Thesis (Ph. D.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 174-192).

Thesis (M.S.)--Montana State University--Bozeman, 2005. / Typescript. Chairperson, Graduate Committee: John Antle. Includes bibliographical references (leaves 115-124).

Thicket degradation within the Addo Elephant National Park (AENP), Eastern Cape, South Africa is a key issue of concern. The increasing elephant densities have over time threatened thicket vegetation, which is endemic to this area. The “elephant problem” within the Park has raised many concerns as to the vulnerability of thicket to elephant impacts. Remote sensing provides an environment in which temporal changes in thicket vegetation condition can be assessed. The main aim of this study was to assess temporal and spatial trends in thicket degradation within the AENP, using multi-temporal satellite imagery. Elephant induced thicket degradation was assessed using multi-temporal satellite imagery from between 1973 and 2010. Changes in thicket condition in relation to the AENP expansion were analysed using the Normalized Difference Vegetation Index (NDVI), post-classification and landscape metrics. The ‘per-pixel’ based classification approach was carried out and change detection of land cover classes was analysed by post-classification. Landscape spatial metrics were used in order to gain an understanding of vegetation fragmentation trends. Temporal changes in vegetation gradients in relation to water points and thicket condition within the botanical reserves were also assessed. Thicket condition was noted to deteriorate as the AENP expanded. An expansion of degraded vegetation away from the water points was identified during the study period. Thicket condition in botanical reserves 1 and 2 fluctuated over time, with a registered increase in intact thicket within botanical reserve 2, with botanical reserve 3 remaining constant. Landscape spatial metric analyses revealed evidence of increased vegetation fragmentation as new areas of the AENP were opened for elephant activity. A progressive decline in intact thicket and increase in degraded thicket were observed. Considering the current elephant densities, thicket degradation within AENP is set to continue, causing a continued threat to the thicket biome.

Thesis (Ph.D.)(Agricultural Economics)--University of Pretoria, 2007. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.

Thesis (Ph.D.) - University of Queensland, 2003. / Includes bibliography.

The potential for using RMP (refiner mechanical process) pulp mill fibre waste as a soil amendment was investigated by determining levels of net carbon mineralization. Under optimum conditions (laboratory incubation study), the pulp fibre waste, being a relatively homogeneous substrate, was found to mineralize at one rate of -0.0078 d⁻¹. In field applications the rate of net mineralization was slower, with rates of -0.0034 d⁻¹ and -0.0037 d⁻¹, as determined by soil respiration and litter bag trials, respectively. A loading effect was noted for this amendment, where increasing the levels of application was found to cause decreases in the mineralization rate. Using pulp fibre waste in forest landing rehabilitation appears to increase the levels of microbial activity in the surface horizon. The higher levels of productivity should lead to improvements in soil structure, and would be a better alternative to only tilling and fertilizing the soil. / Land and Food Systems, Faculty of / Graduate

Thesis (M.Sc.) - University of KwaZulu-Natal, Pietermaritzburg, 2009. / Full text also available online. Scroll down for electronic link.

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

Soil degradation in the lowland soils of the Lower Fraser Valley area is an off-season (September-April) problem. The legacy of the degradation process is encountered every year in the form of ponding which delays farming operations such as cultivation and seeding. It is common for the lowland soils in west Delta to be left in a bare, loose, and therefore unstable state in the fall after harvest. As the result of raindrop impact on such a soil, a disaggregation process takes place which decreases the saturated hydraulic conductivity, the saturated water content, the air entry pressure head, and the water releasing ability of a soil. As a result of these changes the hydrologic responsiveness of a soil will decrease, decreasing its ability to allow rapid infiltration and drainage. The objective of this thesis was firstly, to investigate the causes of the soil structural degradation and secondly, to use some of the soil structural parameters to optimize the responsiveness of a soil and thirdly, to suggest a management model with the objective of improving the hydrologic responsiveness of a lowland soil. To fulfill the above objectives, in the first chapter, the process of soil degradation was studied on large undisturbed soil columns removed from two adjacent locations within an area of Ladner in west Delta, British Columbia. It was found that a disaggregation process caused by the impact of raindrops on a weakly aggregated soil was the main cause of a low hydrologic responsiveness at the beginning of the cultivation season. As a result of degradation of the soil surface layer, a surface seal can form with a saturated hydraulic conductivity in the order of 9.7x10⁻¹⁰ m s⁻¹. A surface seal can effectively decrease the infiltration rate, leading to the formation of a persistent pond which will make a soil untrafficable and unworkable. In the second chapter, a concept of "designer soil" was developed, where a set of "design hydrologic parameters" were identified for a partially hypothetical soil. A soil possessing hydrologic parameters better than the design parameters would therefore display a certain desired hydrologic responsiveness. In the third chapter, a descriptive management model was suggested with the objective of achieving the design parameters as identified in the second chapter. / Land and Food Systems, Faculty of / Graduate

Thesis (doctoral)--Wageningen University, 2004. / Includes bibliographical references.