The virgin beech-hemlock forest at Tionesta Research Natural Area (TRNA) is the last remaining 4,000 acres of a vast forest ecosystem that once dominated the northern Allegheny Plateau. Some believe that restoration of this pre-settlement beech-hemlock forest should be the goal of all forest management. This natural climax type evolved in the absence of both Beech Bark Disease (BBD) and the Hemlock Wooly Adelgid and with their presence it no longer may be attainable. Very large populations of beech scale (Cryptococcus fagisuga) were observed in 2000 while investigating areas of discoloration observed from the air at TRNA. Beech mortality reached 52% in the first 5 years, and it became obvious that the impact of BBD on old growth beech hemlock forests required deeper evaluation. We revisited a grid of 676 points established at TRNA by Zimmermann in 1984 to establish a baseline for monitoring forest change. Fifty-two of those 676 plots were chosen as a stratified random sample to study patterns of beech mortality and the influence of topographic position. Species, diameter, and crown position were recorded on prism plots following methods used by Zimmermann. Crown characteristics were recorded using Forest Health Monitoring protocols with additional records of beech scale, fungal conks and insect attacks from wood boring insects.
Results/Conclusions
In 1984, the American beech trees were healthy with only 4 to 13 percent mortality, mostly concentrated in lower slope positions. Otherwise, beech trees were healthy in 1984. In 2007, after the killing front passed through TRNA, the percent mortality in American beech was 50 percent initially, then reaching 80% by 3 years, with some variation among slope positions. Approximately 10 percent of the living trees had less than 50 percent live crown and 10 percent of the beech trees were healthy. Only the hemlock component of the beech-hemlock forest type remains in the main crown canopy. Hemlock wooly adelgid has not yet reached TRNA, but if it does, the beech-hemlock forest type will no longer exist at TRNA. The evidence of high mortality in this unmanaged forest, suggests that a goal of allowing succession to simply restore the beech-hemlock forest type is unrealistic.
