ASSESSMENT OF SOIL ACIDIFICATION EFFECTS ON FOREST GROWTH IN SWEDEN

The results of mapping critical loads, areas where they have been exce eded and steady state (Ca+Mg+K)/Al ratios of soils in Sweden, has been used to assess the order of magnitude of the ecological and economic risks involved with acid deposition for Swedish forests. The results o f the calculations indicate that 81% of the Swedish forested area rece ive acid deposition in excess of the critical load at present. Under c ontinued deposition at 1990 level, forest die-back is predicted to occ ur on approximately 1% of the forested area, and significant growth ra te reductions are predicted for 80% of the Swedish forested area. For Sweden, growth losses in the order of 17.5 million m(-3) yr(-1) is pre dicted, equivalent to approximately 19% of current growth. Comparable losses can be predicted for other Nordic countries. The soil acidifica tion situation is predicted to deteriorate significantly during the ne xt 5-15 years, unless rapid emission reductions can be achieved. A min imum deposition reduction over Sweden of 85% on sulphur deposition and 30% on the N deposition in relation to 1990 level is required in orde r to protect 95% of the Swedish forest ecosystems from adverse effects of acidification. A minimum reduction of 60% on sulphur deposition an d 30% on the N deposition is required to keep forest harvest at planne d levels.