Study On The Relationship Between AM Fungi Community And Soil Lead Content In Cinnamomum Bodinieri Soil In Nanchang City

Cinnamomum bodinieri is a common greening tree species in southern China.Because of its magnificent appearance and dense canopy,it is mainly used for road greening in cities,such as street trees and courtyard trees.Among the existing street tree species in Nanchang city,Cinnamomum bodinieri is the most widely used.Arbuscular mycorrhizal fungi（AM fungi）are microbial groups that can form mutually beneficial symbiotic relationships with most higher plants.AM fungi play an important role in promoting plant growth,increasing plant mineral nutrient uptake and enhancing plant resistance to adverse environmental conditions.With the acceleration of urbanization and the increase of car ownership in cities,the accumulation of heavy metals in urban soils caused by human activities has gradually accelerated,and lead is one of the heavy metal which are harmful and concerned by people.How the accumulation of lead in urban soils affects the underground ecosystem of the pavement tree growth environment,and how this effect feeds back to the above-ground plants.At present,there is no clear research conclusion.This paper takes Cinnamomum bodinieri which is the common roadway tree species in Nanchang as the research object,and chooses urban trunk roads with different traffic pressures and types to investigate.The response laws of Cinnamomum bodinieri to different traffic pressure and types of urban trunk road soil lead accumulation was studied by sampling the root system and rhizosphere soil of Cinnamomum bodinieri at different developmental stages.The symbiosis and adaptation mechanism of AM fungi-camphor symbiosis under lead accumulation in urban soils were observed by studying the characteristics of soil AM fungi community.The results are of positive significance for understanding the adaptive mechanism of pavement trees in southern cities under the environment of lead accumulation in soil,and can provide a new focus for urban ecological research,with distinct regional characteristics and broad application prospects.The results are as follows:1.According to the law of lead accumulation in soil,the longer the road operation time and the more traffic flow,the more available lead content in soil.The available lead concentration in the upper soil layer was significantly higher than that in the lower soil layer（p<0.05）.In spring,the order of lead concentration in plant organs was leaf>stem,and in autumn,leaf>stem>fruit>root.The content of available lead in surface soil was positively correlated with that in leaves and stems of Cinnamomum bodinieri（p<0.01;p<0.05）.2.In this study,from rhizosphere soil of Cinnamomum bodinieri in different main road in Nanchang city,20 species in 8 genus of AM fungi were isolated,including six species of Acaulospora,three species of Rhizophagus,three species of Glomus,two species of Ambispora,two species of Funneliformis,two species of Scutellospora,one species of Septoglomus and one species of Claroidelomus.AM fungi in the rhizosphere soil of Cinnamomum bodinieri in Nanchang are mainly Acaulospora,which is the dominant genus.3.The roots of Cinnamomum bodinieri growing on Nanchang trunk road and soil AM fungi formed a good symbiosis,and the roots of camphor trees were well infected.The infection intensity of AM fungi to camphor roots increased significantly with the increase of soil p H value（p<0.05）（soil p H value ranged from 5.61 to 8.75）;and the infection intensity of AM fungi to camphor roots was significantly positively correlated with soil organic matter and total nitrogen content（p<0.05）(soil organic matter content ranged from 14.53 to 79.75 g·kg^-1,soil total nitrogen content ranged from 0.65 to 3.30 g·kg^-1).Both sampling showed that the spore density of upper layer was higher than that of lower layer,but did not reach a significant level.In the same plot,the spore density in autumn was higher than that in spring.PH,total nitrogen content and organic matter content are all important factors affecting spore density of AM fungi.4.Available lead concentration in soil was negatively correlated with AM fungal infection rate in camphor root system,but not significantly.