| Summary: | Thesis (Ph.D.) University of Alaska Fairbanks, 2001 The purpose of this research was to evaluate bioavailability and chemical characteristics of soil organic matter (SOM) in Arctic tundra soils. Five soil horizons in three different sites located in the Arctic Slope of Alaska were used for this research. This thesis comprises five chapters, each of which described a method that can be used to study the bioavailability and chemical characteristics of SOM in these samples. Chapter One used laboratory incubation technique to determine CO2 evolution from the soils. The cumulative CO2 respired from the samples during the incubation period was used as index of bioavailability of SOM. Chapter Two utilized cross polarization magic angle spinning (CPMAS) 13C NMR and liquid-state 13C NMR techniques to evaluate the chemical composition of SOM. Chapter Three described how pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was used to characterize SOM. Chapter Four summarized different approaches for characterizing SOM, and Chapter Five used amino sugar contents in soils to assess the microbial contribution to SOM. The laboratory incubation study indicated that temperature had a positive effect on the CO2 evolution from these samples, and the tundra soils would have higher potential to contribute to greenhouse gas emissions with elevated temperature. Among the extractable soil organic fractions, neutrals such as hydrophilic neutrals (HIN), hydrophobic neutrals (HON) and low-molecular-weight neutrals (LMN) are more bioavailable than these such as humic acid (HA) and fulvic acid (FA). Liquid-state and solid-state 13C NMR and Py-GC/MS techniques exhibited more potential for evaluating the relative quality of SOM compared to the wet chemical analysis method. Together with the laboratory incubation method, these techniques can be used to identify the chemical composition of SOM, and to establish correlations between the chemical composition and bioavailability of SOM. Amino sugars in soil can provide insights into the ...
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