Betsy Colburn

Harvard Forest

Primary Interests:

freshwater ecology, streams, vernal pools, macroinvertebrate communities, functional feeding groups, stream salamanders

HWA Objectives:

Stream flora and fauna, as well as ecosystem processes such as carbon processing and transport, are tightly coupled to plant community composition and structure in the watershed. Changes in watershed land use or plant communities can affect hydrology, water temperatures, and water chemistry, and through them, the stream biota. Hemlock (Tsuga canadensis (L.) Carriere), one of the longest-lived and most shade-tolerant forest trees, is an important riparian species in cool, shaded ravines, and it is found commonly in wooded swamps and in mid-slope communities. In New England, where many small streams are surrounded by hemlock, the potential loss of hemlock forests to invasion by an introduced insect, the hemlock woolly adelgid (HWA), has the potential to alter radically the physical, chemical, and biological conditions in streams. Preliminary research by the US Geological Survey in the Delaware Water Gap National Recreation Area suggests significant differences in water quality and biota of streams draining hemlock and hardwood-dominated stands. We are initiating studies in which we compare small, headwater streams in hemlock-dominated catchments with streams in deciduous forests. This research is complementary to ongoing studies on forest community composition and ecosystem function in relation to HWA and should further promote our understanding of potential regional-scale impacts of hemlock decline.We predict that watershed-level changes associated with woolly adelgid-induced hemlock decline will alter stream habitat (hydrology; chemistry, including color, DOC, pH, alkalinity, and dissolved nutrients; temperature; and physical structure) and will produce reorganization of food webs including distribution of functional feeding groups and dominance of top predators.