The aim of this research project was to use 15N nuclear magnetic resonance (NMR) spectroscopy to better understand nitrogen (N) cycling processes in forest plantations. In particular, the studies were designed to link to the effects of forest management practices and environmental conditions. 15N NMR cross polarization/magic angle spinning (CPMAS) and dipolar dephasing (DD)-CPMAS experiments of some simple N-containing compounds found widely in nature were first undertaken. This was done in order to understand how different sample conditions, such as the presence of moisture, sample mixing and dilution, affected the intensity and the observability of the NMR peaks corresponding to N containing functional groups. Our results exhibited changes in NMR signal intensities and various time constants calculated. In the case of variable contact time experiments, use of an equation that predicts both a bi-exponential rise and decay was found to fit the data obtained more accurately. The optimised parameters for 15N NMR CPMAS were then used along with other analytical techniques such as ion chromatography, total C and N and elemental analyses to study plant nutrient uptake, plant decomposition and the effect of forest ecosystem disturbances, in this case an insect infestation. These analytical data were also correlated with the changes in the 13C NMR spectra in order to gain a more comprehensive understanding of the chemical transformations in the forest ecosystem. / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:ADTP/235511 |
| Date | January 2008 |
| Creators | George, Laurel, University of Western Sydney, College of Health and Science, School of Natural Sciences |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
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