Community Structure And Degradation Mechanism Of Riparian Vegetation In Lake Qinghai Basin

Lake Qinghai, the important international wetland, is of great importance for protecting the ecology safety of northeast Qinghai-Tibet plateau. The vegetation degradated during the past decaeds of years due to climate change, overgrazing and human activity. River is the main wetland type of Lake Qinghai basin, and the degradation of riparian vegetation threated not noly the ecosystem health of of river system but also the eco-environment safety of Lake Qinghai basin, so the study on the community structure and degradation mechanism of riparian vegetation in Lake Qinghai basin not only can provide scientific basis for the study of riparian vegetation degradation but also is helpful to vegetation restoration, and so as to make sure that the social economy of the basin has a healthy development.Based on the samples of the riparian vegetation of Lake Qinghai basin, the community structure, biodiversity and niche of riparian vegetation was studied, and also the energy balance and microclimate of riparian vegetation was studied by the data of microclimate and soil evaporation. The cause of vegetation degradation was studied by analyzing the climate change of Lake Qinghai basin, streamflow of Shaliu river, stable infiltration and saturated hydraulic conductivity on the banks of Shaliu river, here are the key conclusions.1. The herbosa raparian vegetation on the banks of Shaliu river was classified into 12 kinds of different groups, and shrubs was classified into 3 kinds of different groups. The distribution of herb communities has a sigificant correlation with altitude and soil salt content, while the fruticetum was not sigificant affected by the distance to Lake Qinghai along Shaliu river and the vertical distance to river.2. The shrub's changing trend of the 5cm underground soil heat flux is the same as the canopy net radiation, while the grassland has an one hour time lapse compared to shrub, the sensible heat flux of shrub and grassland is negative during the daytime, while the latent heat flux is positive. During the growing season, the daily evapotranspiration of shrub is 0.7mm lager than grassland, and the monthly evapotranspiration of shrubs is 148.7~223.6mm, while the grassland is 146.2~179.3mm, the water consumption of shrub evapotranspiration is supplied by the streamflows of Shaliu river, while the grassland by the precipitation.3. Almost all the herbosa have a great value of diversity index, species richness and species evenness, while the shrubs have a small value of diversity index, species richness and species evenness. The herbosa of the raparian vegetation shows the small similarity index , while the shrubs shows the big similarity index. Almost all the herb dominant species have the great niche overlap, so dose all the shrub dominant species but Salix qinghaiensis Y.L.Chou.4. The vegetation degradation is mainly caused by overgrazing in this area, and overgrazing can cause the decrease of the biomass and the change of community composition. The rise of temperature and the streamflow change of Shaliu river can affected the biomass and degradation of the riparian vegetation, and moreover the vegetation degradation can also affected by construction and grassland rodent.5. Enclosure, planting and optimum stock capacity are the main reparation method in the study area, and during the reparation species with palatability and wide niche breadth can be selected to plant, and the natural distribution law of the species should be followed. The streamflow should be kept more than 0.075 billion m3, and prevent and cure the grassland rodent and poisonous weeds and reduce the damage to riparian by human should also be the effective method.