Ernfors,M., von Arnold,K., Stendahl,J., Olsson,M. and Klemedtsson,L.(2008): Nitrous oxide emissions from drained organic forest soils−an up-scaling based on C:N ratios. Biogeochemistry, 89, 29-41.

『灌漑された有機森林土からの亜酸化窒素の放出−C：N比に基づいた規模の拡大』

『Abstract
　Total emissions of N2O from drained organic forest soils in Sweden were estimated using an equation linking the C:N ratio of the soil to N2O emissions. Information on soil C:N ratios was derived from a national database. It was estimated that the emissions from Histosols amount to 2,820 tonnes N2O a-1. This is almost five times the value calculated for the same soils using the method suggested by the Intergovernmental Panel on Climate Change: 580 tonnes N2O a-1. The higher value in the present study can mainly be explained by improved accuracy of estimates of N2O emissions from nutrient-rich soils, including former agricultural soils. In Sweden, in addition to 0.94 Mha of drained Histosols, there are 0.55 Mha of other types of drained organic soils. The annual emissions from these soils were estimated to amount to 1,890 tonnes of N2O. The total emission value calculated for drained organic forest soils was thus 4,700 tonnes N2O a-1, which, if added, would increase the current estimate of the Swedish anthropogenic N2O source strength by 18％. Of these emissions, 88％ occur from sites with C:N ratios lower than 25. The exponential relationship between C:N ratio and N2O emissions. in combination with a scarcity of data, resulted in large confidence intervals around the estimates. However, by using the C:N ratio-based method, N2O emission estimates can be calculated from a variable that is readily available in databases. Also, the recent findings that there are exceptionally large emissions of N2O from the most nitrogen-rich drained organic forest soils are taken into account.

Keywords: C:N ratio; Drained; Emissions; Forest; Nitrous oxide; Organic soils』

Introduction
Materials and methods
　N2O flux estimates
　The forest soil database
　Definition of drained soil and soil categories
　　Category A. Histosols
　　Category B. Soils with a 0.15-0.30 m peaty horizon
　　Category C. Organic soils without a peat layer
　Scaling of the results
Results
　Database area estimates and C:N values
　N2O emissions
Discussion
　Estimates
　Soil categories
　　Soil category B
　　Soil category C
　Statistics and uncertainties
　Consequences
Conclusions
Acknowledgements
References

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