Heavy Metal Pollution and Decomposition of Spruce Needle Litter

Comparisons were made on the decomposition rates of different fractions of spruce needle litter from numerous sites around two metal processing industries in central and southeastern Sweden, emitting Cu, Zn, Cd and Ni, and Pb, Ni and Cd, respectively. All measurements were performed under controlled laboratory conditions. At water capacity and 15?C a C02 evolution rate in partly disintegrated litter of ca 0.23 mg C/g dry matter, 24 hr was measured in samples with > 10 prmol Zn + Cu + Cd + Ni per g, compared with ca 0.50 mg C in samples with < 5 jimol/g. Highly significant negative correlations were obtained in all materials between heavy metal concentration and C02 evolution rate or dehydrogenase activity. It is concluded that, in acid forest sites, the general decomposition rate will be depressed even by moderate concentrations of heavy metal ions, at least during those parts of the year when the water supply is adequate.