Effects of enclosure on plant community structure and quality in desert steppe

In order to monitor the different lots restoration of desert steppe and the influence of poisonous plant on enclosed steppe in Yanchi County of Ningxia Province, a piece of steppe with same restoration years and ways was chosen as an experimental field. Within the experimental field there were 4 plots being selected to investigate the vegetation according to growth of poisonous plants in each plot. Basic characteristics of communities were investigated by quadrat survey; and PCA sort method, correlation analysis and a linear regression model were used to analyze data obtained from the experimental field. Results showed that after 9 years of fencing, although composition species of communities did not change a lot, dominant species changed significantly in each plot; and there were different dominant species in different plots with different recovery rates. A large number of miscellaneous toxic grasses reduced the total cover of vegetation, species abundance, biomass of good forage and dominance of dominant species, so that the community structure presented simplificative and pasture growth patterns of clusters were promoted. The natural recovery process of grassland systems can not significantly control the growth and reproduction of poisonous plants, such as Cynanchum komarovii and Oxytropis aciphylla. Therefore, human being should give appropriate disturbance during the restoration of desert steppe.