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.

The aim of the research presented in this dissertation was to further the implementation of push-pull for control of Eldana saccharina on sugarcane in the Midlands North region, KwaZulu-Natal, South Africa. Eldana saccharina, an indigenous stem borer, is the most damaging pest of sugarcane in South Africa, and sustainable control has still not been achieved. The push-pull strategy, a form of habitat management, has been developed for E. saccharina and is recommended as part of an integrated pest management (IPM) approach. Implementation of this strategy for both large- and small-scale farmers was facilitated through mixed methods social research. It included a novel exploratory network analysis to understand the process of technology adoption by farmers. Surveys showed that large-scale farmers have a good knowledge of E. saccharina, IPM and push-pull but that they needed more practical knowledge for implementation of the strategy. Farmers recommended experiential learning opportunities such as field days and model farms to get to know more about this technology. Despite demonstrating a positive attitude towards push-pull, farmers perceived it to be a ‘hassle’ and this is potentially the biggest barrier to its adoption. However, with suitable learning opportunities for farmers and good support for planting inputs, implementation of push-pull is likely to succeed. Sugarcane was shown to play an important role in the livelihoods and farming systems of small-scale growers. They did not perceive E. saccharina as a serious production constraint and had poor knowledge of the pest and its control. Extension for small-scale growers in this region should focus primarily on weed management and on reducing input costs, but still raising awareness of the increasing threat of E. saccharina. On-farm push-pull field trials showed a significant reduction of E. saccharina damage on two farms. Mean percentage damaged internodes decreased from 4.1% to 2.7% and from 1.7% to 1.1% in the presence of the repellent grass species, Melinis minutiflora. Where farmers did not manage their crops well, push-pull was not effective. It is therefore crucial that push-pull within an IPM framework be implemented together with good crop management practices. Stem borer surveys in wetlands on sugarcane farms revealed a high diversity of indigenous stem borers and parasitoids, including a stem borer species, Pirateolea piscator, which may pose a threat to crops in the future. These findings, together with a literature review on the significance of on-farm biodiversity and ecosystem services, demonstrated the value which wetlands have for pest management on sugarcane farms. Wetland health assessments were used to develop a tool for farmers to assess and utilise the wetlands on their farms for improved management of E. saccharina. This study highlights the importance of a farmer-participatory approach to implementation of knowledge-intensive farming practices such as push-pull. The importance of wetlands for providing pest regulatory services on sugarcane farms has shown that environmental sustainability needs to become a fundamental principle of farming and agricultural research. Participatory implementation of push-pull, as recommended in this dissertation, could act as a driving force for agroecology in the South African sugar industry and move sustainable farming practices off the pages of journals and manuals onto farmers’ fields. / Thesis (MSc (Zoology))--North-West University, Potchefstroom Campus, 2013

The aim of the research presented in this dissertation was to further the implementation of push-pull for control of Eldana saccharina on sugarcane in the Midlands North region, KwaZulu-Natal, South Africa. Eldana saccharina, an indigenous stem borer, is the most damaging pest of sugarcane in South Africa, and sustainable control has still not been achieved. The push-pull strategy, a form of habitat management, has been developed for E. saccharina and is recommended as part of an integrated pest management (IPM) approach. Implementation of this strategy for both large- and small-scale farmers was facilitated through mixed methods social research. It included a novel exploratory network analysis to understand the process of technology adoption by farmers. Surveys showed that large-scale farmers have a good knowledge of E. saccharina, IPM and push-pull but that they needed more practical knowledge for implementation of the strategy. Farmers recommended experiential learning opportunities such as field days and model farms to get to know more about this technology. Despite demonstrating a positive attitude towards push-pull, farmers perceived it to be a ‘hassle’ and this is potentially the biggest barrier to its adoption. However, with suitable learning opportunities for farmers and good support for planting inputs, implementation of push-pull is likely to succeed. Sugarcane was shown to play an important role in the livelihoods and farming systems of small-scale growers. They did not perceive E. saccharina as a serious production constraint and had poor knowledge of the pest and its control. Extension for small-scale growers in this region should focus primarily on weed management and on reducing input costs, but still raising awareness of the increasing threat of E. saccharina. On-farm push-pull field trials showed a significant reduction of E. saccharina damage on two farms. Mean percentage damaged internodes decreased from 4.1% to 2.7% and from 1.7% to 1.1% in the presence of the repellent grass species, Melinis minutiflora. Where farmers did not manage their crops well, push-pull was not effective. It is therefore crucial that push-pull within an IPM framework be implemented together with good crop management practices. Stem borer surveys in wetlands on sugarcane farms revealed a high diversity of indigenous stem borers and parasitoids, including a stem borer species, Pirateolea piscator, which may pose a threat to crops in the future. These findings, together with a literature review on the significance of on-farm biodiversity and ecosystem services, demonstrated the value which wetlands have for pest management on sugarcane farms. Wetland health assessments were used to develop a tool for farmers to assess and utilise the wetlands on their farms for improved management of E. saccharina. This study highlights the importance of a farmer-participatory approach to implementation of knowledge-intensive farming practices such as push-pull. The importance of wetlands for providing pest regulatory services on sugarcane farms has shown that environmental sustainability needs to become a fundamental principle of farming and agricultural research. Participatory implementation of push-pull, as recommended in this dissertation, could act as a driving force for agroecology in the South African sugar industry and move sustainable farming practices off the pages of journals and manuals onto farmers’ fields. / Thesis (MSc (Zoology))--North-West University, Potchefstroom Campus, 2013

MENVSC / Department of Geography and Geo-Information Sciences / This is a case study research that focuses on the assessment of the impacts of land use changes on the Duthuni wetland ecosystem in Limpopo Province using geospatial techniques and Social Survey. SPOT 4 satellite images which covered the time frame between 1999, 2005 to 2012, were used. The unit of analysis included different institutions such as the local municipality, farmers, the heads of the households and Chief of the Village. In this study, different methods of sampling were used in different context for selecting participants and for sample size determination. The different instruments for data collection included the questionnaires, interviews, focus group interviews and documents review. Socio-economic survey and review of documents were carried out to understand historical trends, collect ground truth and other secondary information required. Data collected from the survey were captured and analysed using the Statistical Package for Scientific Solutions (SPSS). For quantitative analysis, Chi-Square and cross tabulation were employed in SPSS. Analysis of satellite imagery was accomplished through integrated use of ERDAS Imagine (version 2015) and ArcGIS (version 10.1) software package. The themes were identified and analysed using the content analysis based on the main research topics. The results show that the land use/ cover changes have occurred at an unprecedented rate over the years 1999 to 2012. From the year 1999 to the year 2012, the total land use/ cover conversions equal to 299.984 ha of land. The trend and spatial extent of land use/ cover changes had undergone considerable changes over the years in the study period. The major contributing factors included population increase, expansion of agriculture and lack of space to settle. The residential area was found to be the major factor contributing to land use change over the years with an increase of (102.87ha.). People residing in Duthuni village especially along the wetland ecosystem consist of the majority of female-headed households. There is no proper facilitation and mentoring in the village by the government in order to resolve social problems when it comes to land use change. Water pollution and soil erosion were found to be the major concern by wetland users such as farmers and residents. Lack of knowledge has also been identified as one of the driving factors of environmental impacts of land use change in the area. Food was the most resources with 41% which the community gets from the wetland.