Relationship Between Desert Plant Diversity And Ecosystem Multifunctionality Along Water And Salt Gradients

The response of biodiversity to global change is obvious.The change of species diversity will cause the change of community structure,which will change the function of natural ecosystem,and ultimately affect the multi-function of ecosystem.In this context,ecosystem multifunctionality requires many species or only a few species,and which of the functional diversity and species diversity can better predict and explain ecosystem multifunctionality.Due to the inconsistency of research areas,ecosystem types and research scales,so far,there is still no definite answer to these questions,in order to be able to do this research.The area enriches the research contents and methods of plant diversity-ecosystem multifunction,and provides theoretical basis for the research and application of desert plant diversity in temperate arid regions.Based on the data of field investigation and laboratory experiment,the relationship between plant diversity and ecosystem multifunctionality along three water-salt gradients was studied in this paper.The results show that:?1?The soil water and salt content of 67 samples are Clustered according to k-means in R3.5.1,and are classified into three categories:high water and high salt(13.113%,5.475 g·kg^-1)?medium water and medium salt(7.025%,3.853 g·kg^-1)?low water and low salt(2.636%,2.388 g·kg^-1).There was significants difference in three categories?P<0.05?.?2?Only Magalef richness index showed significant difference in high water,high salinity and low water and low salinity samples?P<0.05?.Specifically,Magalef richness index showed low water,low salinity>middle water salinity>high water and high salinity sample plots.In functional diversity index,except functional evenness index,the other four functional diversity indices were functional richness index and functional energy dispersion index showed different degrees of difference?P<0.05?,and the evenness index of species and functional diversity showed no significant difference in three plots.Therefore,species richness index may be more suitable for characterizing species diversity in this area,while functional dispersion and functional richness are more suitable for characterizing functional diversity in this area.The relationship between functional diversity and species diversity and their close degree are not fixed.With the decrease of water content,the correlation between species diversity and functional diversity is strengthened.?3?Relative weight of ecosystem functional parameters were as follows:alkaline hydrolysis nitrogen?29.404%?>beta-glucosidase?28.276%?>ammonium nitrogen?16.928%?>available phosphorus?7.210%?>nitrate nitrogen?5.987%?>total nitrogen?4.295%?>organic carbon?3.918%?>alkaline phosphatase?2.539%?>total phosphorus?1.442%?.The indexes of ecosystem multifunctionality are ranked as follows:The plot of high water content and salt content?0.645?>plot of middle water content and salt content?-0.090?>plot of low content and salt content?-0.348?along three water-salt gradient environments,and the indexes of ecosystem multifunctionality was lower in all three plots.?4?When considering the effects of the interaction of water content and salinity on the multi-function of ecosystem,soil salinity has a positive effect on the ecosystem mltifunctionality,soil moisture has a negative effect on the ecosystem mltifunctionality,and the interaction between them has a negative effect on the ecosystem mltifunctionality.Soil salinity accounted for 20.939%,soil moisture accounted for30.048%,the interaction between soil water and salinity explained 49.013%.?5?The best fit between species diversity,functional diversity and ecosystem multifunctionality is quadratic term function rather than straight line,which further shows that biodiversity is not the only factor driving ecosystem multifunctionality change.Besides biological factors,other factors determine the development and change of ecosystem multifunctionality in this area,and also explain the relationship between them,it also shows that the relationship between species diversity and functional diversity is not fixed and different in different thresholds.?6?The relationship between biodiversity and ecosystem multifunctionality is different along three water and salt environments.Compared with species diversity,functional diversity can better explain and predict the ecosystem multifunctionality in this area.The ecoosystem of multi-functionality of was most affected by soil water content in abiotic factors?environmental factors??P<0.001?,path coefficient was0.763,followed by functional richness index?P<0.001?and path coefficient was 0.408.The species richness does not directly affect the ecosystem multifunctionality?P>0.05?,but it can indirectly affect the ecosystem multifunctionality by influencing the functional richness.