Soil carbon dynamics in perennial biomass crops on marginally productive cropland in southern Canada

Predicting changes in soil organic carbon (SOC) in perennial biomass crops using process-based models provides a greater understanding of land management impacts on climate mitigation through long-term soil carbon sequestration. The objective of this study was to predict long-term SOC dynamics in different perennial biomass crops [miscanthus ( Miscanthus giganteus L.), switchgrass ( Panicum virgatum L.), willow ( Salix miyabeana L.)] as compared to secondary regrowth vegetation (successional site) and a row crop system. The Century model accurately predicted SOC when simulated values were compared to measured field data. Average SOC stocks over the 162-year simulation period to 20 cm, were highest in miscanthus (8521 g C m −2 ), followed by the successional site (6877 g C m −2 ), switchgrass (6480 g C m −2 ), willow (5448 g C m −2 ) and lowest in the row crop system (3995 g C m −2 ). Higher SOC stocks in the miscanthus than the successional site indicates that, despite frequent biomass harvest, perennial biomass crops can accumulate higher carbon in soil than when a marginally productive cropland is left to undergo secondary regrowth. However, this depends on the crop species, since the miscanthus was the only biomass crop that reached pre-cultivation (1911) SOC stock of 8288 g C m −2 . Moreover, the perennial biomass crops enhanced SOC in the slow fraction, whereas row crops depleted SOC in this fraction. This indicates the vital contribution of perennial biomass crops in long-term SOC sequestration and their role in climate change mitigation, especially when grown on marginally productive croplands. • Perennial biomass crops can enhance SOC storage. • The Century model accurately predicted SOC stocks in perennial biomass crops. • Perennial biomass crops on marginally productive land yielded greater SOC storage. • Soil organic carbon in biomass crops was associated with stabilized C fractions. • Biomass crops on marginal land can mitigate climate change via soil C sequestration.