Winter injury to red spruce at Mount Moosilauke, New Hampshire

Abstract

We report the severity and detailed spatial patterns of winter injury to red spruce (Picearubens Sarg.) in the winter of 1988–1989 and assess support for the desiccation and freezing hypotheses. Foliar injury was quantified at three elevations (840, 990, and 1140 m) and on east- and west-facing slopes in the spruce-fir zone at Mount Moosilauke, New Hampshire. Overall, 29% of current-year foliage on red spruce trees was killed by winter injury. Injury increased with elevation. There was a weak tendency for winter injury to be higher on the sun-exposed south sides of crowns, but substantial injury also occurred on shaded foliage. Injury increased markedly with height in crown at high elevation, but decreased with height at low elevation. The results appear inconsistent with desiccation as the main cause of winter injury. Elevational trends in foliar injury are consistent with the freezing hypothesis, but the strong trends in foliar injury by height within trees cannot be fully explained without further data on spatial variation in microclimate and freezing tolerance. Failure to break bud was assessed on the same spatial scales as foliar injury. Bud break was least in trees and crown sections with severe foliar injury. No evidence for winter injury was found on balsam fir (Abiesbalsamea (L.) Mill.). The results support the hypothesis that winter injury may contribute to the current decline of red spruce in the northern Appalachians.