Laurent Lamarque

Natural Resources Canada | NRCan · Canadian Forest Service

Water‐use efficiency (WUE) is affected by multiple leaf traits, including stomatal morphology. However, the impact of stomatal morphology on WUE across different ontogenetic stages of tree species is not well‐documented. Here, we investigated the relationship between stomatal morphology, intrinsic water‐use efficiency (iWUE) and leaf carbon isotope...

Increases in shrub height, biomass and canopy cover are key whole‐plant features of warming‐induced vegetation change in tundra. We investigated leaf functional traits underlying photosynthetic capacity of Arctic shrub species, particularly its main limiting processes such as mesophyll conductance. In this nutrient‐limited ecosystem, we expect leaf...

Key message The elapsed times to deplete starch concentrations and to reach a null hydraulic safety margin were related to tree seedling mortality under experimental drought. Starch concentration showed an accelerated decline across all species during the early stages of dehydration, while the concentrations of soluble sugars and total nonstructura...

Water-use efficiency (WUE) is affected by multiple leaf traits, including stomatal morphology. However, the impact of stomatal morphology on WUE across different ontogenetic stages of tree species is not well-documented. Here, we investigated the relationship between stomatal morphology intrinsic water-use efficiency (iWUE=A/gs) and leaf carbon iso...

Plant hydraulics is crucial for assessing the plants' capacity to extract and transport water from the soil up to their aerial organs. Along with their capacity to exchange water between plant compartments and regulate evaporation, hydraulic properties determine plant water relations, water status and susceptibility to pathogen attacks. Consequentl...

Background and Aims Plant vascular diseases significantly impact crop yield worldwide. Esca is a grapevine vascular disease found globally in vineyards which causes a loss of hydraulic conductance due to the occlusion of xylem vessels by tyloses. However, the integrated response of plant radial growth and physiology in maintaining xylem integrity i...

The main parameters determining photosynthesis are stomatal and mesophyll conductance and electron transport rate, and for hydraulic dynamics they are leaf hydraulic conductance and the spread of embolism. These parameters have scarcely been studied in desiccation‐tolerant (resurrection) plants exposed to drought. Here, we characterized photosynthe...

The regulation of water loss and the spread of xylem embolism have mostly been considered separately. The development of an integrated approach taking into account the temporal dynamics and relative contributions of these mechanisms to plant drought responses is urgently needed. Do conifer species native to mesic and xeric environments display diff...

The increasing evaporative demand due to climate change will significantly affect the balance of carbon assimilation and water losses of plants worldwide. The development of crop varieties with improved water use efficiency (WUE) will be critical for adapting agricultural strategies under predicted future climate. This review aims to summarize the...

Climate change is leading to species redistributions. In the tundra biome, shrubs are generally expanding, but not all tundra shrub species will benefit from warming. Winner and loser species, and the characteristics that may determine success or failure, have not yet been fully identified. Here, we investigate whether past abundance changes, curre...

Maintaining wine production under global warming partly relies on optimizing the choice of plant material for a given viticultural region and developing drought-resistant cultivars. However, progress in these directions is hampered by the lack of understanding of differences in drought resistance among Vitis genotypes. We investigated patterns of x...

Evidence points out that increasing plant productivity associated with greater erect shrub abundance alters soil organic carbon (SOC) stocks in the Arctic. However, the underlying plant economic traits remain poorly examined, which limits our understanding of plant–environment interactions driving tundra carbon cycling. We explored how erect shrub...

Xylem anatomy may change in response to environmental or biotic stresses. Vascular occlusion, an anatomical modification of mature xylem, contributes to plant resistance and susceptibility to different stresses. In woody organs, xylem occlusions have been examined as part of the senescence process, but their presence and function in leaves remain o...

Background Plants have adapted to survive seasonal life-threatening frost and drought. However, the timing and frequency of such events are impacted by climate change, jeopardising plant survival. Understanding better the strategies of survival to dehydration stress is therefore timely and can be enhanced by the cross-fertilization of research betw...

European beech is one of the most common tree species in Europe and is generally suggested to play even more prominent role in forestry in the future. It seems to have the potential to partially replace Norway spruce, as it is less sensitive to expected warmer and drier conditions. It is, however, not well known in which regions these new plantings...

