The changes of main plant communities in Xilingol grassland

Vegetation survey with fixedlocation has important significance to reveal the influence of the climate change and human activities on vegetation. In order to provide reference for the protection and rational utilization of meadow steppe, the field investigation data in 1983 and 2014 which had 31 years interval were analyzed using the methods of summed dominance ratio, relative height, relative coverage, relative abundance, relative frequency, relative weight, community diversity and similarity indices to real the main vegetation communities change in Xilingol meadow steppe under free grazing condition. The results showed that the meadow steppe adjacent to typical steppe shrunk to the east and Xilingol meadow steppe area decreased. The biggest change happened in Filifolium sibiricum steppe whose area decreased and transformed to Stipa baicalensis steppe and Leymus chinense steppe. The tested indices of Gramineae plants representing by S. baicalensis, L. chinense and Cleistogenes squarrosa including dominance, relative height, relative coverage, relative abundance, relative frequency and relative weight increased obviously whereas those of Compositae plants representing by F. sibiricum decreased obviously. There were no significant changes in Margarlef index and the number of families, genera and species. Simpson index, Pielou index and Similarity coefficient significantly decreased (P0.05).