MODELING THE RESPONSE OF TERRESTRIAL ECOSYSTEMS TO ACIDIFICATION AND DESICCATION SCENARIOS

Changes in vegetation are often caused by changes in abiotic site fact ors, such as pH, nitrogen availability and soil moisture. It has been recognized that abiotic site factors are affected by atmospheric depos ition and groundwater-table changes. In order to evaluate the effects of eutrophication, acidification and desiccation on site factors, the model SMART2 has been developed. For the Netherlands combinations of t wo acidification and two seepage scenarios (1990-2050) were evaluated with SMART2. The results are focused on pH, nitrogen availability and base saturation. Calculations were made for combinations of five veget ation structures on seven soil types and the five groundwater-table cl asses, using a 1 km(2) grid. Results showed that deposition reductions lead to a relatively fast improvement of the site factors, increase i n pH and base saturation and decrease in N availability. Whereas a red uction in groundwater abstractions of 25% has little or no effect on t he pH and N availability.