Hydraulic Failure Research Articles

Anomaly Detection Based on Time Series Data of Hydraulic Accumulator

Although hydraulic accumulators play a vital role in the hydraulic system, they face the challenges of being broken by continuous abnormal pulsating pressure which occurs due to the malfunction of hydraulic systems. Hence, this study develops anomaly detection algorithms to detect abnormalities of pulsating pressure for hydraulic accumulators. A digital pressure sensor was installed in a hydraulic accumulator to acquire the pulsating pressure data. Six anomaly detection algorithms were developed based on the acquired data. A threshold averaging algorithm over a period based on the averaged maximum/minimum thresholds detected anomalies 2.5 h before the hydraulic accumulator failure. In the support vector machine (SVM) and XGBoost model that distinguish normal and abnormal pulsating pressure data, the SVM model had an accuracy of 0.8571 on the test set and the XGBoost model had an accuracy of 0.8857. In a convolutional neural network (CNN) and CNN autoencoder model trained with normal and abnormal pulsating pressure images, the CNN model had an accuracy of 0.9714, and the CNN autoencoder model correctly detected the 8 abnormal images out of 11 abnormal images. The long short-term memory (LSTM) autoencoder model detected 36 abnormal data points in the test set.

A new multi-objective evolutionary algorithm for the optimization of water distribution networks

Abstract This work introduces a new bi-objective optimization model for the design of a water distribution network (WDN). Reliability and design cost are two contradicting objectives that are optimized. The evolutionary technique multi-objective (MO) Jaya, hereafter referred as MO-JAYANET, is developed for the optimal design of WDN. EPANET is used as a hydraulic network solver in this study. The concept of constraint violation, dominance, non-dominance and crowding distance is used to develop MO-JAYANET. As the Jaya algorithm is a parameter-less technique, and with the concept of constraint dominance involved in the MO model, the penalty parameter required to penalize the non-feasible solution is also dropped. This makes MO-JAYANET a completely parameter-less technique, requiring no tuning at all. MO-JAYANET is applied on two benchmark networks from the literature using three different reliability indices that are Resilience Index, Network Resilience Index, and Modified Resilience Index. MO-JAYANET is found to be very easy and efficient for WDN optimization. The present work obtains a smooth Pareto Front (PF) that overlaps the best-known PF. The maximum reliability diameters obtained by the MO-JAYANET for the three indices are also simulated for both hydraulic and mechanical failures under different scenarios to identify a better-performing index.

Hydraulic traits are not robust predictors of tree species stem growth during a severe drought in a wet tropical forest

Abstract Severe droughts have led to lower plant growth and high mortality in many ecosystems worldwide, including tropical forests. Drought vulnerability differs among species, but there is limited consensus on the nature and degree of this variation in tropical forest communities. Understanding species‐level vulnerability to drought requires examination of hydraulic traits since these reflect the different strategies species employ for surviving drought. Here, we examined hydraulic traits and growth reductions during a severe drought for 12 common woody species in a wet tropical forest community in Puerto Rico to ask: Q1. To what extent can hydraulic traits predict growth declines during drought? We expected that species with more hydraulically vulnerable xylem and narrower safety margins (SMP50) would grow less during drought. Q2. How does species successional association relate to the levels of vulnerability to drought and hydraulic strategies? We predicted that early‐ and mid‐successional species would exhibit more acquisitive strategies, making them more susceptible to drought than shade‐tolerant species. Q3. What are the different hydraulic strategies employed by species and are there trade‐offs between drought avoidance and drought tolerance? We anticipated that species with greater water storage capacity would have leaves that lose turgor at higher xylem water potential and be less resistant to embolism forming in their xylem (P50). We found a large range of variation in hydraulic traits across species; however, they did not closely capture the magnitude of growth declines during drought. Among larger trees (≥10 cm diameter at breast height—DBH), some tree species with high xylem embolism vulnerability (P50) and risk of hydraulic failure (SMP50) experienced substantial growth declines during drought, but this pattern was not consistent across species. We found a trade‐off among species between drought avoidance (capacitance) and drought tolerating (P50) in this tropical forest community. Hydraulic strategies did not align with successional associations. Instead, some of the more drought‐vulnerable species were shade‐tolerant dominants in the community, suggesting that a drying climate could lead to shifts in long‐term forest composition and function in Puerto Rico and the Caribbean. Read the free Plain Language Summary for this article on the Journal blog.

