Effects of smelter pollutants on forest leaf litter decomposition near a nickel–copper smelter at Sudbury, Ontario

Abstract

Forest soils and litter in the vicinity of a large nickel–copper smelter at Sudbury, Ont. are known to be contaminated with a variety of heavy metals. In view of this, studies were carried out to determine if forest litter decomposition processes have been affected. The effects of nickel and copper on the decomposition of forest litter were investigated using a variety of techniques in which contaminated and control sites were compared. At contaminated sites an increase in litter standing crop was found. This was related to lower rates of litter decomposition at these sites, as evidenced by reduced rates of breakdown of litter in mesh bags, compared with uncontaminated sites. Lower rates of CO₂ flux and acid phosphatase activity were also found at the contaminated sites. In a laboratory experiment, the addition of copper and (or) nickel to a homogenate of leaf litter was shown to depress the rate of dry weight loss and CO₂ flux. Negative effects commenced at metal concentrations comparable to those observed in litter at contaminated sites in the field.