Comportamento do fogo em espécies nativas na região geográfica imediata de Patos-PB.

Abstract

The use of fire in a controlled way in vegetation can provide positive results, however, it can spread in an uncontrolled way in the area, causing damage in the most diverse aspects. Thus, the objective of this research was to evaluate the characteristics of species found in the immediate geographical region of Patos when submitted to the action of fire. Twig, branches and leaf samples were collected from ten species that occur in the immediate region of Patos. Each treatment material was packed in 60kg nylon bags and were properly identified. The design used was entirely randomized, in which 10 treatments were tested with 3 repetitions, consisting of combustible material from the following species: angico (Anadenanthera colubrina), capim panasco (Aristida adscensionis), catingueira (Cenostigma bracteosum), craibeira (Tabebuia aurea), faveleira (Cnidoscolus quercifolius), juazeiro (Sarcomphalus joazeiro), jurema preta (Mimosa tenuiflora), marmeleiro (Croton sonderianus), oiticica (Microdesmia rigida) and pereiro (Aspidosperma pyrifolium). In fire behavior, parameters such as material and soil temperature before and after burning, flame height and temperature, ignition time and frequency, propagation speed, burning duration, and fire intensity were evaluated. In addition, the ash content was also evaluated. The meteorological conditions varied little, with averages of 33.47ºC, 52.33% and 0.93 m s-1 for temperature, relative humidity and wind speed, respectively. The temperature of the material did not differ statistically between treatments; however, there were statistical differences after burning, especially for the craibeira, marmeleiro and oiticica. Significant differences were found for the height of the flames, where the lowest heights were observed in the faveleira, catingueira, angico and jurema preta. However, for flame temperature, the treatments were statistically similar. Some species had some difficulty in igniting, such as the pereiro and, especially the faveleira, the flames ceased quickly. In the speed of propagation, we identified statistical superiority of capim panasco with 0.0335 m s-1, being the only species classified as medium speed and the jurema preta obtained the lowest rate, with 0.0025 m s-1, classified as slow. Besides these, the velocity of the faveleira was null, since the fire was extinguished in a short time. The maximum burning duration was found in the angico plots, with an average of 24 min in the combustion process, being statistically different from the faveleira plots, which accounted for about 3 min in combustion. The capim panasco stood out in fire intensity, in which 402.43 kcal m-1s -1 were responsible for the classification in very high severity. In contrast, species such as catingueira and jurema preta were rated low and moderately low, respectively. The jurema preta obtained the lowest wood ash content, which is favorable for its energy potential. When affected by fire, the species found in the caatinga have different responses. C. quercifolius is a species of low flammability, in view of the difficulty in igniting and maintaining combustion. Places with the abundant presence of A. adscensionis should be monitored frequently for the risk of occurrence of fires, especially in times with atmospheric conditions favorable to the occurrence of fire.