Comparative Apparent Hydraulic Conductance, Leaf Gas Exchange, and Water Resource Partitioning of Populus euphratica Trees and Saplings

Water acquisition via the root system of woody species is a key factor governing plant physiology. In order to compare the impact of water acquisition on the hydraulic and photosynthetic characteristics of different-sized Populus euphratic, which is a desert riparian tree species, we quantified leaf hydraulic conductance (KL), stomatal conductance (gs), net photosynthetic rate (PN), predawn and midday leaf water potential (Ψ), and the stem δ18O of the saplings and mature trees. The results showed that the saplings had a lower predawn leaf water potential (Ψpd) and soil-to-leaf water potential gradient (ΔΨ) and a higher KL than the mature trees but had a similar gs and PN to the mature trees. In arid zones, probably due to root limitation, the saplings were more likely to use unreliable topsoil water (<80 cm), whereas the mature trees typically uptake reliable deep soil water (>80 cm) and groundwater due to having deeper root systems. The unreliability of the water supply might make saplings hold a higher hydraulic conductance to ensure that the water is transported efficiently to the leaves and to satisfy their transpiration need. In contrast, the mature trees, which uptake the more reliable deeper water resources, had a relatively low leaf-specific hydraulic conductance because of the increased path length versus the saplings. However, adult trees can maintain stomatal conductance by upregulating ΔΨ, thereby facilitating their ability to maintain a carbon assimilation rate similar to that of the saplings. This regulating behavior benefits mature trees’ net carbon gain, but it comes at the expense of an increased risk of hydraulic failure. These results imply that the top priority for saplings should be to maintain hydraulic system functioning, whereas, for mature trees, the priority is to assure stable net carbon gain for their growth.

Effects of Water Deficit Stress on Growth Parameters of Robinia pseudoacacia L. Selected Clones under In Vitro Conditions

Rapid screening methods for drought-resistant genotypes are urgently needed in tree improvement programs in the face of current climate change. We used a plant tissue culture technique to assess the phenotypic response of three highly productive genotypes of Robinia pseudoacacia to water deficit induced by mannitol and sucrose in a range of water potentials from 0 MPa to −1.5 MPa in an eight-week experiment. Our study showed genotype-specific responses to induced drought stress, indicating the potential for tree improvement in productivity and stress tolerance. Considering that all plantlets were constantly supplied with carbon, from the medium during the drought-induced experiment, our results suggest that hydraulic failure rather than carbon starvation may be the main cause of drought-induced mortality. Furthermore, our results showed different metabolic pathways of sucrose depending on the concentration of sucrose in the medium and different responses to osmoticum (mannitol vs. sucrose) and its concentration among the clones tested. We believe, that for large-scale breeding programs wanting to select for drought-tolerant genotypes, the use of culture media containing 90 gL−1 mannitol or 90 gL−1 sucrose at an early selection stage should provide satisfactory screening results. However, lab-based screening should be supported by further field trials, preferably at multiple sites, to assess the long-term impact and phenotypic stability of the early selection strategies.

Esca grapevine disease involves leaf hydraulic failure and represents a unique premature senescence process.

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 obscure. In grapevine, many stresses are associated with premature leaf senescence inducing discolorations and scorched tissue in leaves. However, we still do not know whether the leaf senescence process follows the same sequence of physiological events and whether leaf xylem anatomy is affected in similar ways. In this study, we quantified vascular occlusions in midribs from leaves with symptoms of the grapevine disease esca, magnesium deficiency and autumn senescence. We found higher amounts of vascular occlusions in leaves with esca symptoms (in 27% of xylem vessels on average), whereas the leaves with other symptoms (as well as the asymptomatic controls) had far fewer occlusions (in 3% of vessels). Therefore, we assessed the relationship between xylem occlusions and esca leaf symptoms in four different countries (California in the USA, France, Italy and Spain) and eight different cultivars. We monitored the plants over the course of the growing season, confirming that vascular occlusions do not evolve with symptom age. Finally, we investigated the hydraulic integrity of leaf xylem vessels by optical visualization of embolism propagation during dehydration. We found that the occlusions lead to hydraulic dysfunction mainly in the peripheral veins compared with the midribs in esca symptomatic leaves. These results open new perspectives on the role of vascular occlusions during the leaf senescence process, highlighting the uniqueness of esca leaf symptoms and its consequence on leaf physiology.

