Toward understanding the nature of the soil microsite in relation to nitrogen and carbon cycling Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/h989r655t

Descriptions

Attribute NameValues
Creator
Abstract or Summary
  • My research has focused on understanding N and C cycling in soils at small scales. Isotope dilution methods commonly used to estimate gross rates of soil chemical transformations assume homogeneous distribution of label. I explored the effects of diffusion limitations on isotope dilution experiments in soil aggregates using spherical diffusion-reaction models. Equations describing transport and reaction assumed Fickian diffusion, linear-equilibrium adsorption, zero-order production of natural abundance NH₄⁺, and either pseudo-first-order or zero-order consumption of ambient and label NH₄⁺. In the case of pseudo-first-order consumption, rate calculations were sensitive to substrate adsorption coefficient, but not to other transport parameters; however, rates calculated from simulations assuming zero-order consumption underestimated both rates of production and consumption. These simulations reemphasize the need to optimize experimental protocols when performing isotope dilution experiments in structured soils. I also explored soil microsite heterogeneity of C and N assimilation using time-of-flight secondary ion mass spectrometry (TOF-SIMS). I have shown that TOF-SIMS is capable of detecting N assimilation in bacterial and fungal biomass and both C and N assimilation in individual bacterial cells. I extended this research to explore factors that might affect differential NH₄⁺ and NO₃⁻ assimilation by soil microbes. Model systems were created with kaolin clay (labeled with ¹⁵NO₃⁻), straw, and manure. The spatial relationship of N assimilation by fungal hyphae was preserved on Si contact slides. Analysis of the slides showed nearly a 100% change between in ¹⁵N content of hyphae that were associated with manure and hyphae that were associated with straw. This was presumably due to a relatively higher ¹⁴NH₄⁺: ¹⁵NO₃⁻ ratio near the manure. This dramatic change in assimilation of N sources occurred over relatively short distances of 40 to 200 μm. Although further experimentation is required to fully understand the mechanisms controlling the bioavailability of NH₄⁺ and NO₃⁻ at this scale, these results illustrate the powerful potential of TOF-SIMS to explore microbial activity at the sub-mm scale in soil systems.
License
Resource Type
Date Available
Date Issued
Degree Level
Degree Name
Degree Field
Degree Grantor
Commencement Year
Advisor
Committee Member
Academic Affiliation
Non-Academic Affiliation
Subject
Rights Statement
Peer Reviewed
Language
Digitization Specifications
  • File scanned at 300 ppi (Monochrome, 256 Grayscale) using Capture Perfect 3.0.82 on a Canon DR-9080C in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR.
Replaces
Additional Information
  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2012-06-15T17:25:47Z (GMT) No. of bitstreams: 1CliffJohnB2002.pdf: 2783783 bytes, checksum: ac2e3a67c9b8d6c8a4070a82ebe364cb (MD5)
  • description.provenance : Submitted by Eric Hepler (ehscanner@gmail.com) on 2012-06-07T22:18:38ZNo. of bitstreams: 1CliffJohnB2002.pdf: 2775268 bytes, checksum: bd9a2659c6530192ec10de26471a1b20 (MD5)
  • description.provenance : Submitted by Eric Hepler (ehscanner@gmail.com) on 2012-06-15T17:18:38ZNo. of bitstreams: 1CliffJohnB2002.pdf: 2783783 bytes, checksum: ac2e3a67c9b8d6c8a4070a82ebe364cb (MD5)
  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2012-06-15T19:26:51Z (GMT) No. of bitstreams: 1CliffJohnB2002.pdf: 2783783 bytes, checksum: ac2e3a67c9b8d6c8a4070a82ebe364cb (MD5)
  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2012-06-15T15:58:08Z (GMT) No. of bitstreams: 1CliffJohnB2002.pdf: 2775268 bytes, checksum: bd9a2659c6530192ec10de26471a1b20 (MD5)
  • description.provenance : Made available in DSpace on 2012-06-15T19:26:51Z (GMT). No. of bitstreams: 1CliffJohnB2002.pdf: 2783783 bytes, checksum: ac2e3a67c9b8d6c8a4070a82ebe364cb (MD5) Previous issue date: 2001-06-08
  • description.provenance : Rejected by Patricia Black(patricia.black@oregonstate.edu), reason: replace file on 2012-06-15T17:14:05Z (GMT)

Relationships

Parents:

This work has no parents.

Last modified

Downloadable Content

Download PDF

Items