Localized Ice Storm Damage in an Appalachian Plateau Watershed

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During 19-20 January 1986 a storm deposited up to 3 cm of glaze ice on trees in lower slope and valley bottom positions in Neotoma Valley, an unglaciated, 72-ha forested watershed in S-central Ohio. In contrast, upper slope and ridge top positions received approximately 7 cm of wet snow but little glaze ice. Most of the ice damage occurred in the valley bottom and on the mid-lower SW-facing slope. In this area, approximately 15.5% of the trees, comprising 13 Yo of the basal area, were severely damaged. A larger proportion of needle-leaved trees suffered severe damage than of broad-leaved canopy trees. Understory trees suffered the least damage. To best estimate species susceptibility, we separated direct storm damage from secondary damage caused by the falling of directly damaged tree limbs and trunks onto other trees. Needle-leaved trees suffered much more direct damage than broad-leaved trees, presumably because of the greater surface area presented by the needles. Among all species the degree of direct damage was positively correlated with tree height, tree diameter and canopy crown diameter, but not with root crown diameter or slope aspect/elevation within the damage area. In contrast, secondary damage was uncorrelated with any biological or physical parameter measured. This indicates that the probability of direct ice damage can be predicted from tree form and overall position in the watershed but that secondary damage is too stochastic in nature for meaningful prediction. On the SW-facing slope most of the trees killed by ice damage were early successional pines; in contrast, most damage on the NE-facing slope was to larger, older oaks and beech. As a result, we predict that succession will be affected differently on the two slopes.