Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 364-378).

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 39-44). Also available on the World Wide Web.

This study aims to understand tourism carrying capacities of diving sites in Hong Kong and Malaysia. Specifically, ecological, psychological and social carrying capacities were assessed. Methodology involved photo quadrat transect survey, questionnaire survey and visual experiment survey. Over a period of two calendar years (2013 and 2014), 13, 12 and 9 photo quadrat transect surveys were conducted in Sharp Island, Tsim Chau and Mabul Island (Ray Point and Eel Garden) respectively to provide data for ecological carrying capacity assessment. In addition, 455 and 342 questionnaires were collected in Hong Kong and Mabul Island respectively to assess divers' satisfaction with diving attributes of the respective dive sites. Regarding social carrying capacity assessment, 247 and 158 visual experiment questionnaires were collected to assess crowding as perceived by divers in the two sites.;The ecological carrying capacity of Sharp Island lies between 172 and (less than) 825 divers every quarter in the absence of better solutions. At Tsim Chau, diving activity is not the most important factor in influencing the coverage of sea anemone. In addition, the use of additional (subjective) data was necessary to define the ecological carrying capacity of Tsim Chau and possibly Sharp Island. In Mabul Island, the results show that the ecological carrying capacity is about 16800-17200 divers per year at Ray Point and about 15600-16800 divers per year at Eel Garden. Based on the findings, it is likely that the usage of the diving sites on Sharp Island, Ray Point and Eel Garden have already exceeded the social carrying capacity. Regarding the psychological carrying capacity, this study found that the most important factor that influences divers' willingness to return to Hong Kong diving sites is "the quality of corals". In Mabul Island, the most important factor is "the value for money of Mabul diving". However, no studied diving sites have exceeded their psychological carrying capacities. Regarding the social carrying capacity, on both Hong Kong and Mabul Island diving sites, the "number of divers" was found to be the most influential factor for divers' perceived crowding. In Hong Kong, divers' begin to feel unacceptably crowded if 78̃ divers are visible to them at one time whereas in Mabul Island, divers would start to feel unacceptably crowded if 8 to 9 divers were visible to them at one time. Based on this, it is likely that the usage of both Hong Kong and Mabul Island diving sites have already exceeded the social carrying capacity.;With the increasing popularity of diving in recent years, divers and diving trips operators around the world need to be aware of divers' impact on coral reef, divers' satisfaction and underwater crowding problem. Finally, a series of management and policy measures to minimise the impact of diving activity on coral, improve divers' satisfaction and mitigate divers' crowding perception in underwater environment are proposed for sustainable use of diving sites in Hong Kong and Mabul Island.

Thesis (Ph.D)--Physics, Georgia Institute of Technology, 2009. / Committee Chair: Weiss, Howard; Committee Member: Cvitanovic , Predrag; Committee Member: Goldman, Daniel; Committee Member: Schatz, Michael; Committee Member: Wiesenfeld, Kurt. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thomas Schelling proposed a simple spatial model to illustrate how, even with relatively mild assumptions on each individual's nearest neighbor preferences, an integrated city would likely unravel to a segregated city, even if all individuals prefer integration. Many authors assumed that the segregation which Schelling observed in simulations on very small cities persists for larger, realistic size cities. We describe how different measures can be used to quantify the segregation and unlock its dependence on city size, disparate neighbor comfortability threshold, and population density. We develop highly efficient simulation algorithms and quantify aggregation in large cities based on thousands of trials. In particular, we show that for the values of disparate neighbor comfortability threshold used by Schelling, the striking global aggregation Schelling observed is strictly a small city phenomenon. Along the way we prove that in the Schelling model, in the process of evolution, the total perimeter of the interface between the different agents always decreases, which provides a useful analytical tool to study the evolution. At the isolated reef Kingman, it was recently discovered that apex predators constitute 85% of the total fish biomass. This is in sharp contrast to most reefs, where the prey biomass substantially dominates the total fish biomass. The recent study at the two pristine reefs, Kingman and Palmyra also indicates that the predator:prey fish biomass ratio is an increasing function of reef cover. Based on these field observations, we model the fish biomass structure at a pristine coral reef. We introduce a new refuge based mechanism for predator-prey interaction with an explicit dependence on refuge size. Our refuge based model does not assume mass action interaction between predators and prey and may provide a new mechanism in ecology to produce inverted biomass pyramids. Our model yields both the inverted biomass pyramid and the increasing dependence of the predator:prey biomass ratio on reef cover. We add various forms of fishing to our model, and show that sufficiently high fishing pressure with quite general types of fishing transforms the inverted biomass pyramid to be bottom heavy.

