Impacts of temperature and soil characteristics on methane production and oxidation in Arctic polygonal tundra

Jianqiu Zheng, Taniya RoyChowdhury, Ziming Yang, Baohua Gu, Stan D. Wullschleger, David E. Graham
2018 Biogeosciences Discussions  
Methane (CH<sub>4</sub>) oxidation mitigates CH<sub>4</sub> emission from soils. However, it is still highly uncertain whether soils in high-latitude ecosystems will function as a net source or sink for this important greenhouse gas. We investigated CH<sub>4</sub> production and oxidation potential in permafrost-affected soils from degraded ice-wedge polygons with carbon-rich soils at the Barrow Environmental Observatory, Utqiaġvik (Barrow) Alaska, USA. Frozen soil cores from flat and
more » ... flat and high-centered polygons were sectioned into active layers, transition zones, and permafrost, and incubated at &amp;minus;2, +4 and +8&amp;thinsp;°C to determine potential CH<sub>4</sub> production and oxidation rates. Organic acids produced by fermentation fueled methanogenesis and competing iron reduction processes responsible for most anaerobic respiration. Significant CH<sub>4</sub> oxidation was observed from the suboxic transition zone and permafrost of flat-centered polygon soil, which also exhibited higher CH<sub>4</sub> production rates during the incubations. Although CH<sub>4</sub> production showed higher temperature sensitivity than CH<sub>4</sub> oxidation, potential rates of CH<sub>4</sub> oxidation exceeded methanogenesis rates at each temperature. Assuming no diffusion limitation, our results suggest that CH<sub>4</sub> oxidation could offset CH<sub>4</sub> production and limit surface CH<sub>4</sub> emissions, in response to elevated temperature, and thus should be considered in model predictions of net CH<sub>4</sub> fluxes in Arctic polygonal tundra.
doi:10.5194/bg-2017-566 fatcat:5vltlhbzvnfnxldcsp7zziszay