Global warming will likely perturb carbon storage and cycling throughout many components of the exogenic carbon cycle, but its net impact on the long-term fate of organic carbon stabilized in soils is unclear. Abrupt warming during the Paleocene-Eocene Thermal Maximum (PETM) profoundly altered vegetation and hydrologic patterns globally. To assess the consequences for soil carbon in a mid-latitude region we measured total organic carbon (%TOC), polycyclic aromatic hydrocarbons (PAHs), charcoal, and sporomorphs (pollen and spores) at two paleo-floodplain depositional sites in the Bighorn Basin, Wyoming, USA. At both sites %TOC, PAHs, charcoal, and sporomorphs declined during the PETM. The decline in pyrogenic carbon, which is more severe than the decline in %TOC, is consistent with isotopic and fossil evidence for degradation of labile organic compounds and preservation of highly refractory allochthonous organic carbon. The severe loss of less-labile contemporaneous PETM (autochthonous) soil carbon, illustrated by the fate of pyrogenic carbon, indicates intensified rates of organic matter decay during the PETM. Because of the highly degraded signature of organic matter in these PETM sections, it is difficult to discern if less pyrogenic carbon is in part a consequence of less fire occurrence during the PETM. We propose that in this mid-latitude region of the western USA increased soil carbon oxidation hindered soil carbon sequestration during this period of hotter climate with more seasonal precipitation.

全球变暖可能会扰动碳在外源碳循环的许多组成部分中的循环和循环，但尚不清楚其对土壤中稳定的有机碳的长期命运的净影响。在古新世-始新世热最大值（PETM）期间的突然变暖深刻地改变了全球的植被和水文模式。为了评估中纬度地区土壤碳的后果，我们在比格霍恩盆地的两个古洪泛平原沉积点测量了总有机碳（％TOC），多环芳烃（PAHs），木炭和孢子体（花粉和孢子） ，美国怀俄明州。在PETM期间，％TOC，PAHs，木炭和子孢子的百分比都下降了。热解碳的下降比％TOC的下降更为严重，与同位素和化石证据表明不稳定的有机化合物降解并保存高度难治的异源有机碳相一致。由热解碳的结局表明，不稳定程度较弱的同期PETM（土生）土壤碳严重流失，这表明在PETM期间有机物的衰减速率加快了。由于在这些PETM部分中有机物的特征高度降解，因此很难确定是否发生了较少的热解碳，部分原因是在PETM过程中发生较少的火灾。我们建议，在美国西部的中纬度地区，土壤碳氧化的增加会在气候更热，季节降水更多的时期阻碍土壤碳的固存。由热解碳的结局表明，不稳定程度较弱的同期PETM（土生）土壤碳严重流失，这表明在PETM期间有机物的衰减速率加快了。由于在这些PETM部分中有机物的特征高度降解，因此很难确定是否发生了较少的热解碳，部分原因是在PETM过程中发生较少的火灾。我们建议，在美国西部的中纬度地区，土壤碳氧化的增加会在气候更热，季节降水更多的时期阻碍土壤碳的固存。由热解碳的结局表明，不稳定程度较弱的同期PETM（土生）土壤碳严重流失，这表明在PETM期间有机物的衰减速率加快了。由于在这些PETM部分中有机物的特征高度降解，因此很难确定是否发生了较少的热解碳，部分原因是在PETM过程中发生较少的火灾。我们建议，在美国西部的中纬度地区，土壤碳氧化的增加会在气候更热，季节降水更多的时期阻碍土壤碳的固存。很难确定是否在PETM期间较少发生火的部分原因是较少的热解碳。我们建议，在美国西部的中纬度地区，土壤碳氧化的增加会在气候更热，季节降水更多的时期阻碍土壤碳的固存。很难确定是否在PETM期间较少发生火的部分原因是较少的热解碳。我们建议，在美国西部的中纬度地区，土壤碳氧化的增加会在气候更热，季节降水更多的时期阻碍土壤碳的固存。