Hervé Cochard

Hervé Cochard
French National Institute for Agriculture, Food, and Environment (INRAE) | INRAE · Department of Forest, Grassland and Freshwater Ecology

http://herve.cochard.free.fr

About

454
Publications
151,257
Reads
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24,374
Citations
Citations since 2017
111 Research Items
13234 Citations
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201720182019202020212022202305001,0001,5002,0002,500
201720182019202020212022202305001,0001,5002,0002,500
201720182019202020212022202305001,0001,5002,0002,500
Additional affiliations
January 2002 - present
Université Clermont Auvergne
Position
  • Research Director

Publications

Publications (454)
Article
Full-text available
Plant resistance to drought has long been thought to be associated with the ability to maintain transpiration and photosynthesis longer during drought, through the opening of stomata. This premise is at the root of most current framework used to assess drought impacts on land plants in vegetation models. We examined this premise by coupling a meta-...
Article
Full-text available
Funders, institutions and journals should challenge the tyranny of metrics.
Article
Survival and growth of woody species in the Mediterranean are mainly restricted by water availability. We tested the hypothesis that Mediterranean species acclimate their xylem vulnerability and osmotic potential along a precipitation gradient. We studied five predominant co‐occurring Mediterranean species; Quercus calliprinos, Pistacia palaestina,...
Preprint
Full-text available
Freeze-thaw-induced embolism is a key limiting factor for perennial plants in frost-exposed environments. Gas bubbles are formed during freezing, when the low chemical potential of the ice reaches a critical cavitation threshold and expand during thawing. However, when water freezes, its volume increases by 9%, generating local pressures, which can...
Article
Full-text available
Context Understanding plant resilience and adaptation to drought is a major challenge in crop and forest sciences. Several methods have been developed to assess the vulnerability to xylem embolism. The in situ flow centrifuge (or cavitron) is the fastest technique allowing to characterise this trait for plants having vessel lengths shorter than the...
Article
The increase in frequency and intensity of drought events have hampered coffee production in the already threatened Amazon region, yet little is known about key aspects underlying the variability in yield potential across genotypes, nor to what extent higher productivity is linked to reduced drought tolerance. Here we explored how variations in mor...
Article
Fuel moisture content is a crucial driver of forest fires in many regions worldwide. Yet, the dynamics of fuel moisture content in forest canopies as well as their physiological and environmental determinants, remain poorly understood, especially under extreme drought We embedded a fuel moisture content module in the trait‐based, plant hydraulic Su...
Article
Xylem hydraulic failure has been identified as a ubiquitous factor in triggering drought‐induced tree mortality through the damages induced by the progressive dehydration of the plant living cells. However, fundamental evidence of the mechanistic link connecting xylem hydraulic failure to cell death has not been identified yet. The main aim of this...
Poster
Full-text available
We evaluated the NMR capacities of a portable, unilateral magnet having the potential to evaluate tree water dynamics in-situ: The Nuclear Magnetic Resonance Mobile Universal Surface Explorer (NMR-MOUSE). We tested the capacity of this device to measure tree water content and to differentiate the conductive tissues, i.e. the xylem and phloem fluxes...
Presentation
Hydraulic traits related to the ability of plants to tolerate and avoid the effects of dehydration represent key mechanisms influencing specie’s survival during drought. However, little is known on how they shape multidimensional plant drought-response strategies and how important they are for survival, especially in tropical rainforest trees. Much...
Poster
Full-text available
The plants’ ability to regulate water loss and the propagation of embolisms in xylem vessels have usually been investigated individually. The development of an integrated approach considering the temporal dynamics and relative inputs of these mechanisms to plant drought responses is urgently needed. Seedlings of three highly embolism-resistant spec...
Article
Full-text available
Climate change is challenging the resilience of grapevine (Vitis), one of the most important crops worldwide. Adapting viticulture to a hotter and drier future will require a multifaceted approach including the breeding of more drought-tolerant genotypes. In this study, we focused on plant hydraulics as a multi-trait system that allows the plant to...
Article
Full-text available
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...
Poster
Global climatic models predict an increment in the frequency and intensity of drought events which have already shown to have important consequences on tree survival and forest dieback. Xylem hydraulic failure has been identified as a ubiquitous factor in triggering drought-induced tree mortality through the damages induced by the progressive desic...
