The South African National Water Act (NWA) (No. 36 of 1998) recognises that in order to sustain the goods and services that are provided by rivers and their associated biological communities, it is necessary to conserve the entire aquatic ecosystem. Conservation and maintenance of ecosystem functioning entails the protection of the biotic components (i.e. fish, macroinvertebrates, riparian vegetation, etc.) and ensuring that the abiotic driver aspects (i.e. required amount and variability of flow, water quality and fluvial geomorphology) are addressed and met (Malan and Day, 2003). According to the Reserve Determination methodology (DWAF, 2003), sustainable utilisation of the river resources requires proper, responsible management and that exploitation without understanding or limits, impacts negatively on the ecological processes, functions and communities, both in the present and the future. Manipulation of the flow regimes of rivers, to provide water when and where people need it, has resulted in a growing deterioration in the condition (health) of riverine ecosystems (King et al., 2000). Stressors on aquatic ecosystems originating from these anthropogenic activities, include point and non-point loadings, land use influences and changes, and stream modification. These are usually defined by the drivers of aquatic ecosystems namely the geomorphology, hydrology and water quality. In turn, the effects on the physical habitat and water quality have both direct and indirect effects on the biotic communities present and are usually defined by biological responses to these changes (Kleynhans et al., 2005). There is currently limited data available to formally propose a methodology to quantify the significance of altered flows in riverine ecosystems brought about by the abstraction or excessive release of water by industrial activities on a reach scale. The aim of this study was to determine the degree and magnitude of habitat-flow alterations caused by pulp and paper mill activities in the Elands and Mvoti Rivers and to link the related biological responses to them. / Prof. V. Wepener

Understanding the first order controls over resource cycling and limitation in ecosystems is critical for predicting ecosystem response to disturbances. Topography and vegetation self-organizing mechanisms are first order controls over resource fluxes across the landscape. Topography controls downslope flow of resources (i.e water and nutrients). Through spatial feedbacks, vegetation is able to actively modify its environment and maximize resource flows towards it. To date, the impacts of these controls on ecosystem dynamics have mostly been investigated separately. As such, there is a knowledge gap in the understanding of how these first order controls together dictate the dynamics of the ecosystem. This dissertation aims to gain a better understanding of how self-organizing mechanisms and topography operate together to affect wetland ecosystem dynamics. A spatially explicit, wetland vegetation patterning model that includes for both vegetation self-organizing control and topographic control is developed (Nutrient Depletion Model, NDM). The model describes a scale dependent feedback between vegetation, transpiration and nutrient accumulation that drives the formation of vegetation patterns. The model is applied to investigate the effects of topography and self-organizing mechanisms on form and orientation of vegetation patterns and vegetation growth dynamics of wetland ecosystems. Results show that the two first order controls synergistically impact the formation of the various patterns as observed in wetland ecosystems. Results also show the following: (1) Self-organizing mechanisms result in a more efficient retention of resources, which result in higher biomass in the model that include for both self-organizing mechanism and topographic control (SO+TC) than in the model that that includes only for topographic control (TC). (2) However, when resources or topographic gradients increase or annual rainfall decrease, the vegetation growth dynamics of the TC+SO and TC models converge. The NDM is applied to arctic Alaska to investigate how do the two first order controls impact present and future C-N dynamics of an arctic ecosystem. Simulation results show no significant difference in the dynamics between the SO+TC model and the TC model. The climate change simulation results suggest that changes in daily variability of temperature and precipitation can impact ecosystem dynamics as much as the changes in mean temperature and precipitation. Results from this dissertation provide a more complete picture on the relative roles of the two first order controls over ecosystem nutrient cycling and vegetative growth dynamics. Finally, in this thesis, in order to simulate small-scale feedbacks over large spatial domains, the NDM is implemented in a GPU computing language, which accelerates computational simulation by at least two orders of magnitude. These tools for grid-based simulations can provide a platform for using GPUs in other areas of scientific investigation.

A lot of habitats have declined or disappeared as the old cultural landscape changed to the modern agricultural landscape of today. Places such as power line corridors, racing tracks, gravel pits and military training sites have become refuges for many species associated with the old cultural landscape. These sites have been exposed to ecological disturbances that create the same type of habitats that were found in the old cultural landscape. The military training sites in Sweden has an impressive diversity of species. Disturbances from the military exercises have created habitats that are important for a wide range of species. The purpose of this thesis is to study some of the ecological disturbances occurring in the military training sites of the Swedish Armed Forces and examine how they affect different types of habitats. The thesis explains through litterateur and field studies the reason to the rich biodiversity often found at military training sites. The training sites and firing ranges of Skövde garrison were used as an example to show how the disturbances affect the environment. The study shows that military exercises (e.g. with combat vehicles) creates habitats that previously existed in the old cultural landscape. Soil damage from combat vehicles benefits insects and creates pools for amphibians. Damages on trees create snags and woody debris which favors a large amount of species. The military exercises also keep an open landscape.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

The central theme of this thesis is a study of the structural changes accompanying chemical modification and denaturation of eukaryotic cytochrome c as characterised by ¹II nuclear magnetic resonance (n.m.r.) spectroscopy. First, however, it was necessary to obtain and confirm assignments for individual resonances; this was achieved by a novel method of cross assignment between ferricytochrome c and ferrocytochrome c and by double resonance techniques. A variety of perturbations were caused to native cytochromes c, which ranged in degree from the elevation of temperature for ferrocytochrome c to the complete denaturation of the protein with urea or methanol. Modification at single sites both on the surface (e.g. Met 65, Tyr 74) and in the core ( e.g. Tyr 67) of the molecule were found to cause only small local effects to the structure, although the dynamic features of the molecules were altered. One single site modification, the breaking of the iron - sulphur cross linking bond, caused considerable disruption to one side of the molecule, although hydrophobic domains in the other side were preserved; this state of the molecule is analogous to the penultimate state in the refolding pathway. Modification of all the charged lysine residues caused small changes to the surface structure of the molecule, though the complete reversal of the charges in maleyl cytochrome c produced a species which unfolded reversibly from a native configuration with the increase of temperature. The unfolding of the protein is virtually identical with both methanol and urea, but the pathways are shown to differ for the oxidised and reduced proteins.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Mémoire (M.Ress.Renouv.)--Université du Québec à Chicoutimi, 1996. / Document électronique également accessible en format PDF. CaQCU

Thesis (Ph.D.) -- University of Montana, 2008. / Title from author supplied metadata. Description based on contents viewed on July 15, 2009. Includes bibliographical references.

Thesis (M.S.)--University of Wyoming, 2008. / Title from PDF title page (viewed on June 26, 2009). Includes bibliographical references (p. 86-111).