Budget of N 2O emissions at the watershed scale: Role of land cover and topography (the Orgeval basin, France)

Abstract

Agricultural basins are the major source of N 2O emissions, with arable land accounting for half of the biogenic emissions worldwide. Moreover, N 2O emission strongly depends on the position of agricultural land in relation with topographical gradients, as footslope soils are often more prone to denitrification. The estimation of land surface area occupied by agricultural soils depends on the available spatial input information and resolution. Surface areas of grassland, forest and arable lands were estimated for the Orgeval sub-basin using two cover representations: the pan European CORINE Land Cover 2006 database (CLC 2006) and a combination of two databases produced by the IAU IDF (Institut d'Aménagement et d'Urbanisme de la Région d'Île-de-France), the MOS (Mode d'Occupation des Sols) combined with the ECOMOS 2000 (a land-use classification). In this study, we have analyzed how different landcover representations influence and introduce errors into the results of regional N 2O emissions inventories. A further introduction of the topography concept was used to better identify the critical zones for N 2O emissions, a crucial issue to better adapt the strategies of N 2O emissions mitigation. Overall, we observed that a refinement of the land-cover database led to a 5%decrease in the estimation of N 2O emissions, while the integration of the topography decreased the estimation of N 2O emissions up to 25 %. © Author(s) 2012.