Article
Plant function arises from a complex network of structural and physiological traits. Explicit representation of these traits, as well as their connections with other biophysical processes, is required to advance our understanding of plant‐soil‐climate interactions. We used the Terrestrial Regional Ecosystem Exchange Simulator (TREES) to evaluate ph...
Article
Even after complete stomatal closure, plants lose water through the leaf cuticles and bark. This residual water conductance of leaves (gleaf‐res) and stems (gbark) can negatively impact plant water balance and affect plant survival in seasonally dry environments. However, little is known about the costs and benefits associated with such water leaks...
Preprint
Full-text available
Woody species employ various strategies to cope with drought stress. We investigated similarities and differences in response to chronic drought to understand resistance strategies in co-occurring Mediterranean species. We studied five predominant Mediterranean species; Quercus calliprinos, Pistacia palaestina, Pistacia lentiscus, Rhamnus lycioides...
Article
Full-text available
Increasing temperature and drought can result in leaf dehydration and defoliation even in drought‐adapted tree species such as the Mediterranean evergreen Quercus ilex L. The stomatal regulation of leaf water potential plays a central role in avoiding this phenomenon and is constrained by a suite of leaf traits including hydraulic conductance and v...
Preprint
Full-text available
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...
Preprint
Full-text available
Plant function arises from a complex network of structural and physiological traits. Explicit representation of these traits, as well as their connections with other biophysical processes, is required to advance our understanding of plant-soil-climate interactions. We used the Terrestrial Regional Ecosystem Exchange Simulator (TREES) to evaluate ph...
Article
Full-text available
Drought-associated woody-plant mortality has been increasing in most regions with multi-decadal records and is projected to increase in the future, impacting terrestrial climate forcing, biodiversity and resource availability. The mechanisms underlying such mortality, however, are debated, owing to complex interactions between the drivers and the p...
Presentation
Full-text available
The rare Mycena chlorinosma Singer (Agaricales, Mycenaceae) was found during a mycological inventory work in the 'bois de Pouciquot', located on the campus of the University of Toulouse (France). This collection is the 8 th known mention of this species in France (mainland and overseas), and the 3 rd mention in the French mainland. A description an...
Chapter
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...
Article
Full-text available
Le rare Mycena chlorinosma Singer (Agaricales, Mycenaceae) a été trouvé lors d'un travail d'inventaire mycologique dans le bois de Pouciquot, situé sur le campus de l'université de Toulouse (France). Cette récolte constitue la huitième mention connue de cette espèce en France (métropole et outre-mer), la troisième en France métropolitaine. Une desc...
Article
Investigating the responses of plant anatomical traits of trees to drought-rewatering cycles helps us to understand their responses to climate change; however, such work has not been adequately reported. In this study, Ginkgo biloba L. saplings were subjected to moderate, severe, extreme and lethal drought conditions by withholding water according...
Article
Xylem hydraulic failure has been recognized as a pervasive factor in the triggering of drought-induced tree mortality. However, foundational evidence of the mechanistic link connecting hydraulic failure with living cell damage and tree death has not been identified yet, compromising our ability to predict mortality events. Meristematic cells are in...
Article
Full-text available
The leaf of deciduous species completes its life cycle in a few months. During leaf maturation, osmolyte accumulation leads to a significant reduction of the turgor loss point (ΨTLP), a known marker for stomatal closure. Here we exposed two grapevine cultivars to drought at three different times during the growing season to explore if the seasonal...
Article
Key message Using several experimental approaches, we have demonstrated that electrical resistivity tomography (ERT) is a reliable nondestructive tool for estimating the moisture content of heartwood in situ. ERT measurements show that water pockets in heartwood (wetwood) are present in a large majority (90%) of silver fir ( Abies alba Mill.) trunk...
Article
The capacity of trees to tolerate and survive increasing drought conditions in situ will depend in part on their ability to acclimate (via phenotypic plasticity) key hydraulic and morphological traits that increase drought tolerance and delay the onset of drought-induced hydraulic failure. However, the effect of water deficit acclimation in key tra...
Article
Full-text available
Key message A new process-based model, SurEau , is described. It predicts the risk of xylem hydraulic failure under drought. Context The increase in drought intensity due to climate change will accentuate the risk of tree mortality. But very few process-based models are currently able to predict this mortality risk. Aims We describe the operating...
