Why is the effect of live fuel moisture content on fire rate of spread underestimated in field experiments in shrublands?
F. Pimont
A , J. Ruffault A , N. K. Martin-StPaul A and J.-L. Dupuy A
+ Author Affiliations
- Author Affiliations
A URFM, INRA, Domaine Saint Paul Site Agroparc 84000 Avignon, France.
B Corresponding author. Email: francois.pimont@inra.fr
International Journal of Wildland Fire 28(2) 127-137 https://doi.org/10.1071/WF18091
Submitted: 20 June 2018 Accepted: 27 November 2018 Published: 18 January 2019
Abstract
Live fuel moisture content (LFMC) influences fire activity at landscape scale and fire behaviour in laboratory experiments. However, field evidence linking LFMC to fire behaviour are very limited, despite numerous field experiments. In this study, we reanalyse a shrubland fire dataset with a special focus on LFMC to investigate this counterintuitive outcome. We found that this controversy might result from three causes. First, the range of experimental LFMC data was too moist to reveal a significant effect with the widespread exponential or power functions. Indeed, LFMC exhibited a strong effect below 100%, but marginal above this threshold, contrary to these functions. Second, we found that the LFMC significance was unlikely when the number of fire experiments was smaller than 40. Finally, an analysis suggested that 10 to 15% measurement error – arising from the estimation of environmental variables from field measurements – could lead to an underestimation by 30% of the LFMC effect. The LFMC effect in field experiments is thus stronger than previously reported in the range of LFMC occurring during the French fire season and in accordance with observations at different scales. This highlights the need to improve our understanding of the relationship between LFMC and fire behaviour to refine fire-danger predictions.
Additional keywords: GAM, generalised additive model, measurement error, Réseau Hydrique, sample size.
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