Modeling the delayed impact of drought on tree architecture as a contribution to forest dieback | Modélisation des effets différés de la sécheresse sur l'architecture des arbres, contribuant au dépérissement forestier
2011
Vennetier, M. | Girard, F. | Ouarnim, S. | Didier, C. | Ripert, C. | Caraglio, Yves | Ecosystèmes méditerranéens et risques (UR EMAX) ; Centre national du machinisme agricole, du génie rural, des eaux et forêts (CEMAGREF) | Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)
[Departement_IRSTEA]Territoires [TR1_IRSTEA]SEDYVIN
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Show more [+] Less [-]English. The impact of drought on tree architectural development was studied in France from 1995 to 2010 on 6 conifers. During and after bad years, a fall occurred in branching rate, polycyclism frequency, size and number of leaves. The resulting simplified architecture limits for several years the capacity of trees to explore available space and contributes to a low LAI and to crown transparency. Small leaves also limit the potential maximum LAI for 3 to 8 years according to their life span. We designed and calibrated a model of branch architectural development with observed data. We also integrated the observed parameters in whole-tree development models. These models were used to simulate the direct and delayed consequences of climate accidents of various intensity and duration (1 to 5 year) on tree potential LAI and photosynthesis. Together, light architecture and smaller needles may cut by up to 75% the potential LAI at the end of a multi-year accident. The full recovery of crown density with an normal climate is delayed from 2 to 8 years according to the severity and duration of the accident. This long lasting deficit contributes to carbon shortage. It helps explaining why forest die-back, partly driven by carbon starvation, may occur many years after climatic accidents.
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