Perda de habitat e efeitos de borda na comunidade de aves de sub-bosque em florestas de areia branca na Amazônia Central

Abstract

Habitat loss and edge effects are the most common human-driven processes affecting biodiversity. The Amazon has lost a large extension of habitat through deforestation, which occurs mostly by clear-cutting and burning practices. Human impacts, however, have mostly been studied in originally continuous terra firme forests. Naturally patchy and poor-nutrient environments may respond differently to landscape change. White-sand ecosystems cover a small proportion of the Amazon, have low resilience after disturbances, and are poorly understood. Here we report on the effects of deforestation, edge effects and road effects on richness, abundance, composition and β-diversity of understory bird communities in a white- sand forest human-modified landscape. We also evaluated the response of insectivorous and frugivorous feeding guilds separately. Using mist-nets, we sampled 14 landscapes (with seven non-consecutive surveys per landscape) and recorded 82 species and 703 individuals. We found a turn-over driven community composition along the disturbance gradient, indicating that species are not lost, but replaced across landscapes, but found no evidence for density compensation because of the arrival of generalist species into more disturbed sites. Deforestation and distance to the edge had a negative effect on bird abundance which was mostly driven by forest insectivore species. Frugivore birds, however, were not strongly affected by landscape metrics. Changes in species composition were mostly driven by deforestation. Given the peculiar characteristics of white-sand forests, we suggest that the minimum amount of habitat cover should be above usual thresholds, to avoid drastic population declines, which can eventually lead to local species extinction.