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Modelling fires as pulses in tree/grass interactions: study of long-term impact in forest-savanna dynamical systems

Tchuinte Tamen A., Dumont Y., Bowong S., Tewa J.J., Couteron P.. 2015. Biomath Communications, 2 (1) : 1 p.. International Conference on Mathematical methods and Models in Biosciences and Young Scientists School, 2015-07-12/2015-07-17, Pretoria (Afrique du Sud).

DOI: 10.11145/475

It is usually admitted that fires play an important role in tree-grass interactions in savanna ecosystems. In this talk, we present a model of tree-grass dynamics using impulsive differential equations, considering fires as discrete events [1]. This framework allows us to carry out a comprehensive qualitative mathematical analysis that revealed more possible outcomes than the analogous continuous model [2]. We investigated local and global properties of the equilibria and show that various states may co-exist. Though fire periodicity may drive the system to different and abrupt shifts between vegetation, we also show that direct shading of grasses by trees, through a facilitation/competition parameter, is an influential process too, leading to bifurcations. Finally, using a suitable numerical approach [3], we carried out numerical simulations related to three main climatic zones, observable in Central Africa, to illustrate our theoretical results. (Texte intégral)

Mots-clés : savane; forêt tropicale; incendie de forêt; herbage; arbre d'ombrage; compétition biologique; dynamique des populations; modèle mathématique; méthode statistique; afrique centrale

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