis revealed that soil total nitrogen was the primary environmental factor affecting SOC changes. The results provide a scientific basis for the effective management and enhancement of carbon sink function of P. edulis forests.