Study On Plant Community And Soil Stoichiometry Characteristics Of Desert Grassland In Urumqi

The desert grassland in Urumqi City is a component of the temperate desert in northern Xinjiang,and the ecosystem is fragile.In-depth research on the ecological stoichiometric characteristics of desert grassland vegetation,litter and soil,and understanding of the changes of each component is of great significance for revealing community characteristics and stability.In this study,different communities in the Urumqi desert grassland（Haloxylon ammodendron community,Haloxylon ammodendron+Ephedra przewalskii community,Ephedra przewalskii+Sarcozygium xanthoxylon community,Seriphidium transiliense community,Nanophyton erinaceum community）were used as the research objects to analyze the species diversity of different communities,plant species,litter and soil ecological stoichiometric characteristics,to clarify the general laws of the stoichiometric characteristics of each component and its internal correlation,in order to provide data support and theoretical basis for the stoichiometric characteristics and restoration mechanisms of Xinjiang desert grassland ecosystems.The main results are as follows:（1）The species composition of the desert grassland community in Urumqi is relatively simple.There are significant differences in vegetation coverage,height and density among the communities.The biomass is in the order of below-ground>above-ground>litter.The below-ground biomass of Ephedra przewalskii+Sarcozygium xanthoxylon community was the highest at 0-5 cm,and the below-ground biomass decreased with the increase of soil depth;the above-ground biomass and the below-ground biomass were in an exponential function relationship,and the litter biomass and the underground biomass showed a significant relationship.Linear relationship;species diversity has a unimodal curve relationship with above-ground biomass,and an exponential function relationship with below-ground biomass.（2）The average plant organic carbon,total nitrogen and total phosphorus in the desert grassland community in Urumqi area were 227.47 g·kg^-1,4.24 g·kg^-1and 0.43 g·kg^-1,which were lower than the average level of 394.00 g·kg^-1,18.4 g·kg^-1,1.14 g·kg^-1in Xinjiang,lower than the national average of438.00 g·kg^-1,20.20 g·kg^-1,1.46 g·kg^-1,and lower than the global terrestrial plants.The average levels of plants were 461.60 g·kg^-1,20.60 g·kg^-1,1.99 g·kg^-1,and the C:N,C:P,N:P of plants were between43.59-62.45,335.16-693.64,7.69-12.97,respectively;The contents of organic carbon,total nitrogen and total phosphorus in the litter were 195.41-216.03 g·kg^-1,3.04-4.92 g·kg^-1,0.13-0.51 g·kg^-1,which were lower than those of plants and higher than those of soil.C:N,C:P,N:P are respectively between 43.88～70.40,423.62～1625.01,117.47～530.60.（3）In the 0-50 cm soil layer,the contents of soil SOC,TN,and TP varied between 1.06-11.81 g·kg^-1,0.14-0.81 g·kg^-1,and 0.15-0.49 g·kg^-1,respectively,all of which were low.Compared with the national average level of 11.12 g·kg^-1,1.06 g·kg^-1,and 0.65 g·kg^-1,it shows that the soil carbon,nitrogen,and phosphorus content in the study area is relatively low,and nutrients are relatively poor;with the deepening of soil depth,the soil carbon,nitrogen and phosphorus in each community showed a gradual decreasing trend,and the"surface aggregation"was more obvious.The C:N expression of different community types was Seriphidium transiliense>Nanophyton erinaceum>Haloxylon ammodendron+Ephedra przewalskii>Ephedra przewalskii+Sarcozygium xanthoxylon>Haloxylon ammodendron,C:P is expressed as Seriphidium transiliense>Haloxylon ammodendron+Ephedra przewalskii>Nanophyton erinaceum>Ephedra przewalskii+Sarcozygium xanthoxylon>Haloxylon ammodendron,N:P is expressed as Haloxylon ammodendron+Ephedra przewalskii>Ephedra przewalskii+Sarcozygium xanthoxylon>Seriphidium transiliense>Haloxylon ammodendron>Nanophyton erinaceum.（4）The correlation analysis showed that there were extremely significant differences between litter TP content and plant TN content and TP content,between plant SOC content and soil TN content,between soil TN content and TP content,and between soil SOC content and litter TP content.Significant positive correlations（P<0.01）were found between plant TP content and litter TP content,soil SOC content and plant TP content,soil N:P and plant C:P,and plant N:P.Positive correlation（P<0.05）;soil C:N and plant C:P,litter C:P,litter N:P,soil C:P and litter C:P were all significantly negatively correlated（P<0.05）;it showed that there is a strong correlation between the contents of carbon,nitrogen and phosphorus and their stoichiometric ratios among the components of the typical desert grassland community in Urumqi.（5）Redundancy analysis（RDA）results preliminarily showed that the diversity of desert grassland communities in Urumqi was comprehensively affected by soil organic carbon,soil total nitrogen,soil N:P,plant organic carbon,plant total phosphorus,plant C:P,and total litter nitrogen.more obvious.In general,the contents of plants,fallen matter,soil organic carbon,total nitrogen and total phosphorus in the desert grassland community in Urumqi City were low,and nutrients were relatively scarce.The relative correlation is strong,and the environmental factors affecting the content of carbon,nitrogen and phosphorus in the community and their stoichiometric ratio need to be further verified.