Restoring vegetation can effectively reduce soil erosion and significantly improve soil properties and quality. To analyze the response of soil organic carbon components and related enzymes to different vegetation types in the northern Loess Plateau, we collected soil samples of four vegetation types: Xanthoceras sorbifolia (XS), Hippophae rhamnoides (HR), Caragana korshinskii (CK), and Grassland (GL). We used these samples to analyze the organic carbon components (i.e., soil organic carbon (SOC), microbial biomass carbon (MBC), easily oxidized carbon (EOC), particulate organic carbon (POC) )and enzyme activities (i.e., amylase, catalase, urease and sucrase). We found that the content of the soil organic carbon fractions and the enzyme activities was greater in the upper layer than in the lower layer for each vegetation type except for MBC and catalase activity, where we observed no significant difference between soil layers. The EOC and amylase of GL vegetation were significantly higher than in other vegetation types. POC, SOC, urease and sucrase were considerably higher in SX vegetation than in other vegetation types. The maximum soil MBC content was found in HR vegetation, and among the four vegetation types, MBC content varied significantly differences in the lower layer, but no significant difference was observed in the surface soil. Correlation analysis demonstrated that the MBC content significantly influenced urease and sucrase activities, and that SOC significantly influenced urease and sucrase activities. These results emphasize the importance of the organic components of soil and the activities of soil enzymes in different kinds of vegetation in the Loess Plateau, providing a basis for improving the sustainable restoration of vegetative ecosystems.

Vegetation restoration can not only preserve soil and water and reduce soil erosion, but also improve soil properties and quality significantly. However, different vegetation types have different effects on soil organic carbon fractions and enzyme activities. In this study, we examined the response of soil organic carbon fractions and enzyme activities to different types of vegetation (i.e., Xanthoceras sorbifolia (XS), Hippophae rhamnoides (HR), Caragana korshinskii (CK), Grassland (GL)) on the northern Loess Plateau. The contents of soil organic carbon (SOC), microbial biomass carbon (MBC), easily oxidized carbon (EOC) and particulate organic carbon (POC) and the enzyme activities (i.e., amylase, catalase, urease and surase) were investigated at the end of plant growth. We found that the content of soil SOC fractions and enzyme activities upper > lower layer in each vegetation types except for MBC and catalase activity. There was no significant difference in MBC content and catalase activity between soil layers. The EOC and amylase of GL vegetation were significantly higher than other vegetation types. POC, SOC, urease and sucrase were significantly higher in SX vegetation than other vegetation types. The maximum soil MBC content was found in HR vegetation, and among the four vegetation types, the MBC content showed significant differences in lower layer, but no significant difference in the surface soil. Correlation analysis showed that the MBC significant influenced on the catalase activities; POC significant affected urease and sucrase activities; SOC extremely significant influenced on the urease and sucrase activities. Therefore, vegetation type was an important factor affecting the change of soil enzyme activities and carbon fractions on the Loess Plateau.