Jean-luc Dupuy

• French National Institute for Agriculture, Food, and Environment (INRAE)

Large-scale mapping of fuel load and fuel vertical distribution is essential for assessing fire danger, setting strategic goals and actions, and determining long-term resource needs. The Airborne LiDAR system can fulfil such goal by accurately capturing the three-dimensional arrangement of vegetation at regional and national scales. We developed a...

Hydraulic failure due to xylem embolism has been identified as one of the main mechanisms involved in drought‐induced forest decline. Trees vulnerability to hydraulic failure depends on their hydraulic safety margin (HSM). While it has been shown that HSM globally converges between tree species and biomes, there is still limited knowledge regarding...

Key Message Understanding the impact of extreme drought on the canopy fuel moisture content ( CFMC ) is crucial to anticipate the effects of climate change on wildfires. Our study demonstrates that foliage mortality, caused by leaf embolism, can substantially diminish CFMC during drought on Pinus halepensis Mill. and Quercus ilex L. It emphasizes t...

Species mixture is promoted as a crucial management option to adapt forests to climate change. However, there is little consensus on how tree diversity affects tree water stress, and the underlying mechanisms remain elusive. By using a greenhouse experiment and a soil-plant-atmosphere hydraulic model, we explored whether and why mixing the isohydri...

Large-scale mapping of fuel load and structure is of great importance for assessing fire danger, setting strategic goals and actions, and determining long-term resource needs. The Airborne LiDAR system (ALS) can fulfill such goal, because it accurately captures the three-dimensional arrangement of vegetation at regional and national scales. We deve...

Forest ecosystems are increasingly threatened by anthropogenic pressures, especially by the increase in drought frequency and intensity. Tree species mixtures could improve resilience to diverse global anthropogenic pressures. However, there is still little consensus on how tree diversity affects water stress. Although some studies suggest that mix...

Vapor Pressure Deficit (VPD, atmospheric drought) and soil water potential (Ψsoil, soil drought) have both been reported to affect terrestrial plant water stress, plant functions (growth, stomatal conductance, transpiration) and vulnerability to ecosystem disturbances (mortality or vulnerability to wildfires). Which of atmospheric drought or soil d...

Wildfires are a global crisis, but current fire models fail to capture vegetation response to changing climate. With drought and elevated temperature increasing the importance of vegetation dynamics to fire behavior, and the advent of next generation models capable of capturing increasingly complex physical processes, we provide a renewed focus on...

Background Identifying if and how climatic and non-climatic factors drive local changes in fire regimes is, as in many other human-dominated landscapes, challenging in south-eastern France where both heterogeneous spatial patterns and complex fire trends are observed. Aim We sought to identify the factors driving the spatial-temporal patterns of f...

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 in...

Background An increase in fire weather is expected in a warming climate, but its translation to fire activity (fire numbers and sizes) remains largely unknown. Additionally, disentangling the extent to which geographic and seasonal extensions as well as intensification contribute to future fire activity remain largely unknown. Aims We aimed to ass...

A widespread increase in tree mortality has been observed around the globe, and this trend is likely to continue because of ongoing climate-induced increases in drought frequency and intensity. This raises the need to identify regions and ecosystems that are likely to experience the most frequent and significant damage. We present SurEau-Ecos, a tr...

Wildland fires are among the most complicated environmental phenomena to model. Fire behavior models are commonly used to predict the direction and rate of spread of wildland fires based on fire history, fuel, and environmental conditions; however, more sophisticated computational fluid dynamic models are now being developed. This quantitative anal...

Many decisions in the field of agriculture, forestry and/or hydrology can get profit from seasonal forecast. However, the skill of such forecast is a critical issue to promote their use in operational context and get profitable decisions. If many methods to assess meteorological forecast performances are available, they are mostly implemented on ra...

Under the influence of climate change, wildfire regimes are expected to intensify and expand to new areas, increasing threats to natural and socioeconomic assets. We explore the environmental and economic implications for the forest sector of climate-induced changes in wildfire regimes. To retain genericity while considering local determinants, we...

A widespread increase in tree mortality has been observed around the globe, and this trend is likely to continue because of ongoing climate-induced increases in drought frequency and intensity. This raises the need to identify regions and ecosystems that are likely to experience the most frequent and significant damages. We present SurEau-Ecos, a t...

