Shifts in Arbuscular Mycorrhizal fungal properties due to vegetative remediation of mine spoil contamination from a dam rupture in Mariana, Brazil

Abstract

The rupture of the Fundão dam in Brazil in November 2015 covered the soil with iron ore mining waste (IOMW) and removed vegetation. Arbuscular mycorrhizal fungi (AMF) can benefit vegetation growth and soil structure, assisting the rehabilitation of degraded areas. Therefore, the objective of the present work was to evaluate the AMF community structure and investigate the effect of the technosol physicochemical properties in these communities after revegetation programs were adopted in areas affected by IOMW. Soil samples were taken from an undisturbed atlantic forest (UND) and two regions influenced by IOMW, under natural recovery process (REC1) and under revegetation process introduced after the dam rupture (REC2) during the rainy season (February, E1) and dry season (September, E2) of 2017. AMF community structure in both seasons was assessed by PCR-DGGE, spore density, and glomalin-related soil protein (GRSP) content. Soil physical and chemical characteristics were also evaluated and related to the AMF community. In the summer, the AMF community profile was affected by the host plants used for revegetation, as REC2 showed 92% similarity with the natural forest against only 73% of REC1. In the winter, REC1 showed a higher similarity rate with REC2 and UND, as there was already vegetation cover in the area. The number of spores and the content of glomalin were not different between REC1 and REC2, but they were lower than UND. The number of spores in both areas was, on average, 12 (summer) and 8 times (winter) less than UND, and the total glomalin was 22 and 10 times less, respectively. The chemical characteristics of UND and soils under the recovery process (REC1 and REC2) were considerably different due to IOMW deposition. A small change in the soil chemical attributes has been observed after the revegetation in both REC areas, which was very slow toward the rehabilitation process, although the changes in the soil physicochemical characteristics were incipient till the period from 14 months (E1) to 21 months (E2). We concluded that the covering by plants of areas affected by IOMW improves AMF diversity since these fungi are biotrophic. Furthermore, the findings suggest that the short period (six months) can alter AMF communities. Therefore, revegetation processes adopted after dam collapse have promoted land reclamation, but this effect requires further monitoring.