Interactions between invasive herbivores and their long-term impact on New England hemlock forests

摘要: The introduction of the hemlock woolly adelgid (Adelges tsugae) in eastern United States has caused extensive damage to (Tsuga canadensis) stands. presence other herbivores can affect density and health. Here, we report results long-term work monitoring forests a 7,500 km2 latitudinal transect southern New England. In biannual surveys between 1997 2011, assessed change basal area, stand-level defoliation, four exotic (A. tsugae, Fiorinia externa, Nuculaspis tsugae an unidentified sp.) explored relationships biotic abiotic variables. Hemlock area decreased by approximately 60 % over 14 years study. stand defoliation increased locally some stands but on average did not throughout study period/area. Local increases were probably driven northward expansion A. certain extent co-occurring F. externa scales. Average during also expanded dramatically northward, although its impact only reduced Stand-level variation densities was most strongly affected scales, which present about 80 While continues be primary threat hemlock, needs studied context broader herbivore community.