Effect of fires on biophysical parameters, energy balance and evapotranspiration in a protected area in the Brazilian Cerrado
Israel Oliveira Ivo, Marcelo Sacardi Bíudes, George L. Vourlitis, Nadja Gomes Machado, Charles Campoe Martim
Abstract
Fires are essential for defining the structure, biodiversity and functioning of the Brazilian Cerrado. Several protected areas have been created in the Cerrado to conserve natural ecosystems by eliminating, minimizing or reducing human pressures and threats operating within their limits. However, impacts of these conservation practices on the local microclimate and change in fire coverage are poorly known. Thus, the aim of this study was to evaluate the impact of the 2017 megafire in the Chapada dos Guimarães National Park (CGNP) on biophysical parameters, energy balance and evapotranspiration. We used data from fire spots between 2000 and 2017 and images from sensors Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS) Landsat 8 between July and October 2017. The satellite images provided data to calculate the Normalized Difference Vegetation Index (NDVI), Surface Albedo (α), Normalized Difference Water Index (NDWI), while the Simplified Surface Energy Balance (SSEB) model provided estimates of the radiation balance (Rn), soil heat flux (G), sensible heat flux (H), latent heat flux (LE), and the daily evapotranspiration (ET). Surface reflectance and energy balance were evaluated before and after fire at three time periods throughout the study. All variables analyzed were affected by the combination of climate dynamics and fire occurrence. NDVI, LE and ET decreased, and α, NDWI, G and H increased throughout the dry season in the CGNP. The fire that occurred in the CGNP in 2017 decreased NDVI, LE, LE/Rn and ET and increased α, NDWI, G, H and H/Rn significantly. This study demonstrated that fires decrease surface biomass and surface-to-atmosphere water transfer and increase surface warming on Cerrado.