Willows (Salix spp.) grown as short rotation coppice (SRC) are viewed as a sustainable
source of biomass with a positive greenhouse gas (GHG) balance due to their potential to fix
and accumulate carbon (C) below ground. However, exploiting this potential has been
limited by the paucity of data available on below ground biomass allocation and the extent
to which it varies between genotypes. Furthermore, it is likely that allocation can be altered
considerably by environment. To investigate the role of genotype and environment on
allocation, four willow genotypes were grown at two replicated field sites in southeast
England and west Wales, UK. Above and below ground biomass was intensively measured
over two two-year rotations. Significant genotypic differences in biomass allocation were
identified, with below ground allocation differing by up to 10% between genotypes.
Importantly, the genotype with the highest below ground biomass also had the highest
above ground yield. Furthermore, leaf area was found to be a good predictor of below
ground biomass. Growth environment significantly impacted allocation; the willow genotypes
grown in west Wales had up to 94% more biomass below ground by the end of the
second rotation. A single investigation into fine roots showed the same pattern with double
the volume of fine roots present. This greater below ground allocation may be attributed
primarily to higher wind speeds, plus differences in humidity and soil characteristics.
These results demonstrate that the capacity exists to breed plants with both high yields
and high potential for C accumulation.
© 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC