Stream Macroinvertebrate Communities in Paired Hemlock and Deciduous Watersheds

Tsuga canadensis (Eastern Hemlock) is a common forest species that is declining throughout its range in the eastern United States because of the invasion of an exotic forest pest, Adelges tsugae (Hemlock Woolly Adelgid). This pest kills infected trees, and over time, infected stands are replaced by deciduous forests. The conversion of forests from hemlock to deciduous species is predicted to impact the hydrology, chemistry, and biology of associated headwater streams. In this study, we examined the macroinvertebrate communities of two adjacent headwater streams with differing hemlock in uence in central Massachusetts. Abundance, taxa richness, diversity, and unique taxa were generally greater in the deciduous stream. Differences in the distribution of functional feeding groups were observed: the hemlock stream had a greater percentage of collector-gatherers while the deciduous stream had a greater percentage of shredders and predators. These  ndings suggest that macroinvertebrate communities in streams draining hemlock and deciduous watersheds may differ in structure and function, and that anticipated hemlock mortality may impact the region’’s stream ecology.