4. Electronic Theses and Dissertations (ETDs) - Faculties submissions
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Item Resolving Inter- and Extra-group Discord Between Forestry and Milling Industries Using Photo-optical Technology(University of the Witwatersrand, Johannesburg, 2022-03) Bierman, Rohan; Penman, NealeTWK Agri timber mills purchase significant volumes of timber from the forestry division of the group and external plantations. A process is followed when timber arrives at a mill to determine the volume of timber to pay in tons, and this process utilises a conversion factor to convert cubic meters to tons. This conversion factor, 1.37 m3/ton, has been in use for many years, although recently it has become apparent that timber suppliers are dissatisfied with this value as they believe it to be longer representative of the state of timber being supplied to the mills. Importantly, the conversion factor has a direct impact on the amount that suppliers are compensated. The implications of low trust relationships with disgruntled suppliers of a key raw material cannot be overstated: if suppliers withdraw from supply agreements, the timber mills will be unable to meet the demand of the mining industry and other markets. This consulting report is concerned with investigating whether the conversion factor is still representative or should be adjusted. The means of conducting this investigation is using a photo-optical mobile device application, Timbeter, which can determine the volume of timber on a truck through photographing every stack and inputting the length of the logs. The application can identify each log and size it accordingly to calculate volume. The implication is that it has greater accuracy than the current manual method to determine volume. Using volume data from the Timbeter application of trucks measured from February to October 2021, along with weighbridge data, the actual factors were statistically analysed in comparison with the current factor, as well as reviewing other variables of stack density for varying timber diameter classes, species, and season. It is shown that the current factor is no longer suitable and should be adjusted to 1.24 m3/ton. This will have a profound impact on suppliers in terms of additional revenue; using volume measurements from Timbeter with the new factor the timber mills would pay a minimum additional R7.2 – R7.8m to all suppliers combined. However, with better recovery from lower input volumes calculated, the timber mills can calculate lower cost prices for products, thereby increasing gross profit. It was also imperative to investigate the perceptions of key individuals employed at the timber mills in relation to technology and the implementation of Timbeter as a technological solution to calculate timber volume on trucks. This qualitative study was conducted through semi-structured interviews and identifying the main themes into which the response data could be grouped. Four main themes were identified, covering operational challenges, supplier treatment, training and implementation and acknowledging the issues that arise with new technology implementation. The main conclusions from the quantitative and qualitative components of the consulting project were presented. Finally, recommendations were made in respect of the conclusions from the quantitative and qualitative components.Item The effects of resource variability on the demographic rates of black and white rhinoceroses(University of the Witwatersrand, Johannesburg, 2023) Ndlovu, Latoya; Marshal, JasonGiven the importance of rhino survival and reproduction to conservation goals, the aim of the study was to investigate the effects of resource variability on the demographic rates of black (Diceros bicornis) and white (Ceratotherium simum) rhinos at Lapalala Wilderness. I used historical rhino-monitoring, rainfall and vegetation greenness data to investigate the vital rates of two rhino populations. I investigated population demographics (mainly density, growth rates, age and sex structure) and survival using stratified Cox models. Black and white rhino density peaked at 0.06 rhinos/km2 and 0.2 rhinos/km2 , respectively during the study period and was below the estimated maximum density for suitable rhino reserves. Average growth rate for the black rhinos was 4.784%, which was almost half of the white rhino’s rate of 8.861%. The survival of both species was stage-specific, and rainfall effects were similar for both species and age groups as low amounts of rainfall, which likely represent decreased forage availability, were associated with increased mortality risk. Decreasing greenness was also associated with increased mortality except with white rhino calves, where mortality increased with greenness. I suggest that this case might have been caused by their nutritional requirements: most grasses lose nutritional value as the season progresses (i.e., represented as increases in greenness values and so reduced access to high quality forage might affect mom’s body condition and her ability to produce nutritious milk, consequently resulting in increased mortality rates of calves. I also investigated the reproductive phenology (mainly conception and birth timing, age at primiparity and inter calving intervals) and birth sex ratios in relation to sex allocation theories. White rhinos conceived and calved at an earlier age compared to the black rhinos; mean age at primiparity for white and black rhinos was 9.448 years (8.467, 10.43) and 11.724 years (10.52, 12.927), respectively. Conceptions for both species peaked during the wet season and were associated with periods of high forage availability; however, births were asynchronous and occurred throughout the year. Effects of rainfall and greenness on age at first conception differed between species; the odds of having their first calf increased with rainfall, EVI and NDVI for white rhinos but decreased with EVI and NDVI for the black rhinos. Increases in wet-season integrated greenness during conception periods might indicate a shorter period of access to high quality forage for the black rhinos. Age at primiparity increased with density for both species because population density increases competition for resources, potentially making it difficult for females to accumulate the body mass and energy reserves needed to reproduce. Inter-calving intervals increased with rainfall, supporting the idea that excessive amounts of rainfall might result in lower forage quality, which then affects maternal body condition. In conclusion, vital rates of black and white rhinos are associated with resource availability as a function of environmental stochasticity and density, which in turn affects productivity and performance as climate change results in more variable conditions.