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Réactions de semis naturels de hêtre (Fagus sylvatica L.) et d'érable sycomore (Acer pseudoplatanus L.) à l'ouverture du couvert : croissance et ajustements fonctionnels

Abstract : Management of mixed forests relies mainly on natural regeneration dynamics and canopy opening is particularly critical during regeneration process. Acquiring knowledge about reactions of different tree species to opening is important as advanced understory sapling bank constitutes an important potential for future stand reconstitution. Gap creation induces rapid change in sapling growth conditions (larger light and soil water availability, higher vapour pressure deficit...). Growth of pre-existing seedlings is often delayed for a few months up to several years after a gap opening. We hypothesized that this delay might be ascribed to the time needed for acclimation of advanced sapling exposed to the new light environment. Four shade tolerant species (beech, sycamore maple, Norway maple and field maple) in advanced seedling banks were studied. For 2 years after canopy opening, the sapling growth response was caracterized and the growth delay was explain by an analysis of morphological and physiological components of growth. Following canopy opening, mortality was low and diameter growth increased from the first year onwards whereas height growth increase was delayed for one year. Beech and sycamore have shown plasticity of leaf structure (increase of LMA) and tree architecture as influenced by canopy opening. Beech reacted also by allocating more biomass to root and cambial growth increasing this capacity to supply water to leaves. Nevertheless leaf carbon assimilation did not increase much the first year. This may be due in part to increased vulnerability to cavitation in beech under gap. The second year after opening, beech and sycamore seedling acclimation was almost achieved, both species having now an active diameter and height growth.
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https://hal.univ-lorraine.fr/tel-01748472
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Blandine Caquet. Réactions de semis naturels de hêtre (Fagus sylvatica L.) et d'érable sycomore (Acer pseudoplatanus L.) à l'ouverture du couvert : croissance et ajustements fonctionnels. Sylviculture, foresterie. Université Henri Poincaré - Nancy 1, 2008. Français. ⟨NNT : 2008NAN10114⟩. ⟨tel-01748472⟩

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