Characteristics of soil enzyme in artificially-established forest of Zhifanggou valley in north of Shaanxi

The characteristics of soil enzyme activities and the relationships between soil enzyme activities and soil nutrients were studied in artificially-established forest on Loess Hilly-Gully region in order to explain the function of artificially-established forest in soil nutrients transformation and fertility status improvement in north of Shaanxi. Three soil enzyme activities of different soil layers in typical artificially-established forest with black locust (Robinia pseudoacacia), Chinese pine (Pinus tabulaeformis), Caragana (Caragana korshinskii) and mixed of Caragana and black locust were studied. Comparing with Caragana pure forest, the activities of soil invertase and alkaline phosphatase increased by 56.81% and 15.89%, respectively, in mixed forest of Caragana and black locust. Geometric mean of three enzyme activities under 31 a black locust were 1.19 and 1.57 times of that under 20 a and 18 a black locust, respectively. Geometric mean of three enzyme activities under 31 a black locust was 1.36 times of that under 30 a Chinese pine. Geometric mean of three enzyme activities in three-year- uncultivated land decreased by 37.89% compared with farm land. There were positive correlations between soil organic carbon, available phosphorus, and available nitrogen and soil invertase, alkaline phosphatase, urease activities, respectively. These results revealed that artificially-established forest was able to significantly improve topsoil enzyme activities.