Bedard-Haughn et al. 2006

Bedard-Haughn A, Matson AL, Pennock DJ. 2006. Land use effects on gross nitrogen mineralization, nitrification, and N2O emissions in ephemeral wetlands. Soil Biology and Biochemistry 38: 3398-3406.

These authors used a combination of stable-isotope and measurements of chemical pools and emissions from soils techniques to examine the role of various microbial-mediated processes in contributing to N2O production in an agricultural landscape. N2O emissions are the result of a complicated suite of metabolic activity in soils, with local oxygen concentrations, driven by soil moisture, and concentrations of reactants in these chemical pathways both contributing to net processes.

In the Canadian prairies, gross N2O production is positively correlated with soil moisture, with the highest emissions associated with lower-slope and wetland soils. This is consistent with the major contributing process in N2O emissions being denitrification, the process that reduces NO3- under anaerobic conditions. However, nitrification, the production of NO3- from NH4+, has also been observed to contribute to N2O emissions, especially from drier and aerobic soils.
Simple measurements of NO3- and NH4+ concentrations in soils will not capture information about the processes cycling N between these and other pools of soil matter. Used in conjunction with measurements of those processes, such as the 15N technique used here, does provide information about the factors controlling those processes. In this case, little variation through time or space in either pool combined with patterned variation in N2O emission and 15N movements allowed these authors to infer that both nitrification and denitrification are not limited by the substrate pools, despite the quite different other aspects of these processes.

This paper provides a very detailed description of the 15N procedures used, as well as a clear discussion of the various N-cycling processes in soils.