Sazonalidade da umidade do material combustível florestal na transição Cerrado-Amazônia

Abstract

Forest fires occur due to the presence of superficial combustible material, together with the influence of meteorological and topographical conditions and sources of ignition. Due to seasonal variations in the balances (inputs and outputs) of litter components of the different forest typologies in the Middle-North region of Mato Grosso, studies to evaluate litter behavior can support fire management techniques and reduce impacts on ecosystems, increasing forest protection. In this context, the present work had as main objective to evaluate the behavior of the humidity of combustible materials in four forest areas (native forest, Eucalyptus urograndis (Clone VM1), Tectona grandis and Acacia mangium) in the climatic conditions of the Cerrado Amazon transition region, and as specific objectives to characterize and classify the fuel materials of these forest areas and to describe the behavior of the humidity and the dry mass of the forest fuel materials under the water seasonality of this region. Litter samples deposited in areas of native forest remnants, forest plantations with Eucalyptus urograndis Clone VM1, Tectona grandis and Acacia mangium were collected. Collections were carried out, with 4 repetitions, in plots of 1.0 m², with monthly intervals. The collected materials were stored in 100-liter plastic bags, sealed with adhesive tape and transported to the Hydraulics and Hydrology Laboratory of the UFMT Campus in Sinop, for separation into the following classes: leaf (Fh), thin branches (diameters less than 0.7mm ), medium branches (diameters ranging from 0.7 to 2.4mm) and thick branches (diameters from 2.4 to 7.6mm), bark and live herbaceous material. Subsequently, drying was carried out in a forced circulation oven for 48 hours, at 65 ± 2.0 ºC or until constant mass, for moisture determination. Thus, through these data, the seasonality of litter in these treatments was characterized and determined. The results were of lower average humidity in the months of May to September (dry season) and higher in October and December (rainy season). The dry mass had a lower average in ton/ha in the dry season and higher in the rainy season. The proportion of combustible material remained predominant by leaves (above 60%) throughout the period and in all forest areas. Thus, it was concluded that the water seasonality of the region influences the moisture content and dry mass of the treatments in a similar way, considering that both have lower averages in the dry season in all treatments.