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...

Climate change is leading to a species redistributions. In the tundra biome, many shrub species are expanding into new areas, a process known as shrubification. However, not all tundra shrub species will benefit from warming. Winner and loser species (those projected to expand and contract their ranges, and/or those that have increased or decreased...

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...

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...

Xylem hydraulic safety and efficiency are key traits determining tree fitness in a warmer and drier world. While numerous plant hydraulic studies have focused on branches, our understanding of root hydraulic functioning remains limited, although roots control water uptake, influence stomatal regulation and have commonly been considered as the most...

OPEN ACCESS LINK: https://academic.oup.com/jxb/advance-article/doi/10.1093/jxb/erab412/6368289 ***************************************************************************************** The Pressure Chamber, the most popular method used to measure xylem water potential, is a discontinuous and destructive technique and therefore not suitable for...

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-...

Significance A fundamental association between sustained water transport and downstream tissue survival should select for xylem that avoids embolism in long-lived woody plants. Previous studies suggest that long-vessel species, such as oaks and vines, are more susceptible to drought-induced loss of function than other species. We show that western...

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...

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...

Photosynthetic ‘least‐cost’ theory posits that the optimal trait combination for a given environment is that where the summed costs of photosynthetic water and nutrient acquisition/use are minimised. The effects of soil water and nutrient availability on photosynthesis should be stronger as climate‐related costs for both resources increase. Two ind...

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 o...

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...

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...

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...

The majority of variation in six traits critical to the growth, survival and reproduction of plant species is thought to be organised along just two dimensions, corresponding to strategies of plant size and resource acquisition. However, it is unknown whether global plant trait relationships extend to climatic extremes, and if these interspecific r...

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...

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...

Drought represents a major abiotic constraint to plant growth and survival. On one hand, plants keep stomata open for efficient carbon assimilation, while on the other hand, they close them to prevent permanent hydraulic impairment from xylem embolism. The order of occurrence of these two processes (stomatal closure and the onset of leaf embolism)...

The vulnerability of forest species and tree populations to climate change is related to the exposure of the ecosystem to extreme climatic conditions and to the adaptive capacity of the population to cope with those conditions. Adaptive capacity is a relatively under-researched topic within the forest science community and there is an urgent need t...

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...

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...

Context and purpose of the study-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...

Background and aims: Hydraulic studies are currently biased towards conifers and dicotyledonous angiosperms; responses of arborescent monocots to increasing temperature and drought remain poorly known. This study aims to assess xylem resistance to drought-induced embolism in palms. Methods: We quantified embolism resistance via P50 (xylem pressu...

This article is a Commentary on Rosas et al. 223: 632–646.

Aim Plant functional groups are widely used in community ecology and earth system modelling to describe trait variation within and across plant communities. However, this approach rests on the assumption that functional groups explain a large proportion of trait variation among species. We test whether four commonly used plant functional groups rep...

Motivation: The Tundra Trait Team (TTT) database includes field‐based measurements of key traits related to plant form and function at multiple sites across the tundra biome. This dataset can be used to address theoretical questions about plant strategy and trade‐offs, trait–environment relationships and environmental filtering, and trait variation...

The tundra is warming more rapidly than any other biome on Earth, and the potential ramifications are far-reaching because of global feedback effects between vegetation and climate. A better understanding of how environmental factors shape plant structure and function is crucial for predicting the consequences of environmental change for ecosystem...

According to the hydraulic vulnerability segmentation hypothesis, leaves are more vulnerable to decline of hydraulic conductivity than branches, but whether stem xylem is more embolism resistant than leaves remains unclear.Drought-induced embolism resistance of leaf xylem was investigated based on X-ray computed tomography (microCT) for Betula pend...

Key message Direct, non-invasive X-ray microtomography and optical technique observations applied in stems and leaves of intact seedlings revealed that laurel is highly resistant to drought-induced xylem embolism. Contrary to what has been brought forward, daily cycles of embolism formation and refilling are unlikely to occur in this species and to...

Methods to estimate xylem embolism resistance generally rely on hydraulic measurements, which can be far from straightforward. Recently, a pneumatic method based on air flow measurements of terminal branch ends was proposed to construct vulnerability curves by linking the amount of air extracted from a branch with the degree of embolism. We applied...

