Abstract: The Qinghai Lake is located in the northeastern part of the Qinghai-Xizang Plateau. It is the largest inland saline lake in China and an important international wetland. It is also of great importance for protecting ecology in the northeast Qinghai-Xizang Plateau. The steppe in the Qinghai Lake Basin is an important component of terrestrial ecosystems and plays a significant role in biodiversity and ecosystem functions. The vegetation and its distribution in this region is affected by the existence of Qinghai Lake and complicated landscape features. The vegetation was degenerated during the past decades due to climate change, overgrazing and human activities, and the richness of plant species in the area was low. The study on the structure of plant communities in Qinghai Lake Basin can provide a scientific basis for researching the degeneration of riparian vegetation. This research would provide a valuable reference for protecting the biodiversity of the steppe and maintaining the grazing ecosystem functions in the headwaters of the three rivers. Therefore, some field samples were surveyed around the Shaliu River in the Qinghai Lake Basin. Plant communities, aboveground biomass productivity and species diversity in the different locations of the Shaliu River Basin were analyzed, and the factors related to the plant communities were lucubrated. Thirteen experimental locations were selected with altitude ranging from 3 200 m to 3 500 m. The research results were as follows: (1) There were 52 plant species in 39 genera and 13 families in the study area. The species richness, aboveground biomass and average vegetation coverage were significantly different from the different sample plots. The average vegetation coverage was 70%, and the average aboveground biomass was 131 g•m^-2. The similarity of species was studied by using Cooccurrence Jaccard Index（CJ）.The result revealed that the value of CJ was decreased with the increase of distance between two profiles. The spatial variability is mainly affected by the local environment conditions; (2) The ShannonWiener index, species richness, species evenness index and aboveground biomass were increased at first and then decreased slight with increasing the distance of sample plots away from the lake, but the average vegetation coverage was increased at first, and then unchanged. Soil moisture content, soil salt content, altitude, [WTBX]etc[WTBZ]. may be the main factors resulted in the difference of spatial distribution of plant communities; (3) There was an inconspicuous linear correlation among the ShannonWiener index, species richness and aboveground biomass.

Key words: meadow, plant community structure, species diversity index, aboveground biomass, dominant species, Shaliu River, Qinghai Lake Basin