Methane-cycling microorganisms in soils of a high-alpine altitudinal gradient

Methanogens and methanotrophs play unique roles as producers and consumers of the greenhouse gas methane (CH4) in soils, respectively. Here, we aimed to reveal whether and to which extent methane-cyclers occur in high-alpine soils, and to assess their spatial distribution along an altitudinal gradient (2700-3500 m) in the Austrian Alps at sites located within the alpine (2700-2900 m), the alpine-nival (3000-3100 m) and the nival belts (3200-3500 m). Methanococcales and Methanocella spp. were most abundant among all quantified methanogenic guilds, whereas Methanosarcinales were not detected in the studied soil. The detected methanogens seem to be capable of persisting despite a highly oxic low-temperature environment. Methanogenic and methanotrophic activities and abundances of methanotrophs, Methanococcales and Methanocella spp. declined with altitude. Methanogenic and methanotrophic abundances were best explained by mean annual soil temperature and dissolved organic carbon, respectively. Alpine belt soils harbored significantly more methane-cyclers than those of the nival belt, indicating some influence of plant cover. Our results show that methanogens are capable of persisting in high-alpine cold soils and might help to understand future changes of these environments caused by climate warming.