Methane fluxes and the functional groups of methanotrophs and methanogens in a young Arctic landscape on Disko Island, West Greenland

Abstract

Arctic soils are known to be important methane (CH 4) consumers and sources. This study integrates in situ fluxes of CH 4 between upland and wetland soils with potential rates of CH 4 oxidation and production as well as abundance and diversity of the methanotrophs and methanogens measured with pyrosequencing of 16S DNA and rRNA fragments in soil and permafrost layers. Here, the spatial patterns of in situ CH 4 fluxes for a 2,000 years old Arctic landscape in West Greenland reveal similar CH 4 uptake rates (-4 ± 0.3 lmol m-2 h-1) as in other Arctic sites, but lower CH 4 emissions (14 ± 1.5 lmol m-2 h-1) at wetland sites compared to other Arctic wetlands. Potential CH 4 oxidation was similar for upland and wetland soils, but the wetter soils produced more CH 4 in active and permafrost layers. Accordingly, the abundance of methanogenic archaea was highest in wetland soils. The methanotrophic community also differed between upland and wetland soils, with predominant activity of Type II methanotrophs in the active layer for upland soils, but only Type I methanotrophs for the wetland. In the permafrost of upland and wetland soils, activity of the methanotrophs belonging to Type I and Type II as well as methanogens were detected. This study indicates that the magnitude of CH 4 oxidation and the direction of the flux, i.e. uptake or emission, are linked to different methanotrophic communities in upland and wetland soils. Also, the observed link between production/consumption rates and the microbial abundance and activity indicates that the age of an Arctic landscape is not important for the CH 4 consumption but can be very important for CH 4 production. Considering the prevalence of dry landscapes and contrasting ages of high Arctic soils, our results highlight that well-drained soils should not be overlooked as an important component of Arctic net CH 4 budget.

Seasonal variations in methane fluxes in response to summer warming and leaf litter addition in a subarctic heath ecosystem

“…Net CH 4 fluxes were primarily negative, rendering the site a net CH 4 sink throughout the snow‐free season. As has been demonstrated in other arctic soils, and considering the soil moisture regime (mean 30% across all treatments), it is likely that both methanogenesis and methanotrophy occur at the site [ Brummell et al ., ; Christiansen et al ., ; Emmerton et al ., ]. Since in situ measurements reveal the net balance between CH 4 production and uptake, actual oxidation rates may be markedly higher.…”

“…Both seasonal mean and maximum CH 4 uptake rates were comparable to, although slightly lower than, fluxes measured in other similar in situ studies, including dry arctic heath [ D'Imperio et al ., ], moist arctic tundra [ Jørgensen et al ., ], arctic upland ecosystems [ Christiansen et al ., ], and temperate forests [ Smith et al ., ; Dubbs and Whalen , ]. Similarly, CH 4 fluxes were slightly lower but of the same order of magnitude as those reported from the nearby mesic heaths, which also functioned as net CH 4 sinks [ Christensen et al ., , ].…”

Methane oxidation in contrasting soil types: responses to experimental warming with implication for landscape‐integrated CH4 budget

“…The range of CH 4 uptake rates recorded at ambient conditions at the BG and at the DH sites were comparable to those measured in previous in situ studies carried out in similar arctic environments (Christiansen et al ., ; Emmerton et al ., ; Jørgensen et al ., ; Lau et al ., ) as well as in temperate forest soils (Smith et al ., ; Hiltbrunner et al ., ).…”

Ground-Level Concentrations of Atmospheric Methane in Southwest Greenland Evaluated Using Open-Path Laser Spectroscopy and Cavity-Enhanced Absorption Spectroscopy

“…2, part B). The upland environment was selected because of the potential for soil methanotrophic communities in drier upland soils to reduce atmospheric CH 4 concentrations (Christiansen et al, 2014). Monitoring the atmospheric CH 4 concentration in Kangerlussuaq served as a control with respect to remote field sites-the area is dominated by highly compacted soils and paved roads.…”