O período entre 2018 e 2022 mostrou-nos que o problema dos incêndios à escala global não está a diminuir, antes pelo contrário. Parece que as consequências das alterações climáticas já estão a afectar a ocorrência de incêndios florestais em várias partes do Mundo, de uma forma que só esperaríamos que acontecesse vários anos mais tarde. Em muitos pa...

O período entre 2018 e 2022 mostrou-nos que o problema dos incêndios à escala global não está a diminuir, antes pelo contrário. Parece que as consequências das alterações climáticas já estão a afectar a ocorrência de incêndios florestais em várias partes do Mundo, de uma forma que só esperaríamos que acontecesse vários anos mais tarde. Em muitos pa...

O período entre 2018 e 2022 mostrou-nos que o problema dos incêndios à escala global não está a diminuir, antes pelo contrário. Parece que as consequências das alterações climáticas já estão a afectar a ocorrência de incêndios florestais em várias partes do Mundo, de uma forma que só esperaríamos que acontecesse vários anos mais tarde. Em muitos pa...

Accurate spatiotemporal modeling of conditions leading to moderate and large wildfires provides better understanding of mechanisms driving fire-prone ecosystems and improves risk management. We study daily summer wildfire data for the French Mediterranean basin during 1995--2018. We jointly model occurrence intensity and wildfire sizes by combining...

The need for fine scale description of vegetation structure is increasing as Leaf Area Density (LAD, m²/m³) becomes a critical parameter to understand ecosystem functioning and energy and mass fluxes in heterogeneous ecosystems. Terrestrial Laser Scanning (TLS) has shown great potential for retrieving the foliage area at stand, plant or voxel scale...

Modeling wildfire activity is crucial for informing science‐based risk management and understanding the spatiotemporal dynamics of fire‐prone ecosystems worldwide. Models help disentangle the relative influences of different factors, understand wildfire predictability, and provide insights into specific events. Here, we develop Firelihood, a two‐co...

Turbulent flows over forest canopies have been successfully modeled using Large-Eddy Simulations (LES). Simulated winds result from the balance between a simplified pressure gradient forcing (e.g., a constant pressure-gradient or a canonical Ekman balance) and the dissipation of momentum, due to vegetation drag. Little attention has been paid to th...

Droughts can have strong environmental and socioeconomic impacts in the Mediterranean region, in particular for countries relying on rain-fed agricultural production, but also in areas in which irrigation plays an important role and in which natural vegetation has been modified or is subject to water stress. The purpose of this review is to provide...

Wildfire activity is expected to increase across the Mediterranean Basin because of climate change. However, the effects of future climate change on the combinations of atmospheric conditions that promote wildfire activity remain largely unknown. Using a fire-weather based classification of wildfires, we show that future climate scenarios point to...

Terrestrial Laser Scanning (TLS) has been used during the past decade to capture the complexity of 3D forest canopy structures, especially Leaf or Plant Area Density (LAD/PAD). TLS data, i.e. point cloud, can be divided into voxels to estimate the three-dimensional distribution of LAD/PAD. However, the combination effects of vegetation occlusion an...

Water content in living vegetation (or live fuel moisture content, LFMC), is increasingly recognized as a key factor linked to vegetation mortality and wildfire ignition and spread. Most often, empirical indices are used as surrogates for direct LFMC measurements. In this paper, we explore the functional and ecophysiological drivers of LFMC during...

Modelling wildfire activity is crucial for informing science-based risk management and understanding fire-prone ecosystem functioning worldwide. Models also help to disentangle the relative roles of different factors, to understand wildfire predictability or to provide insights into specific events. Here, we develop a two-component Bayesian hierarc...

Une recrudescence des incendies extrêmes est observée sur tous les continents. Trois principaux facteurs aggravants sont discutés. La croissance démographique et l’étalement urbain augmentent l’exposition des biens et des personnes, et multiplient les mises à feu accidentelles. Les changements d’usage des sols favorisent le développement de la biom...

