Publication Date:
2017-07-13
Description:
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 non-carbon permafrost climate feedback.
Print ISSN:
0094-8276
Electronic ISSN:
1944-8007
Topics:
Geosciences
,
Physics
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