Spatial distribution of soil organic carbon in the Zoige alpine wetland, northeastern Qinghai–Tibet Plateau

• SOC decreased with increasing depth in the soil.
• The SOC density averaged 65 kg C m− 3 in the top 1 m of the soil of wetland
• The SOC stock in the top 1 m of wetland soils totaled 514 Tg C.
• This stock was 8.3 to 10.2% of SOC in the top 1 m of the soils of China's wetlands.

Regional-scale soil organic carbon (SOC) field investigations would significantly improve our understanding of national and global SOC sequestration and carbon (C) cycles. The Zoige wetland is the world's largest high-altitude wetland. It is located in northeastern Qinghai–Tibet Plateau. Although considered sensitive to global climate change, little is known of its wetland SOC stocks and spatial distribution patterns. Accordingly, we investigated SOC stocks and spatial distribution patterns in the uppermost 1 m soil layer in Ruoergai and Hongyuan counties in the Zoige wetland. We found that SOC decreased with increasing soil depth, which was highest in the topmost 0.3 m soil layer. Total nitrogen and water content were positively correlated to SOC content while bulk density was negatively correlated to SOC content in both wetland and grassland areas. Wetlands had a higher SOC density than grassland. In the uppermost 1 m of wetland soil, average SOC density was 69.5 kg C m− 3, greater by a factor of three compared to mean wetland SOC density in China and greater by a factor of six compared to the national average. SOC stock in the uppermost 1 m of wetland soils totaled 514 Tg C, of which 50% was stored in the topmost 0.3 m. This indicated that the two counties in the Zoige wetland stores from 8.3 to 10.2% of the total SOC in China in the topmost 1 m of wetland soils. This vast SOC pool and high SOC density requires sound land use practices to sustain and protect Zoige wetland ecosystem services and C stocks.