Modeling of the long-term effect of tree species (Norway spruce and European beech) on soil acidification in the Ore Mountains

Abstract

The MAGIC model was applied to estimate soil and soil water (−90 cm) chemistry between 1854 and 2094 at two experimental stands (Načetín, Ore Mountains), one covered by a Norway spruce monoculture and the other by a natural European beech forest. The primary aims were to evaluate the influence of tree species on long-term acidification and to predict future development under different forest management scenarios. Depletion of base cations from the soils, caused by high acidic deposition, resulted in low base saturations of 8.2% at the spruce stand and of 6.4% at the beech stand in 2003. The concentration of aluminum in soil water was 135 μmol l −1 and pH 4.32 at the spruce stand, and 70 μmol l −1 and pH 4.4 at the beech stand, respectively, in 2005. During the peak of acidification in the mid 1980s, modeled aluminum concentrations contributed 70% to neutralizing acidity at the spruce stand, and 55% at the beech stand. In addition, SO 4 concentration was significantly higher at the spruce stand (525 μequiv. l −1) compared to the beech stand (330 μequiv. l −1) as a result of higher dry deposition onto the spruce canopy. The enhanced leaching of base cations was comparable at both stands (191 μequiv. l −1 at the spruce stand and 215 μequiv. l −1 at the beech stand). The higher deposition of base cations onto the spruce canopy was able to partially mitigate the effect of high leaching. The model results suggest that future recovery of soil water will be significantly better at the beech stand (higher pH, ANC, Bc/Al ratio and lower SO 4 2− and Al concentrations). Interestingly, modeled soil base saturation for 2094 will be lower at the beech stand. Alternative scenarios such as clear-cutting and new re-forestation resulted in more favorable soil chemistry for the beech plantations compared to the spruce. The best regeneration of the soil environment is predicted for the scenario with an absence of forest. This suggests, that future soil recovery from acidification will be delayed by the removal of base cations through harvesting.