『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