Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第16849号 / 工博第3570号 / 新制||工||1539(附属図書館) / 29524 / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 河合 潤, 教授 白井 泰治, 教授 乾 晴行 / 学位規則第4条第1項該当

Master of Science / Department of Biology / David C. Hartnett / Herbivory is one of the major biotic interactions shaping the structure and dynamics of grassland plant populations and community structure. The two major grass growth forms, rhizomatous and caespitose species, may show different grazing tolerance and short-term overcompensation may offset long-term reductions in plant performance and fitness. The objectives of this study were to assess 1) the effects of long-term ungulate grazing on plant architecture, population structure, and life history traits of the caespitose perennial grass, Schizachyrium scoparium (little bluestem), and the rhizomatous Bouteloua curtipendula (sideoats grama) in tallgrass prairie, and 2) the effects of grazing intensity (frequency of defoliation) on growth responses of little bluestem. Long-term bison grazing decreased the cover, frequency, tiller height, and proportion of tillers producing seed in little bluestem, but caused no changes in tiller density and total genet size. Grazed little bluestem plants maintained a significantly larger below ground bud bank. Bison grazing had no long-term effect on the abundance, bud bank densities, or rhizome growth of the rhizomatous side-oats grama grass. Biomass, tiller density, relative growth rates, and proportion of tillers flowering in little bluestem all decreased with increasing frequency of defoliation. However, even an intense grazing regime (9 defoliations over a 12 month period) caused no plant mortality and no changes in new tiller emergence rates, or bud bank densities. Increasing defoliation frequency did result in shifts in plant architecture, as an increasing proportion of extravaginal tillers led to a more lateral, decumbent growth form. These results show that the rhizomatous side-oats grama grass has a significantly higher grazing tolerance than does little bluestem, and/or that bison selectively graze little bluestem. Results from responses to the experimental defoliation regimes suggest that little bluestem shows lower tolerance to high frequency of defoliation, and its maintenance of a reserve below ground bud bank may be its primary tolerance mechanism, allowing tiller populations to recover following severe defoliation.

Magister Scientiae (Biodiversity and Conservation Biology) / This study investigated the role of grazing as a possible cause for the upper limit of distribution of algae on a typical South African south coast. / South Africa

Magister Scientiae (Biodiversity and Conservation Biology) / Heavy grazing of rangelands in the succulent karoo has placed the biodiversity of these areas at risk. In Paulshoek, overgrazing has resulted in the removal of much of the palatable vegetation from low lying areas. The remaining vegetation is dominated by Galenia africana, an unpalatable shrub. Loss of favourable microsites, competition from Galenia africana, as well as loss of seed banks, may be the cause of poor seedling establishment of palatable species. I explored how high grazing pressure has changed this system by comparing with surrounding private farms, which have a history of less concentrated grazing pressure. I found that heavy grazing increased the seed bank of Galenia africana in the soil and reduced that of palatable perennials. Vegetation cover was significantly lower (p<0.0001) under heavy grazing and consisted mainly of Galenia africana and few palatable perennials. The aim of this study was to test techniques that could restore this area to a more productive palatable shrubland. I propose that rehabilitation can be used to gain an understanding of the ecological factors that may be sustaining this altered vegetation state. My methodology involved biophysical interventions to manipulate this system. Grazing pressure was removed from the study area and vegetation changes were monitored under grazed and protected regimes. No change in plant cover was found after two years. However, there was an increase in cover of palatable perennials in relation to overall cover. I physically manipulated the environment by introducing microcatchments and brushpacks to act as traps for water, seed and organic material. These interventions resulted in few changes, however, I found higher soil moisture levels in microcatchments and under brushpacks than open positions. Cover of ephemerals was also significantly higher (p<0.001) in areas that had been brushpacked. In the absence of a seedbank, I tested whether the introduction of seed would result in recruitment. Seed of four palatable perennial species was sown into open, packed and tilled soil. A low number of seeds germinated in the first year and most seedlings died. Further germination occurred after a rainfall event in the second year, but still in very low numbers. Various microhabitats were implemented to assess seedling establishment requirements. Seedlings were transplanted in microcatchments and open positions; in areas cleared of Galenia, under adult Galenia and brush packs and in bare soil. Microhabitats did not facilitate seedling establishment, and few seedlings survived. Survival of seedlings was influenced by the size of seedling at transplantation and site differences. I conclude that the factors underlying vegetation change are complex. Individual physical and biological interventions offered no immediate change in vegetation cover and composition. However, a combination of interventions may over time and under favourable climatic conditions allow the return of a viable palatable shrubland. / South Africa

