Plant hydraulic modelling of leaf and canopy fuel moisture content reveals increasing vulnerability of a Mediterranean forest to wildfires under extreme drought

Abstract

-- Fuel moisture content (FMC) is a crucial driver of forest fires in many regions world-wide. Yet, the dynamics of FMC in forest canopies as well as their physiological and environmental determinants remain poorly understood, especially under extreme drought. -- We embedded a FMC module in the trait-based, plant-hydraulic SurEau-Ecos model to provide innovative process-based predictions of leaf live fuel moisture content (LFMC) and canopy fuel moisture content (CFMC) based on leaf water potential (ψLeaf). SurEau-Ecos- FMC relies on pressure–volume (p-v) curves to simulate LFMC and vulnerability curves to cavitation to simulate foliage mortality. -- SurEau-Ecos-FMC accurately reproduced ψLeaf and LFMC dynamics as well as the occurrence of foliage mortality in a Mediterranean Quercus ilex forest. Several traits related to water use (leaf area index, available soil water, and transpiration regulation), vulnerability to cavitation, and p-v curves (full turgor osmotic potential) had the greatest influence on LFMC and CFMC dynamics. As the climate gets drier, our results showed that drought-induced foliage mortality is expected to increase, thereby significantly decreasing CFMC. -- Our results represent an important advance in our capacity to understand and predict the sensitivity of forests to wildfires.

Citation

Ruffault, Julien; Limousin, Jean-Marc; Pimont, Francois; Dupuy, Jean-Luc; De Caceres, Miquel; Cochard, Herve; Mouillot, Florent; Blackman, Chris J.; Torres-Ruiz, Jose M.; Parsons, Russell A.; Moreno, Myriam; Delzon, Sylvain; Jansen, Steven; Olioso, Albert; Choat, Brendan; Martin-StPaul, Nicolas. 2022. Plant hydraulic modelling of leaf and canopy fuel moisture content reveals increasing vulnerability of a Mediterranean forest to wildfires under extreme drought. New Phytologist. 237: 1256-1269.