Influência da cobertura florestal nas comunidades de aves e funções ecossistêmicas

Abstract

This thesis aims to understand diversity and the processes that modulate changes in bird assemblages and ecosystem functions across a landscape-level gradient in the Atlantic Forest. In the first chapter, I used data on bird assemblage structure (richness and composition), specifically on forest-dependent and habitat-generalist birds, to assess the effects of forest cover in high Montane Atlantic Forest landscapes. In addition, I assessed species distribution thresholds in relation to the forest cover gradient. I found that decreasing forest cover reduced the richness of forest-dependent species and increased the richness of habitat generalist birds. However, the gain of habitat generalists did not compensate for the loss of forest-dependent birds. Furthermore, in landscapes with less than 32% forest cover, the exclusion of forest- dependent species can reach 23%. Thus, the amount of forest cover is a determining factor for the structure of bird communities. In the second chapter, I assess the effects of forest cover on the abundance and species composition of frugivorous and insectivorous birds in the Montane Atlantic Forest and how these changes may affect ecosystem functions, frugivory and predation. I measured frugivory and predation through the consumption of artificial fruits and caterpillars. I observed that landscapes with less forest cover showed a lower abundance of both frugivorous and insectivorous birds. I also verified that changes in species composition for frugivorous birds occur due to the loss or gain of species, while for insectivorous birds, they occur by replacement of species. Regarding the functions evaluated, I found an increase in the consumption of large fruits and a decrease in the consumption of small fruits in landscapes with a low abundance of frugivorous birds. However, for predation, I did not find any effect on insectivorous bird abundance. Thus, forest cover in Montane Atlantic Forest landscapes is an important shaping force for frugivorous birds and their functions. Moreover, maintaining forest cover in montane environments is fundamental to preserving forest- dependent species and ecosystem functions such as frugivory. Landscapes, where more than 30% of the original forest area has been lost, can have an irreversible effect on the bird community and its ecosystem functions. Moreover, the percentage of 20% native Atlantic Forest in all rural properties, proposed by the Forest Code, is not effective for the protection of forest-dependent species. Therefore, we highlight the importance of actions to restore forest cover in montane environments where this habitat has been lost by anthropogenic actions and is often neglected.