Cross-landscape fuel moisture differences impact simulated fire behaviour

Background: Predicting fire behaviour is an ongoing challenge in temperate peatlands and heathlands, where live fuels can form the dominant fuel load for wildfire spread, and where spatial heterogeneity in fuel moisture is important but not typically represented in fuel models. Aims: We examine the impact of fuel moisture variation on simulated fire behaviour across a temperate peatland/heathland landscape. Methods: We collected field measurements of fuel moisture content in Calluna vulgaris shrub from 36 sites across the North Yorkshire Moors, United Kingdom. We used these to define fuel moisture inputs within existing shrubland fuel models to simulate fire behaviour in BehavePlus. Key results: Simulated rates of spread varied with fuel moisture content; average mean variance of 23-80% from the landscape average rate of spread. The driest sites had simulated rates of spread up to 135% above the landscape average and the wettest sites up to 86% below average. Fuel model selection dramatically impacted simulated rates of spread by a factor of five. Conclusions: We need to constrain the role of live fuel moisture within temperate fuel models to develop accurate fire behaviour predictions. Implications: Capturing cross-landscape heterogeneity in fire behaviour is important for safe and effective land and wildfire management decision-making.