Effects of permafrost collapse on soil carbon, nitrogen, and metal elements on the Qinghai-Tibet Plateau

Permafrost degradation can lead to the decomposition of organic matter and the remobilization of metal elements (MEs). However, the changes in MEs, as well as the relationships between soil organic carbon (SOC), total nitrogen (TN), and MEs in permafrost collapse areas remain unknown. Here, we investigated the changes in SOC, TN, and MEs and their driving factors in three stages (control, drape, and exposed) of four thermokarst sites on the Qinghai-Tibet Plateau (QTP). The results revealed that SOC and TN decreased by 20–30% and 11–17% from control to drape areas, respectively. The concentrations of Fe, Mn, Zn, Cr, Ni, Cu, Pb, and Cd declined by 3.11% to 45.07% from drape to exposed areas. Furthermore, soil water content, bulk density, and pH were correlated with SOC and TN. Soil inorganic carbon (SIC) and pH regulated the connection of SOC and TN with MEs. Our results suggest that permafrost collapse changes SOC, TN, and MEs, and also indirectly strengthens the relationship of SOC and TN with MEs via SIC and pH, which might be a critical mechanism for SOC and TN pools in thermokarst-affected terrains.