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

Abstract

Methane (CH 4 ) oxidation mitigates CH 4 emission from soils. However, it is still highly uncertain whether soils in highlatitude ecosystems will function as a net source or sink for this important greenhouse gas. We investigated CH 4 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 high-centered polygons were 25 sectioned into active layers, transition zones, and permafrost, and incubated at -2, +4 and +8°C to determine potential CH 4 production and oxidation rates. Organic acids produced by fermentation fueled methanogenesis and competing iron reduction processes responsible for most anaerobic respiration. Significant CH 4 oxidation was observed from the suboxic transition zone and permafrost of flat-centered polygon soil, which also exhibited higher CH 4 production rates during the incubations. Although CH 4 production showed higher temperature sensitivity than CH 4 oxidation, potential rates of CH 4 30 oxidation exceeded methanogenesis rates at each temperature. Assuming no diffusion limitation, our results suggest that CH 4Biogeosciences Discuss., https://doi.org/10.5194/bg-2017-566 Manuscript under review for journal Biogeosciences Discussion started: 29 January 2018 c Author(s) 2018. CC BY 4.0 License. 2 oxidation could offset CH 4 production and limit surface CH 4 emissions, in response to elevated temperature, and thus should be considered in model predictions of net CH 4 fluxes in Arctic polygonal tundra.

Simulated Hydrological Dynamics and Coupled Iron Redox Cycling Impact Methane Production in an Arctic Soil

“…Model simulations were parameterized using previously published measurements from laboratory microcosm incubations of seasonally thawed soil from the active layer of permafrost‐underlain polygons (Figure 2; Figure S5 in Supporting Information ), as synthesized by Zheng, RoyChowdhury, Herndon et al. (2018), Zheng, RoyChowdhury, Yang et al. (2018), and Zheng et al.…”

“…Briefly, intact frozen soil cores were collected from Utqiagvik, Alaska and include trough, ridge, and center locations in ice‐wedge polygons. Frozen soils were processed under anoxic conditions, and 15 g of soil from organic or mineral layers was used to establish triplicate microcosm incubations under anoxic conditions (N 2 headspace) or oxic conditions (air) (Roy Chowdhury et al., 2015; Zheng, RoyChowdhury, Herndon et al., 2018; Zheng, RoyChowdhury, Yang et al., 2018). Layers were distinguished by color and abundance of soil organic carbon.…”

“… Comparisons between incubation measurements and model simulations. Measurements (Zheng, RoyChowdhury, Herndon et al., 2018; Zheng, RoyChowdhury, Yang et al., 2018; Zheng et al., 2019) are shown on the horizontal axis and corresponding simulated values are shown on the vertical axis. The dotted line shows a 1‐1 relationship.…”

“…The presence of electron acceptors such as ferric Fe (Fe(III)) has been shown to suppress the production of CH 4 , which provides a lower energy benefit to microbial metabolism, when Fe reducers are able to outcompete methanogens for substrates (Lipson et al., 2012; Miller et al., 2015). Simultaneous methanogenesis and Fe(III) reduction have been observed in Arctic soils, however, indicating that microbial processes do not necessarily strictly follow the redox ladder (Herndon et al., 2015; Reiche et al., 2008; Roy Chowdhury et al., 2015; Yang et al., 2016; Zheng, RoyChowdhury, Herndon et al., 2018; Zheng, RoyChowdhury, Yang et al., 2018). Many Arctic soils are rich in Fe(III)‐bearing minerals and OM‐bound Fe(III), and as a result, redox cycling of Fe can be an important control on OM degradation and C mineralization in permafrost soils (Herndon et al., 2017).…”