The concentrations of Fe, Zn and Co in successive needle age classes of Norway spruce [Picea abies (L.) Karst.]

The concentrations of Fe, Zn and Co were determined in up to five successive needle age classes in 54 individual Norway spruce trees from eight different sites (soil pH 3.1-7.7). Fe concentrations (12-25 mu g in needles from the current year) were lower than most published values, due to the removal of surface contamination prior to analysis. Fe showed a significant positive correlation with Al. Successive needle age classes either had constant values or showed an increase for Fe concentrations; individual trees on a given site were rather uniform in their behaviour. Zn concentrations were 19-40 mu g/g. On acid sites, they showed a positive correlation with total soil concentrations. The majority of trees showed decreasing Zn concentrations in successive needle age classes, but constant or increasing concentrations were also found: site homogeneity was less than with Fe. Co concentrations differed between trees on a neutral soil (12 ng/g) and on acid soils (41-174 ng/g). They showed a significant positive correlation with Mn needle concentrations. The changes of Co with needle age in most, but not all, trees were similar to those of Zn. The different changes of Fe, Zn and Co with needle age may be due to a different retranslocation. A modest retranslocation of Fe as opposed to a high retranslocation of Zn and Co (in most trees) is consistent with the observed behaviour.