Divergent responses of particulate and mineral-associated organic carbon to permafrost degradation

The net effects of permafrost degradation on soil organic carbon (SOC) stock and the underlying mechanisms are unclear due to poor understanding of the response of particulate (POC) and mineral-associated organic carbon (MAOC) pools. To explore changes in POC, MAOC, and SOC across permafrost degradation, we collected 72 soil samples at 0–10, 10–20, and 20–30 cm from three permafrost types characterized by an increasing degradation. While the overall SOC content remained stable, POC content decreased by 45–77 g kg−1 by permafrost degradation and increased MAOC content by 57–96 g kg−1 across the three soil depths. Specifically, permafrost degradation decreased the portion of POC in SOC by 15–37 %, but increased the portion of MAOC in SOC by 16–37 %. Using random forest modeling, we identified that the content of total nitrogen (TN), microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) are key factors influencing the contribution of POC and MAOC to the overall SOC. These variables together explained 45 % and 46 % variations of POC/SOC and MAOC/SOC, respectively. Altogether, this study demonstrates how POC and MAOC content and their contributions to SOC change across permafrost degradation, and highlights the distinct roles of POC and MAOC in sustaining SOC storage under climate change. © 2025 Elsevier B.V.