| Objective: The purpose of this study was to investigate the biodiversity of soil nematode communities and soil heavy metal pollution along the Lijiang River,so as to better evaluate the degree of soil and water pollution and its biological effects,and to formulate effective environmental protection measures,sewage treatment techniques and soil restoration programs based on this.To promote the international influence of Guilin tourism city to achieve econom-ic and ecological win-win situation.Methods: The sampling points are selected comprehensively and representatively by the Global Positioning System(GPS)along the Lijiang River,and they are carried out by the "diagonal layout method".The moisture and p H values of soil samples were measured by drying method and glass electrode method respectively.The contents of heavy metals such as Cd,Cu,Pb,Zn and Cr in soil were measured by extraction-flame atomic absorption method and flame atomic absorption spectrophotometry,and the heavy metal pollution index was calculated to determine the degree of soil pollution by various heavy metals.The soil nematodes were separated by sucrose centrifuge flotation method,counted under a microscope,made into temporary slides,and placed under an optical microscope.The nematodes were classified into families and genera by reference to the Retrieval Map of Soil Fauna in China.C.elegans were divided into four trophic groups according to feeding habits,and c-p values,maturity index and biodiversity index were calculated.Geographic information System(GIS)was used to visualize the distribution of soil basic properties and nematode quantity along the Lijiang River.At the same time,statistical methods were used to establish soil nematode as indicator organisms,and to evaluate the environmental pollution status,and the change rule of soil nematode with soil heavy metal pollution status.Results: There were significant differences in soil moisture and p H values along the Lijiang River(p<0.05),and all of them were polluted by heavy metals in different degrees.The upstream and downstream were relatively lightly polluted,however the middlestream were seriously polluted,among which Cr and Cu were lightly polluted,while Pb and Cd were seriously polluted.The community structure,trophic groups and ecological indices of soil nematodes along the Li River showed high diversity at various points,and would change with the changes of soil pollution.Bacteria-eating nematodes and plant-eating nematodes showed great dominance in this area.Protophyllidae,Cephalopoliaceae,Diogastridae,Diogastridae,and Diogastridae belong to c-p1 and c-p2 nematodes and are the dominant groups in this region.Among the nematodes of the family Lanceophora,the family Frontalophora,the sphaeria of the family Lanceophora and the family Lanceophora belong to classes c-p3,c-p4 and c-p5,which are rare groups in this region.Through calculating the ecological index of nematodes and correlation analysis,it was found that Shannon-Wiener diversity index H ’and Simpson dominance index C were negatively correlated with five heavy metals,species number S was negatively correlated with heavy metal Cu,total maturity index ΣMI was negatively correlated with heavy metal Cd(p< 0.05).The results showed that species number(S)and nematode ecological index(H ’,C,ΣMI)could directly and effectively measure the degree of soil heavy metal pollution.Conclusion : Soil nematodes can sensitively indicate soil heavy metal pollution,and can be used as good indicators of environmental pollution in the Lijiang River Basin.At the same time,the analysis of soil pollution in Guilin represented by the Lijiang River basin can provide a reliable theoretical basis for us to deal with the changes of Guilin’s natural environment,so as to propose effective solutions for potential ecological problems. |
