Changes in Red Spruce Populations in Montane Forests of the Appalachians, 1982-1987

Abstract

-A resurvey of red spruce (Picea rubens Sarg.) along 10.4 km of transects showed that between 1982 and 1987 there was a substantial increase in the proportion of dead canopy-sized spruce at elevations between 650 and 1220 m at three sites in the Adirondack, Green and White mountains of the northeastern United States. Overall, the percent of dead canopy spruce (>10 cm dbh and >1.37 m tall) along the transects increased from 26.1% in 1982 to 36.7% in 1987. Most of the mortality at higher elevations (>900 m) appears to have resulted from the death of individuals that were severely declining in 1982. There was no change in dead spruce or crown vigor between 1982 and 1987 at four of the six southern Appalachian sites. A decrease in crown vigor was observed at Mt. Mitchell (N.C.) and Roan Mt. (Tenn.), at least some of which was associated with damage from a recent ice storm. INTRODUCTION A marked decrease in the basal area and density of live red spruce (Picea rubens Sarg.) occurred in high-elevation (>900 m) spruce-fir forests of the northeastern United States between the mid-1960s and the early 1980s (Siccama et al., 1982; Johnson and Siccama, 1983; Scott et al., 1984; Johnson and McLaughlin, 1986). This reduction in live trees was concentrated in three regions of the northern Appalachian Mountain chain: the Adirondacks, the Green Mountains and the White Mountains. There is no agreement on the causes of the mortality which has most often been called a because several factors such as air pollution, climatic events and secondary pathogens are probably involved. A survey of 11 mountains in 1982 showed that there was about 25% standing dead spruce and extensive crown dieback of live trees at elevations above 900 m at five sites in the northern Appalachians and Adirondacks (Johnson and McLaughlin, 1986). In 1982, there was little evidence of severe dieback (death of needles and twigs in the live crown) below 900 m in the northern Appalachians, and no evidence of dieback or decline of red spruce at the southern Appalachian sites. In 1987 we repeated the 1982 study following the same sampling design to monitor changes over time in the proportion of dead and declining spruce trees in the region. METHODS Five northern and six southern Appalachian sites were sampled in each survey (Fig. 1). All forest sites were considered multiaged stands (Johnson and McLaughlin, 1986). Three of the northern sites, Mt. Mansfield (Vt.), Mt. Washington (N.H.), and Whiteface Mountain (N.Y.) were intensively sampled. At these sites, a total of 56 transects, 100 m long and parallel to the topographic contours, were located on Eand W-facing slopes at 50-m altitudinal intervals. Elevations were chosen to cover the widest range of spruce importance: the lower elevational limit of the transects was 650 or 700 m depending on the presence of spruce in the forest; the upper limit was usually 1150 m, which is near the upper limit of