Carbon isotope compositions (δ13C) of leaf, wood and holocellulose differ among genotypes of poplar and between previous land uses in a short-rotation biomass plantation.

The efficiency of water use to produce biomass is a key trait in designing sustainable bioenergy-devoted systems. We characterized variations in the carbon isotope composition (δ¹³ C) of leaves, current year wood and holocellulose (as proxies for water use efficiency, WUE) among six poplar genotypes in a short-rotation plantation. Values of δ¹³ C_wood and δ¹³ C_{holocellulose} were tightly and positively correlated, but the offset varied significantly among genotypes (0.79-1.01‰). Leaf phenology was strongly correlated with δ¹³ C, and genotypes with a longer growing season showed a higher WUE. In contrast, traits related to growth and carbon uptake were poorly linked to δ¹³ C. Trees growing on former pasture with higher N-availability displayed higher δ¹³ C as compared with trees growing on former cropland. The positive relationships between δ¹³C_leaf and leaf N suggested that spatial variations in WUE over the plantation were mainly driven by an N-related effect on photosynthetic capacities. The very coherent genotype ranking obtained with δ¹³C in the different tree compartments has some practical outreach. Because WUE remains largely uncoupled from growth in poplar plantations, there is potential to identify genotypes with satisfactory growth and higher WUE. [ABSTRACT FROM AUTHOR]