Maintenance Mechanism Of Multi-dimensional Diversity Of Desert Plants In Hexi Corridor

Although the arid desert area in the Hexi Corridor has poor soil,little rain,strong wind and large temperature difference between day and night,it breeds abundant desert plants such as xerophyte,super xerophyte,halophyte and psammophyte.The research on plant diversity and its maintenance mechanism in arid desert areas can reveal the ecosystem function comprehensively and deeply.In this paper,along the decreasing gradient of natural precipitation from southeast to northwest of the Hexi Corridor,desert plants were taken as the research object,transects were set up and community surveys were carried out,leaves and soil samples were collected,and environmental information such as geography and climate were got,and the core functional traits of desert plants were determined.This paper analyzes the distribution pattern of species diversity,functional diversity and phylogenetic diversity of communities,herbs and shrubs,and expounds the relationship and maintenance mechanism of multi-dimensional diversity of plant communities.This study provides theoretical and scientific basis for maintaining stable and sustainable desert ecosystem.The main findings and conclusions are as follows:(1)A total of 40 species of desert plants belonging to 14 families and 37 genera were investigated in Hexi Corridor,including 18 species of shrubs belonging to 10 families and 16 genera and 22 species of herbs belonging to 11 families and 22 genera.The Margalef richness index(R)ranges from 0.18 to 1.86,and the Pielou evenness index(E)and Simpson index(D)range from 0.12 to 0.98 and 0.04 to 0.81,respectively.The results of multiple regression between species diversity and environmental factors showed that environmental factors accounted for 75.90% of the change of R.Latitude(Lat),average annual temperature(MAT),sunshine duration(SD),average annual wind speed(AWS)and soil total nitrogen(TN)were negatively correlated with R(P< 0.05).Longitude(Long),average annual precipitation(MAP),evaporation(EP)and specific humidity(SH)are all positively correlated with R.Environmental factors account for 57.80% of the change of E,SD is negatively correlated with E,and SH is positively correlated with E.Environmental factors account for 89.40% of the change of D,and Lat,MAT,SD,AWS,TN,Sand are all negatively correlated with D,while Long,MAP,EP,SH,soil water content(SW)and soil available nitrogen(AN)are all positively correlated with D.(2)The range of functional richness index(FRic)was 0.01～0.07,and the range of functional traits and occupied functional niche were small.Functional evenness index(FEve)and functional divergence index(FDiv)ranged from 0.05 to 1.00 and0.18 to 1.10,respectively.Compared with the west of Hexi Corridor,the indexes of FRic,FEve and FDiv in the eastern and central shrubs are higher.The results of multiple regression between functional diversity and environmental factors showed that environmental factors accounted for 74.80% of the change of FRic,and there was a significant negative correlation between Sand and FRic(P< 0.05),and there was a significant positive correlation between Clay and FRic.Environmental factors accounted for 75.00% of the change of FEve,SD was negatively correlated with FEve,and SH was positively correlated with FEve.Environmental factors accounted for74.00% of the change of FDiv.SD,p H and Silt were negatively correlated with FDiv,while SH was positively correlated with FDiv.(3)Faith’s phylogenetic diversity index(PD)ranged from 259.49 to 1244.66,while that of herbs and shrubs ranged from 135.76 to 1050.24 and 135.76 to 497.95 respectively.The average phylogenetic distance index(MPD)of the community ranged from 2.99 to 200.39.Herbs and shrubs vary from 25.99 to 140.14 and 2.99 to168.18,respectively,indicating that the phylogenetic tree of herbs has a short branching distance and close genetic relationship among groups.The net relatedness index(NRI)showed that the phylogenetic structure of 3 transects was significantly aggregated and structure of 4 transects was significantly divergent.The results of multiple regression between phylogenetic diversity and environmental factors showed that environmental factors accounted for 57.10% of the change of PD,SD was negatively correlated with PD(P< 0.05),and SH was positively correlated with PD.Environmental factors accounted for 80.90% of the change of MPD.Lat,MAT,SD and Sand were all negatively correlated with MPD,while Long,MAP,EP,SH and Clay were positively correlated with MPD.(4)The correlation analysis between multi-dimensional diversity shows that the functional evenness index is positively correlated with Pielou evenness index and Simpson index(P< 0.05).Margalef species richness was positively correlated with Faith’s phylogenetic diversity index and average phylogenetic distance index,which indicated that desert plants in the Hexi Corridor showed niche conservation in the long-term evolution process.The correlation between functional richness index and species diversity and phylogenetic diversity is not significant,which may be due to the functional redundancy of plants under the action of environmental filtration.