Dynamics of Miscanthus spp. Overwinter Leaf Litter Drop and Decomposition

Perennial biomass crops represent a rapidly deployable technology to contribute to climate change mitigation, both reducing greenhouse gas emissions through providing alternative energy sources to fossil fuels, and direct photosynthetic removal of CO2 from the atmosphere and sequestration into biomass and soil organic carbon (SOC). The giant perennial grass, Miscanthus × giganteus is one of the leading commercial crops currently deployed at scale, with its associated overwinter leaf litter production and decomposition providing a key pathway to SOC sequestration. However, challenges in the scalability of propagative material from this sterile, naturally occurring hybrid have led to great interest from breeding programs to develop novel varieties better suited to replication and specific end‐use requirements. This study compares leaf litter production and decomposition from six Miscanthus genotypes to better understand their comparative potential contribution to carbon cycling across a range of morphologies. Our results showed that, despite genotypic differences in growing season leaf production, differences in overwinter retention rates resulted in similar absolute amounts being dropped to the ground, excepting M. × sinensis (our sinensis × sinensis hybrid) which both produced and dropped significantly greater litter material than the other genotypes, 14.9 Mg DM ha−1 compared with an average across the other genotypes of 2.8 Mg ha−1, and was associated with one of the lowest decomposition rates. Major shifts in the litter microbiome were observed during the first 6 months of decomposition with important plant material decomposers likely migrating from soil communities; these changes appeared to be statistically consistent across all genotypes. Excepting M. × sinensis, the relative consistency of litter production suggests that breeding programs may focus on yields without paying a penalty in leaf carbon cycling, though if outright leaf litter production for carbon sequestration and soil surface protection were the primary goal, M. × sinensis may represent an optimal choice.