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Harvard Forest Research Project 2022

  • Title: Chronic Nitrogen Amendment Plots
  • Principal investigator: Serita Frey (
  • Institution: University of New Hampshire - Main Campus
  • Primary contact: Serita Frey (
  • Team members: Serita Frey; Melissa Knorr; Jennie Wuest
  • Abstract:

    The Chronic Nitrogen Amendment Study, started in 1988, is an investigation into the effects of increasing anthropogenic atmospheric nitrogen (N) deposition on forests in the eastern United States. Located in a mixed hardwood forest, the treated plots have received 50 and 150 kg N per hectare per year, as ammonium nitrate fertilizer, in six equal monthly applications during the growing season each year since the start of the experiment (the highest N level was terminated in 2019). Regular measurements have been made over the past 32 years to assess tree biomass production and mortality, foliar chemistry, litter fall, and soil carbon, nutrient and microbial community dynamics.