Effect Of Dominant Grass Loss On Plant Eco-physiological Characteristics And Community Structure In Subalpine Meadows On The Tibetan Plateau

Due to global climate change and human activities,a large number of species have been lost.Loss of species has different effects on ecosystems in different ecological types and ecological processes.In this paper,we removed the combination of Elymus dahuricus,Roegneria kamoji and Leymus secalinus which are dominant grasses in a subalpine meadow on the Qinghai-Tibet Plateau over 7 years,in order to study the effect of dominant species loss on the eco-physiological characteristics of common species include Artemisia tangutica,Geranium wilfordii,Potentilla fragarioides,Viola striatella and Medicago sativa,as well as on the diversity and productivity of community and functional groups.The result showed that:1.The removal of dominant species combination had no significant effect on the net photosynthetic rate(PN)of common species.However,removing dominant species reduced the stomatal conductance(Gs)of Potentilla fragarioides,the water use efficiency(WUE)of Viola striatella and the intercellular CO2 concentration(Ci)of Geranium wilfordii significantly.On the other hand,removing dominant species significantly increased the transpiration rate(E)and the aboveground biomass of Artemisia tangutica.Overall,the responses of the common species to the removal of dominant grass were not significant and these responses were species-specific.2.Removing the combination of dominant grasses did not have a significant effect on the community richness,but increased the forb richness and the magnitude of increase was different in different years.There was no significant effect on the Shannon-Winner index and evenness.However,there were significant differences in the Shannon-Wiener index and evenness in different treatment years.These indicate that there is a competitive effect between dominant species and subdominant species.After two years of removal,this competitive effect was significant,but this competition effect weakens or even disappears with the increase of removal year.3.Removal of dominant grass significantly decreased total community biomass and total coverage,suggested that the remaining plant functional groups did not fully compensate for the lost biomass,supporting the mass ratio theory.