DIURNAL EVOLUTION OF FIRE BEHAVIOR AND MICROCLIMATE IN AREAS OF Eucalyptus urograndis (CLONE H13) IN THE CERRADO AMAZONIA TRANSITION ZONE

Abstract

<p><strong>Background. </strong>Forest fires generate several economic, social and environmental losses in native and planted forests. For the prevention and combat of forest fires it is important to know the behavior of fire in each environment potential for its development. This analysis depends on the direct measurement in the field of the parameters associated with the speed of propagation of the fire line and the length of the flames. The fire behavior is influenced by the interaction between meteorological and topographic conditions and plant residues (combustible material) inherent to the environment in which they occur<strong>. Objective.</strong> This paper evaluated of the fire behavior and microclimate in prescribed burnings performed at different times of the day, on the areas of 5.5-year-old <em>Eucalyptus urograndis</em> (clone H13), in the Cerrado Amazonia transition zone, Mato Grosso state, Brazil. <strong>Methodology</strong>. Prescribed burnings was carried out in eucalyptus/crop (EC), eucalyptus/eucalyptus (EE), and eucalyptus/forest (EF) interfaces from 8:00 to 16:00 (considering solar time), in subdivided plots with ten replications. We conducted characterizations of the combustible material - CM (density, moisture, and dry mass), meteorological variables (air temperature, relative air humidity, and wind speed/ direction), and fire behavior (flame length, fire spread rate, and fire intensity). <strong>Results.</strong> The EF interface showed the highest density, moisture, and herbaceous material. The changes in solar energy scattering represented by the zenith angle (Z) directly affected the meteorological variables, with a gradual increase in the interfaces EC, EE, and EF, respectively. <strong>Implications.</strong> The results obtained allow the definition of the best times to carry out burns prescribed in forest monocultures, optimizing the available resources (water, retardants, labor, among others) in the direct fight against forest fires.<strong> </strong><strong>Conclusion.</strong> Diurnal evolution of Z affected the fire behavior; in addition, the greater solar radiation between 10:00 and 14:00 resulted in fire intensification in the environmental interfaces.</p>