FOREST FUEL MOISTURE VARIATION IN TERMS OF FOREST FIRE DANGER INDEX

Abstract

This research was carried out in a Pinus elliottii plantation, established in 1984, located in the Rio Negro Forest Research Station- Rio Negro – Paraná, owned by the Paraná Federal University, Paraná State, Brazil. The research objectives were to analyze the correlations between the FMA and FMA+ fire danger indices and the fine fuel moisture, and develop mathematical models to estimate the fuel moisture based on these indices. The meteorological variables were obtained from a SIMEPAR weather station, located 50km away, and from a pluviograph and a thermo-hygrograph installed in the study area. The dead forest fuels were collected from 30x30cm plots, between 12 noon and 2:00PM, and classified as: AA – surface layer; AB – intermediate layer; AC – lower layer; and B -woody material with 0.7 to 2.5cm diameter. The total fuel load varied from 3185.50 to 4266.01g.m-2. The fire danger indices were daily calculated and the values obtained in the fuel colleting days were used to calculate the correlations. The correlation coefficients between relative humidity and fuel classes were 0.42; 0.36; 0.32; and 0.41 for the AA, AB, AC, and B classes, respectively. The correlation coefficients between precipitation and fuel classes were 0.57; 0.38; 0.34; and 0.15 for the AA, AB, AC, and B classes, respectively. The correlation coefficients between the fuel classes and the FMA+ were -0.53; -0.56; -0.63; and 0.81 for the classes B, AB, AA, and AC, respectively. The FMA+ was the most efficient variable in modeling development to estimate dead forest fuel moisture.