Application of the SAFE model to the Solling clean rain roof experiment

Abstract The SAFE dynamic geochemical model [Warfvinge, P., Falkengren-Grerup, U., Sverdrup, H., Andersen, B., 1993. Environ. Pollut. 80, 1–14] was applied to a ‘clean rain’ manipulation project performed on the Solling spruce experimental forest, Solling, Germany. The experiment included a roof-covered plot where ambient throughfall was replaced with synthetic throughfall, approximately corresponding to the calculated critical loads of acidity for this soil. Input of S and N to the system was reduced by 85 and 90%, respectively. The results of the modelling show that the model well reproduces the time scale and level of changes taking place in the soil solution chemistry due to the manipulation. Soil solution pH, A1 concentration and base cation concentration in the O and E horizons are very well reproduced in both the control and manipulation experiments. Differences between simulated and measured soil solution ANC in the deeper mineral soil are attributed to the release of previously stored S, which is not explicitly included in the SAFE model. This release would then increase in the clean rain experiment after the beginning of the experimental manipulation.