Variation in soil organic carbon stability and driving factors after vegetation restoration in different vegetation zones on the Loess Plateau, China

Vegetation restoration is considered to be an important pathway for ecosystem improvement; however, information remains limited about how the soil organic carbon (SOC) stability changes after vegetation restoration. This could be evaluated by measuring the response of SOC stability to soil physicochemical properties, soil enzyme activity, and environmental factors [recovery years, vegetation types, mean annual precipitation (MAP) and mean annual temperature (MAT)]. Here, the soils of shrub and forest land in different vegetation zones (steppe zone [SZ], forest-steppe zone [FSZ], and forest zone [FZ]) in the Loess Plateau of China were evaluated over different time periods. As the number of years increased, the active carbon fractions [very labile (Cl) and labile (C2) fractions of oxidizable carbon] and carbon management index (CMI) increased, whereas the SOC stability index (SI) decreased for both vegetation types in the three vegetation zones. However, the factors driving the changes in SOC stability varied with respect to the vegetation type and zone. Specifically, the rate of change in active carbon fractions was greater in FZ, whereas the rate of change of SI was higher in FSZ, and was correlated with higher MAP and MAT. Overall, the SOC stability decreased after vegetation restoration, with MAP, MAT, vegetation type, and years of recovery representing the main factors driving the changes in SOC stability. These results are expected to facilitate future studies on SOC aimed at enhancing the management of different vegetation zones during recovery in the Loess Plateau of China, in response to global climate change.