Distribution, composition, and orientation of down deadwood in riparian old-growth woodlands of Zoar Valley Canyon, western New York State, USA

During 2005, we catalogued down deadwood (DDW) in forty-one 30-m × 30-m quadrats on 10 riparian upper terraces within the minimally disturbed Zoar Valley Canyon of western New York State. Woodlands on these former floodplains represent late-successional stages of a diversity of broadleaf ecotypes, with increment core-based stand ages up to 351 years. Volume of DDW averaged 84.9 ± 9.7 (±S.E.) m3/ha among all quadrats, and ranged up to 145.3 ± 43.2 m3/ha on individual terraces. Abundance of downed sugar maple reflected this species’ prevalence in the live overstory, but American beech deadwood was markedly overabundant due to beech bark disease mortality. Prevalence of very-shade-tolerant (sugar maple, American beech, eastern hemlock) DDW was modest for northern hardwood old growth (46.4 ± 4.3% among all quadrats), and was not related to stand age. We speculate this may reflect the floodplain origin of these woodlands. Down deadwood volume was positively associated with stand age among terraces (R2 = 0.446, P = 0.035), but not at the neighborhood scale of 30-m quadrats (R2 = 0.027), where individual tree mortality may obscure broader patterns. Orientation of DDW was non-uniform (Kolmogorov–Smirnov goodness-of-fit, P < 0.05) on five of the ten study terraces, where statistical trends in treefall direction suggested the influence of prevailing westerly winds blowing through the east-west canyon (this DDW orientation was also opposite to stream flow). This was an unexpected result, however, as we otherwise found very limited evidence of episodic wind-throw within the study area.