White birch (Betula papyrifera Marshall) foliar litter decomposition in relation to trace metal atmospheric inputs at metal-contaminated and uncontaminated sites near Sudbury, Ontario and Rouyn-Noranda, Quebec, Canada.

Decomposition of white birch (Betula papyrifera Marshall) foliar litter was examined at metal-contaminated and uncontaminated sites established along gradients of soil Cu, Ni, Pb and Zn concentrations near Sudbury, Ontario and Rouyn-Noranda, Quebec. Over an 18-month study period, a significantly lower rate of litter mass loss was observed at the Sudbury contaminated site (S1) than at the uncontaminated site (S2). This result was not duplicated at corresponding sites (RN1, RN2) in Rouyn-Noranda, despite similar levels of soil metal contaminants and atmospheric inputs. Concentrations of metals in litter increased at all sites with time. However, the greatest litter Cu and Ni concentrations were observed at S1 (188 and 192 microg/g, respectively), a result of substantial net gains of these elements from atmospheric inputs. On a per hectare basis, Cu accumulation in litter at S1 approached recommended application rates of Cu as copper sulphate for control of fungal diseases in agricultural operations, indicating that the current rate of Cu smelter emissions in Sudbury may cause the observed impairment of decomposition.