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Harvard Forest REU Symposium Abstract 2015

  • Title: Metatranscriptomic Analysis of warmed forest soils suggests divergence of community biogeochemical functions over time
  • Author: Josia V DeChiara (Hampshire College)
  • Abstract:

    The soil has been shown to be one of the largest carbon stores, of which as much as 50-70% is stored by roots or root-associated microorganisms. As the global temperature continues to rise, the relationship between temperature and microbial carbon cycling is ever pertinent. At the Harvard Forest in Petersham, MA, three experimental warming plots have simulated climate change since 1991, 2003, and 2006 by heating the soil to 5º C above the ambient temperature using underground heating cables. An initial increase in respiration and nitrogen mineralization yielded higher growth rates in plants. As the experiment progressed, plant growth stagnated, hypothetically due to a different limiting nutrient. Through measurements of phosphorus content in green and dead leaves, it was observed that phosphorus was being reabsorbed by trees at a higher rate in the heated plots. This led to the hypothesis that phosphorus was stoichiometrically limiting the amount of usable carbon and nitrogen. Phosphorus is found in organisms in phospholipid bilayer, nucleic acids, and adenosine triphosphate, making it an essential biological element. In this study, the role of phosphorus metabolism was examined through analysis of metatranscriptomic data. Nucleic acids were extracted from soils, sequenced, and annotated to determine biological functions. The Mann-Whitney-Wilcoxon test was used to determine genes whose abundance changed with the treatment. These analyses revealed: (1) transcript abundance diverges as heating time increases; (2) changes in gene abundance are evident in in phosphorus and other biogeochemical cycles; and (3) indicator genes for specific metabolic pathways.

  • Research Category: Ecological Informatics and Modelling; Group Projects; Large Experiments and Permanent Plot Studies; Soil Carbon and Nitrogen Dynamics