A flammability phenology for dry mixed heaths and its implications for modelling fire behaviour

Claire M. Belcher; Rayanne Vitali; Tadas Nikonovas; Kerryn Little; Andrew Elliott; Sarah J. Baker; Alastair J. Crawford; Stefan H. Doerr; Nicholas Kettridge; Gareth D. Clay

doi:10.1071/WF24123

RESEARCH ARTICLE (Open Access)

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A flammability phenology for dry mixed heaths and its implications for modelling fire behaviour

Claire M. Belcher

^A ^* , Rayanne Vitali ^A , Tadas Nikonovas ^B , Kerryn Little

^C , Andrew Elliott ^A , Sarah J. Baker ^A , Alastair J. Crawford

^A , Stefan H. Doerr

^B , Nicholas Kettridge

^C and Gareth D. Clay ^D

+ Author Affiliations

- Author Affiliations

^A wildFIRE Lab, Department of Geography, University of Exeter, Exeter, UK.

^B Centre for Wildfire Research, Department of Geography, Swansea University, Swansea, UK.

^C Department of Geography, Earth and Environmental Science, University of Birmingham, Birmingham, UK.

^D Department of Geography, University of Manchester, Manchester, UK.

^* Correspondence to: c.belcher@exeter.ac.uk

International Journal of Wildland Fire 34, WF24123 https://doi.org/10.1071/WF24123

Submitted: 29 July 2024 Accepted: 28 June 2025 Published: 24 July 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 4.0 International License (CC BY)

Abstract

Background

Fires in temperate dry heaths burn dead and live fuels and are increasing in frequency. Models that describe these fuels and their contribution to fire behaviour is becoming of greater importance.

Aims

We sought to identify variations in fuel moisture and flammability in dry heath fuel types throughout the year and assess the strength of phenological shifts to influence predicted fire behaviour.

Methods

Six plant species from three dry heaths in the United Kingdom (UK) were collected throughout the year, their moisture content and effective heat of combustion measured. Data were used to parameterise a dynamic fuel model and undertake a sensitivity analysis using BehavePlus.

Key results

Phenological changes in live fuel moisture had the greatest effect on predicted fire behaviour where variations between late winter–early spring and late spring–summer, led to a four-fold difference in fire rate of spread. Dead fuel moisture had an effect in the summer months but was dampened significantly by phenologically high live fuel moisture content.

Conclusions

Phenological drivers of live fuel moisture in temperate shrubland fuels must be included in models that predict fire behaviour.

Implications

Using the data presented, models such as BehavePlus can be adapted to include this variability to predict fire behaviour in temperate heathland ecosystems.

Keywords: fire behaviour, fire ecology, flammability, fuel moisture, heathlands, heat content, heat of combustion, shrub fuels.

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