Thesis (Ph. D.)(Pasture Science)--University of Pretoria, 2006. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.

Deserts comprise the largest terrestrial biome, making up approximately one third of the Earth’s land mass. They are defined in terms of moisture deficit using the Aridity Index with values <1. A further delineation based on mean annual temperatures into hot (>18°C), cold (<18°C) and polar (<0°C) deserts is employed. In the absence of significant macrobiota, microorganisms are key to desert ecosystems. They are located in near-surface soils, and include a widespread hypolithic mode of colonization, where microbial biomass develops on the ventral surfaces of quartz and other translucent stones. A literature review was conducted to appreciate the status of existing knowledge on these systems. Amongst unresolved questions that arose were the following, which form the basis of this inquiry: What are the taxonomic and functional differences between hypolithic and near-soil communities? Do hypolithic communities assemble differently in deserts of different xeric and thermal stresses? Can the keystone cyanobacterial taxa be cultivated under laboratory conditions to allow manipulative studies? The Mojave Desert in the USA was used as a model to test the extent to which hypolithic and near-surface soil communities vary in both taxonomic and putative functional composition. A common phylogenetic marker (16S rRNA gene ITS region) was used to conclude that soil and hypolithic communities are significantly different, although both were dominated by cyanobacteria. The ubiquitous hypolithic cyanobacterial taxon Chroococcidiopsis was encountered, although communities appeared to be dominated functionally by the diazotrophic genus Nostoc. The data strongly suggest that carbon and nitrogen fixation pathways in desert soils are mediated by the same taxa, although heterotrophic pathways may differ and support distinct assemblages of heterotrophic bacteria. An opportunistic sampling of three sites along a latitudinal gradient in China allowed some inference about adaptations in hypoliths. Communities recovered from the cold Tibetan Desert, Taklamakan Basin Desert, and exposed hillsides in tropical Hong Kong, did not display significant differences at the level of community assembly. This suggests that hypolithic taxa undergo strong selection for xeric and extreme thermal stresses. A cultivation strategy for the keystone taxon Chroococcidiopsis has been lacking and is an obvious impediment to manipulative physiological studies. Here various methods for laboratory cultivation were attempted. This bacterium proved extremely fastidious and displayed slow growth rates. After extensive trials a novel cultivation method was developed. This involved using plastic petri dishes containing liquid growth medium, into which glass coverslips were introduced along with cell suspensions. The surface energy of glass served as a nucleation site for Chroococcidiopsis biofilms (which do not develop on plastic surfaces) and this method was evaluated in growth studies as a means of quantifying growth. This research includes key advances to demonstrate that hypoliths and soil, whilst supporting different communities, likely perform similar functional roles in the desert soil. Selection due to the severe environmental stresses results in similar communities across large latitudinal and environmental gradients. The development of a cultivation strategy paves the way for manipulative physiological studies on these important organisms. / published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

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Satellite images have been used as a complementary information for geological studies. In order to realise the maximum potential of satillite imagery, then improvements are needed, both in the visual presentation of such images, and in their automatic classification , in order to reveal the rock differences. Methods of processing imagery, were evaluated (band ratio, principal components, decorrelated stretch and maximum likelihood) and new (canonical regression, hue-saturation-intensity HSI transform, with modified manipulation, and watershed) were evaluated with respect to their ability to reveal rock differences. It was found that the HSI method gave the best results, both for visual presentation and automatic classifcation. This method has the ability to enhance both spectral and spatial information simultaneously without any data loss which is not the case in the other image enhancement methods (band ratio, principal components or decorrelation stretch). For automatic classification, the 'hue' images produced by the HSI transformation typically gave accurate (91%) classification of all the major rock types. Further, it was shown that the watershed method of classification was superior error rate = 9% to the maximum likelihood method (error rate 14%) for the same inputs. The new method of canonical regression was evaluated and although it was not very successful, the results were encouraging and it was concluded that this method may enable the estimation of the chemical composition of exposed rocks directly from satellite imagery.

Thesis (M.Env.St.) - Dept. of Environment Studies, University of Adelaide, 1978. / Typescript (photocopy).

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Sustainable Built Environments Senior Capstone Project / There is a worldwide movement towards sustainability. A stepping-stone towards a sustainability conscience population starts in the education of the younger generation. Focusing on improving education specifically in middle schools in arid regions regarding sustainability will shift and shape youths’ interests and lifestyles into an educated community. This sustainability conscience community will continue to make moral sustainable decisions in their future endeavors. The curriculum implemented will reduce the dropout rate because it is a hand-on curriculum that is interesting and enjoyable for kids. The focus of the curriculum is to rely on outdoor activities to create an outdoor learning environment. The curriculum is based on three different sections: 1) campus-wide adaptable strategies implemented by the students, 2) long term investments implemented by professionals, 3) and hands-on activities that will encourage students to go outdoors and experience real-life problems. To create this education system, the author will propose design guidelines and applications that will be used to improve middle schools particularly in arid regions to become “Green Schools”. This program will validate the sustainable strategies, projects, and efforts done at schools and will also market their school as a model to follow. This will explain what it takes to become a Green School in arid regions and how to achieve these standards.

