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Harvard Forest Symposium Abstract 2011

• Title: Chronic N amendment experiment alters bacterial community structure at Harvard forest, MA.
• Primary Author: Rakesh Minocha (USDA Forest Service)
• Additional Authors: Premsai Bhiravarasa (University of New Hampshire - Main Campus); Subhash Minocha (University of New Hampshire); William Thomas (University of New Hampshire); Louis Tisa (University of New Hampshire); Swathi Turlapati (University of New Hampshire - Main Campus)
• Abstract:

  Swathi A. Turlapati1, Rakesh Minocha*2, Premsai S. Bhiravarasa1, Louis S. Tisa3, William K. Thomas3,4, Subhash C. Minocha1
  
  1Department of Biological sciences, University of New Hampshire, Durham, NH 03824, USA
  
  2*USDA Forest Service, Northern Research Station, Durham, NH 03824, USA
  
  3Department of Molecular, Cellular and Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA
  
  4Hubbard Center for Genome Studies, University of New Hampshire, Durham, NH 03824, USA
  
  
  
  
  
  This study was undertaken to examine the potential impacts of N fertilization on forest soil bacterial communities at a Long-Term Ecological Research site; Harvard Forest, MA). At Harvard Forest, chronic nitrogen plots were established in the year 1988. Nitrogen was applied in the form of ammonium nitrate. To analyze the composition and diversity of the bacterial communities, we used bar-coded pyrosequencing technique. PCRs were conducted on DNA isolated from 30 soil samples (5reps*3treatments*2 organic and mineral soil horizon) collected in fall of 2009 from a control plot (untreated plot), low N (receives 50kg ha-1year-1) and high N (receives 150 kg ha-1year-1). Primers that target the V6-V8 hypervariable regions of the bacterial 16SrRNA universal gene with 30 different MID tags were used to amplify a 434 base pairs product. These products were sequenced by 454 pyrosequencing. Data were analyzed using QIIME (Quantitative insights into microbial ecology) workflow with 40.4k reads obtained from a single lane (1/16) of a 454 full plate. Among the various groups identified, Acidobacteria represented the dominant phylum followed by Proteobacteria and Verrucomicrobia. The proportions of several bacterial phyla varied greatly among the three treatments. Alpha diversity and Beta diversity determinations included rarefaction analyses with richness indicators, pairwise UniFrac distances among samples and Principal Coordinate analysis demonstrated variability in the bacterial community composition among the 3 treatments. Diversity Richness indicators depicted greater bacterial diversity in the high N treatment plots than in the control plots. Together, these results highlight the importance of nitrogen in structuring bacterial communities. Soil chemistry of organic soils is different from mineral soils in having significantly higher levels of most measured parameters. However, unlike previous observations during 1990's, N treatments had very little effect on soil chemistry of both horizons 20 years after chronic N additions. Data analysis with 1.3 million reads obtained from a whole plate run is in progress.

• Research Category: Biodiversity Studies
  Ecological Informatics and Modelling
  Large Experiments and Permanent Plot Studies


• Figures:
Fig. 1-org and Min soils.pdf
Fig. 2 Treatment effects.pdf
Fig 3. PCA Plot.pdf
Fig. 4 Soil Chemistry Table.pdf