Modelling sorption processes of 10-h dead Pinus pinaster branches

Abstract

Background Forest fuel moisture content (FMC) is an important parameter that determines wildfire risk; therefore, its accurate prediction is of great importance. In the absence of rainfall, dead FMC changes mainly by water vapour sorption processes.Aims In the present work, sorption processes of 10-h dead Pinus pinaster branches (PPBs) were studied in order to develop a moisture content prediction model for this fuel type.Methods Laboratory tests were used to determine sorption curves, timelag and equilibrium moisture content (EMC) for different environmental conditions. Sorption curves and EMC were modelled with existing sorption models. Dead PPBs moisture content was determined in field tests carried out in central Portugal to validate the sorption models.Key results Sorption curves were not pure exponential functions, but had different timelag values until equilibrium was reached. EMC values allowed us to obtain a sigmoid curve and hysteresis effect.Conclusions Comparing predicted and observed FMCs of PPB, the Modified Henderson and Pabis models for sorption curves and the Van Wagner model for EMC show high prediction ability.Implications The model can be applied in early fire risk assessment, in particular in the methods that use other fuels besides fine forest fuels.