Soil carbon and nitrogen in the active layers of the permafrost regions in the Three Rivers’ Headstream

The pedogenesis, soil organic carbon (SOC), soil inorganic carbon (SIC), hot water-soluble organic carbon (WSOC) and total nitrogen (TN) of the active layers were examined beneath four typical vegetation communities in the permafrost regions in the Three Rivers’ Headstream region in the Qinghai-Tibetan Plateau. In all soil areas, except for in the steppe, the SOC and TN showed rapidly decreasing trends with increasing depth. The highest SOC, WSOC and TN contents were found in the wet meadow, with contents in the eluviate layer being 180.9, 40.2 and 10.9 g kg−1, respectively. In the steppe, the average SOC, WSOC and TN at 180 cm depth were 6.2, 0.67 and 0.59 g kg−1, respectively. The SIC contents showed increasing trends with increasing depth in the soils of the steppe community. The correlation analysis suggested that the moisture and fine particle fractions positively correlated to SOC, TN and WSOC, while bulk density and pH negatively correlated to SOC, TN and WSOC. The SOC and TN were significantly related to bulk density. The SIC was positively correlated with pH but negatively correlated with SOC, TN and WSOC. The C/N ratios were negatively correlated with pH while positively correlated with SOC, TN and fine soil particles. The results suggest that the SOC in the wet meadow soils in the permafrost regions of Qinghai-Tibetan have the largest potential contributions to the emissions of greenhouse gases and cause future global warming.