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Modelling resilience of vegetation patterns in semi-arid regions for changing precipitation conditions by Lilian VANDERVEKEN -
Mardi 18 mars 2025 à 16h15 - Auditoire SUD03 - Croix du Sud - 1348 Louvain-la-Neuve
Semi-arid regions, like the Sahel, face significant challenges due to climate change. In these areas, vegetation forms spatial patterns to cope with water scarcity. Understanding the resilience of these patterns is crucial for predicting ecosystem responses to changing environmental conditions. This thesis investigates vegetation patterns in semi-arid ecosystems using the Rietkerk model, a system of partial differential equations. We focus on bifurcations, rate-induced tipping (R-tipping), and the effects of stochastic precipitation.
An in-depth bifurcation analysis of the Rietkerk model reveals stable patterned states even under low rainfall, where no vegetation persists in a homogeneous system. We identify and classify stable and unstable equilibria. We also discover "mixed states," novel unstable equilibria that slow down transitions between stable patterns and offer insights into tipping points in spatial systems.
To assess resilience, we examine the system’s response to perturbations and link this response to internal timescales. The spatio-temporal structure of perturbations is crucial for resilience. The co-existence of multiple equilibria and unstable states enhances resilience by offering stable configurations under fluctuating conditions.
Finally, incorporating intermittent precipitation dynamics shows that the effects on vegetation depend on rainfall intermittency and water uptake. This research advances our understanding of vegetation pattern dynamics, offering a framework to assess ecosystem resilience in water-limited environments.
Jury members :
Prof. Michel Crucifix (UCLouvain)(Supervisor)
Prof. Qiuzhen Yin (UCLouvain) (Chairperson)
Prof. Valentin Couvreur (UCLouvain) (Secretary)
Prof. Max Rietker (Utrecht University)
Prof. Robbin Bastiaansen (Utrecht University)
Pay attention : the public defense of Lilian VANDERVEKEN will also take place in the form of a videoconference
