PARENT SESSION
Poster Session 23: Soil Ecology
Wednesday, August 10, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrčs de Montréal
Total N2O emissions from drained forest histosols in Sweden – an upscaling based on C:N ratios.
Gustafsson, Maria*,1, von Arnold, Karin1, Stendahl, Johan2, Olsson, Mats2, Klemedtsson, Leif1, 1 Göteborg University, Göteborg, Sweden2 Swedish University of Agricultural Sciences, Uppsala, Sweden
ABSTRACT- Nitrous oxide (N2O) is a potent greenhouse gas and its concentration is increasing rapidly in the atmosphere. Finding methods to efficiently map its sources is crucial to greenhouse gas budget calculations. N2O production occurs mainly in soils. In forest soils, it shows large temporal and spatial variations, since it is strongly dependent on soil texture and nitrogen availability. Hence, upscaling of N2O emissions from forest soils is generally associated with large uncertainties and often requires advanced modelling. Drained forest histosols are potentially large anthropogenic sources of N2O and models have not yet been used to quantify their N2O emissions. However, a strong correlation (r2 adj = 0.96) has been found between the C:N ratio and the N2O emissions of these soils. The correlation has been suggested as a possible means to scale up emissions from the field level to regional and national levels. The Swedish National Inventory of Forests (RIS; http://www-nfi.slu.se) provides information on C:N ratios of statistically selected plots covering the whole country. This data, combined with the C:N ratio-N2O emission correlation mentioned, gives an estimate of 2660 tonnes N2O y-1 being emitted from drained forest histosols in Sweden. In comparison, the method suggested by GPG-LULUCF for scaling up N2O emissions, with default emission factors for nutrient rich and nutrient poor soils, produces an estimate of 1130 tonnes N2O y-1 for the same area, assuming that soils with C:N ratios below 25 are classified as nutrient rich. Some types of drained forest histosols, e.g. afforested agricultural soils, have in recent studies been found to emit several times more N2O than the GPG-LULUCF emission factor for nutrient rich soil suggests. These soils are not treated separately with the GPG-LULUCF approach, which most likely leads to an underestimation of the emissions. ccording to the C:N ratio based method, drained forest histosols contribute by about 13 % to the Swedish anthropogenic N2O source strength.
Key words: nitrous oxide, upscaling, C:N ratio, histosols