EFFECTS OF VITALITY FERTILIZATION ON THE RESIN FLOW AND VIGOR OF SCOTS PINE IN FINLAND

The vitality and defence of Scots pine were measured in order to study how different fertilizer combinations affect these traits, and to det ermine whether an increase in growth leads to reduced defence as predi cted by the theories based on the assumption of the existence of a tra de-off between growth and carbon-based defence compounds, Stem diamete r growth and vigour index were measured as indicators of vitality and stem resin flow and the concentration of phloem phenolics were used as indicators of defence level, Fertilizer treatments containing nitroge n had a growth-promoting effect and the vigour index was higher in the nitrogen-fertilized treatments than in the control and non-nitrogenou s fertilizer treatments. Four of the ten experimental sites were situa ted along a heavy metal pollution gradient at 0.5, 2.5, 4 and 8 km dis tance from the emission source, The vigour index in the severely pollu ted site closest to the emission source was considerably lower than th at in the other three sites along the gradient, but even there nitroge n gave a clear growth response, In spite of the large within-and betwe en-toe variation in resin flow, the average resin exudation differed l ittle between the experimental sites, In most sites the resin flow was highest in the control treatment. A weak negative correlation was fou nd between resin flow and vigour index. In the pollution gradient the mean resin flow was lowest at the most polluted site and increased alo ng the gradient up to 4 km from the emission source, The phenolic conc entration of the phloem was not affected by fertilization in any of th e experiments apart from the severely polluted one. indications of a w eak negative linear correlation between vigour index and phloem phenol ics were found. There was no significant correlation between the pheno lic concentration and the amount of resin flow in any of the different sites. Except for the liming treatment in the polluted experiments, w e did nor detect any response to non-nitrogenous fertilizer treatments . (C) 1998 Elsevier Science B.V.