Effects Of Different Remediation Plants And Cropping Patterns On Microbial Community Structure And The Influence Of Repair Efficiency In Copper-contaminated Soil

Phytoremediation is one of the important techniques for soil remediation of heavy metal contaminated soils.The selection of different planting seasons and different species may greatly affect the physicochemical properties and remediation efficiency of soils.In this study,Oenothera glazioviana,a copper-resistant economic crop,and Elsholtzia haichowensi,a copper-accumulated plant,were used as remediation plants to compare the effects of continuous cropping,intercropping and rotation on the microbial community structure and remediation efficiency of copper-contaminated soil after 6 years of continuous planting.The effects of different planting patterns on the bacterial community structure in rhizosphere and non-rhizosphere soils were also analysed.The results showed that:1.Compared with the no planting soil,the diversity index(Sobs,Chao and Ace index)and richness index(Shannon and Simpson index)of soil bacteria diversity increased significantly.In the rotation mode,the index were largest in the rhizosphere soil of Oenothera glazioviana under rotation mode.2.Principal component and cluster analysis showed that there were significant differences in bacterial community structure between rhizosphere and nonrhizosphere areas of Oenothera glazioviana and Elsholtzia haichowensi.3.The functional analysis of PICRUSt showed that the functions of cell communication,energy metabolism,environmental adaptation,nucleotide metabolism,signal transduction,cell motility and so on in the treatment group of planting plants were significantly enhanced.4.At the level of phylum bacteria,the relative abundance of beneficial bacteria Actinobacteria and Chloroflexi increased in rhizosphere areas of Oenothera galazioviana in rotation compared with the continuous cropping of Oenothera.Compared with Elsholtzia haichowensi in continuous cropping,the relative abundance of beneficial bacteria Acidobacteria,Chloroflexi and Rokubacteria in the rhizosphere soil of Elsholtzia haichowensi increased under rotation mode.The relative abundance of Acidobacteria and Planctomycetes increased in the rhizosphere soil of Oenothera glazioviana and Elsholtzia haichowensi under intercropping mode compared with the continuous cropping patterns.5.At the level of genus bacteria.Sphingomonas?Gemmata?Nitrospira are regarded as the beneficial bacteria.The relative abundance of Sphingomonas in the rhizosphere soil of the two plants decreased in rotation compared with the continuous cropping and no planting soil.Compared with the continuous cropping of Oenothera glazioviana,the relative abundance of Gemmata increased significantly in the intercropping mode.However,the relative abundance of Nitrospira did not change significantly under these treatments.The effects of different planting patterns on the fungal community structure in rhizosphere and non-rhizosphere soils were analysed.The results showed that:1.Under the rotation mode,the diversity index and richness index of Oenothera glazioviana in the rhizosphere soil under rotation mode were the largest,but the differences of the indexes under other treatments were not significant.2.Principal component and cluster analysis showed that the fungal community structure of Oenothera glazioviana and Elsholtzia haichowensi in the rhizosphere and non-rhizosphere regions were significantly different.3.The beneficial fungus at the phylum level were Ascomycota and Basidiomycota.Compared with the continuous cropping system,the relative abundance of Ascomycota in the intercropping and rotation systems was significantly increased,and the relative abundance of Ascomycota in the intercropping systems was higher.Compared with continuous and rotation cropping,the relative abundance of Basidiomycota in rhizosphere soils of Oenothera glazioviana and Elsholtzia haichowensi under intercropping mode was the most significant.4.Compared with continuous cropping,the relative abundance of Chaetomium,a beneficial fungus on the genus level,in rhizosphere soils of Oenothera glazioviana under rotation cropping mode increased significantly.Compared with the continuous cropping and blanked soil,the relative abundance of Fusarium,as a harmful fungi,in rhizosphere soils of Elsholtzia haichowensi under rotation cropping mode significantly decreased.5,Through Lefse multistage species difference discriminant analysis,the advantage fungus in the rhizosphere soils of Oenothera glazioviana under rotation and interplanting mode are Funneliformis_mosseae and Meira respectively,Paraglomus;the dominant fungus in the rhizosphere soils of Elsholtzia haichowensi under rotation and interplanting mode are Physcomitrella_patens and Tripylin,respectively.By comparing the effects of different planting modes on soil physical and chemical properties and remediation efficiency,it was found that 1.Crop rotation could remove copper from the soil more efficiently.Under the rotation mode,the total copper accumulation in the shoot of Oenothera glazioviana and Elsholtzia haichowensi reached 13.25 mg for three consecutive years.For three consecutive years,the accumulative dry weight of Oenothera glazioviana and Elsholtzia haichowensi reached 18.82 g and 1 5.98 g.respectively.2.There was no significant difference in soil physical and chemical properties under different tillage modes.Compared with the continuous cropping mode,the pH of soil under rotation and intercropping modes increased.The soil organic carbon content was the highest in intercropping.3.SOC is the environmental factor that has the greatest impact on the composition of soil microbial community.The relative abundance of Planctomycetes in intercropping and in the rotation cropping model of Elsholtzia haichowensi is high,and the relative abundance of Chloroflexi in the rotation cropping model of Oenothera glazioviana is high,both of which are positively correlated with SOC and TN.The relative abundance of Acidobacteria was positively correlated with AP,and the relative abundance of the bacteria was relatively high under the rotation mode of Elsholtzia haichowensi.The relative abundance pH of Gemmatimonadetes was positively correlated,and the relative abundanceof Gemmatimonadetes was higher in the continuous cropping mode of Oenothera glazioviana.In addition,the relative abundance of Proteobacteria and Actinobacteria was positively correlated with Soil Cu and AK.4.By comparing the relationships among tillage patterns,fungus species and soil physical and chemical properties,it was found that Spizellomyces and Cyperus were significantly positively correlated with pH.Prismatolaimus and Talaromyces were positively correlated with Soil_Cu,and the relative abundance was higher under the rotation pattern of Elsholtzia haichowensi and the continuous cropping pattern of Oenothera glazioviana.The relative abundance of Alternaria,Cephaliophora and Enchytraeus was relatively high in the intercropping mode and positively correlated with SOC,TN,AP and AK.According to the research of this paper,for copper-contaminated farmland,the plant remediation can be carried out by the planting mode of Oenothera glazioviana and Elsholtzia haichowensi in rotation or intercropping pattern,so as to realize the "remediation and utilization" of copper-polluted soils.