Peak accumulation of soil organic carbon in the early Holocene.

Soil holds significant potential to mitigate atmospheric CO₂ concentrations through the sequestration of organic carbon, yet its contribution to fluctuations in atmospheric CO₂ over the Holocene has been a matter of much speculation. Here we explored analyses of 5190 radiocarbon data and 442,737 content observations of soil organic carbon (SOC) to visualize the global abundance-persistence spectrum of SOC and its depth distribution. We found that the present-day soil carbon pool began to accumulate since the Late Pleistocene and reached its peak accumulation in the early Holocene, approximately 8-10 thousand years ago. High-latitude regions contain significant amounts of ancient carbon, even in shallow soil layers, with maximum sequestration driven by post-glacial vegetation recovery and peatland development, which contributed to reducing CO₂ and temperature fluctuations during the early Holocene. However, higher temperatures correspond to suppressed carbon accumulation in the Holocene, implying that ongoing global warming may further deplete soil carbon pools and threaten the sustainability of soil carbon sequestration.