Thesis (MSc. (Pasture Science)) -- University of Limpopo, 2019 / An experiment was conducted at the University of Limpopo to determine the diet selection of cattle in the Petersburg Plateau Bushveld, the aim being to identify important and palatable grass species during four seasons of the year and to determine their above-ground biomass production. For diet selection data, five permanently marked transects were randomly laid out per camp, each 100 m long. On each transect, grass tufts were identified and permanently marked at 1 m intervals (100 tufts per transect). Turfs were surveyed on a weekly basis to determine frequency, intensity of utilization and tuft height. A palatability index was determined for each species. Diet selection data were analysed, using descriptive statistics. For biomass production, five permanent 20 m x 20 m plots were randomly laid out per camp, in which biomass of grass were measured. Within each plot, five 1 x 1 m quadrates were randomly harvested. The biomass data was analysed using the General Linear Mixed Model. Means were compared, using a Tukey test at the 5% significance level. Digitaria eriantha, Eragrostis rigidior and Heteropogon contortus were the dominant grass species. On average, Brachiaria nigropedata, Panicum maximum and Digitaria eriantha were utilized at higher frequencies and intensities. Brachiaria nigropedata, P. maximum, Urochloa mosambicensis, Themeda triandra, D. eriantha, Schmidtia pappophoroides and H. contortus were regarded as the most palatable species. The circumference of the tuft of S. pappophoroides, E. rigidior and D. eriantha decreased highly significantly (P<0.01). The height of utilizable leaves of B. nigropedata, D. eriantha, P. maximum and S. pappophoroides decreased highly significantly, while the height of highest leaves of B. nigropedata, D. eriantha, P. maximum, S. pappophoroides, H. contortus and T. triandra also decreased highly significantly. Total biomass production was significantly higher (P<0.05) during autumn, while total biomass production during winter was low, compared to other seasons. Total biomass production did not differ significantly between spring and summer. Panicum maximum, x B. nigropedata, D. eriantha, T. triandra, H. contortus, S. pappophoroides and U. mosambicensis were regarded as “key species” in the diet selected by cattle. Farmers in the Pietersburg Plateau Bushveld should graze their camps to assure the maintenance or improvement of perennial palatable grasses with high biomass production, which will result in overall improvement of veld condition.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / Soil degradation can occur because of inadequate management, which may result in soil unproductive and, in certain situations, lead to the desertification process. One of the causes of degradation is overgrazing, causing loss of biodiversity of plant strata by the pressure of ramoneio and soil compaction by excessive trampling of animals, bringing implications to the ground in the physical, chemical and biological properties, thereby undermining the sustainability of the agroecosystem. An alternative to recover soil degradation is the practice of fallow, because that is easy to perform and inexpensive to restore soil properties that provides input of organic matter, important soil conditioner. With that aimed to prove the hypothesis that the time of 14 year fallow improves the physical and chemical soil in degraded areas in the process of desertification. The areas selected for the study are located in the municipality of IrauÃuba in the state of CearÃ, Brazil. Soil samples were taken in five areas of overgrazing, in five areas of fallow and in a forest area, is serving as the reference area. Physical and chemical analysis of the soil as soil density, total porosity, flocculation, pH, electrical conductivity, cation exchange capacity (CTC), total organic carbon, carbon management index and physical fractions of organic carbon, were done to assess the changes the physical and chemical attributes of these areas. The management of fallow showed improvements in physical and chemical soil when assessed after 14 years of withdrawal of animals, but when compared to the work done in the same area in 2009, with 7 years of fallow, evidence that the areas are still in the process of degradation. The organic carbon content was higher in the areas of fallow and the fraction with the highest proportion was the organic carbon associated to minerals. / A degradaÃÃo do solo pode ocorrer em funÃÃo do manejo inadequado, o qual pode acarretar na improdutividade do solo e, em certas situaÃÃes, levar ao processo de desertificaÃÃo. Uma das causas da degradaÃÃo à o sobrepastejo, ocasionando perda da biodiversidade do estrato vegetal pela pressÃo do ramoneio e compactaÃÃo do solo pelo pisoteio excessivo dos animais, trazendo implicaÃÃes ao solo nas propriedades fÃsicas, quÃmicas e biolÃgicas, comprometendo assim a sustentabilidade do agrossistema. Uma alternativa para recuperar a degradaÃÃo do solo à a prÃtica do pousio, pois essa à de fÃcil execuÃÃo e de baixo custo para restaurar as propriedades do solo que proporciona aporte de matÃria orgÃnica, importante condicionador do solo. Com isso, objetivou-se comprovar a hipÃtese que o tempo de pousio de 14 anos melhora os atributos fÃsicos e quÃmicos do solo em Ãreas degradadas em processo de desertificaÃÃo. As Ãreas selecionadas para o estudo estÃo localizadas no municÃpio de IrauÃuba, no Estado do CearÃ, Brasil. Foram realizadas coletas de solo em cinco Ãreas de sobrepastejo, em cinco Ãreas de pousio e em uma Ãrea de mata, esta servindo como Ãrea de referÃncia. AnÃlises fÃsicas e quÃmicas do solo como: densidade do solo, porosidade total, grau de floculaÃÃo, pH, condutividade elÃtrica, capacidade de troca de cÃtions (CTC), carbono orgÃnico total, Ãndice de manejo de carbono e fracionamento fÃsico do carbono orgÃnico, foram feitas a fim de avaliar as modificaÃÃes nos atributos fÃsicos e quÃmicos destas Ãreas. O manejo de pousio apresentou melhorias em atributos fÃsicos e quÃmicos do solo quando avaliado apÃs 14 anos de retirada dos animais, mas quando comparada ao trabalho realizado na mesma Ãrea em 2009, com 7 anos de pousio, evidÃncia que as Ãreas ainda estÃo em processo de degradaÃÃo. O teor de carbono orgÃnico foi maior nas Ãreas de pousio e a fraÃÃo com maior proporÃÃo foi o carbono orgÃnico associado aos minerais.

