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为探究CO₂浓度升高下冬小麦-土壤碳（C）、氮（N）化学计量特征及其关联关系，依托北京昌平试验站长期开放式CO₂浓度升高试验平台（FACE），测定和分析了常规CO₂浓度（aCO₂：400 μmol·mol^-1）和高CO₂浓度（eCO₂：550 μmol·mol^-1）条件下冬小麦不同器官（叶片、茎秆、籽粒）和土壤的C、N元素含量。结果表明，冬小麦植株和土壤C、N元素含量及计量比对CO₂浓度升高的响应不一致。冬小麦各器官C、N含量、C∶N不受CO₂浓度升高的影响；CO₂浓度升高后土壤全碳（TC）含量显著增加，全氮（TN）含量和全碳氮比（TC∶TN）未发生显著变化。冬小麦-土壤C、N化学计量特征在小麦生育期的变化程度高于CO₂升高的影响。从拔节至成熟期，叶片和茎秆C∶N不断增加，籽粒C∶N则从灌浆至成熟期显著降低。冬小麦整体C元素的内稳性高于N元素，不同器官元素内稳性存在一定差异，表现为籽粒的元素内稳性高于叶片和茎秆。aCO₂处理下，土壤与冬小麦叶片或茎秆C、N计量特征间存在强烈的相关关系，但eCO₂处理下土壤与冬小麦叶片和茎秆间关联关系消失或削弱，说明未来气候变化可能导致小麦地上-地下关系的不确定性增加。

英文摘要:

To explore the winter wheat-soil carbon(C) and nitrogen(N) stoichiometry, we measured the concentrations of C and N in different winter wheat organs(e.g. leaf, stem and grain) and soil, as well as their response to elevated CO₂. This study was conducted at the long-term free air carbon dioxide enrichment platform(FACE) in Changping, Beijing. Two CO₂ concentration treatments were conducted, which were ambient CO₂ (aCO₂： 400 μmol·mol^-1) treatment and elevated CO₂ (eCO₂： 550 μmol·mol^-1) treatment. Results showed that the responses of wheat and soil C and N stoichiometry to elevated CO₂ differed. The leaf, stem and grain C and N stoichiometry were not affected by elevated CO₂. However, the soil total carbon(TC) content significantly increased in response to eCO₂ treatment, while the total nitrogen(TN) content and the TC∶TN ratio remained unchanged. In comparison to elevated CO₂ treatment, the winter wheat and soil C and N stoichiometry showed greater sensitivity to changes in crop stages. The C∶N ratio of leaf and stem increased from the jointing stage to the maturity stage, while the grain C∶N ratio decreased from the filling stage to the maturity stage. The homeostasis of the C element was higher than that of the N element in winter wheat. There were differences in the homeostasis of winter wheat organs, with the grain showing a higher level compared to the leaf and stem. Under aCO₂ treatment, the correlation between soil and winter wheat leaf and stem C and N stoichiometry was significant. However, the strong correlation between soil and winter wheat C and N stoichiometry was no longer exist or weakened under eCO₂ treatment. These findings indicated that future climate change might enhance the obscure of the relationship between aboveground and belowground.

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