Dinâmica e composição da avifauna do sub-bosque sob influência de diferentes históricos de queimada em uma savana Amazônica

Abstract

Bird dynamics and composition under different fire regimes in an Amazonian Savanna. Savannas are ecosystems maintained by fires, characterized by a fire-adapted biota. Different fire regimes can generate structurally diverse vegetation, and savanna birds are known to be closely related to vegetation structure. However, long-term approaches and interaction of fire with other environmental factors need to be explored for the better understanding of the effects of fire on birds. The effects of different fire regimes were investigated in a 12-ha area for a period of 23 years, and in a short-term post-fire survey in an area not burned for 13 years. The effects of frequency and extent of fires, tree cover, and forest distance on bird composition were assessed in twelve 3.7- ha plots. Birds were surveyed with mist-nets and species were classified as to their habitat use by comparison of registers in forest and savanna plots through visual/acoustical surveys. The avifauna, represented by the first axes obtained in a NMDS ordination based on quantitative and qualitative species, changed little in a 10-year period with regular fires. After 13 years of fire suppression, many forest species colonized the area and some savanna species were lost. However, after one fire event some savanna species returned. Fire frequency was the variable with most effect on avifauna. Species richness was higher in plots closer to the forest, and lower in plots where fires were more frequent. The avifauna was sensitive to the occurrence of fires, independent of fire extent. These results indicate that many savanna bird species depend on the occurrence of regular fires.