Comunidades de aves em paisagens fragmentadas de Goiás
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Data
2016-09-06
Autores
Jesus, Shayana de [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O Cerrado, mesmo sendo o terceiro bioma brasileiro com maior riqueza de aves, ainda apresenta lacunas de conhecimento sobre sua avifauna. A crescente e rápida destruição desse bioma nas últimas décadas representa uma ameaça à diversas espécies, e por isso é fundamental conhecer as comunidades de aves e os efeitos da fragmentação sobre elas. Este trabalho visa contribuir para o conhecimento da avifauna em fragmentos florestais do Cerrado, suprir as lacunas acerca dos efeitos da fragmentação em escala local e na escala da paisagem e identificar os fatores responsáveis pela mudança na composição das comunidades nestes fragmentos. As amostragens foram realizadas em 17 fragmentos florestais situados ao longo do estado de Goiás. Cada fragmento foi amostrado durante seis dias (três na estação seca e três na estação chuvosa). Foram empregados os métodos de captura com redes ornitológicas e pontos de escuta. Registros obtidos ocasionalmente serviram para complementar os dados de composição específica e de riqueza específica. A tese está estruturada em três capítulos. O primeiro capítulo reúne informações sobre a riqueza e composição das comunidades de aves dos fragmentos, discutindo aspectos biogeográficos e conservacionistas. O segundo capítulo mostra os efeitos da fragmentação florestal sobre a riqueza específica e a riqueza de grupos funcionais de aves, tanto na escala do fragmento, quanto na escala da paisagem. O terceiro capítulo elucida o padrão de estruturação das comunidades e a influência da distância geográfica, de variáveis ambientais na escala local e de variáveis ambientais na escala da paisagem sobre a diversidade beta. Foram registradas 271 espécies e a riqueza dos fragmentos variou de 74 a 114 espécies. Alguns fragmentos na região central e noroeste do estado se destacaram pela riqueza de espécies e pelo número de espécies exclusivas, além da presença de elementos de outros biomas, Atlânticos e Amazônicos, para a região central e noroeste, respectivamente. Constatou-se que apenas variáveis locais tiveram efeitos sobre a riqueza específica e a riqueza dos grupos funcionais. Essa relação mais forte com fatores locais é explicada pela maior heterogeneidade ambiental dos fragmentos do Cerrado, propiciada pelo contato com fitofisionomias adjacentes. A substituição espacial foi o padrão predominante na estruturação das comunidades. As variações na diversidade beta foram explicadas somente pelas variáveis ambientais das paisagens, sendo a configuração mais importante que a composição da paisagem. Isso indica que processos ecológicos determinísticos, associados às diferentes respostas das espécies à conectividade e isolamento das paisagens, são mais importantes do que processos estocásticos, dirigidos pela dispersão das espécies. Os resultados obtidos destacam o valor biogeográfico e conservacionista dos fragmentos florestais do Cerrado. Alertam ainda para a necessidade de desenvolver estratégias de manutenção de todo o mosaico natural do bioma para garantir a conservação da avifauna florestal. Ainda que áreas florestais sejam mantidas intactas, caso a destruição de fitofisionomias campestres e savânicas persista, ocorrerá um aumento no isolamento entre fragmentos. Isso prejudicará o deslocamento de muitas espécies de aves nessas paisagens e, consequentemente, poderá levar à extinção local de espécies sensíveis ao isolamento, inclusive espécies com distribuições restritas à essas paisagens.
