Response of soil specific enzyme activity to vegetation restoration in the Loess hilly region of China

It is well-established that changes to land use changes affect soil enzyme activity; however, little is known about the changes in soil specific enzyme activity per unit soil organic carbon (SOCE) and soil microbial biomass carbon (MBCE) after vegetation restoration in the arid and semi-arid regions of China. The objectives of this study were to investigate the effects of long-term vegetation restoration on soil specific enzyme activity and to elucidate the relationship between specific enzyme activity and soil organic carbon (SOC) stability in the Loess hilly region of China. We determined three enzymes (saccharase, urease, and phosphatase) activity at 0-50 cm soil depths in plots under vegetation restoration for different lengths of time and supporting different vegetation types (grassland, 2-30 recovery years; shrubland, 5-47 recovery years; and forestland, 5-56 recovery years). SOCE and the geometric mean of enzyme activity (GMEA) at 0-20 cm depth initially increased and then decreased, whereas overall MBCE at 0-10 cm depth decreased with time. Overall, SOCE and GMEA decreased with soil depth, and were significantly and negatively correlated with SOC stability index (SI). In comparison, the relationship between MBCE and SI was non-significant. Overall, our data showed that specific enzyme activity and GMEA responded to vegetation restoration, with SOCE and GMEA negatively impacting SOC stability.