Doctoral Degrees (Conservation Ecology and Entomology)

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Now showing 1 - 5 of 114
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    Characterisation of soil macro- and mesofauna diversity and their contribution to soil health in grain agroecosystems
    (Stellenbosch : Stellenbosch University, 2023-03) Mamabolo, Emogine; Pryke, James S. ; Gaigher, Rene; Stellenbosch University. Faculty of Agrisciences. Dept. of Conservation Ecology and Entomology.
    ENGLISH ABSTRACT: Agriculture is the most important source of food and critical to the South African economy, yet it is detrimental to the environment, including the soil. We need to find innovative ways to achieve agricultural sustainability. Sustainable models are increasingly being adopted, but the major challenge remains measuring their effectiveness. Soils are inextricably linked to sustainable agriculture, as good soils promote crop growth and yields, while sensitive to chemical inputs that farmers place on the croplands. Due to the importance and sensitivity of soil, the assessment of soil health and soil fauna biodiversity has been proposed as an indicator of sustainability yet rarely considered when making recommendation for sustainable agricultural intensification. This dissertation explores the differences in diversity of soil macro-and mesofauna (from here on called soil fauna) under different agricultural land uses, namely conventional, conservation, integrated and natural grasslands, and how this affects the soil physicochemical environment and decomposition processes. The status of macrofauna as bioindicators of soil health was explored to provide a more direct tool in measuring soil function and sustainability. Biodiversity metrics revealed that cultivation under minimum soil disturbance coupled with complex vegetation and soil cover benefited soil fauna and allowed the establishment of most functional groups, which are crucial for pest control, nutrient cycling, and decomposition. Therefore, reduced tillage and increased structural complexity are recommended for preserving soil arthropod diversity and associated ecosystem services. Litter decomposition was positively linked to soil fauna species richness and not abundance or diversity. Results also showed that, soil fauna significantly contributed to decomposition, but contributions are highly depended on temperature, soil moisture and land use intensity. These findings highlight the importance in understanding management effects on soil fauna functional roles in maintaining nutrient cycling and soil health. Soil characterisation showed that conventional land uses favoured some important soil properties, however the overall effects of the soil physicochemical environment on fauna were complex, implying that sustainable intensification will not only be beneficial for productivity but also for the promotion of soil fauna and ecosystem services. Multivariate analyses of soil health characterisation allowed for the development of a simple but robust soil health assessment tool using soil macrofauna as indicators. The tool is important for assessing land use management and associated effects on soil health and ecosystem function. Overall, this dissertation shows that sustainable management, increased biodiversity, and increased soil health complement each other. Compared to their conventional counterparts, the conservation and livestock integrated land uses optimised favourable and stable conditions for various soil fauna groups and were more like that of the natural grasslands. As some of the important soil variables are favoured by more intensive land uses, designing sustainable and functional schemes is a lengthy process which requires patience, as soil itself is an ever-evolving entity which needs time to generate and/or restore. Here it is shown that low intensity agriculture promotes health soil fauna, thus sustainable management of soils in agriculture has the potential to increase the overall soil health, biodiversity, and function, meaning they (ecosystem engineers) can restore degraded soils and ecosystem services.
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    “A social-ecological systems approach to sustainable production of endemic rooibos (Aspalathus linearis) and honeybush (Cyclopia spp.) species amongst agrarian communities in the Cape Floristic Region (CFR)”
    (Stellenbosch : Stellenbosch University, 2022-12) Malgas, Rhoda Ronette; Esler, Karen J.; Jacobs, Shayne Martin; Schaminee, Joop Hendrik Jacque; Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology.
