Soil Microbial Ecology Of Phytoremediating Plants In Ionic-absorbed Type Rare Earth Tailings

Extensive vegetations were destroyed due to the early overexploitation of ionic-absorbed-type rare earth mining areas in Ganzhou Jiangxi,thereby causing a large amounts of tailings.At present,phytoremediation of tailings is one of the most important restoration measurements.However,it is still not clear how the phytoremediation affects the microbial of the tailing soils.In this study,based on the high-throughput sequencing and metabolomics technologies,the soils from tailings,soils by remediated pine slash alone or plus guest soils were investigated in atailing area in Longnan,Ganzhou.To provide scientific data and theoretical basis for the phytoremediation in improving microecology of tailings,The physiochemical properties,structure and composition of microbial communities,type and quantity of metabolites were determined and compared among the above three types of soils.The important findings are as follows:(1)The effects on soil properties were investigated.Compared with the tailings,the content of sulfate ion in the tailings remediated by slash pine alone increased significantly,while the contents of sulfate ion,total nitrogen,organic matter,organic carbon,total phosphorus and available phosphorus in the tailings remediated by slash pine with guest soils were significantly increased.With regard to trace elements,there was no significant change in trace elements in the tailings remediated by slash pine alone compared with the tailings.Rare earth elements such as Tb,Dy,Ho,Er,Tm,Yb,Lu,Y and metallic elements Al and K in the tailings remediated by slash pine with nearby soil were significantly reduced,and Mg was significantly increased.The content of protease in the tailings remediated by slash pine alone increased significantly,while the enzymatic activities of urease,phosphatase,sucrase,protease,catalase and polyphenol oxidase all increased significantly in the tailings remediated by slash pine plus guest soil.These results indicated that the effect of alien soil restoration on soil properties is better than that of slash pine itself.(2)The effects on microbial community structure and composition were investigated.Compared to tailings,both alpha-and beta-diversity of bacteria and fungi changed in the tailings remediated by slash pine alone or plus guest soil.Compared to tailings,the significant changes were found in both bacteria and fungi at phylum and class levels in the tailings remediated by slash pine alone or plus guest soil.The ecological networks of the three samples were significantly different.The tailings remediated by slash pine alone or plus guestchanged the levels in average clustering coefficient,average degree,average path length and modularity in the bacterial and fungal ecological networks.Regarding to the prediction of microbial function,the effects of slash pine alone on the improving bacteria of ionic rare earth tailings was stronger than that of remediation by slash pine plus guest soil.Compared to tailings,fungal nutrition has changed differently by slash pine alone or plus guest soil.(3)The effects on correlation analysis were investigated.In tailings,the rare earth Y was significantly positively correlated with protease.The bacteria Acidobacteria Gp2 and the fungi Eurotiomycetes are significantly correlated with Y and protease.Yb significantly positively correlated with total nitrogen in tailings remediated by slash pine alone.The bacteria Betaproteobacteria and the fungi Pezizomycotinaand Xylariales are significantly correlated with Yb and total nitrogen.There was a significant positive correlation between K and phosphatase in tailings remediated by slash pine alone.The bacteria Solirubrobacterales and the fungi Tremellomycetes and Agaricale are significantly correlated with K and phosphatase.There was significant positive correlation between Mg and organic matter in the soil after remediation by slash pine plus guest soil.The fungi Alphaproteobacteria,Erysipelotrichia,and Actinobacteria,and Trichosphaeriales are significantly related to Mg and organic matter.There was a significant positive correlation between Yb and phosphatase in the soil after remediation by by slash pine plus guest soil.The bacteria Alphaproteobacteria,Erysipelotrichia,and the fungi Boletale are significantly correlated with Yb and phosphatase.K was significantly negatively correlated with polyphenol oxidase in the tailings remediated by slash pine plus guest soil.The bacteria Caulobacterales and the fungi Saccharomycetes,Tremellales,Cantharellales and Dothideales were both significantly related to K and polyphenol oxidase in the tailings remediated by slash pine plus guest soil.(4)The effects on microbial metabolome were investigated.Compared to tailings,123 metabolites in the tailings remediated by slash pine alone or plus guest soil changed,of which78 metabolites were upregulated while 45 were downregulated.But only 13 metabolites significantly changed after remediation by slash pine plus guest soil compared with tailings remediated by slash pine alone.These findings indicated that the effects of phytoremediation by slash pine on metabolites are better than thoes by plus guest soil.