Dynamics of soil active organic carbon fractions during Salix cupularis shrub restoration in alpine grasslands of northwestern Sichuan

Context Soil active organic carbon, the labile fraction of soil organic carbon (SOC), serves as a sensitive indicator of soil health. However, its dynamics under long-term restoration in SOC-depleted sandy soils remain poorly understood. Aims To unravel how multi-decadal Salix cupularis shrub restoration (0–34 years) in alpine desertified grasslands of northwestern Sichuan modulates soil active organic carbon fractions – dissolved organic carbon (DOC), microbial biomass carbon (MBC), and readily