Moisture Content of Fine Forest Fuels and Fire Occurrence in Central Portugal

Abstract

Moisture content of ten fine fuels frequent in the forests of CentralPortugal and in other Mediterranean areas was measured daily since 1986. Average monthly results are presented for the period of 1987-1990. Pinuspinaster sticks were used as a predictor of dead fuel moisture content. A reasonable correlation was obtained with the moisture content of Pinus pinaster dead needles and Eucalyptus globulus dead leaves. Two options of the MOISTURE module of BEHAVE system were also tested to predict the daily minimum value of fine dead fuel moisture content. Predicted values were always lower than direct measurements, specially when only meteorological data was used. A better agreement was obtained when known moisture content of the previous day was introduced. Using statistical data of oily fire occurrence in some districts around the site where the tests were made, for the same period of time, the probability of fire occurrence, the average number of daily fires and the average area burned each year was analysed as a function of dead pine needles moisture content. Three distinct zones, around and adjacent to the test site showed a very similar behaviour.