Research interests
Above the cascade d'Ars (Ariège, France)
I am theoretical ecologist interested in linking community ecology and functional ecology. I use mathematical models to represent the interactions between species and between species and their abiotic environment. My aim is to understand the main processes driving ecosystems dynamics, from species level to ecosystem level, and ecosystem stability.
My models represent food webs thanks to Lotka-Volterra type equations. To represent large communities with dozen of species while keeping the number of parameters as low as possible, I use allometric parametrisation to compute biological rates (e.g. respiration and ingestion) as functions of species body mass. These biological rates represent flows of matter and energy from one compartment of the ecosystem to another, thus link population dynamics to ecosystem dynamics by scaling up the flows of carbon and nitrogen from species level to ecosystem level.
The modelled food web is usually size-structured with large organisms eating smaller ones but I am really interested in exploring the effect of other traits affecting species interactions such as stoichiometry or trophic type (herbivore, carnivore, detritivore...).
Linking community ecology and functional ecology needs the explicit representation of particular functional groups of species. For instance, carbon enters ecosystems through primary producers (e.g. phytoplankton and plants) and flows across trophic levels each time a consumer eats resources. All these organisms die and excrete wastes that are resources for decomposers. By consuming this dead matter, decomposer recycle nutrient such as nitrogen or phosphorus and greatly contribute to ecosystem fertility.
All these particular functional groups are coupled by various direct or indirect interactions (common predators, competition for resources, mutualism by complementarity in the biogeochemical cycle...) and I aim to disentangle all these interactions to truly grasp the role of each species in ecosystem functioning and understand the response of ecosystems to perturbations.
The ecosystems I try to model are actually part of metaecosystems. In a metaecosystem, each ecosystem occupies a patch and is linked to other patches through the dispersal of organisms (e.g. migration and foraging) and the flows of abiotic resources (e.g. mineral nutrient leaching). The particularities of each patch (e.g. spatial heterogeneity) and of the dispersal of each species (e.g. directional dispersal and density-dependent dispersal) alter the dynamics at local scale and govern the dynamics at landscape scale.
The spatial dimension of ecosystem introduces new couplings between ecosystems (e.g. benthic pelagic and aboveground-belowground) that have a major impact on ecosystem functioning with the spatial dissociation of primary production and dead organic matter decomposition for instance. My aim is to integrate this spatial dimension in my models to accurately represent the ecology of each functional group and to understand the propagation of perturbations across ecosystems.
My interests are not restricted to theoretical ecology since I took part to several empirical studies in the past. In particular, I performed a mesocosm experiment at the CEREEP Ecotron Île-de-France to test the coupling between green and brown food webs in freshwater ecosystems. Linking theory to empirical data is crucial to build relevant models and a direct touch with nature is always inspiring to do theory. Although I am a theoretician, I have a biology training and naturalistic sensitivity!
I am also interested in terrestrial ecosystems. I try to model the impact of soil fauna on ecosystem functioning to go beyond the usual consideration of microbial activity to represent the impact of the biological activity on biogeochemical cycles. However, soil fauna strongly impact the functioning of soil ecosystems through the processing of plant litter by invertebrate detritivores or the trophic control of microbes by predators.
I have built a general soil food web model capturing the main trophic groups and coupling trophic dynamics with the C and N cycles through ecological stoichiometry. In particular, I am interested in understanding how the various trophic groups shape element cycles and how the variations of the abundance and stoichiometry of resources cascade across the multiple energy channels forming the food web.
Currently, I am working on the functional diversity of soil microbes. they are important drivers of carbon and nutrient fluxes in terrestrial ecosystems through their strong contribution to organic matter decomposition and nutrient cycling. However, these ecological processes are supported by a large diversity of microbes with a wide range of life history traits. For example, fast-growing microbes (-r strategy) take up labile carbon, immobilise nutrients in their biomass and stabilise soil carbon in their necromass, while slow-growing microbes (-K strategies) decompose recalcitrant organic matter and recycle nutrients stored in the soil. Other strategies have been proposed and their classification according to functional traits is still under debate. Recent metagenomic studies have shed light on the combination of traits that characterise microbial communities depending on their environment, but species-level uncertainty remains. i am developing a trait- and individual-based and spatially explicit model of microbial communities to understand how the interactions between theses different strategies newly described shape soil functioning. In particular, I consider the evolution of key microbial traits to explore the emergence of ecological strategies. We consider three main trade-offs linking traits: energetic expenditure of physiological processes, allocation of biomass in the cell and stoichiometry of cell components, which interact with environmental factors such as organic matter quality, availability, stoichiometry and stress.
