Intensive plantations of trees for bioenergy (short rotation coppice, SRC) are often synonymous with soil depletion. To maintain productivity in the long term while reducing inputs (water, fertilizer), an optimized matching between (1) the characteristics of plant material (genera, species and genotypes, mixed or not) particularly in terms of efficiencies of resource use (WUE, NUE), (2) cultural practices (spraying, densities, pruning, etc.) and (3) the soil and climate conditions is to find. The approach taken to meet this objective is to study the effects of the three categories of above factors on productivity and its determinants through the study of cycles of carbon, nitrogen and water in a network of plantations spread throughout the north of France. Under the framework of three running ambitious projects, about 20 willow and poplar plantations are extensively monitored in northern France with the objective to test the impact of various cultural practices and pedoclimatic contexts on the links between biomass production and resource use efficiencies. The impact of (1) planting densities, (2) clonal mixing, (3) mixture with nitrogen fixing species (Robinia), (4) sludge spreading, (5) first year coppicing, (6) harvest period during the year are tested, (7) cultural antecedent, (8) fertilization, are currently studied