Post-drought conditions and hydraulic dysfunction determine tree resilience and mortality across Mediterranean Aleppo pine (<i>Pinus halepensis</i>) populations after an extreme drought event

Morcillo, Luna; Muñoz-Rengifo, Jc; Torres‐Ruiz, José M.; Delzon, Sylvain; Moutahir, Hassane; Vilagrosa, Alberto

doi:10.1093/treephys/tpac001

Cited by 17 publications

(7 citation statements)

References 69 publications

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“…The vulnerability curve we show in Figure 6 represents an "empiric" curve, meaning it is constructed from Ψ x and PLA values that were measured simultaneously on naturally dehydrating intact plants rather than cut branches, similar to what was done in Paudel et al (2020) and Gerbi et al (2022). The P 50 (i.e., the Ψ x in which 50% of the xylem is embolized) was similar (<0.5 MPa difference) to the P 50 that was found for multiple populations of Aleppo pine from Israel (David-Schwartz et al, 2016), France (Davi et al, 2020), or Spain (Morcillo et al, 2022) using the Cavitron, meaning that the fast method (Cavitron) provides functional data that is relevant for naturally dehydrating trees. Strangely, when we tested the same trees using the Cavitron or optical vulnerability and μCT for bench dehydrating shoots, they were found to be less resistant in $1 MPa (Feng et al, 2023).…”

Section: Empiric Vulnerability Curvementioning

confidence: 88%

Relationships between xylem embolism and tree functioning during drought, recovery, and recurring drought in Aleppo pine

Wagner,

Volkov,

Nadal‐Sala

et al. 2023

Physiologia Plantarum

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Recent findings suggest that trees can survive high levels of drought‐induced xylem embolism. In many cases, the embolism is irreversible and, therefore, can potentially affect post‐drought recovery and tree function under recurring droughts. We examined the development of embolism in potted Aleppo pines, a common species in hot, dry Mediterranean habitats. We asked (1) how post‐drought recovery is affected by different levels of embolism and (2) what consequences this drought‐induced damage has under a recurring drought scenario. Young trees were dehydrated to target water potential (Ψx) values of −3.5, −5.2 and −9.5 MPa (which corresponded to ~6%, ~41% and ~76% embolism), and recovery of the surviving trees was measured over an 8‐months period (i.e., embolism, leaf gas‐exchange, Ψx). An additional group of trees was exposed to Ψx of −6.0 MPa, either with or without preceding drought (Ψx of −5.2 MPa) to test the effect of hydraulic damage during repeated drought. Trees that reached −9.5 MPa died, but none from the other groups. Embolism levels in dying trees were on average 76% of conductive xylem and no tree was dying below 62% embolism. Stomatal recovery was negatively proportional to the level of hydraulic damage sustained during drought, for at least a month after drought relief. Trees that experienced drought for the second time took longer to reach fatal Ψx levels than first‐time dehydrating trees. Decreased stomatal conductance following drought can be seen as “drought legacy,” impeding recovery of tree functioning, but also as a safety mechanism during a consecutive drought.

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Section: Empiric Vulnerability Curvementioning

confidence: 88%

Relationships between xylem embolism and tree functioning during drought, recovery, and recurring drought in Aleppo pine

Wagner,

Volkov,

Nadal‐Sala

et al. 2023

Physiologia Plantarum

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“…Several studies have shown that the effect of drought episodes in SE Spain, such as those recorded in 1994, 2003 and 2014, has caused considerable damage to plant communities, along with decay processes and further generalized plant mortality (Peñuelas & Filella, 2001; Herrero et al, 2013; García de la Serrana et al, 2015; Morcillo et al, 2022). Mediterranean shrublands are quite vulnerable to rising temperatures and decreasing water availability (Bellot et al, 2004), and the expected increasing aridity in regions that are already dry in large areas of the Mediterranean Basin may have serious ecological and socio‐economic consequences (IPCC, 2021).…”

Section: Discussionmentioning

confidence: 99%

“…In this context, we analyzed the effect of an intense drought that occurred in the 2014 hydrological year on some Mediterranean areas of SE Spain. Annual rainfall was less than 50% of the long‐term average, which caused notable tree mortality in several zones (García de la Serrana et al, 2015; Morcillo et al, 2022). Spread plant dieback and mortality were detected in four monitored Mediterranean shrublands.…”

Section: Introductionmentioning

confidence: 99%

The main factors that drive plant dieback under extreme drought differ among Mediterranean shrubland plant biotypes

