Forest soils are a significant source for the primary and secondary greenhouse gases N₂O and NO. However, current estimates are still uncertain due to the still limited number of field measurements and the herein observed pronounced variability of N trace gas fluxes in space and time, which are due to the variation of environmental factors such as soil and vegetation properties or meteorological conditions. To overcome these problems we further developed a process-oriented model, the PnET-N-DNDC model, which simulates the N trace gas exchange on the basis of the processes involved in production, consumption and emission of N trace gases. This model was validated against field observations of N trace gas fluxes from 19 sites obtained within the EU project NOFRETETE, and shown to perform well for N₂O (r²=0.68, slope=0.76) and NO (r²=0.78, slope=0.73). For the calculation of a European-wide emission inventory we linked the model to a detailed, regionally and temporally resolved database, comprising climatic properties (daily resolution), and soil parameters, and information on forest areas and types for the years 1990, 1995 and 2000. Our calculations show that N trace gas fluxes from forest soils may vary substantial from year to year and that distinct regional patterns can be observed. Our central estimate of NO emissions from forest soils in the EU amounts to 98.4, 84.9 and 99.2 kt N yr⁻¹, using meteorology from 1990, 1995 and year 2000, respectively. This is <1.0% of pyrogenic NO_x emissions. For N₂O emissions the central estimates were 86.8, 77.6 and 81.6 kt N yr⁻¹, respectively, which is approx. 14.5% of the source strength coming from agricultural soils. An extensive sensitivity analysis was conducted which showed a range in emissions from 44.4 to 254.0 kt N yr⁻¹ for NO and 50.7 to 96.9 kt N yr⁻¹ for N₂O, for year 2000 meteorology. The results show that process-oriented models coupled to a GIS are useful tools for the calculation of regional, national, or global inventories of biogenic N trace gas emissions from soils. This work represents the most comprehensive effort to date to simulate NO and N₂O emissions from European forest soils.

Core Ideas: Pre‐alpine areas face more intense warming and extreme hydrological events than the global average. Climate and land management change have far‐reaching impacts on ecosystem functions and services. We have improved knowledge of water, energy, and matter exchange by long‐term observations and modeling. Global change has triggered several transformations, such as alterations in climate, land productivity, water resources, and atmospheric chemistry, with far reaching impacts on ecosystem functions and services. Finding solutions to climate and land cover change‐driven impacts on our terrestrial environment is one of the most important scientific challenges of the 21st century, with far‐reaching interlinkages to the socio‐economy. The setup of the German Terrestrial Environmental Observatories (TERENO) Pre‐Alpine Observatory was motivated by the fact that mountain areas, such as the pre‐alpine region in southern Germany, have been exposed to more intense warming compared with the global average trend and to higher frequencies of extreme hydrological events, such as droughts and intense rainfall. Scientific research questions in the TERENO Pre‐Alpine Observatory focus on improved process understanding and closing of combined energy, water, C, and N cycles at site to regional scales. The main long‐term objectives of the TERENO Pre‐Alpine Observatory include the characterization and quantification of climate change and land cover–management effects on terrestrial hydrology and biogeochemical processes at site and regional scales by joint measuring and modeling approaches. Here we present a detailed climatic and biogeophysical characterization of the TERENO Pre‐Alpine Observatory and a summary of novel scientific findings from observations and projects. Finally, we reflect on future directions of climate impact research in this particularly vulnerable region of Germany.