Influência dos estágios sucessionais na conservação de aves em uma região de floresta subtropical no sul do Brasil

Abstract

The heterogeneity of environments resulting from the processes of forest restructuring influence the composition and richness of the birds in secondary successional stages of forest recovery. In this way, understanding how birds are distributed through the different stages of succession can provide important information in the definition of conservation strategies for the group, or indicate how areas in secondary stages of regeneration can contribute to the maintenance of bird communities. This study aimed to record the richness and abundance of birds at different stages of succession in a subtropical forest in southern Brazil and to discuss which factors influence this distribution. The study was carried out in the Municipal Natural Park Mata do Rio Uruguai Teixeira Soares (PTS), located in the municipality of Marcelino Ramos, in the north of the State of Rio Grande do Sul. For the data collection, three sample areas within the PTS were selected, representative of the three successional stages of the secondary forest. Area 1, Secondary forest in initial regeneration stage; Area 2, Secondary secondary forest; and Area 3, Secondary forest in advanced stage. In each area eight sampling points were established, distant 100 meters apart and arranged in two transects with four points. To compare the similarity between transects, the Jaccard similarity coefficient was used to compare the richness and abundance and the ecological characteristics between the areas was analyzed by variance analysis (One-way ANOVA). The diversity among the three areas was compared using the Shannon H Index. Overall wealth was estimated for each area. 147 bird species were registered in the three areas. About 90% of the species richness estimated for the Park was registered. The largest number of species was recorded in Area 2 (N = 95) followed by Area 1 (N = 93) and Area 3 (N = 88). There was no significant difference in the number of species recorded in each sampling between the areas (F2, 15 = 0.38, p = 0.68). Area 1 showed higher number of exclusive species (N = 16). The predominant eating habits in the study area were Onivorous (N = 52) and Insetívoro (N = 46). The most common habitat use was Forest (N = 63). There was a difference in species composition among areas and consequently in eating habits and habitat use. Differences in species composition and diversity between areas indicate that the structure of the bird community is directly linked to successional stages. This relationship is reinforced by the differences in the occurrence of birds of certain ecological characteristics between the areas. The size, connectivity of the fragments and the availability of habitats directly influence the distribution of the avifauna. Changes in the landscape promote a restructuring of these communities, where species with certain ecological characteristics can be favored or excluded. The main contribution of the most advanced stages of regeneration to birds is in the maintenance of more sensitive populations, which may be threatened with extinction.