Potencial de propagação e eficiência de fungos micorrízicos arbusculares em áreas afetados pela deposição de rejeito de mineração de ferro

Abstract

The mining of metals in Brazil has historical importance. This activity, to this day, still remains active throughout the country, which is suitable for such practices. In this context, the Fundão Dam in the Bento Rodrigues district, belonging to Samarco, stands out, as the company also carried out iron ore extraction. The collapse of the Fundão dam in Mariana (MG) occurred due to negligence by the responsible companies. Biodiversity was severely impacted, including arbuscular mycorrhizal fungi, which have great environmental importance and are essential for maintaining the plant ecosystem. In this context, the study aims to evaluate the propagation potential and efficiency of arbuscular mycorrhizal fungi in areas affected by iron mining tailings deposition under rehabilitation. For this purpose, soils were collected from areas affected with 3, 4, and 5 years of revegetation and from a reference area (non-affected), with 12 samples per area. From the field material, analyses of the soil’s physical and chemical characterization and spore density were performed. To evaluate propagation potential, multiplication was carried out using trap cultivation in pots with inoculated soil from the areas and trap plants (Brachiaria brizantha – BRS Piatã, Helianthus annuus L., and Glycine max L.). After 4 months, the system was dismantled, and spore density and mycorrhizal colonization were analyzed. The inoculumsoil produced by the trap cultivation was used in the efficiency test for plant growth of a native species, the purple ipê (Tabebuia heptaphylla (Mart.) Mart.), in sterilized technosol. The treatments consisted of the different revegetation ages (3, 4, and 5 years), the reference area, and a control (without inoculated soil), totaling 5 treatments and 12 replications. At the end of 127 days, the experiment was dismantled, and spore density, mycorrhizal colonization, and seedling vigor were analyzed again. After obtaining the data, they were analyzed through multivariate analysis, mean comparison using Tukey’s test when more than two variables were present, and Student’s t-test when only two variables were present, both at 5% probability. The spore density values of the revegetated areas are higher than those of the reference area and different from it; however, among themselves, the three areas are similar, indicating that ecological succession may be reaching equilibrium. Five years of revegetation helped restore mycorrhizal fungi in the soil, which improved seedling survival and vigor. Areas with older vegetation have greater potential for ecological restoration.