Historic mine tailings pose a significant health risk to surrounding ecosystems and communities because of high residual concentrations of contaminant metals. The initial tailings mineral assemblage, metal sulfides, silicates, and carbonates are unstable at earth surface conditions and undergo oxidative and proton-promoted weathering. The weathering of metal sulfides generally produces acid that, if not balanced by protonconsuming dissolution of silicates and carbonates, leads to progressive acidification. The Klondyke State Superfund Site in Graham County, Arizona contains high concentrations of Pb (up to 13 g kg⁻¹) and Zn (up to 6 g kg⁻¹), and remains unvegetated 50 years after mining cessation. Field-scale investigation revealed a wide range of pH (2.5-8.0) and plant-available (DTPA-extractable) metals in the near surface of the tailings pile. Four samples were chosen for in-depth characterization ranging in pH, as denoted by subscript, from 2.6 to 5.4. The mineral transformations occurring in these four samples were investigated using a variety of techniques and the data indicated an increase in tailings weathering extent with increasing acidification (decreasing pH). Lead speciation, studied by a combination of chemical sequential extraction and X-ray absorption fine structure (XAFS) spectroscopy, was found to vary with tailings depth. The principle lead-bearing mineral was plumbojarosite (PbFe₆(SO₄)₄(OH)₁₂), with smaller amounts of anglesite (PbSO₄) and lead-sorbed iron-oxide. Anglesite, the most bioavailable mineral form of Pb in the tailings, was found to accumulate at the tailings surface, which has important implications for health risks. Total Zn content decreased by an order of magnitude (from 6 to 0.4 g kg⁻¹) and showed a change in molecular speciation with decreasing pH. Zinc-rich phyllosilicates and Zn-containing manganese oxides predominate at high pH, whereas low pH samples contained principally Zn-sorbed iron oxides. One of the overarching goals of the project is to remediate the Klondyke site using phytostabilization to keep contaminant metals from eroding offsite either by wind or water transport mechanisms. However, the impacts of plant growth on metal bonding environment are unknown. To address that gap in knowledge, we have developed a technique for the study of root-microbe-mineral-metal interactions that occur in the rhizosphere, the volume of soil surrounding, and affected by, plant roots. This technique involves the conjunctive use of fluorescence in-situ hybridization, X-ray fluorescence elemental mapping, XAFS and Raman micro-spectroscopies, and electron microscopy on single roots. Manganese and iron root plaques collocalized with elevated Pb, Zn, and Cr demonstrate that the rhizosphere can affect metal speciation. Metal speciation is an important factor in determining metal bioavailability, and thus is critical for understanding the health risk associated with mine tailings. The results of this research provides site-specific information about Pb and Zn speciation, which will be used to evaluate the effectiveness of site remediation within the context of metal toxicity.

An unsettling trend is gaining momentum - many Americans may be losing their interest in the `natural world'. According to research undertaken by Patricia Zaradic, an Environmental Leadership Program fellow in Bryn Mawr, and Oliver Pergams of the University of Illinois at Chicago, "nature just isn't as entertaining as it used to be." Studies of Americans' recreational habits show a nearly 25 percent per capita decline in camping, fishing, hunting and visits to state and national parks since the mid-1980s (Gambino 2008). Like "climate change," some suggest that the downward trend in outdoor recreation by Americans is a manifestation of fiction rather than fact. But the trend is unmistakable: A smaller percentage of people in the United States and elsewhere are participating in outdoor recreation (Smith 2008). Pergams and Zaradic show a trend in human behavior that ultimately may be far more foreboding for the environment than declining tropical forest cover or increasing greenhouse gas emissions - widespread declines in nature-based recreation (Kareiva 2008). The question that has yet to be answered is to what degree this trend will have in influencing our society's future and in how we will value - or devalue - our natural environment. Will future generations that grow up and live in a world estranged from the natural environment want to protect it? America's 200-year conservation tradition may be at risk. Two dominant factors influenced the environmental philosophies of notable historic American conservationists. One was their direct and repeated interaction with the natural world beginning at a very early age; the other was an environment-focused family tradition. These same factors influenced the environmental ethos of today's conservationists, land managers and environmental educators. It is impossible to determine if these factors will be of equal significance one hundred years from now. However, we can predict with reasonable certainty based on the recent historic record, motivators identified by current environmentalists, and the results of independent surveys of adolescent subjects reported in this study that, at least for now and for the foreseeable future, if implemented in combination with others variables, these will favorably influence the conservation ethic of our youngest citizens.