Influence of air pollution on the foliar nutrition of conifers in Great Britain.

The nutritional status of needles from Sitka spruce, Norway spruce and Scots pine in a total of 108 stands was assessed. There was little evidence of nutritional deficiency, although potassium levels were frequently quite low. Analysis of some heavy metals (lead and copper) failed to reveal any likely toxicity problems. Sulphur, nitrogen and iron levels in/on the foliage were all related to various measures of sulphur and nitrogen pollution, determined using improved deposition models that take into account cloud deposition and the seeder-feeder mechanism. The analysis strongly suggested that direct air pollution has a greater effect on sulphur, nitrogen and iron foliar analyses than indirect pollution (wet deposition). The relationships were identified for levels of pollution that were generally lower than those seen in traditional gradient studies.