Sea salt impact on forests in western Norway

Abstract

Summary Several strong westerly storms hit western Norway during the winter of 1986/87. We studied the uptake, loss and visible effects of sea salt aerosols in Scots pine and Norway spruce. Foliage was sampled at distances 0‐100 km from the coastline between 59o and 65oN, and analysed for chloride, sodium and other elements. The range of chloride and sodium concentrations in needles was 0.5‐5.0, and 0.1‐3.0 mg g ‐1 , respectively. The local variation was very large close to the coast. The relation to distance from the sea was improved by using distance from the nearest fjord rather than from the outer coastline. Other elements were less variable and not related to distance from the sea, or to sea salt concentrations. Only 1‐10 per cent of the needles’ sea salt content could be removed by 2 min washing in distilled water, and even less for other elements. The amount of sea salt removed by washing was less related to distance from the sea than was the total content. Visible damage to the foliage occurred at chloride concentrations above 1 mg g ‐1 in the needles. Our conclusions are that analysis of the needles’ chloride or sodium content is a robust method for confirming damage to tree foliage by sea salt aerosols. Fjords as well as the ocean are significant sources of sea salt aerosols. Large local variations in salt deposition and damage will occur near a rugged coastline. Nutrients and other elements are not significantly affected by the sea salt deposition. The use of chloride or sodium as a tracer for dry deposition should take into account not only the enrichment of these elements in canopy throughfall, but also the accumulation in the needles.