Effects of a major ice storm on the foliage of four New England conifers

The mechanical damage to forests caused by winter ice storms is well known. The January 1998 ice storm in the northeastern United States and adjacent regions of Canada caused major forest damage to the area. Here we report on the physiological effects on four conifers that did not show visible signs of damage after the January 1998 ice storm. Cuticular conductances normally increase during winter. In this winter, they were high immediately after the storm, then fell 17-74% in the following 30-45 days in hemlock, red pine, and red spruce. We hypothesize that this was caused by the loss of damaged foliage with high cuticular conductances, over that period. Alternatively, damaged cuticles may have been repaired, although this seems less likely. Relative water contents were higher than normal in some species in the weeks after the storm, due either to an artifact of measurement introduced by the ice that coated needles or to short-term changes in the water-holding capacity of foliage. Water relations of white pine were least affected by this ice storm, whereas hemlock's were most affected. These ecophysiological results contrast with the structural effects of ice storms. Red pine is considered to be most sensitive to mechanical injury, while hemlock and red spruce are the least; white pine is intermediate. The order of sensitivity to physiological effects from a major ice storm appears to be hemlock and red spruce, followed by red pine, with white pine the least sensitive. Results from this study suggest that the physiological effects of ice storms can linger long after the ice melts from the canopy.