Habitat preference and vulnerability to drought of three Hypericum species of the páramo

ABSTRACT Background Páramos are tropical alpine ecosystems where climate change is expected to cause yet unknown consequences for plant growth, ecosystem structure, ecosystem function and the provision of ecosystem services. Aim To quantify the relationship between environmental factors (abiotic and biotic) and the spatial distribution of three common Hypericum species in the páramo and their physiological vulnerability to drought. Methods We recorded soil water content, soil temperature, and vegetation cover in 10 plots along a moisture gradient. Additionally, we measured a series of physiological traits associated with the risk of drought-induced mortality. Results We found that H. goyanesii and H. juniperinum mainly grew in areas with high soil water content, and similar high vegetation cover. These two species had wider xylem vessels, showed anisohydric behaviour and were equally vulnerable to cavitation with low safety margins against hydraulic failure. H. mexicanum grew in places with less vegetation cover, lower soil water content, and higher soil temperatures. H. mexicanum showed a different strategy that probably allows it to thrive in these conditions; it maintains high values of water potential at noon and has narrower xylem vessels, making it less vulnerable to cavitation. Conclusion The distribution of the three Hypericum species in the páramo responds essentially to soil water content, in line with the physiological mechanisms of the species to cope with water deficit. Hypericum species from moist habitats could decline if longer drought episodes become more common in the future.

Hydraulic failure as a primary driver of xylem network evolution in early vascular plants

The earliest vascular plants had stems with a central cylindrical strand of water-conducting xylem, which rapidly diversified into more complex shapes. This diversification is understood to coincide with increases in plant body size and branching; however, no selection pressure favoring xylem strand-shape complexity is known. We show that incremental changes in xylem network organization that diverge from the cylindrical ancestral form lead to progressively greater drought resistance by reducing the risk of hydraulic failure. As xylem strand complexity increases, independent pathways for embolism spread become fewer and increasingly concentrated in more centrally located conduits, thus limiting the systemic spread of embolism during drought. Selection by drought may thus explain observed trajectories of xylem strand evolution in the fossil record and the diversity of extant forms.

Elevated Wildfire and Ecosystem Carbon Loss Risks Due to Plant Hydraulic Stress Functions: A Global Modeling Perspective

Wildfire risks are increasing due to the atmospheric and vegetation aridity under global warming. Plant hydraulic stress (PHS) functions regulate water transport along the soil–plant–atmosphere continuum under water stress conditions, which probably results in shifts in ecosystem wildfire regimes. Currently, how the PHS functions affect wildfire occurrence and subsequently the ecosystem carbon cycle via carbon loss at a global scale remains unclear. Here, we conducted global simulations during 1850–2010 using Community Land Model version 5 with and without the PHS configuration and quantified the PHS-induced changes. From the global perspective, the PHS functions increased plant transpiration, induced hydraulic redistribution (HR) of soil water by root, and decreased soil moisture; then, the functions increased fire occurrence (count), fire induced carbon loss, and ecosystem net primary productivity by 72%, 49%, and 15%, respectively. Spatially, the PHS functions greatly promoted fire occurrence and the consequent carbon loss in circumboreal forests and tropical savannas; whereas, the fire occurrence was limitedly affected or even decreased in equatorial rainforests. The strong downward HR process in the humid rainforests transported rainwater into deep soil layers, and strict stomatal regulation of the tropical trees restricted transpiration increment under atmospheric aridity, both of which helped to buffer the rainforests against drought and thus decreased fire risk. In contrast, dry savannas showed substantial upward HR, which increased water loss via soil evaporation and transpiration of the grasses with shallow roots. The tree–grass competition for limited soil moisture in the savannas benefited soil evaporation, which could aggravate plant hydraulic failure and increase wildfire risk.

A digital twin framework for aircraft hydraulic systems failure detection using machine learning techniques

Since the last decade, aircraft systems, such as flight control and landing gear, have been requiring increasing power, and consequently, the complexity of hydraulic aircraft systems has escalated. Inevitably, this complexity has resulted in the need for the troubleshooting of hydraulic aircraft systems that are dispersed around an aircraft and supply power to critical flight systems. This study proposes a novel digital twin-based health monitoring system for aircraft hydraulic systems to enable diagnostics of system failures early in the design cycle using machine learning (ML) methods. The scope of the systems is limited to hydraulic systems at the aircraft level using 20 failure scenarios. The support vector machine and several ensemble learning algorithms of ML methods were used to identify these failures. A comparison of the ML methods revealed that the random forest algorithm performed superior to the other ML algorithms. The developed digital twin framework for hydraulic system of aerial vehicle platforms, can help researchers and engineers to evaluate diagnostics systems early in the design phase.

