The application of the model nap to the Solling spruce site

The nap (Nutrient Availability and Productivity) model is an integrated forest-soil model for analysing indirect effects of acidification on forest growth. The nap model is applied here to the Solling spruce site in Germany. The model was validated and tested for the years 1969–1990. In addition, two scenarios, one with continuing deposition at the 1990 level and the other with a reduced deposition, were evaluated. The simulations show that forest growth is strongly enhanced by anthropogenic N deposition. Unchanged deposition will lead to a Mg-limited forest growth. This growth will be higher than forest growth in an improved environment. However, forest growth in the no-reduction scenario is accompanied by an unbalanced nutritional status, whereas in the improved environment the forest has a balanced nutrient status with lower growth and no risks for Mg limitation.