Magister Scientiae - MSc / Pastoralists in Africa have developed complex mechanisms by which they can alleviate the threat of drought. They practice mobility as one of the strategies to avoid the worst effects of natural stress and disperse grazing pressure. In the past in South Africa, the indigenous Nama people occupied large areas of land and moved around extensively to exploit seasonal differences in the availability of forage and water. With the settlement of the Europeans in the Cape the indigenous people lost most of their land to the colonists. The Nama people were, therefore, restricted to smaller rangelands and their patterns of rangeland use had to adapt to the spatial constraints. Descendants now herd livestock from semi-permanent stockposts that are scattered throughout the commons. Herders use a range of practices to manage their livestock. The aims of this study was to assess the agro-ecological knowledge of livestock keepers; assess the condition of the rangeland during drought; determine the herding strategies of herders during drought. / South Africa

This study, undertaken under the auspices of the Centre of Wildlife Management and the former Centre for Indigenous Knowledge (University of Pretoria) was conducted in Maputaland, with special reference to the Tembe Elephant Park, Sileza Nature Reserve and in the neighbouring traditional wards (izigodi) of Mbangweni, Bhekabantu, Kwandaba, Zama-zama, Tsokotho, Manqakulani (which includes the Tshanini Community Conservation Area), Lulwane, Mntikini, Ndlondlweni, Ndovu and Sibonisweni. The main objective of this study was to evaluate the range condition and grazing capacity of the natural veld. A management plan for the Tshanni Community Conservation Area is presented, which could potentially serve as template for similar areas. To accomplish these objectives a cattle as well as a vegetation survey were conducted. The cattle surveys were conducted among the local communities (mentioned above) to identify and to evaluate the role played by cattle in the everyday lives of the communual people and to identify the types of grazing regime (practices). The vegetation surveys were undertaken to evaluate the range condition, grazing capacity and grazing quality of the herbaceous vegetation. The study also included methods to determine the number, distribution and health status of cattle present in the study area. The results indicated that social and religious values that were associated with cattle in the older Zulu culture have clearly faded in the Tembe Traditional Area. The current values of local communal people regarding cattle were concentrated on utilization and investment for future uncertainties. Cattle were still seen as wealth and status symbols in the local communities and were highly prized possessions if they could be obtained. The official cattle numbers did not seem to reflect the actual cattle numbers in the study area at the time of study. It was also clear that cattle were distributed in areas where the water supply was sufficient. The main grazing areas were thus in the east of the study area in the hygrophilous vegetation to the east of Manqakulani and mainly in Ndlondlweni. No specific grazing management practices could be identified and the grazing system could be best described by a continuous grazing practice. Grazing was not restricted to any part or piece of land inside the specific isigodi as long as the cattle stayed out of other people’s cultivated land. Overstocking the grazing area was not occurring at the time of the study as the stocking density was well below the area’s capacity. The general perception of the majority of the cattle owners was that their cattle were in a good condition. An analysis of the results obtained from the vegetation survey indicated that the herbaceous biomass yield did not vary noticeably among the management units within a site as well as among the different sites. The small fuel loads in the Tshanini Community Conservation Area did not necessitate burning and were probably below fuel loads needed for fires to spread. However, it was frequently observed that fire could be maintained in areas where the herbaceous biomass yield was below 2 000 kg/ha. The results represented in this study also indicated that the management units of the Tshanini Community Conservation Area were generally in a good condition and that the range condition of the Tshanini Community Conservation Area compared relatively well with the other reserves in the study area. The modified Ecological Index Method was reliable and time saving, yet simplistic enough for assessing the range condition of the management units of the Tshanini Community Conservation Area and the entire Tembe Traditional Area. The stocking density must be adaptable and based on the quantity and quality of grazing available at any time. The model that was used to calculate the stocking density of the study area allows for several elements to be modified to suit the conditions on a particular wildlife reserve at a particular time. For example, in future it may become necessary to adjust the percentage composition of graze and browse in the diet of some animal types for the calculation of Grazer Units (GU) and Browser Units (BU), mainly because the diet of the same type of animal may vary regionally. Finally, changes in the choice of the types of wildlife can be accommodated depending on the preferences and objectives of the management and steering committee of the Tshanini Community Conservation Area. This model can be applied as a tool for active adaptive management because it allows more control over the quantity and quality of available food plant resources and hence the stocking density of animal resources. It is proposed that the results of the present study be combined and integrated into a Geographic Information System (G.I.S.) database that could form the ecological basis for future management planning of the Tembe Traditional Area as part of the Usuthu-Tembe-Futi Transfrontier Conservation Area. / Dissertation (MSc)--University of Pretoria, 2009. / Animal and Wildlife Sciences / unrestricted

No description available.