Water use dynamics of trees in a Pinus tabuliformis plantation in semiarid sandy regions, Northeast China

Quantifying tree water use and its environmental controlling mechanisms are significantly important for understanding of adaptation strategy of trees and plantation management in semiarid and arid regions. Here, tree water consumption and tree conductance of Chinese pine (Pinus tabuliformis) plantation were quantified using sap flow measurements. Environmental variables were measured concurrently during the growing seasons of 2019 and 2020. Results showed that daily, daytime and nighttime tree water consumption averaged 27.4, 24.7, and 2.7 kg d-1 across two years, respectively. Nighttime tree water consumption accounted for 10% of the daily’s, which was mainly used for recharging stem water storage deficit caused by daytime transpiration to avoid hydraulic failure. Daytime tree water consumption was more driven by solar radiation than by vapor pressure deficit. Moreover, daytime tree conductance was 0.9 mm s-1, and significantly decreased with increasing vapor pressure deficit and decreasing soil moisture, indicating that trees had strict stomatal regulation on tree transpiration. Scaling-up from tree to stand transpiration, daytime stand transpiration averaged 1.1 mm d-1 across two years, while accumulated stand transpiration was 112.8 mm and 126.8 mm in 2019 and 2020, respectively, accounting for 33% and 37% of precipitation. However, soil evaporation occupied 35% and 51% of precipitation in 2019 and 2020, respectively. This indicated that most of water in the plantation was consumed by soil evaporation. Difference between precipitation and sum of daytime stand transpiration, canopy interception, soil evaporation, and change in soil water storage was positive in two years, indicating that water budget was balanced. These findings indicated that Chinese pine trees had strict stomatal regulation on tree transpiration, and could recharge stem water storage deficit by nighttime sap flow. Moreover, stand transpiration occupied a small part of the water balance, and thus water supply was surplus, resulting in maintaining the stability of Chinese pine plantation.

Modeling the topographic influence on aboveground biomass using a coupled model of hillslope hydrology and ecosystem dynamics

Abstract. Topographic heterogeneity and lateral subsurface flow at the hillslope scale of ≤1 km may have outsized impacts on tropical forest through their impacts on water available to plants under water-stressed conditions. However, vegetation dynamics and finer-scale hydrologic processes are not concurrently represented in Earth system models. In this study, we integrate the Energy Exascale Earth System Model (E3SM) land model (ELM) that includes the Functionally Assembled Terrestrial Ecosystem Simulator (FATES), with a three-dimensional hydrology model (ParFlow) to explicitly resolve hillslope topography and subsurface flow and perform numerical experiments to understand how hillslope-scale hydrologic processes modulate vegetation along water availability gradients at Barro Colorado Island (BCI), Panama. Our simulations show that groundwater table depth (WTD) can play a large role in governing aboveground biomass (AGB) when drought-induced tree mortality is triggered by hydraulic failure. Analyzing the simulations using random forest (RF) models, we find that the domain-wide simulated AGB and WTD can be well predicted by static topographic attributes, including surface elevation, slope, and convexity, and adding soil moisture or groundwater table depth as predictors further improves the RF models. Different model representations of mortality due to hydraulic failure can change the dominant topographic driver for the simulated AGB. Contrary to the simulations, the observed AGB in the well-drained 50 ha forest census plot within BCI cannot be well predicted by the RF models using topographic attributes and observed soil moisture as predictors, suggesting other factors such as nutrient status may have a larger influence on the observed AGB. The new coupled model may be useful for understanding the diverse impact of local heterogeneity by isolating the water availability and nutrient availability from the other external and internal factors in ecosystem modeling.

