Modeling the effects of plant-fire and plant-nutrient feedbacks on succession dynamics and ecosystem functioning
Context
Fire is a major ecological force that shapes ecosystems worldwide. Due to their long evolutionary history with fire, plants in fire-prone ecosystems showcase specific adaptations such as postfire resprouting or fire-stimulated germination, and display variable temporal niches during post-fire succession (Pausas & Keeley 2014). Beyond its direct impacts on vegetation, fire also affects plant communities indirectly by modulating soil fertility. Fire events make essential nutrients such as phosphorus (P) readily available in the short-term, but can accelerate ecosystem nutrient depletion in the longer term. Vegetation, in turn, can modulate fire frequency and intensity. For example, the C- rich/nutrient-poor litter of Australian Eucalypt species (Myrtaceae) (Orians & Milewski 2007) and, more generally, of plants adapted to nutrient-poor soils, can contribute to the high flammability of these communities. Together, these interactions can in some instances lead to self-reinforcing, positive feedbacks that “trap” vegetation in highly flammable states. Such fire-vegetation feedback loops may thereby play a key role in the maintenance of alternative stable states, including at large spatial scales (Pausas & Bond 2020). As the frequency and severity of wildfire increases with climate change, a deep understanding of the conditions under which highly flammable ecosystem states emerge will be essential to sustainable land management and human health.
Goals of the internship
The student will build a dynamical plant-fire model that explicitly models fire events and postfire recolonization dynamics, and use it to investigate how interactions between two plant strategies and fire drive succession dynamics and ecosystem properties, including the emergent fire regime. We will then explore how changing environmental conditions (e.g. a drier climate) affect the system, looking in particular for alternative stable states between low flammability and high flammability ecosystem states.
A first version of this model will be kept as simple as possible, acting as a proof of concept. Then, depending on the preferences of the student, the model can be complexified by, for example, 1) including soil nitrogen (N) and phosphorus (P) dynamics explicitly and plant stoichiometric traits, 2) increasing the diversity of plant strategies that recolonize during post-fire succession, 3) considering a diverse set of fire-adapted strategies, such as resistance and tolerance, where the latter could be divided between resprouting and seeding, etc.
Preferred skills
This internship concerns 2nd year master students, either from “Biodiversity, Ecology & Evolution” curricula or from applied mathematics. A strong motivation for ecological theory and modeling is necessary and associated technical skills will be appreciated.
Location and work conditions
The internship will take place in the Laboratoire de Biométrie et de Biologie Évolutive (UMR 5558, Lyon, https://lbbe.univ-lyon1.fr) in close collaboration with the Institute of Ecology and Environmental Sciences (iEES) in Paris (https://iees-paris.fr) and remote collaboration with Griffith University, Australia, and will last 4 to 6 months starting in January-February 2024.
Mentoring & contact-me
The internship will be overseen by:
– Thomas Koffel (Université Lyon 1)
– Nicolas Loeuille (Sorbonne Université)
– Orpheus Butler (Griffith University)
To contact us or ask for further information, please send an email to Thomas Koffel (thomas.koffel@univ-lyon1.fr), Nicolas Loeuille (nicolas.loeuille@sorbonne-universite.fr) and Orpheus Butler (orpheus_butler@outlook.com). Formal applications require a CV, a motivation letter and transcripts including grades and rankings (when available).
References
• Orians, G. H., & Milewski, A. V. (2007). Ecology of Australia: the effects of nutrient‐poor soils and intense fires. Biological Reviews, 82(3), 393-423.
• Pausas, J. G., & Bond, W. J. (2020). Alternative biome states in terrestrial ecosystems. Trends in Plant Science, 25(3), 250-263.
• Pausas, J. G., & Keeley, J. E. (2014). Evolutionary ecology of resprouting and seeding in fire‐ prone ecosystems. New Phytologist, 204(1), 55-65.
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