Soils are the major source of atmospheric N 2 O, and better estimates of fluxes are needed to improve the input to climatic general circulation models. We developed a system in a semicontrolled environment to investigate relationships between fluxes of N 2 O and controlling variables. It consists of 12 soil monoliths (1‐m diam., ≈ 0.6 m deep) in glass fiber casings, the tops of which have been converted into gas flux chambers. These chambers are connected to a gas chromatograph for measurement of N 2 O and CO 2 . Gas sampling and analysis is computer controlled and can be done continuously. Temperatures and soil water potential are also recorded continuously. The system has performed reliably since continuous operation began in September 1993. We conducted three experiments, examining the effects of soil water potential, organic matter input, and diurnal temperature variation on N 2 O fluxes, to illustrate the capabilities of the system. In these experiments, the major emissions of N 2 O (>800 εg N 2 O‐N m −2 h −1 ) occurred when the water potential was above −5 kPa. When plant material was incorporated into the soil, a highly significant correlation was found between N 2 O and CO 2 emissions; the N 2 O emissions showed pronounced diurnal cycles, with the maxima occurring at night, 4 h after the temperature maxima at 0.1‐m depth. Data interpretation was greatly aided by the frequency and continuity of measurement.
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Thomson et al. (1997) studied this question.