The response of soil organic carbon (SOC) dynamics to nitrogen enrichment in the scale of whole-soil profiles, especially in deeper soil layers containing approximately half of SOC, remains unclear. Here, the incorporation of new vegetation-derived carbon into whole-soil profiles is estimated by combining natural stable isotopes (¹³C and ¹⁵N) with radiocarbon analyses under elevated nitrogen inputs with field experiments. The new mechanism responsible for nitrogen-induced carbon sinking in soils is the increased allocation of new carbon to deep soil layers at high nitrogen enrichment resulting from enhanced vertical transport of SOC. Our work provides an unprecedented representation of deep carbon dynamics under elevated nitrogen input and thus supports the development of policies on soil carbon management.

土壤有机碳 (SOC) 动态对全土壤剖面尺度的氮富集的响应，尤其是在含有大约一半 SOC 的较深土层中，仍不清楚。在这里，通过结合天然稳定同位素（¹³ C 和¹⁵N) 在高氮输入下进行放射性碳分析和现场实验。导致土壤中氮诱导碳下沉的新机制是由于 SOC 的垂直迁移增强，在高氮富集下，新碳向深层土壤的分配增加。我们的工作提供了氮输入增加下深层碳动态的前所未有的表征，从而支持了土壤碳管理政策的制定。