Effects of fertilisation, temperature and water content on microbial properties and methane production and methane oxidation in subalpine soils

In the context of the current debate on climate change, studies on methane emission and methane consumption are of particular interest, and information about methane-producing and -consuming microorganisms and the parameters that influence their abundance and activity are urgently required. Hence, over a period of six months we conducted a laboratory experiment to test the effects of temperature, water content and fertilisation on soil microbiology, methane production and methane consumption of soil from fallow land. Soil treatments with soil from the fallow land were created in order to test the individual and/or the combined effects of the aforementioned parameters. These soil treatments were analysed for physical and chemical parameters, microbial activity in terms of enzyme activities and microbial biomass, methanogenic community composition and the potential to produce and consume methane. Overall, under water-saturated conditions and over time, ammonification rate, dehydrogenase activity and microbial biomass decreased. Potentials to produce methane were determined at psychro-, meso- and thermophilic conditions, and results indicated that the highest methane emission occurred under mesophilic conditions, meaning 37 °C. Water content was observed as a major influencing factor regarding both methane production and methane consumption potentials. Regardless of the incubation temperature, fertilisation with cattle manure led to an increase in the formation of methane. Ammonium concentration promoted both potentials to produce and oxidize methane. Molecular analysis revealed differences in methanogenic community compositions within the soil treatments. We found a representative of Methanosarcinaceae to be present in all soil treatments. Furthermore, Methanobrevibacter woesei, a typical gut organism of herbivores, was identified in all fertilised soil treatments. This indicates that this methanogen has survived in the microcosms for 6 months, which emphasised the survival potential of methanogens in soils.