Patterns And Drivers Of Diversity Of Early Spring Annual Ephemeral Plants In Xinjiang

As one of central issue in community ecology,variation of plant diversity and community composition were widely explored in a large of ecosystems.The existing research findings have integrated hundreds of hypotheses,such as climate hypothesis and water energy dynamic hypothesis to reveal the formation mechanism of large-scale pattern of species diversity.However,most of these researches focus on the impact of single factor on species diversity,while their effects and relative importance on plant diversity is still unknown due to lack of comprehensive study.Here this study used the survey data of species richness across32 sites in 2017 and 2018 for early spring annual ephemeral plants(ESAE)in Xinjiang,to explore relationships of mean species richness(SR)of ESAE with elevation,climate(annual mean temperature,precipitation in winter,precipitation from February to May and anomaly of precipitation from February to May since The Last Glacial Maximum),soil nutrients availability(p H;soil organic carbon,SOC;total nitrogen,TN;total phosphorus,TP;ratio of SOC to TN,C:N;ratio of SOC to TP,C:P,ratio of TN to TP,N:P)and AGB on the scale of space and time.The main conclusions are as follows:Spatial distribution and influential factors of early spring annual ephemeral plants:(1)SR of ESAE exhibited a significant unimodal pattern with increasing elevation,annual mean temperature,precipitation from February to May,anomaly of precipitation from February to May since The Last Glacial Maximum,soil p H,C:N and AGB,but decreased firstly and then increased with increasing precipitation in winter.(2)Elevation,climate and soil nutrients availability could affect SR of ESAE via their direct and indirect effect by altering AGB.(3)These findings have demonstrated that SR of ESAE was simultaneously controlled by a lot of factors.Elevation,climate and soil nutrients availability could affect SR of ESAE via their direct and indirect effect by altering AGB.In addition,the total effects of climate factors and aboveground biomass were positive,while the total effects of elevation and soil nutrients availability were negative.Interannual variation and influential factors of early spring annual ephemeral plants:(1)The abundance of early spring annual ephemeral plants varied in interannual.Among the 32 sites investigated,there were 4 sites without interannual variation,accounting for 12.5% of the total number of investigated sites,and 28 sites with interannual variation,accounting for 81.25% of the total number of investigated sites.The richness of this kind of plants showed an increasing trend in 18 sites and a decreasing trend in 10 sites;(2)The early spring annual variation of ephemeral plants diversity was mainly affected by the change of precipitation,and had no significant correlation with the change of aboveground biomass and soil nutrients;(3)With the increase of variation coefficient of precipitation in winter and growing season,the variation coefficient of annual ephemeral plant richness in early spring showed an increasing trend;(4)It was found that the variation of precipitation in December and January had an important impact on the diversity of annual ephemeral plants in early spring.The results show that the spatial distribution pattern of plant diversity is mainly influenced by altitude,climate,soil nutrients and aboveground biomass.Climate factors and aboveground biomass have positive effects on the geographical spatial distribution pattern of these plants,and altitude and soil factors are positive.The negative effect indicates that the comprehensive analysis of the effects of all potential factors on plant diversity can help us to understand the characteristics and influencing factors of diversity change.Secondly,the study also found that the variation of annual ephemeral plants diversity in the early spring of the year is mainly related to the change of precipitation,which shows that precipitation has an important role in the diversity of short-lived plants in the early spring.The results of this study analyzed the factors influencing the diversity of short-lived plants in early spring of the year from the time-space scale,which provided some reference for understanding the environmental adaptability of the plants.