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Impact de la disponibilité en nutriments sur le fonctionnement hydrique et carboné de peupliers dans des contextes de sécheresse variés

Abstract : The availability of water and nutrients are two main factors limiting tree growth and forest productivity. Despite the strong legacy of research on forest nutrition, the role of nutrients in modulating tree drought responses remains largely unknown. This thesis aimed to evaluate the role of nutrient availability on key traits related to water and carbon relations such as growth and its determinants, water-use efficiency (WUE), vulnerability to cavitation, or non-structural carbohydrate (NSC) contents, in poplars under contrasting drought intensities. Research experiments relied on two complementary experimental designs, one in a greenhouse and the other in an outdoor common garden, and considered a maximum of four genotypes primarily selected for their contrasting growth and stomatal regulation. The main findings are as follows: 1) a higher nutrient availability increases growth and WUE under moderate drought, 2) a higher nutrient availability does not necessarily increase the risk of xylem hydraulic failure, 3) NSC depletion, in particular starch, co-occurs with massive xylem embolism under lethal drought, and 4) a higher nutrient availability reduces NSC storage, especially under moderate drought. This study shows for the first time the temporal covariance between the dynamics of xylem hydraulic failure and carbon starvation in a fast-growing but highly vulnerable tree species, and gives an example of how these relationships are modulated by nutrient availability.
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Laure Bouyer. Impact de la disponibilité en nutriments sur le fonctionnement hydrique et carboné de peupliers dans des contextes de sécheresse variés. Biodiversité et Ecologie. Université d'Orléans, 2019. Français. ⟨NNT : 2019ORLE3100⟩. ⟨tel-03215603⟩

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