|Indication of S and N Inputs by Means of Needle Analyses Based on the Austrian Bio-Indicator Grid|
The evaluation of the investigation results is based on the data from the Austrian Bio-Indicator Grid, an all-Austrian monitoring programme which, since 1983, has included annual collection of needle samples from 611 sample plots (spruce and pine) and determination of the S, N, P, K, Ca and Mg concentrations.
Although impacts of large-scale sulphur pollution from Austrian emitters have decreased in recent years no overall decreasing trend exists for Austria because, due to S imports, recent years have seen increasing sulphur concentrations, particularly in needle samples collected near the Slovenian and Hungarian borders. The most significant impacts of S pollution were observed at altitudes under 800 m a.s.l..
In Austria, nitrogen is the nutrient element with which the investigated conifers are most poorly supplied. Since 1983, nitrogen supply has deteriorated and the temporal development of results does not indicate an improvement or eutrophication. The nitrogen supply proved to be best at low altitudes (up to 600 m a.s.l.).
Apart from absolute nutrient concentrations, which are of significance for the evaluation of the nutrient supply, nutrient ratios play alos an important role. The highest percentage shares of plots above the harmonious ranges for N/P, N/K and N/Mg ratios were observed in main growth regions 4, 7 and 9 (Nördliche Randalpen, Nördliches Alpenvorland, Mühl- und Waldviertel). This meas that, in case of additional N input through air pollution, these regions would be subject to the greatest risk in connection with inharmonious nutrient supply.