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Harvard Forest Research Project 2022

  • Title: Variations in soil legacy effects after a hemlock removal experiment
  • Principal investigator: Corey Palmer (
  • Institution: University of Massachusetts - Amherst
  • Primary contact: Corey Palmer (
  • Team members: Ashley Keiser
  • Abstract:

    Soil communities can retain many of the functional characteristics of their former ecosystem after disturbance events (Crowther et al., 2019). These historical legacies can influence function in a post-disturbance environment. A common disturbance to northeastern forests has been the introduction of invasive species, including the hemlock woolly adelgid (HWA). The HWA was found in the Northeast in the 1980s, and since then has changed forest ecosystem dynamics by causing the decline of eastern hemlock stands throughout the region (McClure, 1990; Orwig et al., 2002). Due to soil microbial functional legacies, we do not know if HWA-invaded forests and those that have transitioned to a new dominant overstory will cycle C and nutrients differently than the surrounding hardwood forest stands. In 2005, Harvard Forest began a Hemlock Removal Experiment to investigate effects on forest dynamics due to the HWA. This experimental manipulation in combination with the subsequent northward progression of the HWA invasion has created a disturbance gradient within Harvard Forest. Our objective is to examine changes in decomposition and biogeochemical cycling in post-HWA invasion stands across an invasion gradient simulated in a natural environment. To address this objective, we are proposing a litterbag decomposition experiment at six sites in the hemlock removal experiment to examine how soil legacy effects have changed in transitional hemlock stands. We plan to sample at the Simes tract and Hemlock Removal Experiment plots 1 – 6. This includes two control plots, two logged hemlock plots, and two girdled hemlock plots. Tree species in each plot will be recorded as well as understory vegetation by percent cover. Litter will be collected from adjacent eastern hemlock stands, as well as from nearby yellow birch and sugar maple stands. Litter bags will be deployed in November 2021 and collected after 6, 11, 18, and 23 months. Soil samples down to 15 cm in the control and experimental plots will be taken corresponding to each litter bag at each collection date. Samples will be brought back to the University of Massachusetts Amherst for analysis of carbon, nitrogen, mass loss, and microbial functional parameters such as microbial biomass and enzyme activity.

    Crowther, T. W., van den Hoogen, J., Wan, J., Mayes, M. A., Keiser, A. D., Mo, L., Averill, C., & Maynard, D. S. (2019). The global soil community and its influence on biogeochemistry. Science, 365(6455).
    McClure, M. S. (1990). Role of Wind, Birds, Deer, and Humans in the Dispersal of Hemlock Woolly Adelgid (Homoptera: Adelgidae). Environ. Entomol, 19(1), 36–43.
    Orwig, D. A., Foster, D. R., Mausel Harvard Forest, D. L., Forest, H., & Box, P. (2002). Landscape patterns of hemlock decline in New England due to the introduced hemlock woolly adelgid. Journal of Biogeography, 29, 1475–1487.