    ENGLISH ABSTRACT: How do we ensure sustainable biomass production of Fynbos endemic plant species to support the livelihoods of small-scale producers in geographically delimited production areas of the Cape Floristic Region (CFR)? This research aims to address that question for the South African small-scale rooibos (Aspalathus linearis) and honeybush (Cyclopia spp.) sectors by applying a systems approach. Social-ecological (SE) variables and their interactions were described and mapped using Ostrom’s Social Ecological Systems Framework (SESF), a novel undertaking for Fynbos-based sectors. The SESF is a conceptual tool designed to describe, characterize, and analyse social-ecological systems (SES). It is used to diagnose problems and to elicit principles for improved SES outcomes, such as sustainable harvesting, agroecological production, sustainable livelihoods and maintaining the ecological integrity of wild rooibos and honeybush populations in natural Cape Fynbos plant communities. Pitfalls and pathways to sustainability were identified by analysing SE variables and their interactions. Variable identification was achieved through three inter-related studies. First, to anchor the conceptual work in a real-life focal action situation, the historical practice of wild-harvesting and contemporary production of honeybush at Genadendal (The Overberg, Western Cape) was used as a case. Interviews with 32 local ecological knowledge (LEK) holders formed the basis for a) collation of LEK to understand the mental models¹ or local perceptions resource-users have of local honeybush species and b) characterisation of LEK in the context of the SESF and potential sustainability outcomes in contemporary harvest systems of honeybush, and sister species, rooibos. Correlations between knowledge-bearer biographies and LEK, and details of knowledge transfer and LEK valuation were amongst the emerging themes. Findings from LEK also included details of species habitats, harvest sites, morphological features, and the status of local wild honeybush. Secondly, barriers that local land-users at Genadendal face in adopting honeybush production as a viable livelihood option were explored in comparison with accounts from rooibos and honeybush small-scale farmers elsewhere in the CFR to formulate a composite framework. Research outcomes highlight biophysical, institutional, and interpersonal barriers that these actors face in deciding whether to adopt indigenous rooibos or honeybush crops into their livelihood strategies. Thirdly, sets of ecological variables were identified from literature on Fynbos ecological research. Phytosocialogical data were used to highlight how conserving wild rooibos and honeybush habitats inadvertently conserve the habitats of co-occurring Fynbos species and concomitant ecological processes across a range of Fynbos vegetation types. A review of published research pointed to guides and recommendations for sustainable ¹ In the language of Ostrom’s Social Ecological Systems Framework, mental models refer to the conceptual ideas people commonly hold of the natural resource and how they interact with it. For instance, Sarah Ives (2014) describes this extensively for rooibos tea amongst different farmer groups. In her paper, she reflects on how the plants are associated with land and patriotism, whereas coloured producers consider the tea part of their heritage as First Nations descendants. biomass production, helping to identify plant functional traits and ecological parameters explicit in biomass production. Abstraction of ecological drivers in rooibos and honeybush sectors highlighted the “ecological rules” implicit in Fynbos-based production systems, but that are often neglected in previous iterations of the SESF. The study thus also addresses the theoretical gap of the “missing E” in SES previously reported in SES research by emphasising how foundational ecological factors are in endemic Fynbos production systems. Pathways to sustainability outcomes were devised by reviewing findings from the studies with conceptual constructs and principles theoretically associated with sustainability outcomes. Ostrom’s SESF has been widely applied to diverse SES across the world, but has rarely been used in South Africa, and to date, has not been operationalised for any of the Fynbos-based sectors, despite their apparent eligibility for its application. This research adds to SESF theory with a unique contribution from the Cape Fynbos and its unique ecology. A grounded approach to SES variable identification focused attention on two entities often neglected in mainstream research: Fynbos genetic crop wild relatives and the small- scale producers who rely on them for their livelihoods. The dissertation concludes with a sector-specific SESF refined for application in the rooibos and honeybush sectors. Ultimately, the result is a revised SESF that may find application in other Fynbos-based SES where sustainable wild-harvesting and sustainable agricultural production are desired outcomes.
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    Fungal endophyte assemblages associated with twigs of olives in the Core Cape Subregion, South Africa
    (Stellenbosch : Stellenbosch University, 2022-04) Ngubane, Nombuso Portia; Roets, Francois; Dreyer, L. L.; Slippers, Bernard; Kemler, Martin; Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology.
