Episodic events can play an important role in influencing forest composition and ecology. Severe climatic events in eastern deciduous forests may contribute to the creation of canopy gaps and influence subsequent forest regeneration. We studied the impact on a forest community of a January 2005 ice storm that affected central Appalachian forests, particularly those at high elevations; while ice storms are common in central Pennsylvania, rarely do they cause the levels of damage that accompanied this particular storm. Our study was conducted in an oak dominated second growth forest at the Hawk Mountain Sanctuary in Kempton, PA. During summer 2005, two 1500 m x 5 m belt transects, one on the ridge and one on a lower elevation slope, were established to evaluate the identity and DBH of damaged and undamaged trees of all species and the proportion of the canopy broken for each damaged tree. In 2006, we initiated a three year study of the total number of seedlings and the height and leaf number of all seedlings growing in a 5 m x 5 m plot surrounding a damaged tree and a second plot surrounding a nearby undamaged tree; seedlings were studied in a set of ten such pairs of canopy-damaged and undamaged trees on the ridge and ten pairs of trees on the lower slope.
Results/Conclusions
A similar proportion of all trees had ice-caused canopy damage on the lower slope forest (23.3%) compared with the ridgetop forest (20.7%); the proportions of damaged trees in the two sites were statistically indistinguishable. On the slope site, trees with damaged canopies had a larger DBH (52 cm) compared with the DBH (35cm) of undamaged trees while on the ridgetop there was no difference in DBH of damaged and undamaged trees. Preliminary assessment of seedling growth data suggests that the size of seedlings beneath ice-damaged trees is not dramatically different from that of seedlings growing beneath the canopy of undamaged trees. The importance of episodic events, as represented by the 2005 ice storm at Hawk Mountain, on subsequent forest regeneration may need to be re-evaluated.
