Abstract. The EMEP MSC-W Eulerian chemical transport model, and its predictions of deposition of acidifying and eutrophying pollutants over Europe, play a key role in the development of emission control strategies for Europe. It is important that this model is tested against observational data. Concerning precipitation, the EMEP model and ICP network showed very similar overall levels (within 4% for 1997 and 11% for 2000). The correlation was, however, poor (r 2 =0.15-0.23). This can be attributed largely to the influence of a few outliers, combined with a small range of rainfall amounts for most points. Correlations between modelled and observed deposition values in this study were rather high (r 2 values between 0.4-0.8 for most components and years), with mean values across all sites being within 30%. The EMEP model tends to give somewhat lower values for SO in precipitation are very similar on average (differences of 0-14%), with good correlation between modelled and observed data (r 2 =0.50-0.78). Differences between the EMEP model and ICP measurements are thought to arise from a mixture of problems with both the observations and model. However, the overall conclusion is that the EMEP model performs rather well in reproducing patterns of S and N deposition to European forests.
Aim The aim of this work was to estimate C sequestration rates in the organic matter layer in Swedish forests.Location The region encompassed the forested area (23 × 10 6 ha) of Sweden ranging from about 55 ° N to 69 ° N.Methods We used the concept of limit values to estimate recalcitrant litter remains, and combined it with amount of litter fall. Four groups of tree species were identified (pine, spruce, birch and 'other deciduous species'). Annual actual evapotranspiration (AET) was estimated for 5 × 5 km grids covering Sweden. For each grid, data of forested area and main species composition were available. The annual input of foliar litter into each grid was calculated using empirical relationships between AET and foliar litter fall in the four groups. Litter input was combined with average limit values for decomposition for the four groups of litter, based on empirical data. Finally, C sequestration rate was calculated using a constant factor of the C concentration in the litter decomposed to the limit value, thus forming soil organic matter (SOM).
ResultsWe obtained a value of 4.8 × 10 6 metric tons of C annually sequestered in SOM in soils of mature forests in Sweden, with an average of 180 kg ha − 1 and a range from 40 to 410 kg ha − 1 . Norway spruce forests accumulated annually an average of 200 kg C ha − 1 . The pine and birch groups had an average of 150 kg ha − 1 and for the group of other deciduous trees, which is limited to south Sweden, the C sequestration was around 400 kg ha − 1 .Conclusions There is a clear C sequestration gradient over Sweden with the highest C sequestration in the south-west, mainly corresponding to the gradient in litter fall. The limit-value method appears useful for scaling up to a regional level to describe the C sequestration in SOM. A development of the limit value approach in combination with process-orientated dynamic models may have a predictive value.
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