THE EFFECTS OF SO2 AND O-3 ON THE FOLIAR NUTRITION OF SCOTS PINE, NORWAY SPRUCE AND SITKA SPRUCE IN THE LIPHOOK OPEN-AIR FUMIGATION EXPERIMENT

Foliar elements were analysed in Scots pine, Sitka spruce and Norway s pruce over a 6 year period before and during continuous exposure to SO 2 and O-3 in an open-air fumigation experiment. Sulphur dioxide treatm ent elevated foliar sulphur concentration in all species, and there we re increases in foliar nitrogen in the two spruce species but not in p ine. The concentrations of cations were frequently increased by SO2 tr eatment, but there was no correlation between the sulphur concentratio n of needles and their total cation charge. SO2-related elevations of foliar magnesium were correlated with the concentration of this elemen t in soil solution, but the mechanism by which other cations were enha nced remains unclear. The only consistent effects on nutrient ratios w ere for SO2 treatments to increase sulphur/cation ratios.