Microbial processes in soils, sediments and organic wastes such as manure are a major source of atmospheric greenhouse gases (GHG). These processes create spatially as well as temporally heterogeneous sources or sinks. Consequently, a thorough understanding of the underlying processes and a quantification of spatio-temporal dynamics of sinks and sources are the bases for a) developing GHG inventories at global, national and regional scales, b) identifying regional hot spots and c) developing strategies for mitigating GHG emissions from terrestrial, specifically agricultural, systems.
At the ecosystem scale, biosphere-atmosphere fluxes of CO2, CH4, and N2O are bi-directional, i.e. what is observed is a net flux of production and consumption processes (e.g. CO2: photosynthesis and autotrophic and heterotrophic respiration; CH4: methanogenesis and methane oxidation; N2O: nitrification and denitrification as source processes and denitrification as a sink process). The same is true for soil-atmosphere exchange processes, though, with regard to CO2, often only respiratory fluxes are measured.