Rumen-undegradable protein might be the first limiting nutrient for high producing dairy cows receiving high levels of maize supplementation while grazing pasture. To test this hypothesis two trials were conducted using fishmeal as a high quality protein source rich in rumen-undegradable protein, Methionine and Lysine. In the first trial cows grazed annual ryegrass for two months in spring. In the second trial cows grazed kikuyu for two months in late summer. In addition to the pasture cows received 6 kg (as is) of a maize-based supplement, including minerals, fed in two equal portions in the milking parlour. A randomised complete block design was used. Three groups of 15 (ryegrass) or 14 (kikuyu trial) cows received control (no fishmeal), low fishmeal (4 % fishmeal replacing maize) or high fishmeal (8 % fishmeal replacing maize) treatments. Multiparous, high producing, Jersey cows in early to mid lactation were used. Milk production was measured and milk samples taken fortnightly. Simultaneous studies were conducted using eight rumen cannulated cows receiving the control and high fishmeal treatments in a cross over design experiment. Ruminal pH, ammonia-N and volatile fatty acid concentrations were measured. In the ryegrass trial milk yield, 4 % fat-corrected milk yield and milk fat and protein percentages of cows on the low and high fishmeal treatments (21.9 and 22.1 kg milk/d, 24.1 and 24.2 kg 4 % fat-corrected milk/d, 4.73 and 4.67 % fat and 3.49 and 3.45 % protein) were significantly higher than the control (20.5 kg milk/d, 20.4 kg 4 % fat-corrected milk/d, 3.97 % fat and 3.25 % protein). There was no treatment effect on milk urea N (16.8, 17.4 and 17.9 mg/dl, for the control, low fishmeal and high fishmeal treatments, respectively). The ruminal ammonia-N concentration was significantly higher in the cows on the high fishmeal treatment than the control (16.67 vs. 14.16 mg/dl). Fishmeal supplementation to cows on ryegrass is profitable under any realistic price scenarios in South Africa. In the kikuyu trial cows on the high fishmeal treatment produced significantly more milk (19.5 kg/d) than the cows on the control (18.2 kg/d), neither differing from the low fishmeal treatment (18.9 kg/d). The cows on the low fishmeal treatment had significantly higher milk fat percentage (4.18 %) than the control (3.71 %), neither differing from the high fishmeal treatment (3.91 %). The cows on the two fishmeal treatments produced significantly more 4 % fat-corrected milk than the control (19.4 and 19.2 vs. 17.3 kg 4 % fat-corrected milk/d). There was no treatment effect on milk protein percentage (3.30, 3.41 and 3.34 % for the control, low and high fishmeal treatments, respectively). Milk urea N was significantly higher for the high fishmeal treatment (10.80 mg/dl) than the control and low fishmeal treatments (9.09 and 9.44 mg/dl). Ruminal ammonia-N concentration was significantly higher in the cows on the high fishmeal treatment than the control (6.52 vs. 4.74 mg/dl). Fishmeal supplementation to cows on kikuyu could be profitable under certain price scenarios. / Dissertation (MSc(Agric) (Animal Science))--University of Pretoria, 2008. / Animal and Wildlife Sciences / unrestricted

Biological indicators measure components of the biota and are used to give general information about complex ecosystems in which they occur, playing key roles in conservation planning and management. This study illustrates the impact of habitat change by factors that are extrinsic to the habitats in question and the importance of spider responses in aiding management decisions. The spider responses illustrated existence of environmental change and represent responses of other biota. The conclusions drawn from this study have important management implications for protected areas with grazing herbivores and occurrence of alien invasive plants. Grazed sites showed the highest abundance, diversity and species richness, while ungrazed had the lowest. The implications from this study are that no grazing has negative implications on lower trophic levels, whereas grazing seems to result in favourable conditions for optimal abundance, diversity and species richness. The higher abundance, diversity and species richness associated with grazed sites could result from increased ground cover, greater variation in habitat structure, increased plant diversity and enhanced soil/plant nutrient concentrations. But, ungrazed sites in turn become more monotonous and provide less habitat diversity. However, the characteristic species for each grazing intensity level demonstrates the difficulty in making generalizations for management even for closely related species. The results further opposed the assumption that grazing lawns are a result of overgrazing and thus highly undesirable. This grassland type in comparison to tall bunch grassland displayed the highest spider diversity and species richness. This evidence further supports the conclusion that grazing lawns are steady state communities of their own and not a sub-set of any other grassland type. Therefore, veld management decisions that eradicate grazing lawns are negative for the park as the fauna and flora associated with this grassland type will be lost, leading to cascading effects. Additionally, this study illustrated that habitat modification by invasion of invasive alien plant species has detrimental consequences for the endemic fauna. C. odorata invasion results in a monotonous habitat structure. Consequently, structural heterogeneity is a primary determinant for spider diversity as opposed to abundance of prey, because plant height and architecture drive spider colonization. Therefore, removal of alien invasive weeds results in returning a system to close approximation of its condition prior to disturbance with both structure and function recreated. Assemblage patterns can be selected as endpoints to measure the ecological rehabilitation; thus, the non-significant differences in assemblage patterns of the control versus cleared sites imply that the system is rehabilitating with clearing without further management intervention. This study adds to the limited information on the implications of grazing intensities, grassland types, short and long-term invasion and clearing of an alien invasive plant on spider communities. Copyright / Dissertation (MSc)--University of Pretoria, 2008. / Animal and Wildlife Sciences / unrestricted

Blumetto Velazco, OR. (2012). Caracterización de sistemas de producción de porcino y vacuno de engorde en Uruguay [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/16002 / Palancia