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

Lynda D. Prior; Kathryn Storey; Grant J. Williamson; David M. J. S. Bowman

doi:10.1071/WF24061

RESEARCH ARTICLE (Open Access)

Previous Next Contents Vol 33(6)

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

Lynda D. Prior

^A ^* , Kathryn Storey ^B , Grant J. Williamson

^A and David M. J. S. Bowman

^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.

References

Bowman DMJS, Rodriguez-Cubillo D, Prior LD (2021) The 2016 Tasmanian Wilderness Fires: Fire Regime Shifts and Climate Change in a Gondwanan Biogeographic Refugium. In ‘Ecosystem Collapse and Climate Change’. (Eds JG Canadell, RB Jackson) pp. 133–153. (Springer International Publishing: Cham, Switzerland)

Bridle K, Cullen P, Russell M (2003) ‘Peatland hydrology, fire management and Holocene fire regimes in southwest Tasmanian Blanket Bogs.’ (Nature Conservation Branch of the Department of Primary Industries, Water and Environment: Tas., Australia)

Burnham KP, Anderson DR (2001) Kullback-Leibler information as a basis for strong inference in ecological studies. Wildlife Research 28, 111-119.
| Crossref | Google Scholar |

Cotching WE, Lynch S, Kidd DB (2009) Dominant soil orders in Tasmania: distribution and selected properties. Australian Journal of Soil Research 47, 537-548.
| Crossref | Google Scholar |

di Folco M-B (2007) Tasmanian organic soils. PhD Thesis, University of Tasmania, Hobart, Tasmania, Australia.

di Folco M-B, Kirkpatrick JB (2011) Topographic variation in burning-induced loss of carbon from organic soils in Tasmanian moorlands. Catena 87, 216-225.
| Crossref | Google Scholar |

Ellis TM, Bowman DMJS, Jain P, Flannigan MD, Williamson GJ (2022) Global increase in wildfire risk due to climate-driven declines in fuel moisture. Global Change Biology 28, 1544-1559.
| Crossref | Google Scholar | PubMed |

Fox-Hughes P, Harris R, Lee G, Grose M, Bindoff N (2014) Future fire danger climatology for Tasmania, Australia, using a dynamically downscaled regional climate model. International Journal of Wildland Fire 23, 309-321.
| Crossref | Google Scholar |

Frandsen WH (1987) The influence of moisture and mineral soil on the combustion limits of smoldering forest duff. Canadian Journal of Forest Research 17, 1540-1544.
| Crossref | Google Scholar |

Frandsen WH (1997) Ignition probability of organic soils. Canadian Journal of Forest Research 27, 1471-1477.
| Crossref | Google Scholar |

French BJ, Prior LD, Williamson GJ, Bowman DMJS (2016) Cause and effects of a megafire in sedge-heathland in the Tasmanian temperate wilderness. Australian Journal of Botany 64, 513-525.
| Crossref | Google Scholar |

Garlough EC, Keyes CR (2011) Influences of moisture content, mineral content and bulk density on smouldering combustion of ponderosa pine duff mounds. International Journal of Wildland Fire 20, 589-596.
| Crossref | Google Scholar |

Goldstein A, Turner WR, Spawn SA, et al. (2020) Protecting irrecoverable carbon in Earth’s ecosystems. Nature Climate Change 10, 287-295.
| Crossref | Google Scholar |

Grose MR, Barnes-Keoghan I, Corney SP, White CJ, Holz GK, Bennett JB, Gaynor SM, Bindoff NL (2010) Climate futures for Tasmania: general climate impacts technical report. The Antarctic Climate & Ecosystems Cooperative Research Centre, Hobart, Tas. https://climatefutures.org.au/wp-content/uploads/2023/05/Climate-Futures-General-Climate-Impacts-Full-Report.pdf

Hill R (1982) Rainforest fire in western Tasmania. Australian Journal of Botany 30, 583-589.
| Crossref | Google Scholar |

Hokanson KJ, Lukenbach MC, Devito KJ, Kettridge N, Petrone RM, Waddington JM (2016) Groundwater connectivity controls peat burn severity in the boreal plains. Ecohydrology 9, 574-584.
| Crossref | Google Scholar |

Isbell RF (2002) ‘The Australian soil classification. Australian Soil and Land Survey Series.’ Revised edn. (CSIRO Publishing: Melbourne, Vic., Australia)

Johnston FH, Henderson SB, Chen Y, Randerson JT, Marlier M, DeFries RS, Kinney P, Bowman DM, Brauer M (2012) Estimated global mortality attributable to smoke from landscape fires. Environmental Health Perspectives 120, 695-701.
| Crossref | Google Scholar | PubMed |

Joosten H (2009) ‘The global peatland CO₂ picture: peatland status and drainage related emissions in all countries of the world.’ (Wetlands International: Netherlands)

Kumar V, Dharssi I (2017) ‘Evaluation of daily soil moisture deficit used in Australian forest fire danger rating system’. Bureau Research Report – BRR 022. (Bureau of Meteorology: Melbourne, Vic.)

