Abstract
Enhancement of terrestrial carbon (C) sequestration on marginal lands in Canada using bioenergy crops has been proposed. However, factors influencing system-level C gain (SLCG) potentials of maturing bioenergy cropping systems, including belowground biomass C and soil organic carbon (SOC) accumulation, are not well documented. This study, therefore, quantified the long-term C sequestration potentials at the system-level in nine-year-old (2009–2018) woody (poplar clone 2293–29 (Populus spp.), hybrid willow clone SX-67 (Salix miyabeana)), and herbaceous (miscanthus (Miscanthus giganteus var. Nagara), switchgrass (Panicum virgatum)) bioenergy crop production systems on marginal lands in Southern Ontario, Canada. Results showed that woody cropping systems had significantly higher aboveground biomass C stock of 10.02 compared to 7.65 Mg C ha−1 in herbaceous cropping systems, although their belowground biomass C was not significantly different. Woody crops and switchgrass were able to increase SOC significantly over the tested period. However, when long term soil organic carbon (∆SOC) gains were compared, woody and herbaceous biomass crops gained 11.0 and 9.8 Mg C ha−1, respectively, which were not statistically different. Results also indicate a significantly higher total C pool [aboveground + belowground + soil organic carbon] in the willow (103 Mg ha−1) biomass system compared to other bioenergy crops. In the nine-year study period, woody crops had only 1.35 Mg C ha−1 more SLCG, suggesting that the influence of woody and herbaceous biomass crops on SLCG and ∆SOC sequestrations were similar. Further, among all tested biomass crops, willow had the highest annual SLCG of 1.66 Mg C ha−1 y−1.
Highlights
Under the Paris Agreement of 2015, Canada became one of 195 countries committed to limiting global average temperature increases to below 2 ◦C above pre-industrial levels, while working to limit the increase to 1.5 ◦C [1]
Results from this study suggest that the higher allocation of C in leaves in willow provides a potential for increased C inputs to soil via litterfall contributing to soil organic carbon (SOC) sequestration
Results from this study suggest that both woody biomass cropping systems and switchgrass are able to increase SOC significantly in the nine-year period of this study (2009–2018)
Summary
Under the Paris Agreement of 2015, Canada became one of 195 countries committed to limiting global average temperature increases to below 2 ◦C above pre-industrial levels, while working to limit the increase to 1.5 ◦C [1]. In 2019, greenhouse gas (GHG) emissions projections were updated, and two scenarios were introduced, including the Additional Measures scenario, which covers GHGs reduction potentials from land use, land use change, and forestry (LULUCF) [3]. Similar projections for biomass crops have been put forward by other authors to move away from fossil fuels and bring about a partial solution for the global energy crises [5,6,7] These systems sequester atmospheric CO2 in their fibre, as well as in the soil through the decomposition of litterfall, coarse root and fine-root turnover [8] in addition to other soil processes that can contribute to soil organic carbon (SOC) sequestration. The cultivation of marginal lands or less productive agricultural lands with bioenergy crops could potentially improve soil health of the land due to their additions to soil organic matter [18]
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