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

Valerie S. Densmore; Taiya K. Barnesby

doi:10.1071/WF24204

RESEARCH ARTICLE (Open Access)

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

Valerie S. Densmore

^A ^C ^* and Taiya K. Barnesby ^B

+ Author Affiliations

- Author Affiliations

^A Biodiversity and Conservation Science, DBCA, Manjimup, WA 6258, Australia.

^B Parks and Wildlife Service, DBCA, Manjimup, WA 6258, Australia.

^C Present address: Wilinggin Aboriginal Corporation, Derby, WA 6728, Australia.

^* Correspondence to: dwc@wilinggin.com.au

International Journal of Wildland Fire 34, WF24204 https://doi.org/10.1071/WF24204

Submitted: 28 November 2024 Accepted: 8 August 2025 Published: 5 September 2025

© 2025 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of IAWF. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)

Abstract

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.

Keywords: flammability, ground fire, peatlands, peat type, planned burning, smouldering combustion, soil moisture, temperate ecosystems.

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