Soil organic carbon (SOC) is an important carbon pool susceptible to land‐use change (LUC). There are concerns that converting grasslands into the C₄ bioenergy crop Miscanthus (to meet demands for renewable energy) could negatively impact SOC, resulting in reductions of greenhouse gas mitigation benefits gained from using Miscanthus as a fuel. This work addresses these concerns by sampling soils (0–30 cm) from a site 12 years (T₁₂) after conversion from marginal agricultural grassland into Miscanthus x giganteus and four other novel Miscanthus hybrids. Soil samples were analysed for changes in below‐ground biomass, SOC and Miscanthus contribution to SOC (using a ¹³C natural abundance approach). Findings are compared to ECOSSE soil carbon model results (run for a LUC from grassland to Miscanthus scenario and continued grassland counterfactual), and wider implications are considered in the context of life cycle assessments based on the heating value of the dry matter (DM) feedstock. The mean T₁₂ SOC stock at the site was 8 (±1 standard error) Mg C/ha lower than baseline time zero stocks (T₀), with assessment of the five individual hybrids showing that while all had lower SOC stock than at T₀ the difference was only significant for a single hybrid. Over the longer term, new Miscanthus C₄ carbon replaces pre‐existing C₃ carbon, though not at a high enough rate to completely offset losses by the end of year 12. At the end of simulated crop lifetime (15 years), the difference in SOC stocks between the two scenarios was 4 Mg C/ha (5 g CO₂‐eq/MJ). Including modelled LUC‐induced SOC loss, along with carbon costs relating to soil nitrous oxide emissions, doubled the greenhouse gas intensity of Miscanthus to give a total global warming potential of 10 g CO₂‐eq/MJ (180 kg CO₂‐eq/Mg DM).

中文翻译：

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12 年后从温带草原到芒草的土地利用变化对土壤碳储量的影响的测量和模拟。

土壤有机碳（SOC）是易受土地利用变化（LUC）影响的重要碳库。有人担心，将草原转变为 C ₄生物能源作物芒草（以满足可再生能源的需求）可能会对 SOC 产生负面影响，从而导致使用芒草作为燃料获得的温室气体减排效益减少。这项工作通过从边际农业草地转变为芒草和其他四种新型芒草杂交种 12 年 (T ₁₂ ) 后对一个地点的土壤 (0-30 厘米) 进行采样来解决这些问题。分析土壤样本的地下生物量、SOC 和芒草对SOC 的贡献的变化（使用¹³ C 自然丰度方法）。将研究结果与 ECOSSE 土壤碳模型结果（针对从草地到芒草情景和持续草地反事实的 LUC 运行）进行比较，并在基于干物质 (DM) 原料热值的生命周期评估背景下考虑更广泛的影响。该地点的平均 T _{12 SOC 储量比基线时间零储量 (T 0} )低 8（±1 标准误差）Mg C/ha ，对五个单独的杂交品种的评估表明，虽然所有品种的 SOC 储量均低于 T 时的 SOC 储量₀差异仅对于单个混合体而言显着。从长远来看，新的芒草C ₄碳取代了先前存在的 C ₃碳，尽管其速度不足以在第 12 年底完全抵消损失。在模拟作物寿命（15 年）结束时，差异两种情景之间的 SOC 储量为 4 Mg C/ha (5 g CO ₂ ‐eq/MJ)。包括模拟的 LUC 引起的 SOC 损失，以及与土壤一氧化二氮排放相关的碳成本，芒草的温室气体强度增加了一倍，使全球变暖总潜力达到 10 g CO ₂ ‐eq/MJ（180 kg CO ₂ ‐eq/镁DM）。