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Harvard Forest REU Symposium Abstract 2005

  • Title: Foundation laid to monitor changes in stream and soil nitrogen dynamics following hemlock woolly adelgid and logging in hemlock-dominated watersheds
  • Author: Charles L Boyd (Centre College)
  • Abstract:

    The hemlock woolly adelgid (Adelges tsugae, HWA) is an exotic aphid-like insect killing hemlock populations in the eastern United States. Harvard Forest research has focused on studying the effects of HWA and logging on forest systems in New England. Research is now beginning to look at HWA’s effect on aquatic systems. This is the first study that begins to look at the direct effects of HWA and HWA-induced salvage logging on stream nitrogen dynamics. Two infested watersheds, one urban site in Boston and one rural site in central MA, were selected for study. Both sites contain mature second-growth hemlock-dominated forests with first order streams. I examined N availability in the soils and N concentrations in the streams draining both hemlock-dominated watersheds. The urban watershed soils had 20 times greater NH4+ availability and 200 times greater NO3- availability than the soils of the rural watershed. Urban stream N concentrations were also higher than the rural watershed. The increased N influx in Boston is likely the result of greater N deposition.

    Both sites have potential for valuable future research. Since the urban N data was collected, Arnold Arboretum clear-cut the hemlocks in four experimental urban plots. The pre-cut urban N data I analyzed will serve as pre-treatment data for ongoing post-cut data. Although present, HWA has not yet significantly reduced hemlock health in the rural site. The data I analyzed from the rural watershed will serve as baseline data for continuing data collection as HWA reduces hemlock health in this site.

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