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

The purpose of this study was to develop and test a predictive understanding of the vegetation dynamics of the Lowveld of South Africa (30°35'E to 30°40'E and 24°00'S to 25°00'S). The study covered about 5000 km2 in Adjacent Private Protected Areas (APPA) adjoining the Kruger National Park (KNP). Data gathering (800 sites; 23 properties) commenced in 1989 and those recorded up to 2004 are reported here. The value, both ecological and economic, of the wildlife and tourism industry dependent on this savanna region is discussed in both historical and current perspectives. A range of land-use objectives and anthropogenic interventions were exposed. The properties ranged in size from 30 to 800 km2 and formed an effective and extensive manipulative experiment for investigating interaction of bush density, animal stocking, use of fire and landscape-scale processes. The first descriptive classification (at 1:250 000) of the area was developed using Inverse Distance Weighted interpolations. This confirms similar landscape/vegetation patterns in the KNP and Mocambique. The current mode of determining stocking density or carrying capacity was interrogated and indices suitable for complex multi-species systems developed. This was done in the context of equilibrial/disequilibrial paradigms. Application of the original indices resulted in drought-related declines in animal biomass of 4000 kg km2 over 20 years due to overestimation of carrying capacity. The model proposed here uses rainfall, animal type, biomass and vegetation parameters to determine stocking density for both coarse (regional) and ranch-specific scales. Principal driving determinants (rainfall, geology, soil type, tree density canopy cover, animal numbers, feeding classes and fire) of vegetation structure and their influence on the herbaceous layer were investigated. Groupings on ecological potential showed 'high' potential areas are less sensitive to animal impact than those classified as 'low' potential. Sustainability, embedded in a forward-looking component viz. Strategic Adaptive Management (SAM) with well-articulated endpoints viz. Thresholds of Potential Concern (TPCs) was used to study fluctuations in animal populations with Connochaetes taurinus (Blue wildebeest) as the case study. The TPC approach provides strong pointers for proactive management aimed at maintaining the system within bands defined by TPCs supporting operationally practical and periodically reviewed objectives. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

Grazing lands in Eritrea are degraded due to decades of overstocking and consequent overgrazing. Since the rangelands are accessible to entire village communities, organisation and coordinated decision making regarding the management of these resources is not often achieved. Farmers are not motivated enough to make investments to improve a communally owned resource due to the prevailing common access grazing systems. A field survey was undertaken interviewing 12 farmers in the private access commercial and 80 farmers in the common access subsistence grazing using face to face interviews in the Barka and Arado cattle farming communities in four out of the six regions in Eritrea. Debub, Gash-Barka, S. Keih Bahri and Maekel regions were selected using stratified and simple random sampling methods. The regions were chosen based on various agroecological zones where the representatives of different grass species and the two most common cattle breeds in Eritrea (Arado and Barka) are found. The survey included the collection of data on village and household characteristics focusing on rangeland grazing management systems and additional sources of supplementary forage. The study uses several stages of analysis like principal component analysis accompanied by regression analysis together with descriptive statistics and ordination diagram. The commercial farmers addressed grazing constraints by investing in improved grazing through planting 258 ha per farmer of drought resistant seeds and 1767 vs. 8 cactus slices per farmer and covered 75% vs. 40% of forage requirements from grazing resources compared to the subsistence farmers, respectively, during 2002. These results were achieved because 78% of the commercial farmers adopted controlled stocking rates. In common access grazing, the costs of collective action to control cattle stocking rates are high, making imple mentation of stocking rate controls difficult. As a consequence, 65% of the subsistence farmers were forced to migrate their cattle looking for grazing forage in the dry season during the year. The outcomes of migration were evidenced by the results of severe overgrazing and degradation on the rangelands proximity to villages in Debub and Maekel regions and the populated area of Gash_Barka region. The increased number of animals resulting in high grazing pressure was the consequence of migration. Ten vs. six percent of mortality rates was reported for the subsistence systems compared to the commercial systems respectively. The lower results of milk yield, calving rates and off- take rate productivity indicated in the different stages of analysis for the subsistence farmers were the consequences of the lack of the adoption of controlled stocking rates primarily constrained by the migration. The Barka and Arado cattle farming systems are kept under common access grazing systems. Compared to the Arado cattle farming, the Barka cattle farming region had relatively better access to grazing forage. The better quality of grazing in this region is attributed to a naturally low stock density in the region. During 2002, the Barka cattle farming had 1087 vs. 721 Lit of milk yield, 63% vs. 53% of calving productivity and 9.3% vs. 10.9% of mortality rates than the Arado cattle farming regions respectively, due to access to a wider area of grazing lands and more labour inputs. The Barka cattle area farmers are agro pastoralists and usually focus on grazing dairy cattle farming than crop farming. They increased calving rate productivity and decreased mortality rates by increasing the proportion of lactating cows and decreasing the proportion of oxen compared to the Arado cattle farming. The Arado cattle farming had higher offtake rates and income from cattle sales compared to the Barka cattle farming region. The higher off- take rate, which is an index of percentage of cattle sold, for the Arado cattle was probably linked to the shortage of grazing forage and increased herding costs. The Barka and Arado cattle farmers had a shortage of quality and quantity crop residue winter forage during 2002. Farmers were dependent only on rain fed cropping. The application of crop rotation, fallow and chemical fertilizers were low to enhance soil nutrients. Out of the total crop residues forage produced, only 22% and 15% of legumes residue DM forage was produced for the Barka and Arado cattle farmers respectively. Agro- industrial and crop farming by-products supplementary feeds were also limited due to the shortage of feeds in the country during the year. In general, government intervention is important to bring institutional changes to promote the adoption of controlled stocking rates to alleviate the shortage of grazing forage. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2007.