Study on dynamic responses of hydraulic pneumatic tensioner for a TLP under hydraulic component failure

This paper takes the hydraulic pneumatic tensioner as the research object. In order to study the dynamic response of hydraulic pneumatic tensioner, a coupled model of tension leg platform was established. Three kinds of sea conditions including first-order irregular wave, second-order wave and freak wave are simulated. The dynamic response of the hydraulic pneumatic tensioner is analyzed under the action of different pressure accumulators. It is found that the greater the pressure of accumulator, the smaller the displacement of hydraulic cylinder and the greater the tension under the action of the second-order wave force and the freak wave force. In the second-order waves, the average drift force has great influence on the amplitude of displacement and tension of hydraulic cylinder, while the second-order sum frequency force has great influence on the frequency of displacement and tension of hydraulic cylinder. In addition, the dynamic responses of the tensioner under second-order waves are also studied when one cylinder fails. When one cylinder fails or is in semi-failure state, the hydraulic pneumatic tensioner can still provide a nearly constant tension to the riser. The remaining normal piston cylinders’ tensions will increase, but the total tension will decrease.

Design, modeling, and simulation of dual-source redundant braking system

Based on the existing theory of EHB braking system, a new dual-source redundant braking system (DSRB) is proposed in this paper. The proposed DSRB is improved on the classic ESP system structure with two sets of motor hydraulic pumps, four throttle valves and two balance valves used to replace the failed oil inlet and outlet valves added in it. Then, the requirements of redundancy, reliability of intelligent vehicle braking system can be met by the system. The wheel cylinder pressure of DSRB system is accurately regulated by PID control algorithm. Finally, the co-simulation based on AMEsim/Simulink were implemented to verify the accuracy and reliability of the braking efficiency of the DSRB. Results show that the designed DSRB has fault tolerance even in the case of partial failure, that is, inlet and outlet valve failure and complete failure, that is, inlet and outlet valve and hydraulic motor failure at the same time. And good braking efficiency, boosting speed and pressure regulation accuracy are still available.

Combination seepage test study of sandy soil and the filter

Abstract Dams are important structures for the development and utilization of water resources, and dam stability is significantly affected by the filter layer. In this paper, eight groups of combination seepage tests of impermeable materials and filter were conducted. The effects of variations in grade, relative density, and thickness of impermeable materials and filter on the combination seepage resistance performance were assessed. The test results showed that: impermeable material and filter grade significantly affect combination seepage resistance. The critical hydraulic gradient and permeability coefficient decrease by 34% with increasing soil coarseness within the design envelope. The critical hydraulic gradient and failure gradient of specimen decreased by 17 and 20%, when the relative density of the filter material decreased from 0.7 to 0.5, respectively. Therefore, in actual engineering applications, the dry density or relative density of the filter material should be strictly controlled during filling. Increasing the thickness of the filter benefits combination seepage. The effect of changes in particle composition and relative density on the combination seepage characteristics can be expressed by controlling constriction size.

Strategies of tree species to adapt to drought from leaf stomatal regulation and stem embolism resistance to root properties.

Considerable evidences highlight the occurrence of increasing widespread tree mortality as a result of global climate change-associated droughts. However, knowledge about the mechanisms underlying divergent strategies of various tree species to adapt to drought has remained remarkably insufficient. Leaf stomatal regulation and embolism resistance of stem xylem serves as two important strategies for tree species to prevent hydraulic failure and carbon starvation, as comprising interconnected physiological mechanisms underlying drought-induced tree mortality. Hence, the physiological and anatomical determinants of leaf stomatal regulation and stems xylem embolism resistance are evaluated and discussed. In addition, root properties related to drought tolerance are also reviewed. Species with greater investment in leaves and stems tend to maintain stomatal opening and resist stem embolism under drought conditions. The coordination between stomatal regulation and stem embolism resistance are summarized and discussed. Previous studies showed that hydraulic safety margin (HSM, the difference between minimum water potential and that causing xylem dysfunction) is a significant predictor of tree species mortality under drought conditions. Compared with HSM, stomatal safety margin (the difference between water potential at stomatal closure and that causing xylem dysfunction) more directly merge stomatal regulation strategies with xylem hydraulic strategies, illustrating a comprehensive framework to characterize plant response to drought. A combination of plant traits reflecting species’ response and adaptation to drought should be established in the future, and we propose four specific urgent issues as future research priorities.

Death from hunger or thirst? Phloem death, rather than xylem hydraulic failure, as a driver of fire-induced conifer mortality.

