Three types of power-law distribution of forest fires in Japan

Study on the forest-fire distribution is not only a phenomenological insight of forest ecological dynamics, but also essential for developing forest-fire danger rating method and system. In this paper, three types of power-law characteristics of forest fires are investigated. The first one is the distribution of fire areas. The frequency-area distribution is found obeying good power-law relation that is invariant with time. The second one is the distribution of fire intervals. It is indicated that the frequency-interval distribution of forest fires in Japan is also accord with power law. What is the most interesting is that the frequency-interval distribution is a power law with periodic change, different to that of frequency-size distribution. The third one is the distribution of fire probability against population density. There is positive-exponent power-law relation between fire probability and population density. The results discussed in this paper are expected to promote the forest-fire danger rating method and are helpful to understand the ecological action of forest fires.