The nutritional status of trees often indicates specific processes in the ecosystem. Inadequate nutrient supply may be a direct cause of low tree vitality or a factor that increases adverse effects of air pollution. High concentrations of certain elements in foliar tissues may be the effect of intoxication or of high air-pollution levels. Foliar sulphur concentrations followed annually since 1987 on 36 Finnish and 71 Austrian ICP Forests Level I plots have been low throughout the monitoring period. Even at this low level, the proportion of trees in the medium and high sulphur concentration classes have decreased reflecting the drastic reduction in sulphur emissions from 1980's to the present. Generally foliar N concentrations in these Finnish and Austrian plots have remained low especially in Austrian forest located in Alpine regions. Nutrient ratios detected in the monitored trees have indicated generally well-balanced nutritional status. Considering the whole Europe in half of the 109 Level II plots, which provided necessary information for calculations, unbalanced nutrition caused by high nitrogen deposition have been observed.