Maturano‐Ruiz

Ruiz-Yanetti

Manrique‐Alba

et al. 2023

J Vegetation Science

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Questions: Knowledge of how extreme drought events induce plant dieback and, eventually, plant mortality, may improve our forecasting of ecosystem change according to future climate projections, especially in Mediterranean drylands. In them, shrublands are the main vegetation communities in transition areas from a subhumid to semi-arid climate. This study analyzed differences in plant dieback after an unusual drought in 2014 and identified their main underlying factors in relation to three groups of explanatory variables: water availability, soil properties and vegetation structure attributes.Location: Four Mediterranean shrublands along a climatic gradient in SE Spain.Methods: At each experimental field site, we sampled a pool of vegetation structure characteristics, soil depth and soil surface properties, and we also determined water availability by continuously monitoring soil moisture and the microclimate conditions. Results:The climatic analysis showed that there was an extreme drought event in 2014, which was below the first percentile of the driest years. Under such conditions, vegetation dieback occurred at all the study sites. However, plant dieback differed between sites and plant biotypes. Subshrubs were the main affected biotype, with diebacks close to 60% at the driest sites, and up to 40% dieback for shrubs depending on their vertical development. Relative extractable water and bare soil surface cover were the best explanatory variables of plant community dieback but changed between plant biotypes. Vegetation structure variables related to plant vertical development (leaf area index [LAI], plant height, phytovolume) were significant explanatory variables of plant dieback in shrubs, subshrubs and grasses. Consecutive dry days fitted the best model to explain subshrub dieback. Conclusions:We found that rainfall pattern rather than total annual rainfall was the climatic factor that best determined water availability for plants in Mediterranean drylands. These results also pointed out the relevance of plant structure and soil properties for explaining ecosystem responses to extreme drought.

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“…Global change scenarios not only predict increasing temperature and changes in precipitation patterns but also higher drought intensity and longer drought duration in the Mediterranean Basin (IPCC, 2021). Climate alterations will affect ecosystem function and survival by promoting plant water use and carbon assimilation changes (Allen et al, 2015; Lindner et al, 2010; Morcillo et al, 2022). Quantifying soil‐vegetation‐atmosphere water fluxes is critical for understanding ecosystem hydrology now and in the future and to, therefore, better define the required adaptive forest management.…”

Section: Introductionmentioning

confidence: 99%

Testing transpiration rates of juvenile Aleppo pine trees using the heat ratio method under laboratory conditions

Sabater,

Valiente,

Bellot

et al. 2023

Ecohydrology

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Tree transpiration considerably contributes to evaporative fluxes to the atmosphere in terrestrial ecosystems. Accurate transpiration quantification provides relevant information about forest water use and may benefit adaptive forest management, especially in a global change context. Tree transpiration can be measured by several methods, and sap flow measurements are one of the most valued. However, species‐specific validations of these techniques are required to avoid undesirable bias. This is especially relevant in species with low transpiration rates where errors may be relevant, such as Aleppo pine trees (Pinus halepensis Mill.). Moreover, another significant source of uncertainty in sap flow measurements is probe misalignment. Hence, the aim of this study was to correlate transpiration rates estimated by sap flow probes using the heat ratio method (THRM) and load cells to independently monitor water transpiration in juvenile Aleppo pine trees. The corrections to improve transpiration measures, including misalignment correction, were applied to THRM results to test if the accuracy of results improved. These measurements were recorded in greenhouse under controlled conditions to implement different environmental conditions. The environmental variables that ruled the experiment, mainly vapour pressure deficit and soil water availability, spanned in a wide range of values. The results showed an accurate linear correspondence between TOBS and THRM for low and medium values, but moderate underestimations at high transpiration rates were observed. These underestimations were partly removed when applying probe misalignment correction. This study supports the notion that HRM offers accurate Aleppo pine transpiration estimations with low and medium values under a variety of abiotic conditions, which also has implications for HRM application in other isohydric species. The results also support the interest in the use of probe misalignment correction to estimate transpiration, mainly when high transpiration values are recorded. The results of this study can be considered as a preliminary approach for future research in order to improve the estimates of the transpiration rates of the Aleppo pine under the limiting conditions of the Mediterranean.

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Post-drought conditions and hydraulic dysfunction determine tree resilience and mortality across Mediterranean Aleppo pine (Pinus halepensis) populations after an extreme drought event

Cited by 17 publications

References 69 publications

Relationships between xylem embolism and tree functioning during drought, recovery, and recurring drought in Aleppo pine

Relationships between xylem embolism and tree functioning during drought, recovery, and recurring drought in Aleppo pine

The main factors that drive plant dieback under extreme drought differ among Mediterranean shrubland plant biotypes

Testing transpiration rates of juvenile Aleppo pine trees using the heat ratio method under laboratory conditions

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