Unexpectedly minor nitrous oxide emissions from fluvial networks draining permafrost catchments of the East Qinghai-Tibet Plateau

• Published in: Nature communications Vol. 13; no. 1; pp. 950 - 8
• Main Authors: Zhang, Liwei, Zhang, Sibo, Xia, Xinghui, Battin, Tom J., Liu, Shaoda, Wang, Qingrui, Liu, Ran, Yang, Zhifeng, Ni, Jinren, Stanley, Emily H.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 17.02.2022; Nature Publishing Group; Nature Portfolio
• Subjects: 38/77; 704/158/2459; 704/242; 704/47/4112; Catchments; Creeks & streams; Denitrification; Drainage; Emissions; Emitters; Fluxes; Humanities and Social Sciences; Melting; multidisciplinary; Nitrite reductase; Nitrogen; Nitrous oxide; Permafrost; Reductases; Rivers; Science; Science (multidisciplinary); Soils; Streams; Thawing; Watersheds; Tibetan Plateau
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-022-28651-8

Streams and rivers emit substantial amounts of nitrous oxide (N 2 O) and are therefore an essential component of global nitrogen (N) cycle. Permafrost soils store a large reservoir of dormant N that, upon thawing, can enter fluvial networks and partly degrade to N 2 O, yet the role of waterborne release of N 2 O in permafrost regions is unclear. Here we report N 2 O concentrations and fluxes during different seasons between 2016 and 2018 in four watersheds on the East Qinghai-Tibet Plateau. Thawing permafrost soils are known to emit N 2 O at a high rate, but permafrost rivers draining the East Qinghai-Tibet Plateau behave as unexpectedly minor sources of atmospheric N 2 O. Such low N 2 O fluxes are associated with low riverine dissolved inorganic N (DIN) after terrestrial plant uptake, unfavorable conditions for N 2 O generation via denitrification, and low N 2 O yield due to a small ratio of nitrite reductase: nitrous oxide reductase in these rivers. We estimate fluvial N 2 O emissions of 0.432 − 0.463 Gg N 2 O-N yr −1 from permafrost landscapes on the entire Qinghai-Tibet Plateau, which is marginal (~0.15%) given their areal contribution to global streams and rivers (0.7%). However, we suggest that these permafrost-affected rivers can shift from minor sources to strong emitters in the warmer future, likely giving rise to the permafrost non-carbon feedback that intensifies warming. Permafrost soils can be substantial sources of nitrous oxide (N 2 O) to the atmosphere, but no data exist on the N 2 O footprints of permafrost rivers. Here, the authors show that alpine permafrost rivers are unexpectedly small sources of atmospheric N 2 O at present.