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Large hydraulic safety margins protect Neotropical canopy rainforest tree species against hydraulic failure during drought

Abstract : Context: Xylem vulnerability to embolism, which is associated to survival under extreme drought conditions, is being increasingly studied in the tropics, but data on the risk of hydraulic failure for lowland Neotropical rainforest canopy-tree species, thought to be highly vulnerable, are lacking. Aims: The purpose of this study was to gain more knowledge on species drought-resistance characteristics in branches and leaves and the risk of hydraulic failure of abundant rainforest canopy-tree species during the dry season. Methods: We first assessed the range of branch xylem vulnerability to embolism using the flow-centrifuge technique on 1-m-long sun-exposed branches and evaluated hydraulic safety margins with leaf turgor loss point and midday water potential during normal- and severe-intensity dry seasons for a large set of Amazonian rainforest canopy-tree species. Results: Tree species exhibited a broad range of embolism resistance, with the pressure threshold inducing 50% loss of branch hydraulic conductivity varying from − 1.86 to − 7.63 MPa. Conversely, we found low variability in leaf turgor loss point and dry season midday leaf water potential, and mostly large, positive hydraulic safety margins. Conclusions: Rainforest canopy-tree species growing under elevated mean annual precipitation can have high resistance to embolism and are more resistant than what was previously thought. Thanks to early leaf turgor loss and high embolism resistance, most species have a low risk of hydraulic failure and are well able to withstand normal and even severe dry seasons.
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https://hal.umontpellier.fr/hal-02432407
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Soumis le : mercredi 8 janvier 2020 - 14:02:40
Dernière modification le : mardi 17 mars 2020 - 02:55:23

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Camille Ziegler, Sabrina Coste, Clement Stahl, Sylvain Delzon, Sebastien Levionnois, et al.. Large hydraulic safety margins protect Neotropical canopy rainforest tree species against hydraulic failure during drought. Annals of Forest Science, Springer Verlag/EDP Sciences, 2019, 76 (4), ⟨10.1007/s13595-019-0905-0⟩. ⟨hal-02432407⟩

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