Modelling of microbial carbon and nitrogen turnover in soil with special emphasis on N-trace gases emission

We present a new model unifying state-of-the-art descriptions of microbial processes for denitrification, nitrification and decomposition of soil organic matter. The model is of medium complexity, filling a gap between simplistic model approaches with low predictive power and complex models, which are difficult to verify experimentally. The model Microbial Carbon and Nitrogen Turnover in soils (MiCNiT) is written in Ansi C++ and embedded into a modelling framework (MoBiLE) that provides initial conditions and accompanying ecosystem processes such as N uptake by plants, litterfall, soil water and soil temperature with established model approaches. The MiCNiT model explicitly calculates decomposition, dynamics of microbial biomass, denitrification, autotrophic and heterotrophic nitrification, applying the microbial activity concept, as well as transport of gases and solutes between anaerobic and aerobic soil fractions and through the soil profile. The model was tested against N2O and CO2 emission as well as C and N pool data from the Höglwald Forest, Germany. Due to a detailed description of the soil biochemistry and gaseous transfers, MiCNiT is capable of simulating soil air NO, N2O and N2 concentrations and the net exchange of these gases at the soil-atmosphere interface, including a possible net uptake of N2O by soils.