Dielectric analyses of a shrub leaf for the modelling of forest fire

Abstract: Most Mediterranean regions face a high risk to forest fires, estimation and anticipation of this risk modeled as a stochastic propagation process reproduces well some fire properties. Our model needs information on different types of vegetation including their bio-physical properties behavior associated to combustion. In this work, an experimental study to analyze the structure of a leaf of Laurel shrub at different biological stages is presented; it allows following the structural exchanges induced on the leaf by the effect of increasing temperature for a better understanding of the pyrolysis phenomenon and to determine accurately the chemical parameters such as activation energy and time associated to each reaction caused by temperature increase. The results obtained provide information on the process of thermal degradation caused by fire. The evolution of the leaf impedance as a function of the applied frequency characterizes the moisture loss in plant species during pyrolysis. The dielectric response confirms our proposition to the equivalent circuit of the leaf of vegetation as a composite of liquid and solid parts.