Analysis of vegetation community structure and productivity of different degraded grasslands of alpine meadows in the Sanjiangyuan area

To study vegetation community structure and productivity status of degraded grasslands in the Sanjiangyuan area of Qinghai Province,the sample areas were set up in different degraded grasslands,and were used to compare the community structure and productivity levels. The result showed that the coverage,biomass and important values of the Cyperaceae plants were significantly lower with the accelerated degradation,whereas there were no significant changes in the indicators of the gramineous plants. All the indicators of weed were increased with the increases of degradation,and the proportion of poisonous grass accounted for the communities showed an ascending trend with the accelerated degradation. Meanwhile,the productivity of the grasslands showed a declining trend.