The Relationship Between Plant Species Diversity And Productivity And Their Response To Extreme Drought In Grassland On The Qinghai-Tibet Plateau

Under global warming,the frequency and intensity of extreme weather events(e.g.extreme drought)are increasing.The effects of drought on resistance and resilience of plant communities are influenced by plant biodiversity.However,few studies tested the effects of extreme drought on relationships between species diversity and ecosystem function of alpine grassland communities on the Qinghai-Tibet Plateau.In this study,we selected 8 common grassland plant species in the eastern margin of the Qinghai-Tibet Plateau and constructed plant communities with diversity of 1,2,4 and8 species.In summer,we firstly recorded plant height and flowering numbers at the beginning of drought,we then investigated how plant height,flowering numbers,and aboveground biomass response after a month of drought,and lastly to test plant survival rate and aboveground biomass after a month of rewetting.We found that: 1)Aboveground biomass of plant communities increased with plant community diversity increasing;2)Extreme drought reduced the aboveground biomass of plant communities and each species.The resistance of grasses to extreme drought was stronger than that of non-grass herbs.Before and after drought,there was no significant difference in aboveground biomass of Elymus nutans Griseb.,Elymus nutans Griseb.,Polygonum viviparum L.,and Delphinium kamaonense Huth var.glabrescens(W.T.Wang)W.T.Wang.,while aboveground biomass changes of Deschampsia cespitosa(L.)P.Beauv.,Koeleria litvinowii Dom.and Rumex acetosa L.in the community with the diversity of 4 and 8 speceis were significant,and the aboveground biomass of Veronica eriogyne H.Winki.in the communities with diversity of 1 and 4species was higher than that in the communities with diversity of 2 and 8 species.3)Extreme drought decreased the survival rate of plants in communities,especially in communities with low diversity.In our experiment,drought significantly reduced the survival rate of plants in communities with diversity of 1 and 2 species,but had no significant effects on the survival of communities with diversity of 4 and 8 species.4)Aboveground biomass of plant communities increased tendency with plant community diversity increasing.Extreme drought had the negatively legacy effect on the shoot biomass of plant communities,particularly between the communities in diversity of 2 and 4 species.The resilience of grass species was greater than non-grass species after rewetting.we found that extreme drought can reduce the total aboveground biomass of plant communities and each plant species,but the influence extent on the differs with plants of different functional groups.The resistance of plant communities was greater when plant diversity is higher,however,their resilience probably varied among different plant species.This study explores the response of plant community diversity and ecosystem function to extreme drought and subsequently rewetting,which helps us to better understand the effects of extreme drought events on grassland plant community composition and stability in the Qinghai-Tibet Plateau.These results will play an important role in predicting ecosystem responses to future climate change and guiding the recovery activities of plant communities in grassland.