Amplificação dos efeitos de borda pelo gado bovino em fragmentos florestais: respostas das comunidades de escarabeíneos e suas funções ambientais

Abstract

Forest fragmentation is produced by the loss of large native forest areas and changes on the ecosystem, leaving small isolated forest fragments. The edge effect arises as a consequence of fragmentation and produces a transition zone between the inside and outside forest interior. It is known that the presence of cattle brings negative effects on the vegetation structure, soil compaction and dispersion of exotic species and pathogenic for the ecosystem, them the cattle´s grazing can exacerbate the edge effect. Although the Atlantic Forest and Cerrado are global biodiversity hotspots, they are in critical condition due to high forest fragmentation rates that have suffered. Activities such as cattle grazing are one of the main causes of fragmentation and are still a common practice in the region of southeastern Brazil. Thus, this work aimed to evaluate the impact of the edge effect and the occurrence of cattle on dung beetles´ communities and their ecological functions in a fragmented landscape of the rural region of Lavras, Minas Gerais, Brazil. The dung beetles were chosen because they are widely used and recommended as excellent bioindicators. In the article, we evaluate the consequences of the edge effect and the presence / absence of cattle on the parameters (abundance, richness and species composition) and ecological functions (dung removal and soil disturbance) of dung beetles´ communities. We chose eight areas of the rural region of Lavras, which were studied three habitats: pasture, edge and forest fragment interior. Four areas had no cattle occurrence on the edge and in the forest interior; the remaining habitats had the presence of cattle. In areas with cattle only dung removal on the edge and forest interior had higher values than the pasture. In areas without presence of cattle, the species richness and abundance differed between the three habitats and was higher in the forest interior. Beside in areas without cattle, the ecological functions had only differences between forest interior and pasture, always being higher in the forest. The species composition also differed significantly between habitats and treatments (with and without cattle), but not between the combination of these factors. However, communities in the forest interior with cattle were present in the communities closest position of the edges. Our study shows that cattle presence exacerbates the edge effects, producing a homogenization of the abundance, richness and composition of species of dung beetles communities of forest interior. However, the ecological functions of dung removal and soil disturbance are not affected.