Disruption of photosynthesis and carbon transport due to damage to the tree crown and stem cambial cells, respectively, can cause tree mortality. It has recently been proposed that fire-induced dysfunction of xylem plays an important role in tree mortality. Here, we simultaneously tested the impact of a lethal fire dose on nonstructural carbohydrates (NSCs) and xylem hydraulics in Pinus ponderosa saplings. Saplings were burned with a known lethal fire dose. Nonstructural carbohydrates were assessed in needles, main stems, roots and whole plants, and xylem hydraulic conductivity was measured in the main stems up to 29 d postfire. Photosynthesis and whole plant NSCs declined postfire. Additionally, all burned saplings showed 100% phloem/cambium necrosis, and roots of burned saplings had reduced NSCs compared to unburned and defoliated saplings. We further show that, contrary to patterns observed with NSCs, water transport was unchanged by fire and there was no evidence of xylem deformation in saplings that experienced a lethal dose of heat from fire. We conclude that phloem and cambium mortality, and not hydraulic failure, were probably the causes of death in these saplings. These findings advance our understanding of the physiological response to fire-induced injuries in conifer trees.

Model tests and numerical simulations on hydraulic fracturing and failure mechanism of rock landslides

Hydraulic fracturing (HF) is an important reason for inducing rock landslides. The impacts of the angle between the transverse pressure stress and the initial fracture, the transverse pressure stress, the length and aperture of the initial fracture on the critical water pressure stress of HF were analyzed based on the model tests of cement mortar specimens. The HF numerical simulations were carried out and the fracture aperture, pore pressure, strain and stiffness degradation index were analyzed, and the HF mechanism of rock was revealed. Taking a rock slope along G205 in China as an example, the landslide stability under high groundwater pressure was studied by numerical simulations, and the whole processes of the expansion, propagation, penetration and the rock slope failure were reproduced. The results showed that when HF occurred on the cement mortar specimens, a large amount of water seeped from the fracture and made a dull sound of failure, the water pressure on the fracture plane decreased rapidly, but not completely penetrated, and there was still a certain residual strength of the specimen. The HF of rock is a quasi-brittle failure, including static stage, micro fracture propagation stage and macro fracture formation stage. There are 3 dangerous rocks on the rock slope, among which WYT3 is in a stable state under the natural condition and in an unstable state under the rainstorm condition and seismic condition. The fracture propagation of WYT3 under the action of high groundwater pressure experienced slow development stage, rapid development stage and penetration stage, among which the slow development stage lasted the longest, and the slope failure occurred immediately after the fracture penetrated.

Functional xylem characteristics associated with drought-induced embolism in angiosperms.

Hydraulic failure resulting from drought-induced embolism in the xylem of plants is a key determinant of reduced productivity and mortality. Methods to assess this vulnerability are difficult to achieve at scale, leading to alternative metrics and correlations with more easily measured traits. These efforts have led to the longstanding and pervasive assumed mechanistic link between vessel diameter and vulnerability in angiosperms. However, there are at least two problems with this assumption that requires critical re-evaluation: (1) our current understanding of drought-induced embolism does not provide a mechanistic explanation why increased vessel width should lead to greater vulnerability, and (2) the most recent advancements in nanoscale embolism processes suggest that vessel diameter is not a direct driver. Here, we review data from physiological and comparative wood anatomy studies, highlighting the potential anatomical and physicochemical drivers of embolism formation and spread. We then put forward key knowledge gaps, emphasising what is known, unknown and speculation. A meaningful evaluation of the diameter-vulnerability link will require a better mechanistic understanding of the biophysical processes at the nanoscale level that determine embolism formation and spread, which will in turn lead to more accurate predictions of how water transport in plants is affected by drought.

How plants cope with heatwaves in a drier environment

Heatwaves are particularly harmful for plants in combination with drought. The direct effects of high temperatures by themselves can be severe and their negative impacts depend on the maximum temperature reached, duration of exposure, time of the year, water availability and ability to acclimate. Usually, with adequate water supply, evaporative cooling through transpiration allow plants to avoid or delay the time for reaching leaf damage during a heatwave. However, when heat and drought stress occur together, plants face a critical trade-off where plants either close stomata to prevent dehydration at the cost of reducing carbon gain and evaporative cooling, or open stomata to enhance transpiration and cool their leaves at the risk of massive hydraulic failure and tissue dehydration. As global warming has increased episodes of hotter droughts and dry heatwaves, drought and heat impacts in forest are becoming progressively stronger and the mortality risk is exacerbated by a myriad of physiological mechanisms that can accelerate hydraulic failure, carbon starvation and susceptibility to pest and pathogens.