A global increase in the demand for wood products has been observed worldwide during the last decades. This trend is expected to continue in the future as a consequence of population growth. Additionally, the need for wood is augmented by the increasing substitution of fossil energy by wood biomass-based energy to mitigate greenhouse gas emissions. This demand will not be satisfied by natural and naturally regenerated forests: they are threatened by high deforestation rates and forest degradation mainly in the tropics and the costs of wood mobilization in the temperate zones is a concern. Forest plantations (FP) are therefore expected to provide a large part of the global wood supply. Their ability to meet wood demand is limited by competing land uses. Higher stand yields must be obtained on soils that may not necessarily support such intensification especially as nitrogen (N) and phosphorus (P) exportations by biomass removal are generally not offset by fertilization. Therefore, FP sustainability is currently a major concern, particularly with regard to serious long-term N and P deficits. Innovative FP management schemes, and attractive to the stakeholders must be then deployed. The Intens&Fix project will deal with the ecological intensification of FP through the association of N2-fixing species (NFS) with the goal to increase stand production as, in particular, a result of better N and P availability in the soil. These systems hould combine positive environmental impacts while ensuring social-economical improvement of livelihood for smallholders or performances for commercial companies. The project will develop an experimental approach on various and complementary FP with associated NFS, both in France (Juglans sp. and Alnus cordata or herbaceous NFS in Languedoc, Populus sp + Robinia pseudoacacia. in North-Est of France) and in the Tropics (mixed-species plantations of Eucalyptus grandis and Acacia mangium in Brazil and Congo). An integrated biophysical model will be developed for the simulation of mixed species in FP. Outputs of virtual experiments performed with the biophysical model will feed a plantation-level model allowing to assess the economical feasibility and to test decision rules for the management of FP with NFS. Crossing models outputs and a survey of stakeholders’ innovation process concerning the use of NFS will entitle us to assess the potential development of these systems. The approach will be multidisciplinary and involve scientists working in ecophysiology, biogeochemistry, soil science, microbiology, silviculture, socio-economics, and modelling. This project will contribute to the production of innovative results i.e. refined methodological techniques for estimation of N transfer, documentation of mechanisms of competition/ facilitation for N and P bioavailability, model coupling water, N and C functioning adapted to mixed-species forests and practices (species, density…) to manage NFS in FP, and socio-economical assessment of these new management schemes. The results will be valorised through publications in high level scientific journals, as well as in R/D journals and participation to international conferences. More generally the involvement of a top resource partner in farm forestry and agroforestry, the participative approach deployed, and the strong partnership developed with producer organisations in France, Brazil and Congo will warrant a large and efficient dissemination of the Intens&Fix results. From an operational view point, the Intens&Fix project will provide tools of ecological intensification to significantly improve FP management with specific targets in eucalyptus plantations in Congo and Brazil (several millions ha), Very Short Rotation Coppices, and high value timber in agroforestry systems (potential of several millions ha in Europe).