Lin SR, Sun PY, Huang XY (2019) Can peat soil support a flaming wildfire? International Journal of Wildland Fire 28, 601-613.
| Crossref | Google Scholar |

Love PT, Fox-Hughes P, Harris R, Remenyi T, Bindoff N (2016) ‘Impact of climate change on weather-related fire risk factors in the TWWHA. Part II report.’ (Tasmanian Government: Hobart, Australia)

Lukenbach MC, Hokanson KJ, Moore PA, Devito KJ, Kettridge N, Thompson DK, Wotton BM, Petrone RM, Waddington JM (2015) Hydrological controls on deep burning in a northern forested peatland. Hydrological Processes 29, 4114-4124.
| Crossref | Google Scholar |

Marsden-Smedley JB (1993) ‘Fuel characteristics and fire behaviour in Tasmanian buttongrass moorlands.’ (Parks and Wildlife Service, Department of Environment and Land Management Tasmania: Hobart)

Marsden-Smedley JB (2009) ‘Planned burning in Tasmania: operational guidelines and review of current knowledge.’ Fire Management Section, Parks and Wildlife Service. (Department of Primary Industries, Parks, Water and the Environment: Hobart, Tas.)

Mount AB (1972) ‘The derivation and testing of a soil dryness index using runoff data.’ (Tasmanian Forestry Commission: Hobart)

Nolan RH, Boer MM, de Dios VR, Caccamo G, Bradstock RA (2016) Large-scale, dynamic transformations in fuel moisture drive wildfire activity across southeastern Australia. Geophysical Research Letters 43, 4229-4238.
| Crossref | Google Scholar |

Prat-Guitart N, Rein G, Hadden RM, Belcher CM, Yearsley JM (2016) Propagation probability and spread rates of self-sustained smouldering fires under controlled moisture content and bulk density conditions. International Journal of Wildland Fire 25, 456-465.
| Crossref | Google Scholar |

Prior LD, French BJ, Storey K, Williamson GJ, Bowman DMJS (2020) Soil moisture thresholds for combustion of organic soils in western Tasmania. International Journal of Wildland Fire 29, 637-647.
| Crossref | Google Scholar |

Prior LD, Nichols SC, Williamson GJ, Bowman DMJS (2023) Post-fire restoration of Sphagnum bogs in the Tasmanian Wilderness World Heritage Area, Australia. Restoration Ecology 31, e13797.
| Crossref | Google Scholar |

R Core Team (2023) ‘R: A language and environment for statistical computing.’ (R Foundation for Statistical Computing: Vienna, Austria)

Santoso MA, Christensen EG, Yang J, Rein G (2019) Review of the transition from smouldering to flaming combustion in wildfires. Frontiers in Mechanical Engineering 5, 49.
| Crossref | Google Scholar |

Su CH, Eizenberg N, Jakob D, Fox-Hughes P, Steinle P, White CJ, Franklin C (2021) BARRA v1.0: kilometre-scale downscaling of an Australian regional atmospheric reanalysis over four midlatitude domains. Geoscientific Model Development 14, 4357-4378.
| Crossref | Google Scholar |

Sullivan AL, McCaw WL, Cruz MG, Matthews S, Ellis PF (2012) Fuel, fire weather and fire behaviour in Australian ecosystems. In ‘Flammable Australia. Fire regimes, biodiversity and ecosystems in a changing world’. (Eds RA Bradstock, AM Gill, RJ Williams) pp. 51–78. (CSIRO Publishing: Melbourne, Vic., Australia)

Turetsky MR, Benscoter B, Page S, Rein G, van der Werf GR, Watts A (2015) Global vulnerability of peatlands to fire and carbon loss. Nature Geoscience 8, 11-14.
| Crossref | Google Scholar |

van Wagner CE (1987) ‘Development and structure of the Canadian Forest Fire Weather Index System.’ (The Canadian Forestry Service: Petawawa National Forestry Institution: Chalk River, Ontario)

Whinam J, Hope G (2005) The peatlands of the Australasian region. Stapfia 85, 397-433.
| Google Scholar |

Wilson BR, Tulau M, Kuginis L, McInnes‐Clarke S, Grover S, Milford H, Jenkins BR (2022) Distribution, nature and threats to soils of the Australian Alps: a review. Austral Ecology 47, 166-188.
| Crossref | Google Scholar |

Wood SW, Hua Q, Bowman DMJS (2011) Fire-patterned vegetation and the development of organic soils in the lowland vegetation mosaics of south-west Tasmania. Australian Journal of Botany 59, 126-136.
| Crossref | Google Scholar |

Wotton BM (2009) Interpreting and using outputs from the Canadian Forest Fire Danger Rating System in research applications. Environmental and Ecological Statistics 16, 107-131.
| Crossref | Google Scholar |