For peat’s sake! Peat type influences critical moisture thresholds that prevent combustion of organic soils in Western Australia

Background Preventing ignition of peatlands presents a particular challenge in Western Australia due to a decreasing trend in annual rainfall over the past several decades. Aims We sought to identify critical moisture thresholds and other factors, including chemical composition, geomorphology or peat type that influence the potential for peatlands to sustain smouldering combustion. Methods We wet soil turves from 16 distinct seasonally waterlogged peatlands to pre-determined moisture contents before exposing samples to a heating element to induce smouldering, and then calculated weight and volume loss due to combustion. Other turve portions were used to conduct physical and chemical analyses. Key results Critical moisture thresholds for ignition and combustion varied by peat type due to differences in bulk density and carbon content. Models predicting combustion that contained the explanatory variables peat type, electrical conductivity (EC) of soil and moisture content achieved R-squared values above 0.8. Conclusions Our results indicate the moisture thresholds to prevent ignition of peatlands differ between peat types; knowledge that is important to inform effective decisions made by fire managers during planned fire and bushfire operations. Implications Determining critical moisture thresholds and peat properties that influence peatland flammability informs potential mitigation techniques to reduce the incidence of smouldering peatlands.