Recovery of white birch (Betula papyrifera Marsh.), red maple (Acer rubrum L.), and red oak ( Quercus rubra L.) growing on a smelter-impacted landscape following reductions of sulfur dioxide (SO2) emissions: A dendrochronological analysis

Dendrochronological methods were used to examine long-term changes in the radial growth of white birch (Betula papyrifera Marsh.), red maple (Acer rubrum L.), and red oak (Quercus rubra L.) trees growing along a 42 km transect from a Cu-Ni smelter in Falconbridge, Ontario, Canada following reductions of sulfur dioxide (SO 2) emissions. Radial growth of red oak was not related to SO2 emissions. In contrast, radial growth of white birch was reduced by 31% and 18% at distances of 1 km and 20 km respectively compared to the reference chronology (42 km from the smelter) between 1960 and 1978, when SO2 emissions were highest. Although less severe, a similar reduction in growth (13%) was observed in red maple chronologies 1 km from the smelter. The observed reductions in radial growth could not be explained by a climatic response model calibrated for the post emission reduction period (1978-2003), i.e. actual and predicted tree-ring chronologies between 1960 and 1978 were significantly different. After 1978, the radial growth of both red maple and white birch in the polluted sites was comparable to the incremental growth of trees growing on the reference site. Changes in radial growth corresponding with changes in emissions of SO2, and a significant negative correlation between radial growth and annual SO2 emission was found within 20 km of the Falconbridge smelter. (Abstract shortened by UMI.)...