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Harvard Forest REU Symposium Abstract 2016

  • Title: Determining the Effects of Deuterium on Active Soil Microbial Communities.
  • Author: Tirsa R Bonilla (University of Massachusetts - Boston)
  • Abstract:

    As simple as the soil may appear, it consists of a whole world of varying microscopic organisms. In the long-term soil warming experiments at Harvard Forest, respiration has increased in the warmed plots as compared to the control. Many microorganisms are found within the soil making it difficult to identify those contributing most to these changes in respiration. This summer, we used stable isotope probing to isolate the active microorganisms in the soil community. The stable isotope used was deuterium (D2O), a form of hydrogen that contains one additional neutron, which is also known as heavy water. Water is linked to the respiration pathway in all organisms because the oxygen in water is used as the final electron acceptor in respiration. Similarly, the oxygen in deuterium oxide will be used to complete respiration. The organisms that take up the isotope are responsible for higher respiration because they comprise the active component of the soil community. Organic and mineral horizon soil samples were collected off-plot at Harvard Forest's Prospect Hill. Data shows that samples treated with 100% deuterium and samples treated with only water have no statistically significant difference in respiration, but have a distinct difference in respiration between homogenized and intact soils. Through the data acquired, it seems that the difference in soil moisture levels affects respiration in homogenized and intact soil samples. Further experimentation must be done to test these hypotheses.

  • Research Category: Large Experiments and Permanent Plot Studies