The influences of forest fires on the repellency, mineralogy and thermogravimetry of soils in a mountainous area of the Atlantic forest biome: The study case of São Pedro da Serra, Rio de Janeiro (Brazil)

Landscapes are systems undergoing constant transformation, associated with different forms of environmental disturbances. Among these disturbances are fires, which depending on the magnitude and frequency can have effects with different severities. In the district of São Pedro da Serra, in the municipality of Nova Friburgo, located in the mountain region of the state of Rio de Janeiro, Brazil, controlled burning is often used to prepare areas for farming. However, in certain atmospheric conditions, type of vegetation and soil moisture levels, among others, these fires can escape control. This study reports the analysis through X-ray diffractometry and thermogravimetric analysis of the characteristics of the soils in two distinct areas Area 1 (Benfica) and Area 2 (Bocaina), in the same pedological regime within the Macaé de Cima Environmental Protection Area. These two areas were affected by forest fires in different periods. We also sought to identify the severity of these fires, for which purpose we collected undeformed soil samples from depths of 0-5, 5-10, 10-15, 15-20 and 20-25 cm. The data obtained showed that the mineralogy of the sand fraction was homogeneous, but the clay fraction in Area 2, unlike Area 1, was characterized by the presence of smectite and goethite. Fire tended to have the greatest impact on the top 5 cm of soil, possibly related to the hydrophobic characteristics, which are not directly linked to the timing of the fires, but rather to their magnitudes. (author)