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Harvard Forest REU Symposium Abstract 2006

  • Title: Chronic Nitrogen Additions Affect Aboveground Sporocarp Diversity in Hardwood Stand
  • Author: ()
  • Abstract:

    Studies in Europe and Alaska have shown that elevated levels of nitrogen deposition affect diverse fungal communities, which play an important role in the forest ecosystem by recycling organic matter and supporting symbiotic relationships with trees. In the Northeastern U.S., forests experience the highest levels of nitrogen deposition in the country, however little is known about the consequences of such nitrogen additions with respect to fungal communities. This study utilized nine subplots within the long-term Chronic Nitrogen Addition Study at Harvard Forest in Petersham, MA to monitor the growth of aboveground fruiting bodies during the summer of 2006. The abundance of ectomycchorizal sporocarps was expected to decrease with increased nitrogen saturation of the soil. At the experimental site, two 30 x 30 m plots have been amended with low and high levels of nitrogen since 1986, and an adjacent control plot serves as reference to a healthy forest. The low nitrogen treatment receives 5 g N m-2yr-1 in the form of NH4NO3 (ammonium nitrate) and the high nitrogen treatment receives 15 g N m-2yr-1. Three 5 x 5 m subplots in each treatment were randomly selected for this sporocarp study. Once a week for six weeks, every mushroom on each subplot was collected for identification. Statistical analysis showed a significant decrease in the number of ectomycchorizal sporocarps across the nitrogen gradient. These findings support the hypothesis that trees growing in nitrogen saturated soil need not utilize a symbiotic relationship with belowground ectomycchorizal fungi. Saprotrophic species also showed sensitivity to nitrogen saturation, such as Marasmius capillaris whose abundance significantly decreased with increasing nitrogen. These results confirm the vulnerability of fungal communities under conditions of elevated nitrogen deposition.

  • Research Category: Soil Carbon and Nitrogen Dynamics