Wood production determinants in poplar: where are we going ?

International audience

English. Because world resources of fossil fuels are rapidly decreasing, it is necessary and urgent to find alternative sources of energy. By 2020, the European Union aims at reaching 20% of the share of total energy produced by renewable energy. One way to achieve this is to use crops specifically dedicated to the production of woody biomass. Currently, woody biomass comes mainly from logging residues or from the waste wood industry. However, cropping systems specifically dedicated to the production of woody biomass as short rotation coppice are presently gaining in importance. In a context of large-scale production of biomass produced from fast growing woody species, it is important to optimize the production by selecting species and genotypes adapted to local conditions. Plant material can be selected either directly for biomass production or for potential determinants of wood production such as phenology, ramification, leaf growth and composition, or water- and nutrient-use efficiencies (WUE and NUE). Then, wood production can be maximized by playing either on the choice of the plant material (species and genotypes within species) for a given pedoclimatic context and/or on the adopted cultural system (notably through planting densities / rotation length). The prerequisite is to evaluate the strength of the relationships between wood production and its potential determinants, and their reliability (plasticity) for the different species, cultural systems, and pedoclimatic contexts. Studies have already been conducted to analyze the effect of the interaction between genotype and environment. The present study will provide new information about this interaction as it takes into account factors that were not studied concurrently in previous studies. Our experiment proposes to study the influence of genetic and environmental factors (and their interaction, GxE) on phenological, architectural, functional (WUE and NUE), and foliar determinants of wood production. The genetic factor is considered at inter-specific level (comparison of three fast-growing species, poplar, willow and black locust) and at intraspecific level (clonal tests for each species). The environmental factor consists of different pedoclimatic contexts in France and different cultural systems (more or less intensive). Two experimental sites at the West and East sides of France are used in this experiment. These sites are located (1) in French Brittany (47°60’N, 1°91’W) with an oceanic climate and (2) in Burgundy (47°18’N, 5°19’E) with a continental climate. Determinants of productivity such as NUE, WUE, bud and leaf phenology, ramification, growth in height and girth, leaf increment, and foliar structure and function will be analyzed throughout the growing season with repeated measurements and observations (from March to October 2010) at the two sites, for the different clones of the three species, and for different planting densities. This monitoring is done under the framework of a French project called SYLVABIOM (2008 to 2012). The SYLVABIOM project is supported by the Bioenergy thematic of the French research national agency (ANR).