DenNit – Experimental analysis and modelling of soil N 2 O efflux in response on changes of soil water content, soil temperature, soil pH, nutrient availability and the time after rain event Sascha Reth 1,3 , Kerstin Hentschel 2 , Matthias Dro¨sler 2 & Eva Falge 2 1 GSF – Research Centre for Environment and Health, Institute of Soil Ecology, D-85764 Neuherberg, Germany. 2 Department of Plant Ecology, University of Bayreuth, D-95440 Bayreuth, Germany. 3 Corresponding author* Received 6 May 2004. Accepted in revised form 8 November 2004 Key words: ammonium, nitrate, non-linear regression model Abstract To quantify the effects of soil temperature (T soil ), and relative soil water content (RSWC) on soil N 2 O emission we measured N 2 O soil efflux with a closed dynamic chamber in situ in the field and from soil cores in a controlled climate chamber experiment. Additionally we analysed the effect of soil acidity, ammonium, and nitrate concentration in the field. The analysis was performed on three meadows, two bare soils and in one forest. We identified soil water content, soil temperature, soil nitrogen content, and pH as the main parameters influencing soil N 2 O emission. The response of N 2 O emission to soil temper- ature and relative soil water content was analysed for the field and climate chamber measurements. A non-linear regression model (DenNit) was developed for the field data to describe soil N 2 O efflux as a function of soil temperature, soil moisture, pH value, and ammonium and nitrate concentration. The model could explain 81% of the variability in soil N 2 O emission of all individual field measurements, except for data with short-term soil water changes, namely during and up to 2 h after rain stopped. We validated the model with an independent dataset. For this additional meadow site 73% of the flux varia- tion could be explained with the model. Introduction The exchange of greenhouse gases between soils, vegetation, and the atmosphere is an important topic of ecological research. In response to con- cerns on climate change, the Kyoto Protocol requires the compilation of national inventories of greenhouse gas emissions and the develop- ment of strategies aimed at reducing such losses during the next decade. Nitrous oxide (N 2 O) is one of the greenhouse gases identified by the Kyoto Protocol (UNFCCC, 1992), and contrib- utes 6% to the global warming (IPCC, 2001). N 2 O is partly responsible for the destruction of the stratospheric ozone layer (Crutzen, 1981). In the atmosphere N 2 O has a long residence time of about 120 years, resulting in a global warm- ing potential 310 times larger than that of CO 2 (IPCC, 1996). Between 60 and 70% of the total N 2 O emis- sions are derived from the soil. The microbial processes of denitrification and nitrification are the major sources of the N 2 O emission in the soil (Davidson, 1991; Oenema et al., 2001). The microorganisms of these two pathways, e.g., Nitrosomonas and Nitrobacter in nitrification and Pseudomonas and Achromobacter in denitrifica- tion (see e.g., Scheffer and Schachtschabel, 2002; * FAX No: +49-089-3187-4431. E-mail: sascha.reth@gsf.de Plant and Soil (2005) 272: 349–363 Ó Springer 2005 DOI 10.1007/s11104-004-5978-2