Contribution à l'intégration des cycles biogéochimiques dans les modèles de croissance forestier à base phénoménologique. Dynamique saisonnière du couvert forestier et décomposition de la matière organique du sol

Abstract : The scientific community, in collaboration with forestry managers, developed decision support tools since thirty years. However, current modelling approaches do not allow simultaneous estimations of global changes impact management policies on forests. The design of a new generation of models dedicated to soil-plant coupling is necessary to help forest managers to adapt forestry practices to face global changes. Phenomenological models arising from dendrometry estimate forest growth \& yield and take into account of silvicultural practices. Their use is limited by their dependence to a fertility index, which combines implicitly the influence of climate and biogeochemical cycles. A re-examination of fertility index concept is necessary to take advantage of concepts developed in ecophysiological and biogeochemical models. Modelling the monthly dynamics of foliar renewal with the Stand Leaf Canopy Dynamics model permited: i) to estimate leaf area index dynamics, ii) to model foliar litter production. This probabilistic model takes into account climate influence, ecosystem water availability and lies on strong ecological hypothesis on mechanisms involved in leaf longevity. This model, associated with an ecophysiological model, permits to integrate water cycle to dendrometric models. The soil organic matter decomposition along a vertical soil profile model introduced by Bosatta et Ågren (1996) was analyzed to study the future of litterfall in forest soil. We proposed: i) a proof of existence and uniqueness of solutions to the integro-differential transport equation of the model, ii) convergent implicit-explicit finite differences schemes estimating model solutions and iii) a discussion on hypothesis underlying a model truncation introduced by Bosatta et Ågren. These two modelling steps are essential to consider biogeochemical cycle with a dendrometric approach. Climate and phenology influence on water cycle, litterfall decomposition and soil chemistry are the elements of a future modelling phase.
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Julien Sainte-Marie. Contribution à l'intégration des cycles biogéochimiques dans les modèles de croissance forestier à base phénoménologique. Dynamique saisonnière du couvert forestier et décomposition de la matière organique du sol. Mathématiques générales [math.GM]. Université de Lorraine, 2014. Français. ⟨NNT : 2014LORR0118⟩. ⟨tel-01750913⟩

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