Experiments on canopy/soil leaching effects of air pollutants in model ecosystems with forest trees

In 1982 an experiment was started at the University of Hohenheim to investigate the long term effects of O₃, SO₂ and simulated acid rain in realistic concentrations, single and in combination, on mineral cycling, biochemistry, physiology and anatomy of spruce-, fir- and beech seedlings in modelecosystems. During the 5 year duration of this experiment definite effects on mineral cycling were observed. Most noticeable are throughfall enrichment with sulfate through dry deposition of SO₂, connected with elevated leaching of calcium, magnesium, manganese, zink and ammonia from needles, in total leading to an enhanced acid input to the soil. The consequence of this was that after 15 months the water percolating the soils in the lysimeters of these treatments was acidified, with elevated flowrates of sulfate, manganese, calcium and magnesium. Effects on mineral cycling are discussed in connection with observations of other groups working in the modelecosystems.