Even though the Cerrado is the Brazilian biome with third greatest bird species richness, there are still some gaps of knowledge regarding its avifauna. The increasing and rapid destruction of this biome in recent decades represents a threat to several species. Therefore, it is essential to know the bird communities and the effects of fragmentation on them. This work aims to contribute to knowledge of the avifauna in forest fragments of the Cerrado, fill the gaps with respect of the effects of fragmentation at both the local and landscape scales and identify the factors responsible for changes in composition of bird communities in these fragments. Sampling of 17 forest fragments were carried out throughout the State of Goiás. Each fragment was sampled for six days (three in the dry season and three in the rainy season). Ornithological nets and point counts were used as sampling methods. Records, where available, served as a complement for species composition and species richness data sets. The thesis is structured in three chapters. The first chapter gathers information on the richness and composition of the bird communities in the fragments, discussing biogeographic and conservation aspects. The second chapter shows the effects of forest fragmentation on species and bird functional group richness, at both fragment and landscape scales. The third chapter elucidates the structuring pattern of the studied bird communities. Moreover, it sheds light on how geographical distance, at a local scale, and environmental variables, at both local and landscape scales, influences beta diversity. Two hundred and seventy one species were recorded. Bird richness of the fragments ranged from 74 to 114 species. Some fragments in Central and Northwest regions of Goias stood out by their species richness and number of unique species. Besides that, Atlantic and Amazonian elements were present in the Central and Northwest regions respectively. Therefore, only local variables have had effects on species and functional group richness. This stronger relationship between bird communities and local factors can be explained by the greater environmental heterogeneity of the Cerrado fragments, due to their contact with adjacent vegetation types. Spatial species turnover was the predominant community structuring pattern. Variations in beta diversity were explained only by the environmental variables of the landscape, being more important than the landscape configuration. This indicates that deterministic ecological processes associated with different species responses to connectivity and isolation of the landscapes are more important than stochastic processes, driven by species dispersion. The results highlight the biogeographic and conservation values of the Cerrado forest fragments. They also emphasize the necessity of developing management strategies for the entire natural mosaic of the Cerrado biome in order to ensure the forest avifauna conservation. If destruction of scrublands and savanna persists, fragment isolation will be increased even if forest areas are kept intact. Consequently, bird species’ movements in these landscapes will be jeopardized. Thus, species that are sensitive to isolation, including species with distributions restricted to these specific landscapes, may become locally extinct.
Even though the Cerrado is the Brazilian biome with third greatest bird species richness, there are still some gaps of knowledge regarding its avifauna. The increasing and rapid destruction of this biome in recent decades represents a threat to several species. Therefore, it is essential to know the bird communities and the effects of fragmentation on them. This work aims to contribute to knowledge of the avifauna in forest fragments of the Cerrado, fill the gaps with respect of the effects of fragmentation at both the local and landscape scales and identify the factors responsible for changes in composition of bird communities in these fragments. Sampling of 17 forest fragments were carried out throughout the State of Goiás. Each fragment was sampled for six days (three in the dry season and three in the rainy season). Ornithological nets and point counts were used as sampling methods. Records, where available, served as a complement for species composition and species richness data sets. The thesis is structured in three chapters. The first chapter gathers information on the richness and composition of the bird communities in the fragments, discussing biogeographic and conservation aspects. The second chapter shows the effects of forest fragmentation on species and bird functional group richness, at both fragment and landscape scales. The third chapter elucidates the structuring pattern of the studied bird communities. Moreover, it sheds light on how geographical distance, at a local scale, and environmental variables, at both local and landscape scales, influences beta diversity. Two hundred and seventy one species were recorded. Bird richness of the fragments ranged from 74 to 114 species. Some fragments in Central and Northwest regions of Goias stood out by their species richness and number of unique species. Besides that, Atlantic and Amazonian elements were present in the Central and Northwest regions respectively. Therefore, only local variables have had effects on species and functional group richness. This stronger relationship between bird communities and local factors can be explained by the greater environmental heterogeneity of the Cerrado fragments, due to their contact with adjacent vegetation types. Spatial species turnover was the predominant community structuring pattern. Variations in beta diversity were explained only by the environmental variables of the landscape, being more important than the landscape configuration. This indicates that deterministic ecological processes associated with different species responses to connectivity and isolation of the landscapes are more important than stochastic processes, driven by species dispersion. The results highlight the biogeographic and conservation values of the Cerrado forest fragments. They also emphasize the necessity of developing management strategies for the entire natural mosaic of the Cerrado biome in order to ensure the forest avifauna conservation. If destruction of scrublands and savanna persists, fragment isolation will be increased even if forest areas are kept intact. Consequently, bird species’ movements in these landscapes will be jeopardized. Thus, species that are sensitive to isolation, including species with distributions restricted to these specific landscapes, may become locally extinct.
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Palavras-chave
Avifauna, Fragmentos florestais, Ecologia de paisagem, Diversidade beta, Conservação, Avifauna, Forest fragments, Landscape ecology, Beta diversity, Conservation