    ENGLISH ABSTRACT: Fungal endophytes are increasingly gaining recognition for their role in plant health. In the face of global change and unprecedented biodiversity loss, it has become an urgent concern to understand these valuable microbes. The main objectives of the work presented here were two-fold, 1) to gain better understanding of the fungal endophytes in a threatened biodiversity hotspot and 2) to improve our understanding of fungal endophyte assemblages associated with ecologically and agriculturally important Olea species. The Core Cape Subregion provides a rare and important study area since it is one of the few areas of olive cultivation with close native relatives, including O. europaea subsp. cuspidata. Many olive (O. europaea subsp. europaea) orchards in the Core Cape Subregion are near natural O. europaea subsp. cuspidata populations. In Chapter 2, I investigated the role of host identity and geographic distance on fungal endophyte assemblages associated with the two Olea europaea subspecies in South Africa. Although many taxa were shared between these hosts, the native host harboured significantly higher alpha diversity. The beta diversity of fungal endophytes also differed significantly between hosts. Geographic distances played a significant role in shaping fungal endophyte assemblages of both hosts, more so in the native host. The native O. europaea subsp. cuspidata is a widely distributed plant growing across a variety of habitats that is also a favoured shade plant, planted in gardens, parks and roadsides. In Chapter 3, the response of fungal endophytes to different levels of disturbance (habitat context) and to differences in surrounding vegetation types (vegetation contrast) were assessed. Endophyte species richness was influenced by habitat context and vegetation contrast. However, fungal endophyte assemblage composition was only affected by habitat context. This suggests that although the host can tolerate different habitat context levels, its fungal endophytes are particularly sensitive to even the mildest of disturbances found in the semi-natural habitat context. In the Core Cape Subregion, two additional Olea species (O. capensis and O. exasperata) are native to South Africa. This made it possible to assess the impact of host identity and relatedness on fungal endophyte assemblages of native hosts (Chapter 4). Fungal endophytes were documented in five native hosts (three Olea and two non-Olea hosts) in the Kogelberg Biosphere. Although fungal endophyte assemblages were significantly different between hosts, this was not correlated to host relatedness (phylogeny). Other factors, other than host phylogeny, were more important to fungal endophytes in this area. The lack of a phylogenetic signal reflected in fungal endophyte assemblages of native Oleaceae hosts suggests that the differences in fungal endophyte assemblages between O. europaea susp. europaea and O. europaea susp. cuspidata are likely due to differences in their histories. The differences in planted African olive trees versus those in the natural context, and the differences between the cultivated and the native olives demonstrate the importance of habitat context. The dynamic nature and diversity of fungal endophytes within the investigated hosts highlights the need to improve our understanding of fungal endophytes in South Africa, especially in native hosts.
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    A mixed method approach towards the evaluation and assessment of integrative research programme outputs: the case of the invasive alien plant management programme working for water
    (Stellenbosch : Stellenbosch University, 2022-04) Abrahams, Brent; Esler, Karen J.; Sitas, Nadia; Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology.
