Flame residence times and rates of weight loss of eucalypt forest fuel particles

Shape, size, composition and arrangement of fuel particles within a fuel ar ray significantly affect the way in which wildland fires behave. Australian eucalypt forest fire behaviour models characterise fine fuels according to the quantity burnt in the flaming zone, and the upper size limit for fine fuel particles is somewhat arbitrarily set at 6 mm for the McArthur Forest Fire Danger Meter and 10 mm for the Forest Fire Behaviour Tables for Wester n Australia. Flame residence time and rate of weight loss during combustion of dry eucal ypt leaves and different dimensions of round wood were measured to provide a scientific basis for standardising litter fuel sampling in dry eucalypt f orests. Eucalypt leaves burnt at a rate equivalent to a piece of 4 mm diame ter round wood, with smaller diameter round wood being the most flammable c omponent of the fuel array. Based on flame residence times of individual fu el particles measured in the laboratory, and eucalypt surface fuel arrays o bserved in the field, fine litter fuel sampling should be standardised to l eaves and round wood less than 6 mm in diameter. This study also enables th e determination of the contribution of larger fuel particles to flaming zon e combustion and intensity.