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Forest tree responses to extreme climatic events

Abstract : Water availability is one of the most constraining factors of tree growth, even under temperate conditions. Annual increments, as recorded in tree-rings, can be measured retrospectively to reconstruct tree live. This approach, so called dendrochronology, allows the detection of low frequency signals (trends dues to tree ageing or to global change) and high frequency signals (inter-annual growth change). Such year-to-year variability is always clearly recorded, with either large or narrow tree-rings. Some years, most of the trees from a stand, a region or some time a country, react in a similar way. This is a pointer year useful for both tree-ring dating and analysing trees responses to extreme climatic events like frost, heat wave, spring water logging, and drought … Forest tree species exhibited contrasted responses to climatic hazards, depending on their sensitivity to water shortage or temperature hardening. These differences, illustrated from our dendrochronological data base, could be interpreted as a result of ecophysiological responses. Tree response analysis to climatic hazards like extreme drought needs first a quantification and description of seasonal progression of water shortage (starting time, duration, intensity …). These criteria, computed from a retrospective calculation of daily and local forest water balance, allow building drought typology and between years or canopy types (broad leaves vs. sempervirens) comparisons. Water balance calculation also helps identifying water logging periods during spring, which impact on tree growth should be as severe as drought. For the forester, a drought is an extreme event if visible and durable symptoms are induced, including leaf discolouration, perennial organs mortality (twig, branches), tree dieback and mortality. This kind of symptoms, lagging one or several years after the climatic event, will be illustrated from forest decline occurred since the 2003 drought or attributed to previous drought events in France. The cumulated impact of recurrent droughts on tree growth response will be illustrated and the physiological interpretation of the long lasting memory of tree will be discussed. Finally, some conclusions of such a coupled approach linking dendrochronology and ecophysiology will be translated to management advices to foresters and arguments helping to select adapted species according to actual and future site water balance.
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Submitted on : Saturday, June 6, 2020 - 12:57:18 PM
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  • HAL Id : hal-02815362, version 1
  • PRODINRA : 8948

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Nathalie Bréda, Vincent Badeau. Forest tree responses to extreme climatic events. Écosystèmes et événements climatiques extrêmes. Ecosystems and extreme climatic events. Colloque de l'Académie des Sciences, Jul 2007, Paris, France. n.p. ⟨hal-02815362⟩

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