Temporal stability of spatial patterns of nitrous oxide fluxes from sloping grassland

Insight into the temporal and spatial variability of nitrous oxide (N2O) fluxes from soils is required to set up efficient sampling protocols of N2O fluxes and to set up strategies to reduce N2O fluxes. The aim of the present study was to assess the temporal stability of the spatial pattern of N2O fluxes along a transect (400 m) on a fertilized sloping grassland soil. Geostatistical analyses of flux chamber measurements over 4 d showed a clear spatial dependency of N2O fluxes. The spatial variability of N2O fluxes was much higher than the temporal variability during the 4 d. Despite the decreasing magnitude of the flues in time, the spatial pattern persisted during 4 d, that is, fluxes were always highest at the steepest part of the transect. The N-15 natural abundance (delta(15)N) in soil N was significantly correlated with N2O fluxes, indicating a long-term effect of N loss as N2O on the N-15 abundance in the soil. It was suggested that topography played a role in the observed spatial patterns of N2O nuxes and Delta(15)N in soil N. The study showed that despite the persistent spatial pattern of N2O fluxes, flux magnitude may strongly fluctuate in time. Therefore, it is often not possible to combine N2O flux measurements made at different times in order to obtain enough data for geostatistical analysis.