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Harvard Forest Research Project 2022

  • Title: Soil Warming at Harvard Forest
  • Principal investigator: Serita Frey (
  • Institution: University of New Hampshire - Main Campus
  • Primary contact: Serita Frey (
  • Team members: Kristen DeAngelis; Melissa Knorr; Thomas Muratore; Joshua Trombley
  • Abstract:

    The Harvard Forest maintains three distinct and complimentary long-term soil warming experiments:

    1. The Prospect Hill Soil Warming Experiment (29 years of soil warming), begun in 1991, was designed to examine the effects of soil warming on soil carbon and nitrogen cycling. More recently, we have also begun studying microbial responses to warming, including changes in microbial community structure and function.

    2. The Barre Woods Soil Warming Experiment (17 years of soil warming), begun in 2003, was designed to explore the effects of soil warming on carbon and nitrogen interactions at the ecosystem level, with a particular focus on how an enhanced nitrogen cycle in response to warming affects carbon storage in the vegetation.

    3. The Soil Warming and Nitrogen Addition Study was initiated in 2006 (14 years of warming) to examine how warming and N additions interact to influence soil microbial metabolism and microbial community dynamics, soil C and N cycling, and soil CO2 flux. This experiment, installed adjacent to the existing soil warming plots on Prospect Hill, has four treatments (control, heated +N, heated+N, +N only) and six replicates in a randomized block design. Average soil temperature in the heated plots is elevated 5C above ambient by the use of buried heating cables placed at 10 cm depth in the soil and spaced 20 cm apart. The heating cables are controlled by a data logger that monitors thermistors (5 per plot) every 10 min. Plots automatically turn on and off to maintain a 5C temperature difference between the heated and control plots. The N addition plots (heated +N, +N only) are fertilized following the protocol of the Harvard Forest Chronic N Addition Study. An aqueous solution of ammonium nitrate is applied at a rate equivalent to the low N plots at the chronic N study (5 g N per square meter per year). Fertilizer is applied in equal monthly doses during the growing season (Apr-Oct). The control plots and unfertilized, heated plots (heated+N) receive water only.