Soils contain more carbon than the atmosphere and vegetation combined. An increased flow of carbon from the atmosphere into soil pools could help mitigate anthropogenic emissions of carbon dioxide and climate change. Yet we do not know how quickly soils might respond because the age distribution of soil carbon is uncertain. Here we used 789 radiocarbon (∆¹⁴C) profiles, along with other geospatial information, to create globally gridded datasets of mineral soil ∆¹⁴C and mean age. We found that soil depth is a primary driver of ∆¹⁴C, whereas climate (for example, mean annual temperature) is a major control on the spatial pattern of ∆¹⁴C in surface soil. Integrated to a depth of 1 m, global soil carbon has a mean age of 4,830 ± 1,730 yr, with older carbon in deeper layers and permafrost regions. In contrast, vertically resolved land models simulate ∆¹⁴C values that imply younger carbon ages and a more rapid carbon turnover. Our data-derived estimates of older mean soil carbon age suggest that soils will accumulate less carbon than predicted by current Earth system models over the twenty-first century. Reconciling these models with the global distribution of soil radiocarbon will require a better representation of the mechanisms that control carbon persistence in soils.

土壤所含碳比大气和植被的总和还要多。从大气中进入土壤池的碳流量的增加可能有助于减轻人为排放的二氧化碳和气候变化。然而，由于土壤碳的年龄分布是不确定的，我们不知道土壤会以多快的速度做出反应。在这里，我们使用789个放射性碳（∆ ¹⁴ C）剖面以及其他地理空间信息，创建了全球网格化的矿物土壤∆ ¹⁴ C和平均年龄的数据集。我们发现土壤深度是∆ ¹⁴ C的主要驱动因素，而气候（例如，年平均温度）是∆ ¹⁴空间格局的主要控制因素C在表层土壤中。整合到1 m的深度中，全球土壤碳的平均年龄为4,830±1,730 yr，而较深的碳层位于更深的层和永久冻土区。相比之下，垂直解决土地模型模拟Δ ¹⁴暗示年轻的碳年龄和更快速的碳转化的C值。我们根据数据得出的对较老的平均土壤碳年龄的估算表明，在21世纪，土壤中的碳累积量将比当前地球系统模型预测的少。将这些模型与土壤放射性碳的全球分布进行协调，将需要更好地表现控制土壤中碳持久性的机制。