This axis aims to analyse and model how, by using agricultural or forestry practices, it is possible to optimise the use of mineral resources to produce sustainably while protecting the environment. It focuses on the sustainability of production services and the effect of practices by taking into account nutrient recycling practices on fertility. This axis concerns forest stands, crops and their spatial assemblages, on time scales from year to several decades. It integrates issues at the management unit level (plot, station) and at encompassing scales (farm, production basin, watershed, territory to global scale). On this axis, a few themes that cut across the teams have emerged.
- The first concerns the necessary multi-elemental analysis of nutrient flows between soil, vegetation and atmosphere compartments. In a context of recycling inputs and increasing pressure on ecological regulations intrinsic to ecosystems through agroecology, it is necessary to reason the production system in order to optimize the availability not only of a target element but of all the resources necessary for the plant. This involves (1) defining naturally coupled processes and those that concern only one element, thus defining the points of interaction and (2) laying the foundations for coupled flow modelling by integrating interactions. Similarly, the study of transfers of elements from the soil to plants requires that we study the coupling with the soil's water status. Modelling the interactions between soil water and its minerals will provide useful elements for understanding and analysing the functioning of systems.
- The second theme aims to reflect on how to combine a functional analysis of exchange flows, taking into account stakeholders and exchanges of materials between plots, farms or activities, with a spatialized analysis of the physical environment. Indeed, in the first approach, material flows are organized between agricultural and non-agricultural actors. In the second approach, exchanges are regulated by water and atmospheric flows. How do these two approaches to material flows complement each other in predicting flows at the scale of a territory?
- Finally, when analysing flows at encompassing scales, the question of flow management arises: do the levers identified at the local level have an effect at intermediate or global scales and vice versa; are there interdependencies between local practices and global socio-economic strategies?