"Global environmental change is predicted in Europe to result in increased frequency and intensity of extreme climatic events, including severe droughts and intense precipitation events. Such changes will affect plant physiology, microbial activity and soil nutrient cycling, inducing changes in ecosystem functioning, with expected consequences on in plant community composition, net primary productivity and carbon balance. Thus, it is crucial to consider the effect of precipitation patterns of contrasted amplitude on the plant-soil interaction. The main objective of this project is to understand the mechanisms of the coupling between precipitation patterns and carbon and nitrogen cycling in the plant-soil microbial system. The effect of precipitation patterns of contrasting amplitude will be addressed in a multidisciplinary approach combining state-of-the-art molecular techniques with stable isotope approaches to enable a detailed understanding of the functioning of the plant-soil system that ultimately relates belowground fluxes to the activity of the soil microbial population. Changes in the structure of the active microbial community over the long term will be assessed using a high-density oligonucleotide microarray chip, a cutting-edge tool which allows to assess which prokaryotic operational taxonomic units are active in the soil. The fluxes of carbon and nitrogen between plant and soil microbes will be determined using isotopic methods. The mechanisms underlying plant-soil microbial interactions in response to contrasting precipitation patterns will be identified under controlled conditions during the outgoing phase then validated in the field during the return phase, enabling valuable insight into the future implications of changes in European summer climate for plant nitrogen availability, and providing crucial information for the development of mitigation strategies."