Objective Investigating the changes of soil enzyme activities and their driving factors in different land types could be used to provide references for vegetation restoration and ecosystem management reconstruction in degraded wetlands, Qinghai Lake, northwestern China.

Method Three study plots involved the lakeside wetlands, grasslands and sandy land were established, and samples at 0−10 cm, 10−20 cm and 20−30 cm soil depth were collected in the Gahai area, Qinghai Lake, respectively. The chemical properties and enzyme activities of soil were analyzed, further redundancy analysis (RDA) was performed to analyze the relationship between chemical properties and enzyme activities of soil by CANOCO 5.0 software.

Result The amounts of soil organic carbon, total nitrogen and dissolved organic carbon and nitrogen in wetlands were significantly higher than that in sandy land, while the amounts of active carbon and ammonium nitrogen in wetland soil were significantly higher than that in grassland and sandy land. Dissolved organic carbon, nitrate nitrogen and available phosphorus in wetlands and grasslands were significantly higher than sandy land. Compared to the wetland, the activities of β-glucosidase, leucine aminopeptidase and glycine aminopeptidase in the soil of grassland decreased significantly by 32.17%, 30.90% and 39.67%, respectively, and those in the soil of the sandy land decreased significantly by 79.22%, 73.46% and 64.84% when comparing with the grassland, respectively. The activities of N-acetyl-glucosaminidase and acid phosphatase in wetland and grassland were significantly higher than those in the sandy land. However, the activities of cellobiohydrolase and alkaline phosphatase in wetland were significantly higher than those in sandy land. The results of redundancy analysis showed that soil dissolved organic carbon and dissolved organic nitrogen were the main factors to influence soil enzyme activity, with the explanatory degree of 58.8% and 29.4%, respectively. Dissolved organic carbon was a major factor explaining the variation of leucine aminopeptidase and acid phosphatase activities, whereas dissolved organic nitrogen was significantly correlated with alkaline phosphatase. A significant positive correlation between organic carbon content and cellobiohydrolase activity was found.

Conclusion Soil organic carbon, nitrogen and soil enzyme activity declined when lakeside wetland degenerated into grassland and sandy land, and soil dissolved organic carbon, dissolved organic nitrogen and organic carbon notably influenced the change of soil enzyme activity.