The role of forest ecosystems in the current global ecological crisis is critical, yet we are far from understanding the full range of factors that affect forest nutrition and that condition their ability to act and respond to climate. The ecosystem services provided by forests are limited by the water and nutrient stresses that threaten them. While the cycles of water, carbon, nitrogen and phosphorus have been and are being studied extensively, not enough attention has been paid to the essential mineral nutrients whose ultimate origin can only be rock weathering. This project aims to improve our knowledge of mineral nutrition processes in trees, and in particular to disentangle the part of mineral nutrients that comes from biological recycling by the plant itself from that which comes from external inputs such as mineral weathering or atmospheric deposition. This distinction between external inputs and internal recycling is crucial to improve current ecophysiological numerical models. To do so, we propose to use boron isotopes that have recently proven their potential to distinguish sources and processes affecting mineral nutrients. We base the project on a scaled approach ranging from controlled experiments in ECOTRONS to the watershed. The project relies on the use of community infrastructures such as ANAEE, OZCAR, ICOS or Renecofor that provide experimental sites to explore environmental gradients and on an exceptional instrumented Eucalyptus plantation in Brazil. The originality of this project lies in its scientific consortium because the communities that build ecophysciological models and those that study and model chemical alteration are not enough working together. The project is part of the critical zone study perspective, an attempt to reconnect the disciplines.