Spatial and temporal variations of N2O evolution at the landscape-scale as affected by land use
van Kessel, C.
Nitrous oxide has been widely recognized as a major scientific and environmental issue because of its involvement in global warming and destruction of the atmospheric ozone layer. Soils generally act as source of N2O, but the actual rates of N2O emission and the controls on these rates remained poorly understood. As a pre-requisite to quantify large-scale N2O emissions over a long term range, this study was conducted to determine the landscape- and seasonal-scale patterns of N2O emission. Nitrous oxide emissions were assessed at a hummocky glacio-lacustrine landscape in the Black soil zone. The study area was divided into three agronomic practices: an unfertilized canola site, a conventional fallow site, and a pasture site. A systematic grid design was employed at each site and N2O emission was monitored using closed chamber method. A clear landscape-scale pattern of N2O emission was observed in the unfertilized canola and conventional fallow sites; lower landscape positions showed higher N2O flux than the upper landscape positions. This pattern remained consistent throughout the season, with increased in N2O flux towards the mid-growing season (summer), decreased towards the end of the growing season (early fall), and virtually ceased by the onset of frost (late fall). Of the three sites tested, the pasture site showed the lowest N2O emission and activity was only observed during the summer samplings. Soil respiration and moisture content followed. similar spatial and temporal patterns as N2O emission. Results indicate that N2O production is controlled at the landform level by soil factors and at seasonal level by precipitation and temperature. Such relationships might be useful in generating a spatially-distributed model for quantifying N2O emission.
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