Atividades antrópicas afetam a biodiversidade? Estudos de caso sobre exploração florestal na Amazônia e mineração de ferro em Minas Gerais

Abstract

The overall main of this thesis was to evaluate the impact and the impact recovery of selective logging and mining over using ants and leaf litter arthropod species and the consequent effect on ecosystem functioning. This work consists of two chapters. First, we evaluated the response of ants to the recovery time and intensity of selective logging in the Amazon. Recent managed areas, with one year of post-cutting, have higher ant species richness. However, the ant species richness in different microhabitats did not differ over time, neither with the selective cutting intensity. Among the measured variables, the density of removed trees and the percentage of clay in the soil had a negative effect on total and epigaeic ant species richness. These variables did not differ between areas and neither between intensities of selective cutting. The total and of each microhabitat species composition were different between areas, but with a high number of shared species, being this parameter explained by the density of extracted timber, cutting intensity, and percentage of sand in the soil. Thus, we verified that the selective logging with reduced impact leads to subtle changes in biodiversity due to how it is performed. In the second chapter, we investigated the effect of the areas in the rehabilitation process after mining over the leaf litter arthropods community and over ecological functions. The richness of species and of arthropods functional groups has not changed with the rehabilitation time, indicating that the assessment time was not enough to show ecosystem changes able to recover the groups studied in the areas. The composition of the arthropod community varied between the areas in rehabilitation process due to the fact that the different groups of arthropods consume a diverse range of resources and that the areas are structurally distinct and have different rehabilitation ages, substrates and proximities to source areas. The arthropod species richness and functional groups did not influence the processes of decomposition and nutrient release. This may indicate redundancy assumed by groups of arthropods and that other factors may be determinant to influence decomposition and nutrient release. In general, areas with mining impact led to subtle changes in ants and other arthropods communities and in environmental variables.