Article
Trees are long‐lived organisms continuously adapting to their environments, for which epigenetic mechanisms are likely to play a key role. By downregulation of the chromatin remodeler DECREASED IN DNA METHYLATION 1 (DDM1) in poplar (Populus tremula x Populus alba) RNAi lines, we examined how DNA methylation coordinates genomic and physiological res...
Article
Hydraulic failure has been extensively studied during drought-induced plant dieback, but its role in plant-pathogen interactions is under debate. During esca, a grapevine (Vitis vinifera) disease, symptomatic leaves are prone to irreversible hydraulic dysfunctions but little is known about the hydraulic integrity of perennial organs over the short-...
Article
Adaptation to drought involves complex interactions of traits that vary within and among species. To date, few data are available to quantify within‐species variation in functional traits and they are rarely integrated into mechanistic models to improve predictions of species response to climate change. ▪We quantified intraspecific variation in fun...
Article
Full-text available
Global climatic models predict an increment in the frequency and intensity of drought events, which have important consequences on forest dieback. However, the mechanisms leading to tree mortality under drought conditions and the physiological thresholds for recovery are not totally understood yet. This study aimed to identify what are the key phys...
Article
Full-text available
Key message Resilience to xylem embolism and the accumulation of cyclitols are promising criteria for the selection of drought-resilient Eucalyptus species. Abstract Due to the aridity of the climate in the southern Mediterranean region, the choice of suitable species for afforestation projects is crucial. The present study aims to compare resilie...
Article
Understanding the variation in drought resistance traits is needed to predict the potential of trees to adapt to severe drought events. Xylem vulnerability to embolism is a critical trait related to drought-induced mortality with a large variability between species. Acclimation of this trait to environmental conditions implies changes in the xylem...
Article
Full-text available
Nighttime transpiration has been previously reported as a significant source of water loss in many species; however there is a need to determine if this trait plays a key role in the response to drought. This study aimed to determine the magnitude, regulation, and relative contribution to whole plant water-use, of nighttime stomatal conductance (gn...
Article
Full-text available
Plants continue to lose water from their leaves even after complete stomatal closure. Although this minimum conductance (gleaf-res ) has substantial impacts on strategies of water use and conservation, little is known about the potential drivers underlying the variability of this trait across species. We thus untangled the relative contribution of...
Preprint
Full-text available
Hydraulic failure has been extensively studied during drought-induced plant dieback, but its role in plant-pathogen interactions is under debate. During esca, a grapevine ( Vitis vinifera ) disease, symptomatic leaves are prone to irreversible hydraulic dysfunctions but little is known about the hydraulic integrity of perennial organs over the shor...
Preprint
Full-text available
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...
Article
Full-text available
Context Hydraulic failure and disconnection of distal organs during protracted drought stress is thought to protect large branches or trunks by reducing water loss and restricting the spread of embolism. Hydraulic segmentation and preferential sacrifice of distal organs such as leaves can be driven by two mechanisms: more negative water potentials...
Preprint
Full-text available
Knowledge on variations of drought resistance traits is needed to predict the potential of trees to adapt to severe drought events expected to be more intense and frequent. Xylem vulnerability to cavitation is among the most important traits related to drought-induced mortality and exhibits a large variability between species. Acclimation of this t...
Preprint
Full-text available
We describe the operating principle of the detailed version of the soil-plant-atmosphere model SurEau that allows, among other things, to predict the risk of hydraulic failure under extreme drought. It is based on the formalization of key physiological processes of plant response to water stress. The hydraulic functioning of the plant is at the cor...
Article
Full-text available
Lycophytes are the earliest diverging extant lineage of vascular plants, sister to all other vascular plants. Given that most species are adapted to ever-wet environments, it has been hypothesized that lycophytes, and by extension the common ancestor of all vascular plants, have few adaptations to drought. We investigated the responses to drought...
Preprint
As fixed and long living organisms subjected to repeated environmental stresses, trees have developed mechanisms such as phenotypic plasticity that help them to cope with fluctuating environmental conditions. Here, we tested the role DNA methylation as a hub of integration, linking plasticity and physiological response to water deficit in the shoot...
Article
Full-text available
Trees are the living foundations on which most terrestrial biodiversity is built. Central to the success of trees are their woody bodies, which connect their elevated photosynthetic canopies with the essential belowground activities of water and nutrient acquisition. The slow construction of these carbon-dense, woody skeletons leads to a slow gener...
