Succession and Changes of Grassland Quality of the Artificial Grassland Communities in Subalpine Meadow in Gannan

The investigation dealt with the changes of the community structure as well as its cause of change, also with the quality of the artificial grassland sown with Elymus nutans at different time in the subalpine meadow in Gannan. The results are described as follows. 1. The aboveground biomass of E. nutans in the 2 year-old artificial grassland was highest and the index of grassland quality (IGQ) was highest in the 2 and 3 year-old communities, whereas it decreased in the other communities. IGQ was the lowest in the 7 year- o1d community. 2. The number and diversity of E. nutans species in the artificial grassland communities increased with the age increase of the communities but differed in their patterns of increase. 3. The decrease in biomass of E. nutans and IGQ correlated with the decrease of available phosphorus and not with the concentration of nitrogen in soil. The time for utilization of the artificial grassland with E. nutans could be lengthened by additional phosphorus supplement in soil.