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A Bacia do Rio Araguaia e uma regiao cujos ambientes mostram-se marcados pelas variacoes anuais de inundacao. A caracterizacao da cobertura da terra tem o potencial de caracterizacao do funcionamento ecossistemico, bem como, avaliar possiveis modificacoes antropicas. O presente trabalho teve como objetivo avaliar as variacoes espectrais de classes de uso e cobertura da terra da Ottobacia 6951, localizada no Medio curso do Rio Araguaia, no ano de 2017. Foram utilizadas imagens de reflectância da superficie terrestre do sensor Operational Land Imager (OLI) do satelite Landsat 8, referente aos periodos de transicao chuva-seca (maio), seca (julho) e transicao seca-chuva (outubro) de 2017. Para cada data foram geradas imagens-fracao, atraves da tecnica de mistura espectral, considerando tres membros finais (natural, pastagem e agua), evidenciando as mudancas da cobertura. Tambem foram gerados indices de vegetacao para cada periodo, evidenciado os aspectos biofisicos da cobertura da terra. Para essa avaliacao foram estabelecidos 50 pontos aleatorios para cada classe considerando a bacia inteira, cada unidade geomorfologica e uso e cobertura da terra. A avaliacao dos padroes temporais da cobertura da terra considerou, especialmente, as relacoes de significância entre os fatores “cobertura” e “periodo”, para a realizacao de Analise Multivariada de Permutacao (PERMANOVA). A avaliacao de agrupamentos foi realizada por meio da Analise de Componentes Principais (ACP), que proporciona a reducao da dimensionalidade dos dados. A cobertura da terra foi a variavel de maior significância das mudancas intra-anuais da Ottobacia. A classe pastagem apresentou a maior variacao intra-anual, expressando um comportamento mais sensivel a sazonalidade. A B S T R A C T The Araguaia River Basin is an area whose environments are marked by annual flood variations. The characterization of the land cover has the potential to characterize the ecosystem functioning, as well as to evaluate possible anthropic changes. The objective of this work was to evaluate the spectral variations of land use and land cover classes of Ottobacia 6951, located in the middle course of the Araguaia River, in the year 2017. Land surface reflectance images of the Operational Land Imager (OLI) ) of the Landsat 8 satellite, referring to the rainy-dry (May), dry (July) and dry-rainy transition (October) periods of 2017. For each date fractional images were generated, using the spectral mixing technique, considering three final members (natural, pasture and water), evidencing changes in coverage. Vegetation indexes were also generated for each period, evidencing the biophysical aspects of the land cover. For this evaluation were established 50 random points for each class considering the entire basin, each geomorphological unit and land use and coverage. The evaluation of temporal patterns of land cover considered, especially, the relations of significance between the factors "coverage" and "period", for the realization of Multivariate Analysis of Permutation (PERMANOVA). The clustering evaluation was performed through the Principal Component Analysis (PCA), which provides a reduction in the dimensionality of the data. Land cover was the most significant variable of Ottobacia's intra-annual changes. The pasture class had the highest intra-annual variation, expressing a behavior more sensitive to seasonality. Keyworks: river geomorphology, land cover seasonality, spectral mixing, vegetation indices, land use and cover.

revista brasileira de geografia física

Variação Intra-Anual da Cobertura da Terra de Uma Ottobacia no Médio Curso do Rio Araguaia (Intra-Annual Variation in Land Cover of an Ottobacia in the Middle Course of the Araguaia River )