Browse selection, intake, utilisation, palatability, quality and production are tightly linked and need to be considered together in trying to improve our understanding of browsing dynamics and the interactions between browsers and vegetation. Such an understanding is necessary in order to re-evaluate determinations of browser carrying capacities and evaluating actual and potential impacts of browsing animals on vegetation composition and diversity. Browser carrying capacity is determined by both the quantity and the nutritive value of forage. The measurement of browse quantity and nutritive value and the matching of browse supply to browser demand are central to sustainable utilisation and the monitoring of vegetation health. South African savannas are poorly studied with respect to tree canopy growth and browse production making it difficult to quantify the available browse biomass on which browsing capacity estimations are based, and consequently difficult to estimate levels of browsing that are sustainable. This study addressed these issues by investigating browse dynamics, broadly aiming to (1) explore factors affecting browse production, biomass and nutritive value; (2) develop models to assess and monitor these parameters across seasons and properties; (3) use the resultant models in improving our understanding of how to determine browser carrying capacities. More specifically, our study sought to examine the effects of plant physiognomy, forage nutritive value, canopy stratum, defoliation, temperature, rainfall and soil nutrient status on the browse production of evergreen (Carissa bispinosa, Euclea divinorum, Gymnosporia senegalensis), semi-deciduous (Spirostachys africana, Ziziphus mucronata) and deciduous (Acacia nilotica, Dichrostachys cinerea) savanna tree species from June 2003 – June 2005 in three sites along the northern Zululand coastline of KwaZulu-Natal. Available browse biomass, during the dry season, of four key savanna tree species (A. nilotica, E. divinorum, G. senegalensis, and S. africana) was estimated through the development of allometric regression equations. Non-linear regression was used to investigate the relation between the leaf dry mass (LDM) and canopy volume (CVol) of each of the four tree species. Exponential regression (y = a + brlnx) of the natural logarithm of CVol data provided the most accurate and precise description of the tree CVol – LDM relation. A study was undertaken to determine which factors may influence browse production in a southern African savanna. Regression tree models for the browse production identified that the dominant factors influencing browse production were CVol (m3), season, species and height to the lowest leaves of the tree canopy (HL) (m). The length of the growing season had a marked effect on the production potential of savanna tree species, suggesting that improved conditions for growth, i.e. greater rainfall, soil moisture content and improved soil nutrient availability result in a longer period of rapid sustained growth. Species was identified as an important contributing factor to differences in browse production rates, suggesting the need for the development of species or species group models. Mean annual browse production of evergreen trees was greater than that of deciduous and semi-deciduous trees. Mean quarterly (three monthly) browse production was highest, for all trees, during the wet season, with the greatest difference between wet and dry season production being observed in deciduous forms. Evergreen forms showed continuous growth over the whole study, with enhanced growth over the wet season. Deciduous forms, on the other hand, concentrated growth in spurts, when environmental conditions became favourable, with most production occurring during a short growing season. Browse nutritive value was found to be greatest during the wet season, when growth and photosynthesis are at their greatest. Further, browse nutritive value was greatest in deciduous species. Evergreen trees were found to have greater acid detergent fibre (ADF) concentrations than both the deciduous and semi-deciduous trees. By contrast, crude protein (CP) concentrations were greater in semi-deciduous and deciduous species than in evergreen species. The daily CP requirements for maintenance for an adult impala (45 kg) were met by all species over all three study areas and all seasons. Daily CP requirements for growth and lactation, however, were only ever met by deciduous and semi-deciduous species, though this result was not consistent over study areas and seasons. Predictive models for the production of browse on deciduous, semi-deciduous and evergreen trees in northern Zululand were developed using multivariate adaptive regression spline functions. The best predictors of growing season browse production in all three tree guilds (defined here as a group of trees having a characteristic mode of living) were primarily measurable tree dimensions, while the prevailing environmental conditions had little impact. Differences in the production, nutritive value and available browse biomass between the different tree forms and seasons have a profound effect on the determination of browser carrying capacities and need to be incorporated into any game or conservation management plan. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

The main aim of this study was to classify and describe the plant communities in the home range of white rhinoceros in order to understand the animal seasonal foraging ecology. To provide a detailed habitat description, forty sample plots were stratified randomly. A TWINSPAN classification, refined by Braun-Blanquet procedures, was carried out on the Viewpoint section of the reserve. Ten plant communities, grouped into five major community types, were identified. The veld condition and ecological carrying capacity in these communities were measured, stating an abundance of food on long grass while the short grass equal the number of short grass feeders. A number of behavioural aspects such as activity data, home range utilization and dietary usage were examined. Statistical methods such as the Spearman rank-order correlation, Wilcoxon sign test and Student T-test were used on rhino data. The difference in usage of the home range during wet and dry seasons was insignificant. / Environmental Sciences / M.Sc. (Environmental Management)