Impact of temperature increase on methane emission from arctic soils

English Abstract:

Arctic tundra is one of the largest carbon stocks, of which amount is estimated up to 1,600 Pg. Global climate change models predict the greatest surface temperature rise in Arctic regions, which may result in faster decomposition of organic carbon and consequent releases of greenhouse gases such as CO₂ and CH₄. In particular, CH₄ is a significant GHG and can contribute to positive feedback on climate change; however, dynamics of CH₄ emission from arctic tundra under warming is yet to be fully understood. In this study, we conducted temperature manipulation experiments for arctic soils at field and laboratory scales and monitored CH₄ fluxes along with related microbial abundances (methanogen and methanotroph). Open-top chambers were installed in Cambridge Bay, Canada and intact soil cores collected along a melting gradient in Nome, Alaska were incubated under increasing temperature (from -20 to 20 ℃) for 60 days. At a field scale, ca. 1 ℃ increase in soil temperature for one growing season induced a slight increase in CH₄ emission while abundances of methanogen and methanotroph did not show any shift. . At a laboratory scale, CH₄ emission from a wetland soil was higher than that from dry soils and appeared to increase at thawing temperature (0.5 ± 1 ℃). However, a little oxidation of CH₄ was observed in dry soils at thawing temperature. Overall results of this study suggest that CH₄ flux from arctic soils under warmer conditions is constrained not only by temperature but also by water availability.