Global soil carbon storage and stability informed by the particulate and mineral-associated organic carbon fractions

Separating soil organic carbon (SOC) into particulate (POC) and mineral-associated organic carbon (MAOC) fractions has provided fundamental knowledge on the structure and protection of SOC. However, the global distribution and key drivers of POC and MAOC remain elusive. Here, we compiled a global database of POC and MAOC with 2744 observations across six continents. Initial analysis showed that the mean POC was 2.73 kg m^-2 and MAOC was 3.85 kg m^-2 at 0-30 cm. At the global scale, POC and MAOC accounted for 39.98 % and 63.48 % of SOC, respectively. The global distribution of POC and MAOC was driven collectively by vegetation, climatic, and soil attributes. The lowest POC and MAOC stock were observed in cropland, suggesting the possibility of increasing C sequestration in soils by using management practices that increase POC and MAOC in croplands. Despite this great potential, we predicted the largest reduction in MAOC in cropland under future climate change, highlighting the high vulnerability of SOC stock in cropland. Understanding the role of environmental controls in the global distribution of POC and MAOC could help designing terrestrial carbon sequestration strategies.