Carbon isotope compositions (delta C-13) of leaf, wood and holocellulose differ among genotypes of poplar and between previous land uses in a short-rotation biomass plantation

摘要

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 (C-13) 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 C-13(wood) and C-13(holocellulose) were tightly and positively correlated, but the offset varied significantly among genotypes (0.79-1.01). Leaf phenology was strongly correlated with C-13, and genotypes with a longer growing season showed a higher WUE. In contrast, traits related to growth and carbon uptake were poorly linked to C-13. Trees growing on former pasture with higher N-availability displayed higher C-13 as compared with trees growing on former cropland. The positive relationships between C-13(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 C-13 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.