Genotype identity has a more important influence than genotype diversity on shoot biomass productivity in willow short‐rotation coppices

Abstract

Willow (Salix spp.) short-rotation coppice is commercially grown to produce lignocellulosic biomass to meet renewable bioenergy demands. Most commercial willow coppices are grown in stands of a single genotype, but biomass productivity may be greater in mixed communities, and the productivity in mixed communities may depend on the specific genotypes involved. We assessed the biomass production of four different Salix genotypes ("Bj€ orn," "Jorr," "Loden," "Tora") grown without additional nutrient fertilization during one cutting cycle at three locations in Europe (Uppsala in Sweden, Rostock and Freiburg in Germany) in plots of pure and mixed communities. We evaluated (i) the effect of genotype diversity on shoot biomass productivity, including the evidence for complementarity and selection effects; (ii) the influence of individual genotypes on mixed community productivity; and (iii) the productivity of individual genotypes in response to pure vs. mixed culture. Mean shoot biomass production after the first cutting cycle decreased in the order Rostock (8.7 Mg ha À1 ) > Freiburg (6.9 Mg ha À1 ) > Uppsala (5.7 Mg ha À1 ), with values similar to those for other nonfertilized willow stands after the first growth cycle. Consistently across all three locations, increasing genotype diversity did not significantly affect shoot biomass production. Using Bayesian statistics, the addition of the genotypes "Jorr" and "Loden" was predicted to enhance shoot biomass production, while "Tora" and "Bj€ orn" are more likely to reduce shoot biomass production in mixed communities. In addition, we found evidence for a negative selection effect due to the genotype "Tora"performing better in mixed than in pure communities in two of the sites (Freiburg, Uppsala). In conclusion, our results imply that increasing genetic richness has no negative effect on productivity and that there is a potential to design site-specific genotype mixtures of short-rotation coppice promoting both high genetic diversity and high biomass production.

Integrated lignocellulosic value chains in a growing bioeconomy: Status quo and perspectives

“…The long‐term soil rest reduces the risk of soil erosion and leads to soil carbon and humus accumulation, thus improving soil fertility and potentially improving degraded lands (Lewandowski, ). PBC can be integrated well into farming systems and provide them with additional biomass for on‐farm use or as cash crops. PBC have the highest productivity of all biomass production systems in Europe. There are promising candidate PBC for temperate (see Clifton‐Brown et al, ; Hoeber et al, ) and Mediterranean (see Fabbrini et al, ) European climates, including switchgrass, miscanthus, giant reed, willow and poplar. Breeding programs are in place for most relevant PBC.…”

“…The supply of sustainably produced biomass is the prerequisite for a lignocellulosic value chain to perform well. It can be provided from sustainable forestry and from agricultural production, with agricultural residues and perennial biomass crops (PBC) being the most favourable resources (Clifton‐Brown et al, ; Fabbrini et al, ; Hoeber et al, ). PBC can be integrated into existing farming systems using less favourable land or land marginal for food crop production, with the additional provision of various ecological benefits (Wagner et al, ).…”

“…• PBC have the highest productivity of all biomass production systems in Europe. There are promising candidate PBC for temperate (see Clifton-Brown et al, 2018;Hoeber et al, 2018) and Mediterranean (see Fabbrini et al, 2018) European climates, including switchgrass, miscanthus, giant reed, willow and poplar. Breeding programs are in place for most relevant PBC.…”

“…Breeding programs are in place for most relevant PBC. These exploit the genetic variability and have already delivered genotypes at varying levels of advancement (Clifton-Brown et al, 2018;Fabbrini et al, 2018;Hoeber et al, 2018) • The chemical composition and physical properties of PBC biomass can be tailored to biomass utilization chains by the optimization of harvest time (Mangold, Lewandowski, & Kiesel, 2019a, 2019b, appropriate selection of available cultivars (Schäfer, Sattler, Iqbal, Lewandowski, & Bunzel, 2019) and, in the long term, through breeding programs (see Clifton-Brown et al, 2018). Biomass from PBC thus has a more consistent composition than biomass from wastes, which come from a variety of sources, and is therefore more suitable for conversion pathways with specific quality requirements.…”

“…with agricultural residues and perennial biomass crops (PBC) being the most favourable resources (Clifton-Brown et al, 2018;Fabbrini et al, 2018;Hoeber et al, 2018). PBC can be integrated into existing farming systems using less favourable land or land marginal for food crop production, with the additional provision of various ecological benefits .…”