Key message Wildfire danger and burnt areas should increase over the century in southern Europe, owing to climate warming. Fire-prone area expansion to the north and to Mediterranean mountains is a concern, while climate-induced burnt area increase might be limited by fuel availability in the most arid areas. Further studies are needed to both asse...

Wildfire activity is expected to increase across the Mediterranean Basin because of climate change. However, the effects of future climate changes on the combinations of atmospheric conditions that promote large wildfires remain largely unknown. Using a fire-weather based classification of wildfires, we show that future climate scenarios point to a...

Wildfire is the main disturbance in forested ecosystems of southern Europe and is due to complex interactions between climate-weather, fuels and people. Warmer and drier conditions projected in this region are expected to profoundly affect wildfires, which will impact ecosystems and humans. We review the scientific literature addressing the assessm...

The spatial distribution of Leaf Area Density (LAD) in a tree canopy has fundamental functions in ecosystems. It can be measured through a variety of methods, including voxel-based methods applied to LiDAR point clouds. A theoretical study recently compared the numerical errors of these methods and showed that the bias-corrected Maximum Likelihood...

Dans les 32 départements les plus méridionaux de la France, le code forestier impose le débroussaillement des lieux habités, de leurs abords, et des réseaux qui les desservent, ainsi que diverses autres mesures de prévention des incendies de forêts. L'Obligation légale de débroussaillement, ou OLD, stipulée dans l'article L.134-6 du Code forestier,...

The amount and spatial distribution of foliage in a tree canopy have fundamental functions in ecosystems as they affect energy and mass fluxes through photosynthesis and transpiration. They are usually described by the Leaf Area Index (LAI) and the Leaf Area Density (LAD), which can be measured through a variety of methods, including voxel-based me...

In this presentation, we show that Live Fuel Moisture Content has a significant impact on both fire occurrence, size and spread rate in Southern France, when LFMC is lower than 100% of the dry mass. Our findings are consistent with levels used by operational services to rate fire danger (67, 54 and 43%). Our results suggest that more fire experimen...

According to climate projections, global warming is associated with increasing temperatures and dry spells in some parts of the world, especially the Mediterranean area. However, it is quite challenging for the scientific community to assess the intensity of these changes, because (i) the trend relies on the greenhouse gases (GHG) emission scenario...

According to climate projections, global warming is associated with increasing temperatures and dry spells in some parts of the world, especially the Mediterranean area. This climate change has already triggered increases in wildfire danger and fire season length in Southern Europe and is expected to amplify in the forthcoming decades. However, it...

Live Fuel Moisture Content (LFMC)-the ratio of water mass to the dry mass of live fuel-is a critical factor of fire behavior and hazard. This parameter is largely controlled by weather conditions and is affected by climate changes. There is therefore an increasing need, to understand its variability, to improve its predictability and its impact on...

Fire experiments generally aim to relate fire behavior to fuel and weather conditions. One of the main factors influencing the fire rate of spread is the wind speed, but its measurement in fire experiments is challenging due to the combination of wind-flow turbulence and the remote location of the sensors relative to the fire front. Differences ari...

Turbulent flows over and within forest canopies have recently been modeled with success using Large Eddy Simulations (LES). Validation exercises against experimental data suggest that models can be applied with a high degree of confidence for many applications, mechanical and physiological plant/atmosphere interaction analysis, seed or pollen dispe...

Reliable measurements of the 3D distribution of Leaf Area Density (LAD) in forest canopy are crucial for describing and modelling microclimatic and eco-physiological processes involved in forest ecosystems functioning. To overcome the obvious limitations of direct measurements, several indirect methods have been developed, including methods based o...

Estimating leaf and plant area density with Terrestrial Laser Scanners (TLS) continues to be more and more popular, as tridimensional point clouds appear as an appealing measurement technique for heterogeneous environments. Some approaches implement a discretization of the point cloud in a grid (referred to as "voxel-based") to account for this veg...

Monitoring live fuel moisture content (LFMC) in Mediterranean area is of great importance for fire risk assessment. LFMC has extensively been estimated based on optical remote sensing data. But the latter can be affected by atmospheric effects. As a complementary data source, microwave data can be used as they are relatively insensitive to atmosphe...

