The contribution of beech bark disease-induced mortality to coarse woody debris loads in northern hardwood stands of Adirondack Park, New York, U.S.A.

Abstract

The objective of this study was to adjust previously published estimates of coarse woody debris (CWD) volume and basal areas in northern hardwood forests to account for elevated CWD inputs due to beech bark disease (a disease complex of the scale insect, Cryptococcus fagisuga Lindinger, and a fungus, Nectria spp., on American beech, Fagus grandifolia Ehrh.). Ratios of snags/live tree densities and downed CWD volume/live tree basal area were compared between beech and the codominant, shade-tolerant sugar maple (Acer saccharum Marsh.). The differences between the beech and the sugar maple ratios were used to define the elevated mortality from beech bark disease. Estimated volumes of downed CWD (stumps [Formula: see text] 1.0 m tall and logs), adjusted for effects of beech bark disease, were 108 ± 18 and 48 ± 11 m3·ha-1in old-growth and even-aged, 90- to 100-year-old maturing stands, respectively, representing reductions of 22 and 21%, respectively, compared with observed volumes. Similarly, snag densities were adjusted from 59.7 ± 21.7 to 41.1 ± 26.3 per hectare in the old-growth stands and from 96.3 ± 48.0 to 87.3 ± 46.5 per hectare in the maturing stands. Snag basal areas were reduced 21 and 17% from their observed values to 6.8 ± 3.5 and 3.5 ± 0.6 m2·ha-1in the old-growth and maturing stands, respectively. The adjusted CWD estimates presented here are more historically accurate and ecologically meaningful than previous observations made in diseased northern hardwood forests and, therefore, provide more appropriate target levels for managing CWD in these forest types.