Rice residue including root and straw are unique carbon (C) source in paddy soils. However, the potential changes in quantity and chemical composition of rice residue under co-elevated atmospheric CO2 concentration ([CO2]) and air temperature (Tair) and the legacy effect of the changed chemical composition on residue decomposition have not been investigated. This study was conducted to investigate biomass, chemical composition, and decomposability of rice root and straw produced under elevated [CO2] and Tair. Root and straw biomass increased by elevated [CO2] and elevated Tair, respectively, and the greatest biomass was achieved under co-elevated [CO2]-Tair for both root and straw. The concentration of lignin (recalcitrant) decreased while that of nonstructural carbohydrates (less recalcitrant) increased by co-elevated [CO2]-Tair. The ratio of lignin-to-nitrogen (lignin/N) decreased by co-elevated [CO2]-Tair compared to ambient [CO2]-Tair due to increased N and decreased lignin concentrations. Decomposability of root (lignin/N, 36.4) produced under co-elevated [CO2]-Tair was greater than that under ambient co-elevated [CO2]-Tair (lignin/N, 53.7); however, there was no difference in decomposability for straw, which had relatively narrow range of lignin/N (27.3–36.5) regardless of [CO2]-Tair conditions. The results of this study provide a novel insight into the changes in quantity and quality of rice residue under elevated [CO2]-Tair that are necessary to predict changes in paddy soil C sequestration under global warming.

中文翻译：

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在 CO2 和温度共同升高的条件下生产的水稻根和秸秆的生物量、化学成分和微生物可分解性

包括根和秸秆在内的水稻残留物是稻田土壤中独特的碳（C）源。然而，尚未研究在大气 CO2 浓度 ([CO2]) 和气温 (Tair) 共同升高的情况下大米残留物数量和化学成分的潜在变化以及化学成分变化对残留物分解的遗留影响。本研究旨在调查在升高的 [CO2] 和 Tair 下生产的水稻根和稻草的生物量、化学成分和可分解性。根和秸秆生物量分别通过升高的 [CO2] 和升高的 Tair 增加，在共同升高的 [CO2]-Tair 下，根和秸秆的生物量最大。木质素（顽固性）的浓度降低，而非结构性碳水化合物（顽固性较低）的浓度因 [CO2]-Tair 的共同升高而增加。与环境 [CO2]-Tair 相比，由于 N 增加和木质素浓度降低，木质素与氮的比率（木质素 / N）因 [CO2]-Tair 的共同升高而降低。共升高[CO2]-Tair 下产生的根(木质素/N, 36.4) 的可分解性大于环境共升高[CO2]-Tair (木质素/N, 53.7) 下的分解能力；然而，秸秆的可分解性没有差异，无论 [CO2]-Tair 条件如何，其木质素/N 的范围相对较窄（27.3-36.5）。这项研究的结果提供了对 [CO2]-Tair 升高下水稻残留物数量和质量变化的新见解，这对于预测全球变暖下水稻土壤碳固存的变化是必要的。共升高[CO2]-Tair 下产生的根(木质素/N, 36.4) 的可分解性大于环境共升高[CO2]-Tair (木质素/N, 53.7) 下的分解能力；然而，秸秆的可分解性没有差异，无论 [CO2]-Tair 条件如何，其木质素/N 的范围相对较窄（27.3-36.5）。这项研究的结果提供了对 [CO2]-Tair 升高下水稻残留物数量和质量变化的新见解，这对于预测全球变暖下水稻土壤碳固存的变化是必要的。共升高[CO2]-Tair 下产生的根(木质素/N, 36.4) 的可分解性大于环境共升高[CO2]-Tair (木质素/N, 53.7) 下的分解能力；然而，秸秆的可分解性没有差异，无论 [CO2]-Tair 条件如何，其木质素/N 的范围相对较窄（27.3-36.5）。这项研究的结果提供了对 [CO2]-Tair 升高下水稻残留物数量和质量变化的新见解，这对于预测全球变暖下水稻土壤碳固存的变化是必要的。