Mortality trends in a southern Appalachian red spruce population

Abstract

Mortality of red spruce ( Picea rubens Sarg.) was assessed in an old-growth spruce-fir forest before and after adelgid-induced mortality of canopy fir at about 1985. Mortality rates of red spruce canopy trees remained low (less than 2% year −1) following the loss of fir from the canopy. However, the proportion of mortality attributable to wind increased from less than 60 to 90%. Transects placed in areas of concentrated wind damage revealed that uprooting or snapping accounted for 94% of the mortality of spruce canopy trees in the winter of 1987–1988. The transect data were biased toward wind-damaged areas and revealed the potential impact of wind-related mortality on spruce. There was no evidence of atypically high wind velocities in the general area, or of a decline in the radial growth of spruce trees prior to death. It was concluded that the loss of Fraser fir ( Abies fraseri (Pursh) Poir.) from adelgid infestation has increased wind exposure to the remaining canopy trees. The increased exposure of southern Appalachian red spruce to wind must be considered in studies of its health.