PhD Thesis, 2010 - University College Cork

General discussion
7. GENERAL DISCUSSION
The aim of this work was to investigate the behaviour and temporal trends in the
nitrous oxide emissions from a managed grassland in the temperate humid climate of
South-Western Ireland.
The first sub-project was devoted to post-hoc analysis of the time series,
attempting to separate the peak and background fluxes. A novel technique was
proposed that allows distinguishing between normally distributed background flux and
more intensive bursts. In our study, about a quarter of all flux was delivered by
emission bursts, occurring over only 7% of the flux period. Applying this technique to
the earlier published data, we found good agreement between our estimate and that of
Hsieh et al. (2005), which was based on DnDc modelling of the background flux. We
also observed that the peak events are more likely to occur within 12–40 and 50–100
hours after the rainfall and fertiliser application, respectively. This information was
further used to develop an environmental-variable based approach for time series gapfilling.
The long-term observations of nitrous oxide flux dynamics in the newly afforested
grassland comprised the second sub-project of this study. We observed a reduction in
emissions from the afforested sector over several years as compared to the grassland. It
was, however, preceded by the very intensive burst, coinciding with the soil
preparatory work at the afforested site. These observations lasted for 5 years and will
need to be continued to assess changes in emission as the forest matures.
The final sub-project was the methodological study on gap-filling of the N 2 O time
series for the purpose of calculating annual sums. We studied both published and new
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