Fire Ecology, 2015
Volume 11, Issue 1
The pioneer Australian study of the effect of fire on soil temperature by Beadle (1940), although not describing the type of fire adequately, at least described the type of fuel in which the fires burnt and gave some dimensions whereby a reasonable estimate of the fire energy could be determined.
Even in very recent studies of fire effects, little attention has been given to a description of the fire which produced the published results. Uggla (1960) talks in general terms of “feeble forest fires” and describes soil heating effects from a number of undefined test fires. Yet the paper states that “the severity of the fire is dependent on several factors such as forest type, the quantity and composition of combustion material and the strength of the wind.”
Byram (1959) was the first to recognise the need for a precise definition of fire behaviour. He introduced terms such as available fuel energy, total fuel energy, fire intensity, total fire intensity, and combustion rate. All these can be used “to define specific combustion and fire behaviour terms and establish units of measurements which thus far have been used in a general sense only.”
The fire behaviour terms defined by Byram were used by McArthur (1962) to describe prescribed burning conditions in eucalypt forests and by Van Wagner (1964) to characterize a fire in red pine stands in Ontario. The fire energy concept has been enlarged on by Van Wagner (1965).
It is now generally accepted that four primary factors must be specified before possible effects of fire on vegetation or soil can be considered. These are:
- Fire frequency
- Heat intensity and duration
- Fuel bed characteristics
- Soil and vegetation characteristics
The purpose of this paper is to outline quantitative methods of describing fires which are meaningful for the purpose of considering fire effects on vegetation, soil or microfaunal activity.