The Study: Linking plant traits to soil carbon outcomes

The study examined 11 diverse Miscanthus genotypes grown under controlled conditions. By analysing the chemical composition of leaves, roots and rhizomes (thick underground stems that store energy and help the plant survive winter and regrow each year), and linking these traits to existing soil carbon data for each genotype, the researchers identified characteristics strongly associated with soil carbon accumulation.

The analysis focused on key components of plant cell walls, including lignin, cellulose and nitrogen content. These are traits known to influence how plant material decomposes and stabilises in soil.

Each tissue contributes differently to carbon cycling. Harvested above-ground biomass which contains carbon, can be stored long-term if used in durable products or combined with carbon capture technologies. Below-ground biomass, such as roots and rhizomes, can contribute to more stable forms of soil carbon that are protected from rapid breakdown by microbes.

Key insights for breeding and management

The results highlight lignin content and lignin-to-nitrogen ratios as important predictors of soil carbon storage, with different plant tissues influencing carbon accumulation at different soil depths:

• Rhizomes: Higher lignin content was associated with increased soil organic carbon at deeper soil layers (10–20 cm), suggesting a role in long-term carbon stabilisation.
• Roots: Lower lignin content and lower lignin-to-nitrogen ratios were linked to greater carbon stocks in surface soils (0–10 cm).
• Leaves: Senesced leaf traits showed weaker relationships overall, though lower lignin-to-nitrogen ratios were associated with some increases in soil carbon.

Together, these findings suggest that an effective Miscanthus ideotype for soil carbon sequestration would combine high below-ground biomass with relatively low lignin and lignin-to-nitrogen ratios in roots.

Implications for Breeding

“Breeding programmes for Miscanthus are still at an early stage,” said lead author Amanda Holder. “These results provide practical guidance on which traits are most likely to support soil carbon storage, helping ensure that future varieties deliver climate benefits alongside high yields.”

For breeders, growers and policy stakeholders, the research offers a clearer evidence base for integrating soil carbon outcomes into biomass crop development. Importantly, the study also shows that enhancing soil carbon storage does not need to come at the expense of productivity, supporting the case for Miscanthus as a multifunctional crop within low-carbon land-use systems.