Stock and carbon sequestration potential of mineral-associated organic carbon in the Qinghai-Tibetan Plateau

The Qinghai-Tibetan Plateau (QTP) is a significant soil organic carbon (SOC) reservoir and highly sensitive to climate change. Enhancing SOC sequestration is critical to mitigating global warming; however, the upper limit of stable SOC and locations with additional storage capacity remain uncertain. This study focuses on mineral-associated organic carbon (MAOC)—a relatively stable SOC fraction—to estimate its stock and sequestration potential across land use types. We analyzed MAOC data from 3561 samples spanning 841 soil profiles. Results indicated that MAOC approached saturation with increasing fine earth (silt + clay) content. Random forest models were employed to map the maximum MAOC potential (MAOCmax), the MAOC deficit (Cdef), and the degree of MAOC saturation (Csat) across the QTP. On the QTP, MAOC stocks are 6.22 Pg in the topsoil (0–30 cm) and 7.45 Pg in the subsoil (30–100 cm), with a maximum storage potential of 61.69 Pg in the 0–100 cm profile. Steppes, meadows, and deserts show high Cdef stocks, indicating strong potential as future carbon sequestration hotspots under warmer and wetter conditions. These findings provide valuable insights can inform targeted SOC management across the QTP.