Simulation of Land Management Effects on Soil N2O Emissions Using a Coupled Hydrology-Biogeochemistry Model on the Landscape Scale

Agricultural soils are the primary anthropogenic source of atmospheric N2O. Greenhouse gas (GHG) emissions from soils are mainly the result of microbial processes such as nitrification/denitrification. These processes have a strong dependency on environmental factors like temperature, moisture, soil and vegetation properties, or the land management. Therefore, emissions occur with a high spatial and temporal variability giving rise to hot spots and hot moments. Quantifying sources and sinks of GHG like CO2, N2O, and CH4 for natural, agricultural, and forest ecosystems is crucial for our understanding of impacts of land management on the biosphere-atmosphere exchange of GHG and for the development of mitigation options. GHG exchange from soils is driven by complex microbial and plant nutrient turnover processes, and it is the net result of all physicochemical and biological processes involved in production, consumption, and transport. Process-oriented biogeochemical models are useful tools for integrating our knowledge of the key processes and drivers to estimate carbon and nitrogen (C and N) trace gas emissions from soils. In this study we have coupled the LandscapeDNDC ecosystem model to the CMF (Catchment Modeling Framework) hydrology model generating a modeling system capable to assess the C and N cycling and their feedbacks to crop growth and microbial processes on the landscape scale. The deployed coupling approach by the use of the parallel MPI-based OpenPALM coupler enables the simulation of lateral exchange of nutrients (nitrate) with the soil water fluxes and therefore to assess the C and N cycling on the landscape scale. In this study we describe the coupling approach and present simulation results of crop growth, nutrient cycling and resulting nitrous oxide emissions on a virtual landscape.