Between 10 and 14 May 1993, a workshop was organized in Leusden, the N
etherlands, in which the concepts and performance of 18 models were di
scussed. These models were generally aimed at the analysis of effects
of acid atmospheric deposition on forest and forest soils. Model conce
pts were analysed by means of a questionnaire. Model performance was a
nalysed by application of the models to a common dataset for the F1 No
rway spruce site, at Selling, for the period 1970-1990. The nature of
the participating models varied widely, but all models were process-or
iented and dynamic. Included were hydrological models, soil chemistry
models as well as integrated models for calculation of forest growth.
Overall, average annual hydrology, soil solution chemistry and forest
growth of the spruce site between 1970-1990 could be reproduced. Diffe
rences between models were attributable more to different parameteriza
tions than to differences of model concepts. Short-term temporal dynam
ics of soil solution chemistry were not reproduced very well, particul
arly for nitrate. Models also gave different predictions of the respon
se of the Norway spruce to maintained or reduced fluxes of atmospheric
deposition, however, confirming a key role for Mg and N. Complex mode
ls did not give better results than more simple models. Integrated mod
els were also judged unbalanced, with respect to description of the hy
drologic, soil chemical and forest subsystems. Therefore, it was recom
mended to improve this balance and to work towards less complex models
for prediction of the long-term behaviour of forest stands. Our knowl
edge about nutrient uptake by forests in nutrient-limited acidified so
il systems, and also about the interaction of various forest stresses
is still inadequate. Future research should therefore emphasize a bett
er integration of model development and experimental research, e.g., a
s presently is the case for experimental field manipulations.