Model application to study the effects of emission reduction scenarios on a forested catchment in Finland

SMART2, a revised version of the dynamic soil acidification model SMART, wa s tested at a forested catchment in Finland. A forest growth routine and a more detailed description of nitrogen processes in soil have been included in SMART2. The aim of the study was to calibrate the model with data set de rived from the catchment and to study the model behavior. A prediction of l ong-term effect of atmospheric deposition, originated from anthropogenic so urces, on soil and runoff water was done, giving different scenarios of fut ure deposition of sulphur and nitrogen. The emphasis was put on studying th e acidifying effects of the deposition. Another aim of the study was to inv estigate the representativity of the catchment compared to a regional map, to which the critical loads of acidity have been calculated at European sca le. The scenario runs showed a decline in soil base saturation and surface water pH in response to the rapid increase of acidifying deposition due to increased emissions starting in 1960's. With the studied reduction strategi es, environment deterioration can be stopped and the recovery will begin. T he timing of the response depends on the stringency of the chosen abatement strategy. Comparisons of the regionally calculated critical loads of sulfu r to the catchment value indicated that the catchment belongs to the most t olerant ecosystems of the grid cell. (C) 1999 Elsevier Science Ltd. All rig hts reserved.