ANDRADE, J. M.; http://lattes.cnpq.br/3512381224827163; ANDRADE, João Maria de.
Resumo:
Accurate information on the land cover is crucial for efficient monitoring and development of
environmental studies in the Brazilian Caatinga forest, one of the largest and most biodiverse
dry forests on the planet. Distinguishing different patterns of land cover through medium
spatialresolution remote sensing, such as the Landsat image series, is challenging to Caatinga due to heterogeneous land cover, complex climatesoil vegetation interactions, and anthropogenic disturbance. Two remote sensing approaches have a high potential for accurate and efficient landcover mapping in Caatinga: single and multidate imagery. The heterogeneity of the land cover of this environment can contribute to a better performance of multispectral approaches that are usually applied for singledate images. In a landcover mapping effort in Caatinga, the temporal factor gains relevance, and the use of time series can bring advantages, but, in general, this approach uses vegetation index, losing multispectral information. This manuscript assesses the accuracies and advantages of singledate multispectral and multidate Normalized Difference Vegetation Index (NDVI) approaches in landcover classification. Both approaches use the Random Forest method, and the results are evaluated based on samples collected during field surveys. Results indicate that landcover classification obtained from multidate NDVI performs better (overall accuracy of 88.8% and kappa of 0.86) than singledate multispectral data (overall accuracy of 81.4% and kappa coefficient of 0.78). The Ztest indicated that the difference in performance between the two approaches was statistically significant. The lower performance observed for singledate multispectral classification is due to similarities in spectral responses for targets of deciduous vegetation that lose their foliage and can be misread as nonvegetated areas. Meanwhile, an accurate classification by time series of plant clusters in seasonal forests allows incorporating seasonal variability of landcover classes during the rainy and dry seasons, as well as transitions between seasons. The most important variables that contributed to the accuracy were the Red, Near Infrared (NIR) and ShortWave Infrared (SWIR) bands in singledate multispectral classification, and the months in the dry season were the most relevant in multidate NDVI classification.