Impactos das mudanças no uso do solo do cerrado baiano em variáveis biofísicas do balanço de radiação por sensoriamento remoto.

Abstract

The Brazilian Cerrado has been subjected to profound changes in land use and occupation, with environmental consequences that need to be properly investigated. This research evaluated the impacts that changes in land use and occupation have been produced on biophysical variables involved in the radiation balance at surface, in the Cerrado of the state of Bahia, and on meteorological variables. The study area has 14,503.3 km2 , a considerable part of them has been used for agricultural production. TM - Landsat 5 and OLI/TIRS - Landsat 8 images, from the years 1984 to 2010 and 2019, respectively, were used to generate thematic maps of biophysical variables of the radiation balance, complemented with meteorological data from the National Institute of Meteorology (INMET. Scripts were created in the Erdas 9.1 Model Maker to calculate the albedo, vegetation indices (Normalized Difference Vegetation Index - NDVI, Leaf Area Index - IAF, Soil Adusted Vegetation Index - SAVI and Vegetation Cover Fraction - FCV), land surface temperature– Tsup (°C), long-wave radiation emitted by the surface – Rol,emi (W/m²) and net radiation – Rn (W/m²). The input images in Model Maker, both from TM and from OLI/TIRS, were obtained from the Google Earth Engine. Statistical tests were used to assess whether there is a significant difference between the mean albedo, NDVI, Tsup and Rn of seven small plots, and also whether the correlation coefficients of the daily maximum and minimum air temperature and ETo data differed significantly from zero. The results show that the replacement of primary vegetation by agricultural and/or pasture areas has modified the patterns and values of NDVI, albedo, surface temperature, surface radiant emittance and radiation balance. The balance of radiation in september 1984 reached values above 580 W/m² in areas with higher vegetative density, while in areas already anthropized there was a significant reduction in the values of Rn, while the Tsup was superior in relation to the non-anthropized areas, both intra and inter images. The highest values of Rn were observed in February in the non-anthropized areas, but also in pivots with NDVI above 0.80. It is evident that although in some months of the year the areas with pivots exhibited very high values of NDVI and Rn, and low values of albedo and Tsup, in most months of the year these areas show opposite patterns, with marked variability, especially in the NDVI, Tsup and Rn. The time series of daily Ta,max and Ta,min and ETo showed an increasing trend in the period 1980 to 2020, with a sample correlation coefficient significantly different from zero, according to the Student's t test. The main conclusion of the study is that the changes in land use and occupation in the study area can be identified as the main responsible for the trends of increase in air temperature locally.