Climate and red spruce growth and decline in the northern Appalachians.

Between the mid-1960s and mid-1980s, red spruce (Picea rubens Sarg.) died at unusual rates on the mountains of New York and western New England. We determined the relationship between standardized tree ring widths and monthly climate data for calibration and verification periods from 1856 to 1981 and found that after about 1960, there was a distinct shift in the temperature variables related to standardized ring widths in vigorous spruce. The beginning of widespread spruce mortality, regionwide growth decreases, and the shift in response to climate in the early 1960s corresponds to the onset of a decade of unusually cold winters and several consecutive years when severe winter damage was noted across the Northeast in this species. We suggest that the episodes of winter damage are an important initiating and synchronizing factor in the red spruce decline.