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Permafrost collapse shifts alpine tundra to a carbon source but reduces N 2 O and CH 4 release on the northern Qinghai‐Tibetan Plateau
Author(s) -
Mu C. C.,
Abbott B. W.,
Zhao Q.,
Su H.,
Wang S. F.,
Wu Q. B.,
Zhang T. J.,
Wu X. D.
Publication year - 2017
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2017gl074338
Subject(s) - permafrost , thermokarst , tundra , environmental science , arctic , soil carbon , carbon sink , atmospheric sciences , ecosystem , carbon cycle , sink (geography) , ecosystem respiration , soil respiration , growing season , total organic carbon , soil science , hydrology (agriculture) , soil water , geology , primary production , environmental chemistry , ecology , chemistry , oceanography , geography , cartography , geotechnical engineering , biology
Important unknowns remain about how abrupt permafrost collapse (thermokarst) affects carbon balance and greenhouse gas flux, limiting our ability to predict the magnitude and timing of the permafrost carbon feedback. We measured monthly, growing‐season fluxes of CO 2 , CH 4 , and N 2 O at a large thermokarst feature in alpine tundra on the northern Qinghai‐Tibetan Plateau (QTP). Thermokarst formation disrupted plant growth and soil hydrology, shifting the ecosystem from a growing‐season carbon sink to a weak source but decreasing feature level CH 4 and N 2 O flux. Temperature‐corrected ecosystem respiration from decomposing permafrost soil was 2.7 to 9.5‐fold higher than in similar features from Arctic and Boreal regions, suggesting that warmer and dryer conditions on the northern QTP could accelerate carbon decomposition following permafrost collapse. N 2 O flux was similar to the highest values reported for Arctic ecosystems and was 60% higher from exposed mineral soil on the feature floor, confirming Arctic observations of coupled nitrification and denitrification in collapsed soils. Q 10 values for respiration were typically over 4, suggesting high‐temperature sensitivity of thawed carbon. Taken together, these results suggest that QTP permafrost carbon in alpine tundra is highly vulnerable to mineralization following thaw, and that N 2 O production could be an important noncarbon permafrost climate feedback. Permafrost collapse altered soil hydrology, shifting the ecosystem from a carbon sink to carbon source but decreasing CH 4 and N 2 O flux. Little to no vegetation recovery after stabilization suggests potentially large net carbon losses. High N 2 O flux compared to Arctic and Boreal systems suggests noncarbon permafrost climate feedback.