Toward an index of desiccation time to tree mortality under drought

Blackman, Christopher J; Pfautsch, Sebastian; Choat, Brendan; Delzon, Sylvain; Gleason, Sean M.; Duursma, Remko A.

doi:10.1111/pce.12758

Cited by 87 publications

(97 citation statements)

References 45 publications

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“…Our data indicate that the 2015 summer drought pushed the study tree species into a range of Ψ midday values which were strongly regulated to avoid a further rapid decrease. However, far more negative Ψ midday have already been shown in temperate trees, suggesting that under extreme conditions when Ψ predawn further decreases, the physiological regulation of Ψ midday cannot keep up with progressive soil drying (Blackman et al, ; Breshears et al, ; Hoffmann et al, ; Martínez‐Vilalta, Poyatos, Aguadé, Retana, & Mencuccini, ; Meinzer et al, ). Interestingly, all species showing Ψ midday to level off with declining Ψ soil suggests that the physiological reaction to drought is rather uniform among these temperate tree species (Figure , Supporting Information Figure ).…”

Section: Discussionmentioning

confidence: 99%

No role for xylem embolism or carbohydrate shortage in temperate trees during the severe 2015 drought

et al. 2018

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Temperate forests are predicted to experience an increased frequency and intensity of climate change‐induced summer droughts and heat waves in the near future. Yet, while previous studies clearly showed a high drought sensitivity of different temperate tree species, the vulnerability of the physiological integrity of these trees remains unclear. Here, we assessed the sensitivity of six temperate tree species to severe water limitation during three consecutive growing seasons, including the exceptional 2015 central European summer drought and heat wave. Specifically, we assessed stem increment growth, sap flow, water potentials, hydraulic vulnerability, and nonstructural carbohydrate contents in leaves and branches to determine how mature temperate trees responded to this exceptional weather event and how the observed responses relate to variation in xylem embolism and carbohydrate economy. We found that the trees' predawn water potentials reached their minimum values during the 2015 summer drought and most species reduced their sap flow by up to 80%. Also, increment growth was strongly impaired with the onset of the drought in all species. Despite the strong responses in the trees' growth and water relations, all species exhibited minimum midday shoot water potentials well away from values associated with severe embolism (P50). In addition, we detected no distinct decrease in nonstructural carbohydrate contents in leaves, bark, and stems throughout the drought event. Synthesis. This study shows that mature individuals of six common central European forest tree species strongly reacted to a severe summer drought by reducing their water consumption and stopping growth. We found, however, no indications for xylem embolism or carbohydrate depletion in these trees. This suggests, that xylem embolism formation and carbohydrate reserve depletion are not routine in temperate trees during seasonal strong drought and reveals a low vulnerability of the physiological integrity of temperate trees during drought events as we describe here.

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Section: Discussionmentioning

confidence: 99%

No role for xylem embolism or carbohydrate shortage in temperate trees during the severe 2015 drought

et al. 2018

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“…The first concept suggests a species-specific approach using measurements of plant hydraulics, tissue characteristics, and branch specific leaf area [11]. This work [11] introduced a theoretical framework around the empirical assessment of the time (T crit ) it takes for a foliated branch to reach critical levels of desiccation following stomatal closure.…”

Section: Tree Mortalitymentioning

confidence: 99%

“…This work [11] introduced a theoretical framework around the empirical assessment of the time (T crit ) it takes for a foliated branch to reach critical levels of desiccation following stomatal closure. The novelty of the concept lies in assessing stomatal and cuticular Bleakinessĉ ombined with quantification of capacitive water stores that can shorten or prolong T crit .…”

Section: Tree Mortalitymentioning

confidence: 99%

“…In line with this research, we have generated an increasingly detailed knowledge of the hydraulic nexus between xylem and phloem, particularly the possible role of photosynthates in hydraulic functioning [5-7, 8••, 9]. In addition, we have progress in deciphering the role of stored water in stems [10], branches [11], and leaves [12] in keeping trees alive. Technological advances allow us to study in-situ fluid transport dynamics in trees-and also its collapse-at a previously unattainable level of detail [13,14].…”

Section: Introductionmentioning

confidence: 99%

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Hydraulic Anatomy and Function of Trees—Basics and Critical Developments

Pfautsch

2016

Curr Forestry Rep

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The study of hydraulic anatomy and function of trees has a long tradition. Motivated by current and projected changes in water availability, the field of tree hydraulics is experiencing a bout of activity. Significant progress has been made in understanding how water transport in trees is organized, how it integrates with other physiological processes, and what it takes for it to malfunction. Many of these advances have been possible, as fields of research that have traditionally been separate are merging, for example, wood anatomy and plant ecophysiology. These developments have led to the creation of powerful and novel approaches that help to answer longstanding questions relating to fundamental aspects of fluid transport in plants and how plants survive in the face of environmental stresses such as drought and freezing. The increased capacities to visualize the ultrastructures of wood in ever-greater detail and the ability for in-situ visualization of long-distance fluid transport have contributed to this progress. This review provides an entry point to the vast and continuously increasing knowledge of how water transport in trees is organized. It scales from cells to tissue anatomy to whole-tree physiology and landscape ecology. Known mechanisms and novel conceptual theories around how trees die as well as ways to prevent this fate are summarized. High-priority research questions for the coming years are formulated.

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“…After accounting for evaporative demand, this rate of water loss is expressed as the minimum conductance of a leaf. There is increasing recognition that the minimum conductance plays an important role in estimating the water fluxes in plant canopies (Barnard & Bauerle, ), during heat waves (Kala et al ., ) and in models of plant drought response (Blackman et al ., ; Martin‐StPaul et al ., ).…”

Section: Introductionmentioning

confidence: 99%

On the minimum leaf conductance: its role in models of plant water use, and ecological and environmental controls

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Contents Summary I. Introduction II. Comparison of various definitions and measurement techniques of minimum conductance III. Cuticular conductance IV. Contribution of stomata V. Environmental and ecological variation in minimum conductance VI. Use of minimum conductance in models VII. Conclusions Acknowledgements References SUMMARY: When the rate of photosynthesis is greatly diminished, such as during severe drought, extreme temperature or low light, it seems advantageous for plants to close stomata and completely halt water loss. However, water loss continues through the cuticle and incompletely closed stomata, together constituting the leaf minimum conductance (g ). In this review, we critically evaluate the sources of variation in g , quantitatively compare various methods for its estimation, and illustrate the role of g in models of leaf gas exchange. A literature compilation of g as measured by the weight loss of detached leaves is presented, which shows much variation in this trait, which is not clearly related to species groups, climate of origin or leaf type. Much evidence points to the idea that g is highly responsive to the growing conditions of the plant, including soil water availability, temperature and air humidity - as we further demonstrate with two case studies. We pay special attention to the role of the minimum conductance in the Ball-Berry model of stomatal conductance, and caution against the usual regression-based method for its estimation. The synthesis presented here provides guidelines for the use of g in ecosystem models, and points to clear research gaps for this drought tolerance trait.

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Toward an index of desiccation time to tree mortality under drought

Cited by 87 publications

References 45 publications

No role for xylem embolism or carbohydrate shortage in temperate trees during the severe 2015 drought

No role for xylem embolism or carbohydrate shortage in temperate trees during the severe 2015 drought

Hydraulic Anatomy and Function of Trees—Basics and Critical Developments

On the minimum leaf conductance: its role in models of plant water use, and ecological and environmental controls

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