Drought-induced xylem embolism is a key process closely related to plant mortality during extreme drought events. However, this process has been little investigated in crop species to date, despite the observed decline of crop productivity under extreme drought conditions. Interspecific variation in hydraulic traits has frequently been reported, bu...

Northern wetlands and their productive tundra vegetation are of prime importance for Arctic wildlife by providing high-quality forage and breeding habitats. However, many wetlands are becoming drier as a function of climate-induced permafrost degradation. This phenomenon is notably the case in cold, ice-rich permafrost regions such as Bylot Island,...

Increasing growth of erect shrubs species, like Salix richardsonii, have been well documented in Arctic tundra. This shrubification of the North causes profound changes in water, energy and nutrient feedbacks between the biosphere, geosphere and atmosphere (REF). However, few studies have yet to examine the impact of these changes on the carbon cyc...

Acer negundo (boxelder maple) is a North American native tree species that currently invades riparian and disturbed areas in Europe, affecting both bank stability and ecosystem biodiversity. As a response to managers' requests, we aimed at finding an eco-friendly method which would locally remove this species and help habitat restoration. Four cont...

Continuous permafrost zones with well-developed polygonal ice-wedge networks are particularly vulnerable to climate change. Thermo-mechanical erosion can initiate the development of gullies that lead to substantial drainage of adjacent wet habitats. How vegetation responds to this particular disturbance is currently unknown but has the potential to...

Continuous permafrost zones with well-developed polygonal ice-wedge networks are particularly vulnerable to climate change. Thermo-mechanical erosion can initiate the development of gullies that lead to substantial drainage of adjacent wet habitats. How vegetation responds to this particular disturbance is currently unknown but has the potential to...

Genetically based phenotypic differentiation between native and invasive populations of exotic plants has been increasingly documented and commonly invoked to explain the success of some invasive species. Nonetheless, this basic information is lacking for invasive trees although they currently represent a major concern worldwide. Reciprocal common...

Background/Question/Methods The positive effect of nurse-plants on beneficiary species can act as a selection process affecting competitive ability of these recipient species. The purpose of this study was to determine if there is evidence for changes in competitive ability of species that associate with nurse-plants but maintain a presence in ope...

Nurse-plants generally have positive effects on understorey species by creating more suitable conditions for stress-intolerant plants relative to open micro-habitats. However, long-term effects of this plant–plant facilitation system have been rarely examined. Seeds of five desert annual species from Atiquipa coastal desert in Southern Peru were us...

Although the genetic aspects of biological invasions are increasingly receiving more attention in the scientific literature, analyses of phenotypic plasticity and genotype-by-environment interactions are still seldom considered in tree invasion biology. Previous studies have shown that invasions of tree species can be affected by intraspecific phen...

Phenotypic plasticity is a key mechanism associated with the spread of exotic plants and previous studies have found that invasive species are generally more plastic than co-occurring species. Comparatively, the evolution of phenotypic plasticity in plant invasion has received less attention, and in particular, the genetic basis of plasticity is la...

Means and Tukey groups per species group for all measured traits and tested experimental conditions. For a given trait different letters on the same column indicate significant differences amongst species groups for a combination of light, fertilisation and disturbance (Tukey test). Species are grouped by strategy: the invasive species is Acer negu...

To identify the determinants of invasiveness, comparisons of traits of invasive and native species are commonly performed. Invasiveness is generally linked to higher values of reproductive, physiological and growth-related traits of the invasives relative to the natives in the introduced range. Phenotypic plasticity of these traits has also been ci...

Trees act as ecosystem engineers and invasions by exotic tree species profoundly impact recipient communities. Recently, research on invasive trees has dramatically increased, enabling the assessment of general trends in tree invasion. Analysing 90 studies dealing with 45 invasive tree species, we conducted a quantitative review and a meta-analysis...

Quantitative comparisons of distribution and abundance of exotic species in their native and non-native ranges represent a first step when studying invaders. However, this approach is rarely applied 2 particularly to tree species. Using biogeographical contrasts coupled with regional dispersal surveys, we assessed whether two exotic maple tree spec...