The vertical distribution of soil organic carbon and nitrogen in a permafrost‐affected wetland on the Qinghai–Tibet Plateau: Implications for Holocene development and environmental change

Abstract

Currently, we know little about accumulation of soil carbon and nitrogen in permafrost‐affected wetlands on the Qinghai–Tibet Plateau (QTP). In this study, we analyze the vertical distribution of concentrations, stocks, and apparent accumulation rates of soil organic carbon (SOC) and total nitrogen (TN) in a wetland underlain by ice‐rich permafrost in the Headwater Area of the Yellow River (HAYR) on the northeastern QTP in the context of Holocene environmental change. SOC and TN stocks at depths of 0–216 cm were 80.0 kg C m−2 and 6.7 kg N m−2, respectively. During the past 7.3 kyr, the general regional climate trend in the HAYR was cooling and drying, as indicated by the decline in chemical weathering in the soil profile. Overall, SOC and TN concentrations increased during this period. Meanwhile, an intense period of SOC and TN accumulation occurred at 1,110–720 yr BP, in contrast to much lower apparent accumulation rates of SOC and TN for the other periods during the past 7.3 kyr. This suggests that the accumulation of SOC and TN in permafrost‐affected wetlands was also affected by local environmental factors, such as soil material deposition rate, in addition to climatic controls as exerted mainly by temperature and precipitation. This study may help integrate relevant studies on plateau wetlands into global models and estimates to better simulate and predict interactions between the carbon cycle and climate changes on a global scale.