Protection by metal (hydr) oxides is one of the key mechanisms for the long-term stabilization of soil organic carbon (SOC). However, the source and turnover of (metal-) bound organic carbon (OC) in soils are poorly constrained. Here we present the first large-scale study on the ¹³C and ¹⁴C characteristics of bound OC in 15 wetland and upland soil profiles. We find that bound OC has similar δ¹³C as SOC, suggesting no preference for plant- or microbe-derived carbon. However, bound OC Δ¹⁴C is more negative than SOC in wetland but not upland mineral soils, and decreases with increasing reactive minerals. Hence, in contrast to the conventional assumption, bound OC is better preserved relative to SOC in wetlands with high contents of reactive metals. Our finding highlights the dynamic exchange of bound OC with SOC in upland soils and calls for a better recognition of reactive metals in stabilizing OC in wetlands.

中文翻译：

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湿地土壤中结合有机碳的长期储存，而非陆地土壤中的结合有机碳储存：13C 和 14C 的观点


金属（氢）氧化物的保护是土壤有机碳 （SOC） 长期稳定的关键机制之一。然而，土壤中（金属）结合有机碳 （OC） 的来源和周转率受到很好的限制。在这里，我们首次对 15 种湿地和高地土壤剖面中结合 OC 的 ¹³ C 和 ¹⁴ C 特性进行了大规模研究。我们发现结合的 OC 与 SOC 具有相似的 δ ¹³ C，表明对植物或微生物衍生的碳没有偏好。然而，在湿地中，结合 OC Δ ¹⁴ C 比 SOC 负性，但在高地矿物土壤中则不然，并且随着活性矿物的增加而降低。因此，与传统假设相反，在活性金属含量高的湿地中，相对于 SOC，结合的 OC 保存得更好。我们的研究结果强调了高地土壤中结合的 OC 与 SOC 的动态交换，并呼吁更好地识别活性金属在稳定湿地 OC 方面的作用。