Soil carbon fractions and enzyme activities under different vegetation types on the Loess Plateau of China

Vegetation restoration was effective way of protecting soil erosion and water conservation on the Loess Plateau. Carbon fractions and enzyme activities were sensitive parameters for assessment of soil remediation through revegetation. Forest, forest steppe and grassland soils were collected at 0–5 cm and 5–20 cm soil layers in Yanhe watershed, Shaanxi Province. Urease, sucrase, alkaline phosphatase, soil organic carbon (SOC), microbial biomass carbon (MBC), easily oxidized organic carbon (EOC) and dissolved organic carbon (DOC) were measured. The results showed that carbon fraction contents and enzyme activities in the same soil layer followed the order that forest was higher than others. Carbon fraction contents and enzyme activities appeared that the 0–5 cm was higher than 5–20 cm soil layer. In addition, correlation analysis showed that urease activity was related to SOC, MBC, EOC and DOC at 0–5 cm layer; it was correlated with SOC, MBC and EOC at 5–20 cm layer. Sucrase activity had significant positive relationship with SOC, MBC and EOC. Alkaline phosphatase activity was related to EOC and DOC at 0–5 cm layer; it was correlated with MBC and EOC at 5–20 cm layer. The CCA reflected the relationship between sucrase activity and SOC. The contributions from the various forms of carbon fractions and enzyme activities as evaluated by the canonical coefficient of CV were on the order of SOC > DOC > MBC > EOC; sucrase > urease > alkaline phosphatase. Vegetation type was an important factor influencing the variation of soil enzyme activities and carbon fractions on the Loess Plateau.