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Harvard Forest Symposium Abstract 2010

  • Title: Soil warming accelerates the nitrogen cycle: implications for changes in species composition
  • Primary Author: Sarah Butler (Marine Biological Laboratory)
  • Additional Authors: Frank Bowles (Research Designs); Jennifer Johnson (Marine Biological Laboratory); Jerry Melillo (Marine Biological Laboratory); Jacqueline Mohan (University of Georgia); Rose Smith (Marine Biological Laboratory); Paul Steudler (Marine Biological Laboratory); Chelsea Vario (Dartmouth College)
  • Abstract:

    Increases in soil temperatures associated with global warming have the potential to accelerate the nitrogen turnover in soils, which could alter other biogeochemical processes and eventually affect the composition of these forests. Over the first seven years of a large soil warming study, we observed significant changes to the nitrogen cycle with consequences for species composition. Since the start of the experiment, we have observed a 45% increase in net nitrogen mineralized. Nitrification rates have also increased in response to warming, growing from less than 5% of the total nitrogen mineralized at the beginning of the experiment to 25% in year seven. To date, we have seen little nitrogen solution and gaseous losses as a result of warming; however, we expect the nitrogen cycle to open as mineralization continues to increase. As warming begins to alter the nitrogen cycle, we may see shifts in forest composition associated with different species’ abilities to access different soil nitrogen pools. Based on nitrate reductase assays on leaves from canopy dominants, we hypothesize that some species, such as red oak, may be more capable of using nitrate as it becomes more readily available to plants, while other species, such as red maple, may use other nitrogen acquisition and retention strategies to compete in a warmer world. Our study suggests that considering species-specific responses to increases in nitrogen amount and form could be important in predicting future forest composition.

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