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

Claire Belcher , Rayanne Vitali, Tadas Nikonovas, Kerryn Little , Andrew Elliott, Sarah Baker, Alastair Crawford , Stefan H Doerr , Nicholas Kettridge , Gareth Clay

Abstract

Abstract Background Fires in temperate dry heaths burn both dead and live fuels and are increasing in frequency. Models that well 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 UK were collected throughout the year their moisture content and effective heat of combustion measured. These 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 4-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 accounted for in models that predict fire behaviour. Implications Using the data presented, freely accessible models such as BehavePlus can be adapted to include this variability to better predict fire behaviour in temperate heathland ecosystems.

WF24123  Accepted 28 June 2025

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