Résumé
Rhizodeposition, the set of processes releasing organic compounds from living roots into soil, would play a key role in soil carbon (C) storage and nitrogen (N) mineralization, which are both essential for nutrient cycling and sustainable agricultural practices. Accounting for around 14% and 17% of annual C and N plant acquisition, respectively, rhizodeposits significantly impact the local availability of C and N on both root and rhizosphere sides, affecting biomass allocation for root growth, nutrient acquisition, and soil biochemical balance. Rhizodeposition has also been described as being very variable at local and plant scale. However, the consequences of this local plasticity once integrated into the plant root-shoot feedback loops for autotrophy are still poorly understood in the context of heterogeneous agricultural soils. This cognitive lock-in is partly due to the lack of mechanistic models integrating local fluxes along roots, measured or simulated, to evaluate their significance at plant scale. To bridge this gap, we developed Wheat-BRIDGES, the first architectured Functional-Structural Plant Model (FSPM) accounting for carbon-nitrogen-water-growth cycles from the organ scale to the whole soil-root-shoot-atmosphere system. By coupling existing compartment- or resource-specific FSPMs, this model accounts for multiscale retroaction mechanisms throughout the crop cycle of spring wheat. Calibrated on experimental data from literature, this model enabled us to study more realistic and complex regulation patterns behind reported rhizodeposition plasticity. This study focuses on spring wheat rhizodeposition during vegetative stage in a patchy soil environment. We show that the model accounts for increased lateral branching in nitrate patches as an emerging pattern of trophic C&N retroactions, correlating with increased local rhizodeposition fluxes and whole root-system rhizodeposition. Enhanced rhizodeposition in these areas was related to increased microbial activity, with contrasted effects on net C storage depending on rhizodeposits C:N ratio. Wheat-BRIDGES provides a unique tool for scaling and analyzing the contributions of individual plant organs within the soil-plant-atmosphere system, offering valuable insights to identify scenarios favoring soil C storage supporting sustainable plant nutrition.