1 Soil Science of Temperate and Boreal Ecosystems Büsgen Institute, University of Göttingen

1. Fig. 1: N and O fluxes during biological N2O formation Fig. 3: N2O fluxes following NH4+-fertilization and associated isotopic signatures 1Soil Science of Temperate and Boreal Ecosystems Büsgen Institute, University of Göttingen Büsgenweg 2, 37077 Göttingen, Germany Laboratory incubation studies to investigate the control of isotopologue signatures of soil-emitted N2O P BA43A-0889 Reinhard Well*1, Heiner Flessa1, Lu Xing2, Ju Xiaotang2, Volker Römheld3 2College of Agricultural Resources and Environmental Sciences, China Agricultural University, Beijing, P.R. China. 3Institut für Pflanzenernährung, University of Hohenheim, Stuttgart, Germany. *Presenting author, Email: rwell@gwdg.de) Fig. 4: N2O fluxes from denitrification and associated isotopic signatures with or without blockage of N2O reduction. Fig. 2: Experimental set-up for studying gas emissions from soil microcosms incubated under controlled conditions.

2. (1) Well et al., 2005; (2) Well et al., unpublished data; (3) Yamulki et al., 2001, Perez et al., 2001, Bol et al., 2003, Bol et al., 2004, Well et al., 2006; Perez et al., 2006; Cardenas et al., 2007 P BA43A-0889 / 2 Part 2 of: Laboratory incubation studies to investigate the control of isotopologue signatures of soil-emitted N2O Fig. 4a: Consumption of added N2O during anaerobic incubation Fig. 4b: 15N site preference (SP) vs. residual N2O and associated fraction factors Comparing isotopic signatures within experiments and with previous studies Fig. 7 a - f: Isotopic signatures of N2O from soils and groundwater (experiments 1 to 3 and previous studies). a. Autotrophic nitrification (Exp. 1) c. Denitrificaion in water-saturated systems (Well et al., 2005) e. 15N site preference (SP vs. d18O) b. Production and reduction by denitrification (Exp. 2) d. Reduction (Exp. 3) f. d15Nbulk vs. d18O