Permeability Comparison of Natural and Artificial Pinus Radiata Forest Litters

Abstract

Forest litter flammability metrics have been extensively studied under laboratory conditions, but little research has been conducted in quantifying the difference between artificially reconstructed litters and natural litters. In order to assess the fire spread behaviour of natural litter beds, a sampling method was designed to obtain almost unperturbed radiata pine litters. As permeability is expected to affect flammability, this property was used for comparison between natural and artificially reconstructed litters. The pressure drop of airflow through undisturbed litter samples was measured in the vertical and horizontal direction for different flow velocities. The permeability of the specimens was obtained by fitting experimental values to the Forchheimer equation. It was found that for natural litter samples the horizontal permeability is almost unaffected by bulk density, while the vertical permeability is a decaying linear function of bulk density. It was further found that the permeability of artificially reconstructed litter samples depends exponentially on the bulk density of the sample. Surface to volume ratio, density and porosity of both types of litter are also informed, and qualitative comparison between them is given. Surface to volume ratio as well as density and porosity were notably different between natural and reconstructed litters.