Grazing affects methanotroph activity and diversity in an alpine meadow soil

The role of methane-oxidizing bacteria (MOB) in alpine environments is poorly understood, but is of importance given the abundance of alpine environments and the role of MOB in the global carbon cycle. Using a combination of approaches we examined both seasonal and land usage effects on the ecology of microbial methane oxidation in an alpine meadow soil. Analysis of the abundance and diversity of MOB demonstrated that the abundance and diversity of the dominant type II MOB, predominantly Metylocystis and relatives, was only influenced by season. Conversely type Ia MOB abundance was significantly affected by season and land usage, while diversity changes were effected predominantly by land use. Assessment of methane oxidation potential and soil physical properties demonstrated a strong link between type Ia MOB abundance and methane oxidation potential as well as a complex series of relationships between soil moisture, pH and MOB abundance, changing with season. The results of this study suggest that, while type II MOB, unaffected by land use, represent the dominant MOB, Methylobacter-related type Ia MOB appear to be responsible for the majority of methane oxidation and are strongly affected by the grazing of cattle.