Above- and below-ground carbon accumulation and biomass allocation in poplar short rotation plantations under Mediterranean conditions

Beside the production of biomass, short rotation coppice (SRC) poplar plantations can also contribute to carbon sequestration in the soil through their below-ground biomass. The present study evaluated the allocation of above and below-ground biomass at the end of the first rotation of four SRC plantations under Mediterranean conditions. The genotypes evaluated are commonly used for biomass plantations, i.e. genotypes 'AF2' and 'I-214' (Populus × canadensis Mönch), and 'Monviso' (P. × generosa Henry × P. nigra L.). No significant differences among genotypes were found with regard to below-ground biomass yield. The root:shoot ratio decreased in line with the growth in shoot basal diameter, with values ranging from 0.15 to 0.26. The accumulation of carbon in the below-ground fraction of the biomass ranged from 0.86 to 0.91 Mg C ha−1 yr−1, whereas the above-ground carbon accumulation ranged from 3.89 to 6.48 Mg C ha−1 yr−1. A general as well as a genotype-specific allometric model allowed to accurately predict the below-ground biomass yield using shoot basal diameter as the predictor variable. Both models provide an important tool to quantify the carbon accumulated in the below-ground fraction of the biomass.