Avaliação temporal da variação da cobertura vegetal pela ação do fogo no município de Lábrea (AM)

Abstract

The objective of this work was to analyze and quantify the areas of fire occurrence and the consequences of its action on vegetation in the area of coverage of the municipality Lábrea, in the southern region of the State of Amazon. Scenes of the sensor were used Operational Land Imager (OLI) aboard the satellite Landsat 8, from the months of August and September, 2014 and 2015, which have undergone treatment by means of remote sensing techniques divided in two Steps: (1) Preprocessing (Radiometric Calibration, atmospheric correction, conversion of values of reflectance and noise removal; 2) Postprocessing (generation of vegetation indexes, Normalized Difference Vegetation Index – NDVI, Normalized Burn Index – NBR, image composition, interpretation, mapping, quantification and spectral behavior of vegetation). There were also used data of heatoutbreaks from the forest burning program of the National Institute for Spatial Research (INPE). The results show the high rise of heat outbreaks in the year 2015, in relation to the year 2014. A location with a greater concentration of heat-outbreaks was the Assentamento Monte Project. The application of the indices of vegetation NDVI and NBR shows the potential of the identification and mapping of burnt areas. The comparison of heat outbreaks with effective burnt-out areas showed the inaccuracy of the location of the forest fire monitoring sensors. The total estimate of burnt areas in two different areas (area 1 and 2) of the municipality was 1,174.37 ha in August and 12.761.26 ha in September of 2014 and 22,403.86 ha in August and 23,320.71 ha in September of 2015. By means of the spectral behavior of vegetation, it may be noted that the reflectance from the surface after a burn, reflected a greater amount of energy in the bands of red and blue. Confronted with the results found that greater quantity of heat outbreaks and burnt areas are in settling projects areas and that the NBR vegetation index has greater potential to distinguish burnt areas of other types of vegetation, the spectral response of the surface is altered with the burning events in which the red band presented greater sensitivity.