APPLICATION OF THE SAFE MODEL TO THE SOLLING CLEAN RAIN ROOF EXPERIMENT

The SAFE dynamic geochemical model [Warfvinge, P., Falkengren-Grerup, U., Sverdrup, H., Andersen, B., 1993. Environ. Pollut. 80, 1-14] was a pplied to a 'clean rain' manipulation project performed on the Selling spruce experimental forest, Selling, Germany. The experiment included a roof-covered plot where ambient throughfall was replaced with synth etic throughfall, approximately corresponding to the calculated critic al 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 ta king place in the soil solution chemistry due to the manipulation. Soi l solution pH, Al concentration and base cation concentration in the O and E horizons are very well reproduced in both the control and manip ulation experiments. Differences between simulated and measured soil s olution ANC in the deeper mineral soil are attributed to the release o f previously stored S, which is not explicitly included in the SAFE mo del. This release would then increase in the clean rain experiment aft er the beginning of the experimental manipulation. (C) 1998 Elsevier S cience B.V.