Avifauna de fragmentos florestais e em área de cultivo de cana de açúcar no Médio Tietê
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Data
2020-01-30
Autores
Mello Junior, José Roberto Silveira
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Universidade Estadual Paulista (Unesp)
Resumo
As constantes alterações no uso do solo e a configuração dos remanescentes florestais remodelam a distribuição das espécies de aves na paisagem. Em 2006/7 a expansão da cana de açúcar, para suprir a demanda de biocombustível, ocupou áreas de pastagens e de outras culturas agrícolas no interior do Estado de São Paulo. As áreas de cultivo de cana de açúcar são caracterizadas por plantio em grandes extensões de terra aumentando o isolamento dos remanescentes florestais e atuando como filtro nas comunidades das aves. Assim, esse trabalho teve como objetivo compreender como a avifauna se distribui no ambiente produtivo de cana de açúcar e nos fragmentos florestais adjacentes, lineares e não-lineares. E de avaliar quais variáveis, locais e/ou da paisagem são importantes para os valores de riqueza e de abundância de espécies de aves. Por fim, a indicação de espécies que apresentassem uma alta especificidade aos ambientes presentes na área produtiva para seu uso em programas de monitoramentos futuros. Foram realizados 200 pontos fixos, com um raio de 50 metros, em cinco ambientes amostrais: fragmentos (não-lineares); fragmentos lineares (matas ciliares); borda dos fragmentos; bordas de fragmentos lineares e nas áreas de cultivo de cana de açúcar. As amostragens ocorreram entre outubro de 2018 a março de 2019. Foram testadas a variância da riqueza e da abundância dos pontos amostrais e a relação entre a composição de espécies com os ambientes amostrais associado ao estágio sucessional. A diversidade foi analisada pelo índice de Shannon e a distribuição das espécies nos ambientes amostrais pela análise de correspondência. As espécies também foram classificadas pelas características de hábito alimentar, preferência de habitat e pela sensibilidade a alterações ambientais. A riqueza e a abundância foram confrontadas com 18 variáveis ambientais, sendo 8 variáveis locais e 10 variáveis da paisagem, para serem correlacionadas com a riqueza e a abundância de espécies através de um modelo aditivo generalizado (GAM). Para testar a preferência e/ou exclusividade das espécies pelos ambientes foi realizada a Análise de Espécies Indicadoras (Indicator Species Analysis). Foram obtidos os registros de 208 espécies de aves. A maior riqueza de espécies (138 sp.) foi observada no ambiente de fragmento linear (mata ciliar), seguida pelos ambientes de borda dos fragmentos lineares (121sp.), bordas de fragmentos não-lineares (106 sp.), fragmentos não-lineares (101 sp.) e com menor riqueza as áreas de cultivo de cana de açúcar (22 sp.). Entre as espécies amostradas, sete estão presentes na lista de espécies ameaçadas de extinção no Estado de São Paulo. A maior variação da riqueza e da abundância foi observada no ambiente de cana de açúcar com os demais ambientes. Os valores do índice de diversidade de Shannon acompanharam o observado na riqueza dos pontos amostrais, de maior valor da riqueza nos ambientes associados aos corpos d’água. Em geral, observou-se um maior número de espécies de baixa sensibilidade, insetívoras e nos ambientes mais alterados houve o predomínio de espécies onívoras. Das 18 variáveis ambientais, foram selecionadas 8 variáveis sem autocorrelação, sendo 4 variáveis locais e 4 variáveis da paisagem. Estas variáveis foram utilizadas nas análise exploratória e para os modelos aditivos generalizados, sendo utilizado o método de Akaike para selecionar o modelo mais parcimonioso. Entre os 8 modelos gerados, o modelo selecionado foi o composto por 2 variáveis locais, classificação do estágio sucessional e classificação do estágio da cultura da cana de açúcar e 2 variáveis da paisagem, porcentagem de área florestada e o índice de isolamento Meshsize. Foram indicadas 60 espécies associadas aos ambientes e/ou à combinação de ambientes, sendo 12 espécies para o ambiente linear de mata ciliar e 11 para os fragmentos florestais não-lineares. Embora a maioria das espécies de aves amostradas possuam uma ampla distribuição na paisagem, foi possível avaliar como as espécies se distribuem na paisagem agrícola e reunir dados para subsidiar ações de conservação para as áreas agrícolas de cultivo de cana de açúcar.
