Winter precipitation and snow accumulation drive the methane sink or source strength of Arctic tussock tundra

• Published in: Global Change Biology
• Main Authors: Blanc‐Betes, Elena, Welker, Jeffrey M., Sturchio, Neil C., Chanton, Jeffrey P., Gonzalez‐Meler, Miquel A.
• Other Authors: U.S. Department of Energy, University of Illinois at Chicago, National Science Foundation, Office of Polar Programs
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2016
• Subjects: Climate change; Global warming; Tundra
• Online Access: http://dx.doi.org/10.1111/gcb.13242; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fgcb.13242; https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.13242; https://onlinelibrary.wiley.com/doi/full-xml/10.1111/gcb.13242; https://onlinelibrary.wiley.com/doi/am-pdf/10.1111/gcb.13242

Abstract Arctic winter precipitation is projected to increase with global warming, but some areas will experience decreases in snow accumulation. Although Arctic CH 4 emissions may represent a significant climate forcing feedback, long‐term impacts of changes in snow accumulation on CH 4 fluxes remain uncertain. We measured ecosystem CH 4 fluxes and soil CH 4 and CO 2 concentrations and 13 C composition to investigate the metabolic pathways and transport mechanisms driving moist acidic tundra CH 4 flux over the growing season (Jun–Aug) after 18 years of experimental snow depth increases and decreases. Deeper snow increased soil wetness and warming, reducing soil %O 2 levels and increasing thaw depth. Soil moisture, through changes in soil %O 2 saturation, determined predominance of methanotrophy or methanogenesis, with soil temperature regulating the ecosystem CH 4 sink or source strength. Reduced snow (RS) increased the fraction of oxidized CH 4 (Fox) by 75–120% compared to Ambient, switching the system from a small source to a net CH 4 sink (21 ± 2 and −31 ± 1 mg CH 4 m −2 season −1 at Ambient and RS). Deeper snow reduced Fox by 35–40% and 90–100% in medium‐ (MS) and high‐ (HS) snow additions relative to Ambient, contributing to increasing the CH 4 source strength of moist acidic tundra (464 ± 15 and 3561 ± 97 mg CH 4 m −2 season −1 at MS and HS). Decreases in Fox with deeper snow were partly due to increases in plant‐mediated CH 4 transport associated with the expansion of tall graminoids. Deeper snow enhanced CH 4 production within newly thawed soils, responding mainly to soil warming rather than to increases in acetate fermentation expected from thaw‐induced increases in SOC availability. Our results suggest that increased winter precipitation will increase the CH 4 source strength of Arctic tundra, but the resulting positive feedback on climate change will depend on the balance between areas with more or less snow accumulation than they are currently facing.