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International Journal of Wildland Fire International Journal of Wildland Fire Society
Journal of the International Association of Wildland Fire
RESEARCH ARTICLE (Open Access)

When soil becomes fuel: identifying a safe window for prescribed burning of Tasmanian vegetation growing on organic soils

Lynda D. Prior https://orcid.org/0000-0002-5511-2320 A * , Kathryn Storey B , Grant J. Williamson https://orcid.org/0000-0002-3469-7550 A and David M. J. S. Bowman https://orcid.org/0000-0001-8075-124X A
+ Author Affiliations
- Author Affiliations

A Fire Centre, School of Natural Sciences, University of Tasmania, Private Bag 55, Hobart, Tas. 7001, Australia.

B Environment, Heritage and Land Division, Department of Natural Resources and Environment Tasmania, GPO Box 44, Hobart, Tas. 7001, Australia.

* Correspondence to: lynda.prior@utas.edu.au

International Journal of Wildland Fire 33, WF24061 https://doi.org/10.1071/WF24061
Submitted: 5 July 2023  Accepted: 16 May 2024  Published: 6 June 2024

© 2024 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

Flammable vegetation in Tasmania, Australia often grows on organic soils that can burn if sufficiently dry.

Aims

To develop an approach to identify a safe window for prescribed burning of vegetation on Tasmanian organic soils, when vegetation is dry enough to be combustible, yet organic soils are unlikely to burn.

Methods

We compiled a dataset of when organic soils did and did not burn when exposed to vegetation fires. Focussing on moorland, we used binomial modelling to estimate the probability of organic soil burning in relation to soil dryness index (SDI) computed from climate data. Vegetation combustibility was inferred from fuel moisture content estimated from climate data and records of area burnt.

Key results

Risk of soil fire varied with vegetation. In moorland, modelling predicted a 17% risk when SDI was 10, a conservative estimate because our dataset was biased towards positive records of soil fire. Using an SDI threshold of 10, the average annual number of ‘safe combustible’ days varied across Tasmania from 26 to 53.

Conclusions

This approach can be used to refine safe burning guidelines on organic soil.

Implications

This approach, when applied to an improved dataset, will assist fire management on organic soils.

Keywords: climate change, fine fuel moisture content, fire risk, organic soils, peat, prescribed fire, soil dryness index, soil fire, Tasmanian Wilderness World Heritage Area, treeless vegetation.

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