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Pierre Couteron

Publications and source records attributed to Pierre Couteron.

2 recordsLinked to original sources

Analysis of a two patch model for disease vector-animal dynamics with non-linear anthropization-driven migration

Landscape dynamics are key drivers of the movement and distribution of sylvatic hematophagous disease vectors and their (wild) animal hosts. Their habitats are undergoing increasing change, particularly fragmentation, through anthropogenic activity. In this article, we present and analyse a novel mathematical model that explicitly combines anthropization-induced landscape dynamics with the population dynamics of hematophagous vectors and (wild) animals dynamics. We develop a phenomenological and analytically tractable two-patch model in which the migration terms between the patches nonlinearly depend on the anthropization level of the patches. Our model analysis comprising analytical stability analysis and numerical bifurcation analysis provides information on how changes in model parameters, especially anthropization levels, shape the long-term dynamics in the model. Precisely, we find that low anthropogenic activity allows for a vector-animal coexistence state, while high anthropization leads to a vector extinction state. However, we establish that for intermediate anthropization levels, the transition between the two states is not necessarily monotonic, but may instead occur via a sequence of concurrent bifurcations along the anthropization axis.

q-bio.PE

Effect of rainfall and fire frequency on tree--grass dynamics: Capturing the forest--savanna distributions along biogeographic gradients

In this work, we improve a previous minimalistic tree-grass savanna model by taking into account water availability, in addition to fire, since both factors are known to be important for shaping savanna physiognomies along a climatic gradient. As in our previous models, we consider two nonlinear functions of grass and tree biomasses to respectively take into account grass-fire feedbacks, and the response of trees to fire of a given intensity. The novelty is that rainfall is taken into account in the tree and grass growth functions and in the biomass carrying capacities. Then, we derive a qualitative analysis of the ODE model, showing existence of equilibria, and studying their stability conditions. We also construct a two dimension bifurcation diagram based on rainfall and fire frequency. This led to summarize different scenarios for the model including multi-stabilities that are proven possible. Next, to bring more realism in the model, pulsed fire events are modelled as part of an IDE (Impulsive differential Equations) system analogous to the ODE system. Numerical simulations are provided and we discuss some important ecological outcomes that our ODE and IDE models are able to predict. Notably, the expansion of forest into tree-poor physiognomies (grassland and savanna) is systematically predicted when fire return period increases, especially in mesic and humid climatic areas.

q-bio.PE