Description

The object of this paper is to show the intercorrelations existing between statistics of wildfires (occurrences: N; areas burned: A), climatic parameters (precipitation: P; temperature: T) and net primary productivity: NPP. To this purpose, statistics of wildfires have been studied in several regions of the world, focusing on temperature and precipitation. The present analysis has been performed on French Mediterranean Departments (Bouches-du-Rhone, Herault, and Var), Northern Ontario (Canada), Alicante Region (Spain), Yellowstone National Park --YNP-(USA), San Diego (California, USA). Concerning the temperature, the monthly analysis of fire occurrence shows two distinct periods with different fire production laws, both being of the Arrhenius type: the first one corresponding to the vegetation during the rest period, the second one during the vegetative production period. Concerning the precipitation, the monthly analysis of fire occurrence led to two distinct laws depending on the region climatic type (or eventually the seasonal characteristics). Thus, the monthly variation of fire occurrence (in log scale) is a linear increasing or decreasing function according to precipitation. In French Mediterranean Regions these expressions are bound to the rate of soil water extraction by the plant roots (a limiting step of plant production?). Out of the intrinsic importance of the presented results, in the field of primary productivity (dependence on Kelvin temperature) it brings a confirmation of the reality of our hypothesis on the role of the limiting steps of plant production in the rate of wildfire production.