Thesis (MScConsEcol (Conservation Ecology and Entomology))--Stellenbosch University, 2008. / The widespread ecological impacts of overgrazing by livestock within the Succulent Karoo have received considerable attention. Literature shows communal and commercial rangelands have been thoroughly studied, and vegetation responses have been investigated in an attempt to understand the effects of overgrazing. Regarding animal species, literature is in short supply. In a one-year study of small mammal assemblages, the effect of the rangelands, and subsequently vegetation, on small mammal assemblages was examined, as well as the effects on number of occupied, unoccupied and collapsed burrows. This study shows that vegetation composition differs between rangelands, with a greater perennial shrub cover on the communal rangelands and a greater perennial succulent cover on commercial rangelands, consequently creating different habitats for animal assemblages. This study supports the notion of small mammal composition relating to vegetation structure, with certain species being impacted by heavy grazing. Four small mammal species were found in greater abundances on commercial rangelands, with one being exclusive, while communal rangelands were exclusively occupied by three nocturnal species. Diet and habitat requirements are the most important factors regarding species occurrence. With small mammal species composition differing between rangelands, and species richness not being affected by rangeland type, this study illustrates that the disappearance of certain species may arise without these different rangelands. This could result in reduced species richness, and thus diversity being lost. Regarding species present on both rangelands, no differences were observed in body mass, body size or body condition. Despite no differences found in body condition, calculating a body condition index is a good method for investigating how a species is coping within an environment. The proportion and number of occupied and collapsed burrows can be seen as a measure of trampling effect. It was expected for grazing intensity, as well as vegetation changes, to affect the occurrence of such burrows. This study showed differences between the communal and commercial rangelands as negligible. As expected, numbers of burrowing small mammal species were negatively correlated with numbers of collapsed burrows. However, a lack of consistency deemed this result unimportant. Results show that the effects of overgrazing on small mammal populations are complex and require more attention if to be fully explained. This study provides insights into the effects of land use on small mammals and burrow numbers, which have implications for the conservation of these species within arid regions.

<p>Seagrasses constitute the basis for diverse and productive ecosystems worldwide. In East Africa, they provide important ecosystem services (e.g. fisheries) but are potentially threatened by increasing resource use and lack of enforced management regulations. The major aim of this PhD thesis was to investigate effects of anthropogenic distur-bances, primarily seaweed farming and coastal fishery, in East African seagrass beds. Seaweed farming, often depicted as a sustainable form of aquaculture, had short- and long-term effects on seagrass growth and abundance that cascaded up through the food web to the level of fishery catches. The coastal fishery, a major subsistence activity in the region, can by removing urchin predators indirectly increase densities of the sea urchin <i>Tripneustes gratilla</i>, which has overgrazed seagrasses in several areas. A study using simulated grazing showed that high magnitude leaf removal – typical of grazing urchins – affected seagrasses more than low magnitude removal, typical of fish grazing. Different responses in two co-occurring seagrass species furthermore indicate that high seagrass diversity in tropical seagrass beds could buffer overgrazing effects in the long run. Finally, a literature synthesis suggests that anthropogenic disturbances could drive shifts in seagrass ecosystems to an array of alternative regimes dominated by other or-ganisms (macroalgae, bivalves, burrowing shrimp, polychaetes, etc.). The formation of novel feedback mechanisms makes these regimes resilient to disturbances like seagrass recovery and transplantation projects. Overall, this suggests that resource use activities linked to seagrasses can have large-scale implications if the scale exceeds critical levels. This emphasizes the need for holistic and adaptive management at the seascape level, specifically involving improved techniques for seaweed farming and fisheries, protection of keystone species, and ecosystem-based management approaches.</p>

