Application of the forsol model to the spruce site at Solling, Germany

In this paper we present and discuss the results of an application of the regional forest simulation model forsol for the Norway spruce site in Solling (Germany). The objective of the application to the Solling site was stated as assessment of the performance of forsol at the site level. The application of forsol has taken place in the context of a comparative study of forest models. udy indicates that forsol, originally developed as a model for production of annually and regionally averaged simulation data, is well capable to simulate average values of relevant site behaviour indicators. It is however not equipped to simulate year to year fluctuations in site-specific forest behaviour. This conclusion is based on the fair agreement between simulated and observed data with respect to DBH, stem biomass, the nutrient contents for most nutrients and the nutrient fluxes and the results of the evaluation of the impact of growth reduction factors. luate the relative impact of the different stress factors, additional simulation runs were done with forsol for the period 1976–1989. The simulations indicate that the shortage of base cations causes the largest growth reduction. The additional impact of soil acidification is relatively small. The negative effects of sulphur dioxide and ozone on potential growth are even smaller. The impact of drought stress varied over the years. aluation of two deposition scenarios indicated that a strong reduction of especially the N deposition may reduce the growth and biomass of forests after some years, when the nitrogen available in the soil is incorporated in the trees. However, base cation concentrations in the leaf compartment recover.