DISTRIBUTION OF Cd, Cu, Pb AND Zn IN SOIL AND VEGETATION COMPARTMENTS IN STANDS OF FIVE BOREAL TREE SPECIES IN N.E. SWEDEN
Concentrations and total quantity of cadmium (Cd), cupper (Cu), lead (Pb) and zink (Zn) were determined in biomass and soil compartments in a replicated tree species experiment with 27-yr-old stands growing on former farmland in N.E. Sweden. Sequential extractions of soil samples were performed in order to estimate the exchangeable and an organically bound fraction of each element. The tree species included were Picea abies (L.) H. Karst., Pinus sylvestris L., Pinus contorta Dougl., Larix sibirica Ledeb., and Betula pendula Roth. Tree species influenced the rate of removal of Cu, Pb and Zn in case of stemwood harvesting, and of Cd, Cu and Zn in the case of whole-tree harvesting. B. pendula and P. abies had higher quantities and average concentrations of Zn in the biomass. For all species, >50% of the Zn in the stems was found in the bark. P. abies and L. sibirica had higher quantities of Cu in the biomass than the other species. P. abies and P. contorta had high quantities of Cd in the biomass in relation to the other species. Branches and stembark contained high concentrations of Cd and Pb in relation to foliage and stemwood. Dead branches had especially high concentrations of Pb. The high accumulation rate of Zn in the biomass of B. pendula was related to a low exchangeable amount of Zn in the A horizon. In the superficial centimeters of the A horizon, a depletion similar to that found for Zn was detected for Cu, whereas for Cd and Pb, no correlations were found between quantities of elements in the trees and element pools in the soil.