| Ionic rare earth mining in Gannan can cause severe soil erosion,leading to a series of environmental and ecological problems such as reduced microbial diversity and ecosystem degradation.Fungi,as important microbial resources,play an important functional role in the ecosystem.Understanding the potential impacts and drivers of different remediation methods on soil fungal communities of rare earth tailings will facilitate the development of more effective tailings soil remediation strategies for soil biological processes to balance the impacts of mining processes on soil ecology and soil productivity.This study is divided into two parts,the first part is an in situ remediation experiment of ionic rare earth tailings in Dingnan County,Jiangxi Province,to study the effects of different remediation methods(plant cover;biochar,organic fertilizer addition)on soil fungal communities;and the response of saprophytic fungi,mycorrhizal fungi and potential pathogenic fungi in tailings soil to the remediation methods was analyzed using linear discriminant effect size.This study also estimated the coupling relationship between soil environmental factors and fungal communities after treatment with different remediation methods by redundancy analysis and variance decomposition analysis,and found that arbuscular mycorrhizal fungi(AM fungi)may play an important role in the remediation process of ionic rare earth tailings.Therefore,based on the in situ study in Dingnan County,we further investigated AM fungi community and response mode during the remediation of an ionic rare earth tailings in Xinfeng County,and the main findings were as follows:(1)In situ remediation experiments in Dingnan County showed that co-remediation(plant cover;soil amendment and organic fertilizer addition)of ionic rare earth tailings increased the diversity of saprophytic fungal communities,promoted the colonization level of AM fungi within plant roots,and facilitated soil nutrient cycling and the restoration and reconstruction of rare earth tailings soil ecosystems.The co-addition of biochar-organic fertilizer(BD)increased the number of the indicator fungus Diaporthe of the Ascomycota in the soil,which poses a certain pathogenic risk to cultivated navel orange trees.In contrast,plant cover(Paspalum wettsteinii & Trifolium repens L.)and organic fertilizer(pig manure,cattle manure)addition may reduce the incidence of this disease.In addition,it was found that the combination of plant mulching and biochar-organic fertilizer addition for ionic rare earth tailings soil remediation was more conducive to the colonization of plant roots by functional fungal taxa such as AM fungi.Soil amendment addition increased the p H of ionic rare earth tailings soils;redundancy analysis and variance partitioning analysis further revealed that soil p H and organic carbon content were the main environmental factors affecting the fungal communities of different treated soils.(2)In situ experiments in Xinfeng County found that high dose of biochar addition(5 %,3.5 kg/plant)was more beneficial to the p H enhancement of rare earth tailings soil and increased soil organic carbon content;different biochar additions significantly promoted phosphorus accumulation in plants;TB2 treatment(Trifolium repens L.cover-5 % biochar addition)had the greatest effect on soil AM fungi community composition.The AM fungi community of Rhizophagus was the most sensitive to the remediationtreatment;the relative abundance of Funneliformis AM fungi decreased after the soil amendment,and this change is likely to be helpful in alleviating drought stress in the tailings soil.The highest alpha diversity index and the highest species richness and evenness were found in the TB1treatment(Trifolium repens L.cover-1 % biochar).In conclusion,the effect of biochar addition alone or vegetative mulching on AM fungi communities of ionic rare earth tailings soils was much less than that of soil amendments-plant cover combined remediation. |
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