Key message: We model the dynamics of fuel characteristics in shrub strata dominated byQuercus cocciferaL. with data gathered in available literature. The model expresses the variability of this important fire-prone fuel type thanks to yield classes, and it can be used to investigate management scenarios. The approach could easily be applied to oth...

The complex interactions between the inclined terrain and the flow generated by the fire make the slope one of the most influencing factors. In order to gain a deeper understanding of the mechanisms involved in wildfires spreading upslope, the investigation of flow dynamics and heat transfers is fundamental. This paper reports a series of fire spre...

Key messageWe describe a modeling system that enables detailed, 3D fire simulations in forest fuels. Using data from three sites, we analyze thinning fuel treatments on fire behavior and fire effects and compare outputs with a more commonly used model.ContextThinning is considered useful in altering fire behavior, reducing fire severity, and restor...

The original article shows unit errors in Table 2: The torching index (TI) and crowning index (CI).

Fire experiments generally aim to relate fire behavior to fuel and weather conditions. One of the main factors influencing the fire rate of spread is the wind speed, but its measurement in fire experiments is challenging due to the combination of wind-flow turbulence and the remote location of the sensors relative to the fire front. Differences ari...

According to climate projections, global warming is associated with increasing temperatures and dry spells in some parts of the world, especially the Mediterranean area. This climate change has already triggered increases in wildfire danger and fire season length in Southern Europe and is expected to amplify in the forthcoming decades. However, it...

9 Terrestrial LiDAR becomes more and more popular to estimate leaf and plant area density. 10 Voxel-based approaches account for this vegetation heterogeneity and significant work has 11 been done in this recent research field, but no general theoretical analysis is available. 12 Although estimators have been proposed and several causes of biases h...

Key messageFuel moisture and chemical content affecting live plant flammability can be measured through laboratory and field techniques, or remotely assessed. Standardization of methodologies and a better understanding of plant attributes and phenological status can improve models for fire management. ContextWildland fire management is subject to m...

Abstract Scientists and managers critically need ways to assess how fuel treatments alter fire behavior, yet few tools currently exist for this purpose. We present a spatially-explicit-fuel-modeling system, FuelManager, which models fuels, vegetation growth, fire behavior (using a physics-based model, FIRETEC), and fire effects. FuelManager's flexi...

Canopy leaf biomass distribution is a factor of fire behaviour, which affects rate of spread, intensity and crown fire potential. At plot scale, the inventory-based approach combines a stem inventory, allometric equation for leaf mass and its vertical cumulative distribution to estimate leaf load and bulk density profile. This approach is still ver...

Scientists and managers need ways to assess how fuel treatments alter fire behavior, yet few tools currently exist for this purpose. FIRETEC and WFDS recently emerged as promising models in this context since they explicitly account for 3D fuel structure, but there is a need for a tool to facilitate the development of heterogeneous landscape-scale...

After publication of the research paper [1] an error during the data analysis process was recognized. [...]

Past fire recurrence impacts the vegetation structure, and it is consequently hypothesized to alter its future fire behaviour. We examined the fire behaviour in shrubland-forest mosaics of southeastern France, which were organized along a range of fire frequency (0 to 3-4 fires along the past 50 years) and had different time intervals between fires...

Highlights: We propose a method to estimate 3D leaf bulk density distribution, based on the calibration of density indices derived from T-LiDAR over small spherical volumes in which vegetation was sampled. The LiDAR-based bulk density distribution compared well to the inventory-based profiles in the upper part of the canopy.

Ce papier présente la mise en œuvre d’une technique de PIV grand champ (2x2 m²) pour la mesure des champs de vitesse lors de la propagation d’un feu sur une couche combustible végétale. Les champs sont pris dans la direction verticale et dans une direction parallèle au plan de propagation. Réalisée sur le banc d’essais Incendie de l’INRA d’Avignon,...

Local dynamic or thermodynamic variables that are the primary time and space dependent variables predicted by the FIRETEC physics - based model of fire behaviour, including gas velocity and gas temperature, have not been tested against experimental measurements to date. In the present study, we attempt to reproduce the FireFlux experiment with the...

