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Harvard Forest Symposium Abstract 2012

  • Title: Effects of Soil Warming on Carbon Storage and Nitrogen Cycling
  • Primary Author: Lindsay Scott (Marine Biological Laboratory)
  • Additional Authors: Chelsea Baldino (Marine Biological Laboratory); Frank Bowles (Research Designs); Sarah Butler (Marine Biological Laboratory); Jerry Melillo (Marine Biological Laboratory); William Werner (Marine Biological Laboratory)
  • Abstract:

    Soil warming has the potential to alter both soil and plant processes that affect carbon storage in forest ecosystems. We have quantified these effects in a large, long-term (nine-year) soil warming study at Harvard Forest. Warming continues to stimulate the decomposition of soil organic matter and the loss of soil carbon as carbon dioxide to the atmosphere. Soil organic matter decay also continues to release inorganic nitrogen into soil solution that is leading to increased plant productivity and carbon storage in woody tissues. Soil warming has resulted in a mean annual net loss of about 1 Mg C from the forested area relative to a control area over the nine-year study, with the annual losses being partially reduced over time as plant C storage increases. On average, woody biomass C has accumulated at a rate of about 1 Mg C per year more in the heated area relative to the control. We attribute the plant gains primarily to warming-induced increases in nitrogen availability. Since the start of the experiment, we have observed a 40% mean annual increase in net nitrogen mineralization and a 15N enrichment of about 1.5 ‰in green leaves at the peak of the growing season in the heated area. Over the nine-year study, the percentage of mineralized nitrogen converted to nitrate in the heated area has ranged from 8% (year 1) to 27% (year 7) with an annual mean nitrification rate of 15 kg N ha-1yr-1. This study underscores the importance of incorporating carbon-nitrogen interactions in coupled earth system models to accurately simulate land feedbacks to the climate system.

  • Research Category: Large Experiments and Permanent Plot Studies
    Soil Carbon and Nitrogen Dynamics