Abstract: In order to examine the restoration effect of exclosure on desert steppe, an investigation was carried out on the plant communities in a degraded grassland after 9-year exclosure in Yanchi County of Ningxia. A total of 34 plant species were recorded, including 12 families and 27 genera. As compared with those before exclosure, the plant species composition after exclosure had less change, but the common species and constructive species changed remarkably. By using PCA ordination and hierarchical clustering methods, the 80 quadrats investigated were grouped into 3 plant formations, i.e., Stipa bungeana, Pennisetum centrasiaticum, and Leymus secalinus, which were characterized by arid, mesophytic, and light salinization habitats, respectively, according to the biological characteristics of the constructive or dominant species. These three plant formations belonged to different succession stages, with the S. bungeana formation as a reaction stage and the L. secalinus formation as a higher stage. There was a strong competition on resources between these formations, and wind erosion could expand L. secalinus formation. Therefore, the rational regulation of grazing time in S. bungeana formation and L. secalinus formation by rotation grazing could improve the use efficiency of the grassland, and decrease the expansion risk of L. secalinus formation.

Key words: Mine soils, Heavy metal pollution, Soil microbial characteristics, Community structure