The constant variations in land use and the configuration of forest remnants reshape the distribution of bird species in the landscape. In 2006 / 7, in order to supply the demand for biofuel, the expansion of sugarcane occupied areas of pastures and other agricultural crops in the interior of the State of São Paulo. Sugarcane cultivation areas are characterized by planting over large areas of land, increasing the isolation of forest remnants and acting as a filter in avian communities. Thus, the present work aimed to understand how the avifauna is distributed in the productive natural environment of sugarcane and in the linear and non-linear adjacent forest fragments. It also intended to assess which variables, locations and / or landscapes are important for the richness and abundance of bird species. Finally, it was also sought to indicate the species that present a high specificity to the environments present in the productive area for use in future monitoring programs. Two hundred fixed points, with a 50 meters radius, were performed in five different sample environments: fragments (non-linear); linear fragments (riparian forests); fragments edge; edges of linear fragments and in sugarcane cultivation areas. Sampling occurred between October 2018 and March 2019. The variance of the richness and abundance of the sampling points and the relationship between the species composition and the sampling environments associated with the successional stage were tested. Diversity was analyzed using the Shannon index, and the distribution of species in the sample environments was performed by correspondence analysis. The species were also classified by characteristics of eating habits, habitat preference and sensitivity to environmental changes. Richness and abundance were compared to 18 environmental variables - 8 local variables and 10 landscape variables - in order to be correlated with species richness and abundance through a generalized additive model (GAM). To test the preference and / or exclusivity of species for the environments, the Indicator Species Analysis was employed. Records of 208 species of birds were obtained. The greatest species richness (138 sp.) was observed in the environment of linear fragments (riparian forest), followed by the environments of linear fragments edges (121sp.), nonlinear fragments edges (106 sp.), and non- linear fragments (101 sp.). The areas of sugar cane cultivation (22 sp.) were the ones presenting the lowest richness. Among the species sampled, seven are present in the list of Endangered Species in the State of São Paulo. The greatest variation in richness and abundance was observed in the sugarcane environment compared to the other environments. The values of the Shannon Diversity Index followed what was observed in the richness of the sampling points, which presented the highest richness value in the environments associated with bodies of water. In general, a greater number of low-sensitivity, insectivore species were observed. In the most altered environments there was a predominance of omnivorous species. Among the 18 environmental variables, 8 variables were selected without autocorrelation - 4 local variables and 4 landscape variables. These variables were subjected to an exploratory analysis and to generalized additive models, using the Akaike method to select the most pragmatic model. Among the 8 models generated, the model selected was the one composed of 2 local variables, classification of the successional stage, classification of the sugarcane culture stage and 2 landscape variables, percentage of forested area and the Mesh Size isolation index. Sixty species associated with the environments and / or combination of environments were indicated - 12 species for the linear environment of riparian forest and 11 for the non-linear forest fragments. Although the majority of sampled bird species present a wide distribution in the landscape, it was possible to evaluate how the species are distributed in the agricultural landscape and to gather data to subsidize conservation actions for agricultural areas of sugarcane cultivation.
The constant variations in land use and the configuration of forest remnants reshape the distribution of bird species in the landscape. In 2006 / 7, in order to supply the demand for biofuel, the expansion of sugarcane occupied areas of pastures and other agricultural crops in the interior of the State of São Paulo. Sugarcane cultivation areas are characterized by planting over large areas of land, increasing the isolation of forest remnants and acting as a filter in avian communities. Thus, the present work aimed to understand how the avifauna is distributed in the productive natural environment of sugarcane and in the linear and non-linear adjacent forest fragments. It also intended to assess which variables, locations and / or landscapes are important for the richness and abundance of bird species. Finally, it was also sought to indicate the species that present a high specificity to the environments present in the productive area for use in future monitoring programs. Two hundred fixed points, with a 50 meters radius, were performed in five different sample environments: fragments (non-linear); linear fragments (riparian forests); fragments edge; edges of linear fragments and in sugarcane cultivation areas. Sampling occurred between October 2018 and March 2019. The variance of the richness and abundance of the sampling points and the relationship between the species composition and the sampling environments associated with the successional stage were tested. Diversity was analyzed using the Shannon index, and the distribution of species in the sample environments was performed by correspondence analysis. The species were also classified by characteristics of eating habits, habitat preference and sensitivity to environmental changes. Richness and abundance were compared to 18 environmental variables - 8 local variables and 10 landscape variables - in order to be correlated with species richness and abundance through a generalized additive model (GAM). To test the preference and / or exclusivity of species for the environments, the Indicator Species Analysis was employed. Records of 208 species of birds were obtained. The greatest species richness (138 sp.) was observed in the environment of linear fragments (riparian forest), followed by the environments of linear fragments edges (121sp.), nonlinear fragments edges (106 sp.), and non- linear fragments (101 sp.). The areas of sugar cane cultivation (22 sp.) were the ones presenting the lowest richness. Among the species sampled, seven are present in the list of Endangered Species in the State of São Paulo. The greatest variation in richness and abundance was observed in the sugarcane environment compared to the other environments. The values of the Shannon Diversity Index followed what was observed in the richness of the sampling points, which presented the highest richness value in the environments associated with bodies of water. In general, a greater number of low-sensitivity, insectivore species were observed. In the most altered environments there was a predominance of omnivorous species. Among the 18 environmental variables, 8 variables were selected without autocorrelation - 4 local variables and 4 landscape variables. These variables were subjected to an exploratory analysis and to generalized additive models, using the Akaike method to select the most pragmatic model. Among the 8 models generated, the model selected was the one composed of 2 local variables, classification of the successional stage, classification of the sugarcane culture stage and 2 landscape variables, percentage of forested area and the Mesh Size isolation index. Sixty species associated with the environments and / or combination of environments were indicated - 12 species for the linear environment of riparian forest and 11 for the non-linear forest fragments. Although the majority of sampled bird species present a wide distribution in the landscape, it was possible to evaluate how the species are distributed in the agricultural landscape and to gather data to subsidize conservation actions for agricultural areas of sugarcane cultivation.
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Palavras-chave
Aves, Matriz agrícola, Cana de açúcar, Indicação de espécies, Paisagem, Modelos aditivos generalizados, Birds, Agricultural matrix, Sugarcane, Fragmentation, Landscape, Indication of species, Generalized additive model