Decreased resistance to embolism in red maple (Acer rubrum L.) saplings within a heavy metal contaminated region

• Cu–Ni smelter effects increase vulnerability of red maple to xylem embolisms.
• Percent loss of conductance correlated with soil metal concentration.
• Branch and stem mortality in metal-affected trees may result from vulnerable xylem.

The effects of smelter-damaged environment on embolism resistance in red maple (Acer rubrum L.) were investigated with stems of saplings collected in situ from within either the metal-contaminated (mainly Cu and Ni) region of Sudbury, Ontario, or from within the uncontaminated surrounding regions. Current levels of aerial pollution in all regions are low. Hydraulic conductivity was measured after stems were flushed for 40 min and then being spun using the centrifuge technique at −3 MPa. Red maple saplings from within the metal contaminated region had about twice the percent loss of conductivity, due to embolisms, as saplings from outside the contaminated region. Sapling vulnerability to embolism shows contrasting trends with age in contaminated and non-contaminated regions. The increased vulnerability of trees to catastrophic xylem dysfunction under drought may contribute to the observed stunted growth and periodic stem-dieback of trees in metal-contaminated landscapes, the effects being exacerbated by the thin soils.