Stability Of Plant Communities And Their Driving Mechanisms In Alpine Grasslands,Qingzang Plateau

The Qingzang Plateau(QZP)is the highest plateau on earth,an important ecological security barrier in China,with an exceptionally sensitive ecosystem that is an indicator and regulator of global climate and ecological changes.Alpine meadows and alpine steppes,accounting for more than 60% of the total area of the plateau and playing a vital role in maintaining the ecosystem functions of the QZP,are two main types of grasslands on the QZP.In recent years,the climate of the QZP has continued to change,which has greatly affected the composition,structure and function of plant communities in alpine grassland.Maintaining the stability of plant communities has a profound impact on the ecological service capacity and sustainability of alpine grassland ecosystems.However,whether and how biotic and abiotic factors affect the community stability in alpine grassland ecosystem along a natural hydrothermal gradient has no unified conclusion.We therefore hypothesize that to test this assertion.In this study,we conducted field investigations on plant community characteristics and soil physicochemical properties of two major vegetation types,including alpine meadows and alpine steppes,on the QZP,and calculated the temporal stability of plant communities in alpine grasslands by the enhanced vegetation index(EVI)from 2001 to 2020.We investigated the effects of plant species diversity,soil microbial diversity,and soil physicochemical properties on the stability of plant communities in alpine meadows under climate change.The aim was to provide a scientific basis for the sustainable development of alpine grasslands on the QZP.(1)The maximum value of plant community stability in alpine meadow was 24.32,the minimum value was 3.95,and the mean value was 10.73,while the maximum value of plant community stability in alpine steppe was 19.90,the minimum value was 2.79,and the mean value was 8.27.One-way ANOVA results showed that the stability of plant community in alpine meadow was significantly greater than that of alpine steppe(P < 0.01).(2)While community stability in alpine meadow increased with annual mean precipitation(AMP),community stability in alpine steppe was not significantly affected by precipitation.Annual mean temperature(AMT)significantly reduced plant community stability in alpine steppe and had no significant effect on plant community stability in alpine meadow.Thus,precipitation is the dominant factor affecting plant community stability in alpine meadow,while temperature is the key climatic factor maintaining plant community stability in alpine steppe.(3)The stability of plant communities in alpine meadow was highly significantly correlated with SR,Shannon-wiener diversity index and Simpson dominance index(P<0.01)and with Pielou index(P<0.05).However,the correlations of community stability with CWM＿LN,CWM＿LC,CWM＿LP,CWM＿H,and functional group asynchrony were not significant.Community stability in alpine steppe was significantly correlated with CWM＿LN,CWM＿LN,CWM＿LN and functional group asynchrony(P < 0.05),while SR,Shannon-wiener index,Simpson index and Pielou index had no significant effect on stability.(4)The community stability of alpine meadow was significantly correlated with SOC and p H(P < 0.01),but not with STP,STN,SWC,SBD and SAP.The community stability of alpine steppes was not significantly correlated with SOC,p H,STP,STN,SWC,SBD and SAP,but Chao1 index significantly increased the community stability of alpine steppe(P <0.01).(5)AMP explained 32.42% of the variation in community stability in alpine meadow,species diversity explained 38.49%,SOC explained 39.17% of the variation in community stability in alpine meadows,and p H explained 29.43%.AMT explained 14.46% of the variation in community stability in alpine steppe,the leaf nutrient content of plant communities explained 5.53% of the variation in community stability,plant functional group asynchrony explained 3.55%,and Chao1 index explained 14.72% of the variation in community stability in alpine steppe.A structural equation model suggested that AMP indirectly affected the community stability of alpine meadow by increasing species diversity and SOC,with path coefficients of 0.29 and 0.54,respectively,and the highest total effect of precipitation on the stability of alpine meadow communities was 0.45.The community stability of alpine steppe was mainly regulated directly by AMT and Chao1 index.Chao1 index had a significant positive effect on community stability(P < 0.01)with a path coefficient of 0.35,while AMT had a significant negative effect on alpine steppe community stability(P < 0.01),and AMT index had the highest total effect on community stability with-0.36.