Article
Full-text available
Adapting agriculture to climate change is driving the need for the selection and breeding of drought tolerant crops. The aim of this study was to identify key drought tolerance traits and determine the sequence of their water potential thresholds across three grapevine cultivars with contrasting water-use behaviors, Grenache, Syrah, and Semillon. W...
Article
Full-text available
Xylem hydraulic failure is a major driver of tree death during drought. However, to better understand mortality risk in trees, especially during hot‐drought events, more information is required on both rates of residual water‐loss from small branches (gres) after stomatal closure, as well as the phase transition temperature (Tp), beyond which gres...
Article
Full-text available
Bark is a structure involved in multiple physiological functions, but which has been traditionally associated with protection against fire. Thus, little is known about how the morpho-anatomical variations of this structure are related to different ecological pressures, especially in tropical savanna species, which are commonly subjected to frequent...
Article
Full-text available
Identifying the drivers of stomatal closure and leaf damage during stress in grasses is a critical prerequisite for understanding crop resilience. Here we investigated whether changes in stomatal conductance (gs) during dehydration were associated with changes in leaf hydraulic conductance (Kleaf), xylem cavitation, xylem collapse and leaf cell tur...
Article
Full-text available
Key message Abundant Neotropical canopy-tree species are more resistant to drought-induced branch embolism than what is currently admitted. Large hydraulic safety margins protect them from hydraulic failure under actual drought conditions. Context Xylem vulnerability to embolism, which is associated to survival under extreme drought conditions, is...
Article
Full-text available
Climate change threatens food security, and plant science researchers have investigated methods of sustaining crop yield under drought. One approach has been to overproduce abscisic acid (ABA) to enhance water use efficiency. However, the concomitant effects of ABA overproduction on plant vascular system functioning are critical as it influences vu...
Article
Full-text available
The fourth edition of the international xylem meeting was held for the first time outside France, where the three first editions were held. This represents an important step forward for the meeting and attests to the resolutely international dimension of this symposium. The conference was organized by the University of Padua in the green setting of...
Article
Full-text available
Vascular pathogens cause disease in a large spectrum of perennial plants, with leaf scorch being one of the most conspicuous symptoms. Esca in grapevine (Vitis vinifera) is a vascular disease with huge negative effects on grape yield and the wine industry. One prominent hypothesis suggests that vascular disease leaf scorch is caused by fungal patho...
Article
Full-text available
Tree mortality during hot and dry conditions presents a stark reminder of the vulnerability of plant species to climatic extremes. The current global warming trend makes predicting the impacts of hot/dry events on species survival an urgent task; yet, the standard tools for this purpose lack a physiological basis. This review examines a diversity o...
Article
Full-text available
Context: Douglas-fir, a fast growing conifer from western North America, recently suffered diebacks following drought in France. We investigated the link between native-source climate and provenance drought resistance in a common garden in France. We compared the adaptive potential of provenances from different parts of the natural area. Methods: W...
Data
Evaluation of xylem embolism is an important challenge in identifying drought tolerant genotypes within the context of climate change. Visualization methods such as the optical vulnerability technique (Brodribb et al. 2016) has been shown to be a reliable and accessible approach to observe the spread of embolism in dehydrating leaves. In this study...
Preprint
Full-text available
A bstract Plants tend to die earlier in hot and drought conditions, but the underlying mechanisms are not yet understood. I propose here a new mechanism by which excessive residual water losses caused by high cuticular permeabilities and a high leaf-to-air vapor pressure deficits would trigger uncontrolled and sudden cavitation events. The combinat...
Article
Leaf hydraulic conductance (Kleaf) and capacitance (Cleaf) are among the key parameters in plant-water regulation. Understanding the responses of these hydraulic traits to drought conditions remains a challenge for describing comprehensive plant-water relationships. The ability of an organism to resist and/or tolerate embolism events, which may occ...
Article
Les sécheresses déciment les forêts françaises. Les arbres, qui recouvrent un tiers du pays, ont une mobilité trop lente pour s’adapter au réchauffement climatique.
Article
Full-text available
En ce début d’été, qui rime bien souvent avec vacances, plages, soleil et farniente, The Forest Time a souhaité se pencher sur un sujet qui nous concerne tous, quelle que soit la saison : le réchauffement climatique en France. C’est dans les locaux de l’INRA (Institut National de la Recherche Agronomique) à Clermont-Ferrand que nous avons rencontré...