Idealized FIRETEC grassfire simulations were used to study some of the roles that three-dimensional aspects of coupled atmosphere/fire interactions play on fire behavior. Domains of various widths that were periodic in the cross-stream direction, simulating an infinite-length fireline, were used to isolate local fireline-scale threedimensional effe...

In France, the clearing distance between buildings and forest edge is 50 m, to allow fire fighters to protect those buildings. Current building recommendations in the wildland-urban interface derive from fire-safety tests on building materials using heat exposures (duration and magnitude) that are expected to be different from those produced by wil...

Adaptive management and restoration practices in mediterranean forests

Pour améliorer la gestion des forêts face aux incendies, il est utile de connaître les caractéristiques qui confèrent au pin d'Alep une forte inflammabilité et favorisent l'ignition et la propagation du feu au sein du peuplement.

Fuel bulk density and fuel moisture content effects on fire rate of spread were assessed in shrub fuels, comparing experimental data observed in outdoor wind tunnel burns and predictions from the physically-based model FIRETEC. Statistical models for the combined effects of bulk density and fuel moisture content were fitted to both the experimental...

Field experiments are one way to develop or validate wildland fire-behavior models. It is important to consider the implications of assumptions relating to the locality of measurements with respect to the fire, the temporal frequency of the measured data, and the changes to local winds that might be caused by the experimental configuration. Twenty...

L’incendie de forêt constitue la première perturbation des écosystèmes forestiers méditerranéens. Il existe de fortes interactions entre l’écosystème, les pratiques sylvicoles et les régimes de feu associés. Cet article constitue une synthèse des connaissances disponibles et les appliquent aux problématiques rencontrées par le gestionnaire forestie...

Introduction Forest fuel management in the context of fire prevention generally induces heterogeneous spatial patterns of vegetation. However, the impact of the canopy structure on both wind flows and fire behavior is not well understood. Material and methods Here, a coupled atmosphere wildfire behavior model, HIGRAD/FIRETEC, was used to investigat...

We examined how fire hazard was affected by prescribed burning and fuel recovery over the first six years following treatment. Eight common Mediterranean fuel complexes managed by means of prescribed burning in limestone Provence (South-Eastern France) were studied, illustrating forest and woodland, garrigue and grassland situations. The coupled at...

Understanding and attempting to predict wildfire behavior is particularly difficult scientific problem, since the length scales of the physics range from those of flame sheets to fire and topography-influenced atmospheric dynamics. Wildfires are driven by very complex processes ranging from combustion of complex natural fuels to local meteorology a...

The wildfire model FIRETEC simulates the large coherent eddies of the wind-flows induced by the canopy. It has been qualitatively validated in its ability to simulate fire behavior, but there is still a need to validate physical submodels separately. In the present study, the dynamics and turbulence of the flow simulated by FIRETEC are validated in...

Wildland fires are driven by the heat transferred from the fire source to the unburned fuel bed and this transfer is likely to be affected by the spatial heterogeneity of fuel element distributions at different scales from shoot to stand. In a context of theoretical fire modelling, we investigated the impact of a departure from randomness of fuel d...

This study focuses on the effects of fuel structure and in particular its spatial heterogeneity in the context of fuel-break design. The coupled atmospherewildfire behaviour model HIGRAD/FIRETEC is used to simulate wind fields and fire propagation in a complex landscape including forest-to-break and breakto- forest transitions. Two different Medite...

The aim of our work is to study numerically crown scorch as the effectsof a fire line spreading through surface fuel under a tree canopy. Theobjective was to assess the usual assumptions made when one uses the Van Wagner criteria, which are indeed simple predictive models for crown scorch height, to estimate crown scorch. For this purpose the FIRES...

L’éclosion d’un feu, puis sa propagation, sont conditionnées par un certain nombre de facteurs naturels, tels que météorologie, topographie et nature du combustible. Cet article décrit comment ces facteurs affectent les mécanismes d’éclosion et de propagation afin de mieux comprendre leurs effets sur le comportement du feu.

We describe emission–transmission measurements performed at different heights in a flame from a cylindrical forest fuel burner, using a camera operating in the thermal infrared (7.5–13 µm). The forest fuel burner was made of a cylindrical wire mesh basket filled with a forest fuel (Pinus pinaster needles), which was ignited at the base of the baske...