The changes of soil quality as affected by different land use in plant communities of Southern Ningxia Loess Hilly Region

The soil quality variation of typical plant communities under different uses was studied in South Ningxia mountainous area. The result indicated that under two land utilization in the Stipa bungeana community, reclamation reduced organic matter, total nitrogen (N), total phosphorus (P), available N, available P, available potassium (K) by 19.5%, 20.1%, 17.6%, 13.0%, 77.8% and 47.5%, respectively, compared with enclosed land soil. Soil urase activities of reclamation land was greater than enclosed land, but sucrase activity was lower. There was no significant difference in neutral phosphatase. (2) Under three soil use patterns in Artemisia sacrorum community, the contents of organic matter, total N, total P, available N, available P and available K were increased in grazing land soil compared with enclosed land soil and reclaimed land soil. The urase and sucrase contents in the grazing land soil were the highest, followed by enclosed land soil and reclaimed land. The urase activity had small change in different layers, with the highest being 177.6 mg/(kg.h) in the surface layer of grazing land soil and the lowest being 114.5 mg/(kg .h) in sublayer of reclaimed land. The sucrase activity was significantly different in different layers, with the surface layer being about 3 times higher than sublayer. The neutral phosphatase of the reclaimed land was higher than the enclosed land soil. Soil micro-aggregates under Stipa bungeana community in the surface layer was better for enclosed land soil than reclaimed land soil. Soil micro-aggregates under Artemisia sacrorum community in the different land utilization ways differed. Structural coefficient of surface layer soil was bigger than sublayer soil, and maintenance coefficient for surface lay was less than sublayer. The structure coefficient and the maintenance rate of the enclosed land were greater than the grazing land, which was greater than farmland. In mildly herd condition, soil nutrient contents and enzyme activity were enhanced, but the structure coefficient and the maintenance rate of soil micro-aggregates were obviously reduced.