An inverse abundance approach to separate soil nitrogen pools and gaseous nitrogen fluxes into fractions related to ammonium,nitrate and soil organic nitrogen

The soil nitrogen (N) cycle exhibits a variety of complex biochemical reactions in which N species such as NO₂⁻, NO and N₂O are produced and consumed by co‐existing processes that respond differently to the local environmental conditions. Key to understanding the soil N cycle in its full complexity is the development and application of methods that allow a quantification of individual pathways and processes that are responsible for the build‐up and/or emission of N compounds. Triplet ¹⁵N tracer experiments (TTE) have been developed and applied to allow a source‐related quantification of N species such as NO₂⁻, and N₂O by different biochemical pathways (e.g. ammonia oxidation and nitrate reduction) that are related to multiple N sources (NH₄⁺, NO₃⁻ and N_org). An analysis of a TTE requires the application of either a numerical or analytical model. Because of the ease of application it is desirable to use analytical models. However, available analytical solutions suffer from serious drawbacks concerning the quantification of N fluxes related to soil organic N. In this paper we describe the development and application of a new inverse abundance approach (IAA) to analyse a TTE. Theoretical and experimental data sets of soil N₂O release were analysed by the new method. The IAA was also applied to an already existing data set to identify fractions of the soil nitrite pool related to NH₄⁺, NO₃⁻ and N_org. We show that the IAA provides a reliable and comprehensive data evaluation of a TTE.