Tropical soil: Contribution of methanotrophs to nitrous oxide emission
Methane (CH4) and N2O are important greenhouse gases. In soils methanotrophic bacteria (MB) oxidize CH4, using it as both an energy and C-source. Principially, MB are not exclusively dependent on indigenous CH4-production but they can utilize CH4 from the atmosphere. There is evidence from pure culture studies and from environmental studies that methanotrophs have the potential to produce nitrite from ammonium and in a less amounts to produce N2O. Nitrite is the precursor of nitrate in soils which is the compound that is used by denitrifiers to produce N2O. In tropical forests soils have a high organic matter input and due to high soil temperature and activity of soil community there is a high mineralisation rate. This leads to an high concentration of ammonium in the soil. Under such conditions it can be expected that existing methanotrophic populations contribute significantly to the N2O emission of the soil by "methanotrophic nitrification".
Thus MB might be relevant for the fluxes of two important greenhouse gases (CH4 and N2O) in a tropical forest soil near to Sao Paulo (Brazil). In a project dealing with this subject we integrate biogeochemistry of gas fluxes and molecular methods to assess methanotrophic communities and their activities.
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