MODIMIV - Modelling the relationship between microbial and plant diversity in multi-species agroecosystems

The central hypotheses are that interactions between plant diversity (e.g. grasses and legumes) and soil microbial diversity play a key role in regulating biogeochemical cycles. Grasslands, which cover about 40% of the Earth's surface, can act as carbon sinks or sources. Processes such as biological nitrogen fixation via legume-rhizobium symbiosis or root dynamics influencing organic matter decomposition contribute to better nutrient synchronisation, reducing losses and improving productivity.

Approaches

The methodological approach is based on combining existing models: ModVege for plant growth, CoSMo for plant species dynamics, and SYMPHONY for soil microbiology. Several M2-level internships have enabled the development of specific modules:

• Integration of nitrogen fixation by legumes, based on functional traits such as specific leaf area and leaf lifespan,
• Addition of a root compartment to simulate exudate flows and root mortality, with adjustments to the C/N ratio
• Analysis of the distribution of functional traits at different spatial scales using the DRY database.

The work is based on numerical simulations, literature reviews and data from field experiments, in particular UREP devices on innovative plant covers such as agroprairies.

Results

The main results include a prototype integrated model of root dynamics, enabling the simulation of new flows, such as the growth gain attributable to biological nitrogen fixation. Functional trait analysis highlights intraspecific variability influencing functional diversity at scales ranging from square metres to ecoregions, with covariations structured by aridity gradients.

Finally, a position paper (Rodríguez et al., under review) compiles more than 300 references and a glossary of 40 terms. It proposes a roadmap for integrating microbial and plant biodiversity into biogeochemical models.

Participants

Structures INRAE

• UREP - Unité de recherche Écosystème Prairial
• UMR SADAPT - Sciences pour l'action et le développement : activités, produits, territoires
• UMR EMMAH - Environnement méditerranéen et modélisation des agro-hydrosystèmes
• UR P3F - Unité de recherche Pluridisciplinaire prairies et plantes fourragères

Partenaires externes

• CREA - Research Centre for Agriculture and Environment, Italy
• CREA - Research Centre for Animal Production and Aquaculture, Italy
• LIEC - Laboratoire interdisciplinaire des environnements continentaux - CNRS
• VetAgroSup, Campus Agronomique de Clermont-Ferrand