Seagrasses constitute the basis for diverse and productive ecosystems worldwide. In East Africa, they provide important ecosystem services (e.g. fisheries) but are potentially threatened by increasing resource use and lack of enforced management regulations. The major aim of this PhD thesis was to investigate effects of anthropogenic distur-bances, primarily seaweed farming and coastal fishery, in East African seagrass beds. Seaweed farming, often depicted as a sustainable form of aquaculture, had short- and long-term effects on seagrass growth and abundance that cascaded up through the food web to the level of fishery catches. The coastal fishery, a major subsistence activity in the region, can by removing urchin predators indirectly increase densities of the sea urchin Tripneustes gratilla, which has overgrazed seagrasses in several areas. A study using simulated grazing showed that high magnitude leaf removal – typical of grazing urchins – affected seagrasses more than low magnitude removal, typical of fish grazing. Different responses in two co-occurring seagrass species furthermore indicate that high seagrass diversity in tropical seagrass beds could buffer overgrazing effects in the long run. Finally, a literature synthesis suggests that anthropogenic disturbances could drive shifts in seagrass ecosystems to an array of alternative regimes dominated by other or-ganisms (macroalgae, bivalves, burrowing shrimp, polychaetes, etc.). The formation of novel feedback mechanisms makes these regimes resilient to disturbances like seagrass recovery and transplantation projects. Overall, this suggests that resource use activities linked to seagrasses can have large-scale implications if the scale exceeds critical levels. This emphasizes the need for holistic and adaptive management at the seascape level, specifically involving improved techniques for seaweed farming and fisheries, protection of keystone species, and ecosystem-based management approaches.

Social dilemmas constitute a broad class of quandaries, including, for example, common pool resource (CPR) dilemmas and public good (PG) dilemmas. CPR's are characterized by non-excludability and rivalry and are often associated with overexploitation. Through similar arguments, the features non-excludability and non-rivalry give rise to under-provision of PG's. The prevalence and inefficiencies often associated with CPR's have given rise to an extensive literature and the role of resource uncertainty has not been ignored. Uncertainty combined with rivalry is often said to augment users' incentive to overexploit. However, underlying most of the theoretical research is an explicit or implicit assumption of symmetric information, or a symmetric lack of information. In reality, people generally have access to different sources of information and they may differ in their abilities to process information. In the first two papers of this thesis, the assumption of symmetry is relaxed and both papers demonstrate that from a welfare perspective, the distribution of uncertainty is also of importance. Many CPR's and PG's are natural, which can complicate the situation. In the traditional resource management literature, the exploited resource is often assumed to be properly characterized by some concave growth function. Today, there is extensive empirical evidence suggesting that many ecosystems have more complex, often non-linear dynamics. Management of such resources can be quite challenging as the non-linear dynamics can make the ecosystem flip between alternate stable states, and even marginal changes can cause radical transformations of such ecosystems. Most of the CPR models assume the shared resource to be of fixed size or to be able to generate a constant flow of services. In the third paper we aim at providing a more complete picture of the overexploitation of a common resource, by combining the institutional structure with complex ecological dynamics. We manage to raise questions and doubts about the standard assumptions. Another feature of convex-concave resources is that a state can become highly robust and sometimes an ecosystem change may even be irreversible. This is problematic if, for example, we wish to restore a degraded ecosystem. The aim of the fourth paper is to empirically analyze this question, by eliciting peoples' preferences through a hypothetical referendum on the issue. / Diss. Stockholm : Handelshögskolan, 2005

Text in English / Biodiversity is a fundamental characteristic of life on Earth and encompasses the whole range of variation in living organisms. Lesotho has been subjected to tremendous biodiversity change over the last two centuries, primarily due to socio-economic activities. A number of socio-economic factors have contributed to the loss of biodiversity. However, worldwide experience has shown that, the consequences emanating from loss of biodiversity are sometimes irreversible as some species are threatened by extinction. The study aimed at exploring the impacts of socio-economic activities that result in loss of large game animals, predators and indigenous plants species in Lesotho. To serve this objective, both quantitative and qualitative research methodologies were used to collect data. Quantitative research method was used in pre-post tests whilst qualitative research method was used in interviews and focus group discussions to collect data. The finding and results of the study show that, impacts of human vectors such as immigration, migration, settlement, economic and recreation activities in Lesotho have the impacts to the loss of large game animals, predators and indigenous plants. It is imperative therefore, for Lesotho to find ways to establish more parks and botanic gardens that could offer opportunities for re-introduction of species in Lesotho, thus, adding value to the existing parks. / Environmental Sciences / M. Sc. (Environmental Management)

Text in English / Biodiversity is a fundamental characteristic of life on Earth and encompasses the whole range of variation in living organisms. Lesotho has been subjected to tremendous biodiversity change over the last two centuries, primarily due to socio-economic activities. A number of socio-economic factors have contributed to the loss of biodiversity. However, worldwide experience has shown that, the consequences emanating from loss of biodiversity are sometimes irreversible as some species are threatened by extinction. The study aimed at exploring the impacts of socio-economic activities that result in loss of large game animals, predators and indigenous plants species in Lesotho. To serve this objective, both quantitative and qualitative research methodologies were used to collect data. Quantitative research method was used in pre-post tests whilst qualitative research method was used in interviews and focus group discussions to collect data. The finding and results of the study show that, impacts of human vectors such as immigration, migration, settlement, economic and recreation activities in Lesotho have the impacts to the loss of large game animals, predators and indigenous plants. It is imperative therefore, for Lesotho to find ways to establish more parks and botanic gardens that could offer opportunities for re-introduction of species in Lesotho, thus, adding value to the existing parks. / Environmental Sciences / M. Sc. (Environmental Management)