Effects Of Heavy Metal Pollution On Arbuscular Mycorrhizal Fungi Diversity In Urban Green Space

As an important environmental problem,heavy metal pollution in urban green space has been widely concerned.Heavy metal pollution can seriously affect arbuscular mycorrhizal fungi(AMF)in urban green space ecosystem,and affect the effective play of the urban green space ecosystem function.However,the mechanisms of heavy metal pollution affecting AMF communities in urban green space ecosystems remain unclear.In this study,green space in Zhengzhou was selected as the research object,and high-throughput sequencing technology was used,based on the analysis of the characteristics of heavy metal pollution and the diversity of AMF in urban green space,the effects of Cd pollution gradient and green space type on AMF were studied.Specific research results are as follows:(1)A total of 60 samples were collected from urban green space in Zhengzhou city,five heavy metal indexes: Cd,Pb,Cu,Zn and Fe were determined,analysis of heavy metal pollution in urban green space in Zhengzhou.The results showed as follows: 1)The average values of heavy metals Cd,Pb,Cu,Zn and Fe in Zhengzhou green space are 3.44,1.31,2.94,1.21 and 1.09 times of the background values of Henan Province,respectively,which are enriched;2)Cd is the most important heavy metal pollutant in the green space of Zhengzhou city,which is in a state of severe pollution.The comprehensive pollution order of the five heavy metals is Cd > Zn >Cu > Pb > Fe;3)The pollution of heavy metals to street green space is greater than that of park green space.The heavy metal pollution of street green space reaches heavy pollution(PN=3.19),and the heavy metal pollution of park green space reaches heavy pollution(PN=2.53).(2)High-throughput sequencing technology was used to analyze the community structure and diversity of AMF in Zhengzhou city.The results showed as follows: 1)A total of AMF 7 families,7 genera,59 species and 571 OTU were detected in all samples,and the main dominant family was Glomeraceae(71.04%);2)Urbanization affects the diversity of AMF,and its phylogenetic diversity decreases significantly with the increase of urban distance(P<0.05);3)The AMF diversity of park green space was significantly higher than that of street green space(P<0.001).(3)Cd pollution is an important factor of heavy metal pollution in urban green space in Zhengzhou city.To this end,this study analyzed the AMF in urban green space soil affected by four different Cd pollution(no pollution,light pollution,moderate pollution and severe pollution).The results showed as follows: 1)Cd pollution leads to increased diversity of all AMF and specialists,and decreased diversity of generalists;2)In different Cd pollution gradients,the community construction mechanism of all AMF and specialists is driven by deterministic processes,while the community construction mechanism of generalists is driven by stochastic processes;3)The network stability of the specialists is higher than the generalists in different Cd pollution gradients.(4)Park green space and street green space are important green space types in Zhengzhou city.To this end,this study conducted a comparative analysis of the AMF diversity of street and park green spaces in Zhengzhou city.The results showed as follows: 1)In the urban green space ecosystem,the community construction process of AMF is mainly dominated by stochastic processes;2)Green space types affect the community construction process of AMF,and the community construction of AMF of street green space is higher than that of park green space;3)All AMF and specialists have higher network stability in park green space,while generalists have higher network stability in street green space.Specialists are the main key species to maintain the stability of the AMF network in urban green space ecosystems.In summary,1)Heavy metals have been enriched in the green space of Zhengzhou city,and Cd is the most important heavy metal pollutant factor in the green space of Zhengzhou city;2)AMF diversity is rich in urban green space in Zhengzhou city,Green space types influence the diversity of AMF;3)Cd pollution leads to increased diversity of all AMF and specialists and decreased the diversity of generalists;4)The species coexistence mechanism of AMF is affected by the types of green space.These results have contributed to a better understanding of the characteristics of heavy metal pollution and the diversity of AMF in Zhengzhou’s urban green spaces,and provided important information for future urban planning and sustainable development in Zhengzhou,it also provides theoretical knowledge for green space management and protection in other cities.