Revegetation process increases the diversity of total and arbuscular mycorrhizal fungi in areas affected by the Fundao dam failure in Mariana, Brazil

Mining activities have environmental impacts. The rupture of the Fundao tailing dam ejected a significant volume of iron ore mining waste (IOMW) and was characterized as the greatest disaster in mining history. The use of microorganisms to monitor the affected soils is ideal due to their sensitivity to environmental changes and their capacity for soil remediation, as they can promote plant growth under stressed conditions. This study aimed to evaluate the total fungi diversity and arbuscular mycorrhizal fungi (AMF) community structure of the area affected by IOMW that is currently under rehabilitation. Soil and root samples were collected from an impacted site without rehabilitation (REC1), two revegetated areas with grass and leguminous species (REC2 and REC3), and one reference area in the undisturbed forest (UND) during two seasons (rainy and dry). The total fungal diversity was analyzed by next generation sequencing. The AMF was identified morphologically and the number of spores, colonization, and denaturing gradient gel electrophoresis (DGGE) were identified for this group of fungi. Total fungi diversity, AMF community structure, and soil chemical indicators differed among areas and between seasons. UND exhibited the highest organic matter content whereas rehabilitated areas were more affected by pH and presented higher values. The total fungal diversity and AMF community structure in REC areas showed that spore number and species richness increased along with the revegetation process. Glomus and Rhizophagus comprised the most abundant genera. In both climate seasons, AMF diversity in UND was higher than in REC areas but increased diversity in REC was observed in subsequent sampling. The fungal community diversity in affected areas was altered by the revegetation process-which increased the total fungal diversity-as well as AMF helping the recovery of this area.