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Hommes, Savanes, Forêts : modélisation de systèmes dynamiques liant l'homme à son environnement

Abstract : This thesis emphasises the interest of models and methods initially developed in physics to study ecological systems with two examples. The first one concerns the dynamic of the interface between humid tropical forests and peri-forest savannas. FORSAT is a stochastic cellular automata modelling the two key processes sustaining the vegetation dynamics: the succession cycle (pioneer forest species installation in savannas) and man-induced savanna fires. The analysis of the model indicates that forest and savanna can be interpreted as two phases of a same system and that a phase transition occurs, the control parameters of which are an environmental factor (representing the ability for forest species to grow in savanna, influenced by climate of soil fertility) and an anthropic factor: the frequency of savanna fires. Increasing fire frequency induces two effects: the critical value of the environmental factor increases as well (the more recurrent fires are, the more favourable environmental conditions must be to sustain forest) and the transition that is of second order or rare fires becomes of first order for regular fires. The FORSAT model is a simple framework in which can be interpreted the humid tropical forest present repartition and their past dynamics as well as the results of a field study led in the forest savanna mosaic in the coastal Congo (Kouilou district). The second example concerns the dynamics of an urban dengue epidemic. Dengue is a tropical human infectious disease transmitted by domestic mosquitoes. The modelling effort includes three components: the disease severity (there are four stages of dengue and the way the factors interact to start one of them are still under debate), the dynamics of an epidemic in a homogeneous population and finally in a heterogeneous one.
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Contributor : Charly Favier <>
Submitted on : Friday, April 22, 2005 - 12:09:09 PM
Last modification on : Friday, March 5, 2021 - 3:08:17 PM
Long-term archiving on: : Monday, September 20, 2010 - 12:11:36 PM

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  • HAL Id : tel-00009014, version 2

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Charly Favier. Hommes, Savanes, Forêts : modélisation de systèmes dynamiques liant l'homme à son environnement. Ecologie, Environnement. Université Paris Sud - Paris XI, 2003. Français. ⟨tel-00009014v2⟩

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