    ENGLISH ABSTRACT: The pervasiveness of threats posed by biological invasions presents significant challenges to human well-being, biodiversity conservation, and natural resource management, which has contributed to the growth of invasion science as a discipline. However, several studies have shown that the social-ecological complexity of invasions, the compartmentalisation of knowledge into disciplines and the lack of integrative research approaches, current invasion research has not informed management decision making effectively. Thus, to maximise the impact of research investments, there is a need to explore and evaluate how research informs management practices and processes linked to biological invasions. Accordingly, this dissertation outlines the state of invasion management-related research in South Africa, using the internationally recognised Working for Water (WfW) programme as a case study. Drawing on insights from science studies and evaluation research, a mixed method approach is used to assess the processes, conditions and outputs associated with research produced under the programme’s auspices. The research comprised two areas of inquiry 1) the exploration of textual information (journal articles, grey literature, and their content), and 2) the social dimensions of research and decision making linked to invasion science and management, with a specific focus on collaborative relationships amongst scientists and decision makers. It sought to determine the extent to which published research aligned with the programme’s needs, research and management strategies. The research also aimed to identify effective ways for organising and producing knowledge relevant to decision making; and to provide insights into how the social dimensions, the people and organisations, their interactions and impact, have shaped research and decision-making processes. Findings suggest that there are significant gaps in the knowledge base particularly in relation to the social dimensions of biological invasions, which were poorly represented and aligned with the mandate and priorities set by the programme. This research showed significant deficiencies in knowledge management and the uptake of research funded by the programme, despite its potential relevance to decision making as evidenced by the recommendations presented in the research. Moreover, research produced under WfW’s auspices was authored by a handful of key researchers who fulfil a significant role in shaping research collaborations both across disciplines and institutions. The loss of these key individuals, including those involved in management-related decision making, would be detrimental to the stability of collaboration networks and research productivity. Finally, findings show that research productivity, collaborative relationships between scientists within and across research organisations, and between research and decision-making processes are positively influenced by collegiality and cooperation between actors, while increased competition and bureaucratisation in the workplace negatively influence research productivity. To address the shortcomings concerning the invasion research and management identified in this dissertation, efforts towards improving the relationship between researchers and decision makers and building more resilient collaboration networks need to be implemented. Firstly, institutions must engage in and fund more targeted, long-term transdisciplinary or integrative research that incorporates appropriate structures that foster collaboration, knowledge coproduction and knowledge sharing. Secondly, systems and strategies for monitoring and evaluating research, including the use of bibliometric indicators, social network analyses and qualitative assessments, should be developed to ensure that research relevant to managing biological invasions is not lost to the decision-making process. Such an undertaking would in turn require the development of an integrated research strategy and action plan that accounts for both the knowledge management and the social processes underpinning research and decision making.
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    Assessing the role of natural open spaces in ecosystem service provision for enhanced urban planning in the global south
    (Stellenbosch : Stellenbosch University, 2022-04) Wessels, Nadia; Esler, Karen J.; Sitas, Nadia; O'Farrell, Patrick; Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology.
    ENGLISH ABSTRACT: Natural open space plays an important role in maintaining biodiversity and providing essential ecosystem services, i.e. the contributions we get from nature. Yet, natural systems within urban areas continue to be exploited and encroached upon, and are often undervalued in urban planning and management decisions, particularly within the context of the Global South where institutional constraints, and complex socio-economic and political priorities prevail. In response to these challenges, this research assessed the role of natural open space in ecosystem service provision for enhanced urban planning in the Global South, by using a case study of the Nelson Mandela Bay Municipality, situated in the Eastern Cape Province, South Africa. The research explored how understanding the benefits (ecosystem services) derived from natural open space can optimise and improve planning, which can, in turn, enable more people to benefit from the ecosystem services provided in cities. Urban natural open space systems form part of complex adaptive social-ecological systems. The realisation and optimisation of the ecosystem services provided by natural open space systems require an understanding of how land cover change affects ecosystem services, and consideration of implementation challenges and opportunities related to mainstreaming ecosystem services into urban planning, which include community and local government needs and priorities within the socio-economic and political context. Developing and implementing natural open space plans requires a transdisciplinary approach that moves beyond disciplines, such as the natural and social sciences only, to incorporate other ways of knowing and feedbacks between different knowledge systems, for example, linking practitioners’ and indigenous and local knowledge, where context-specific human needs, attitudes and values are recognised. The multidimensional outcomes of implementing urban conservation plans (or natural open space plans) are rarely critically evaluated. By providing a framework for monitoring and evaluating conservation outcomes and understanding the causal linkages and reasons for the success and failure of conservation outcomes, this research facilitates the institutionalisation of adaptive management approaches, enhancing urban planning and conservation and social outcomes. Through qualitative interviews with community members representing the city’s diverse socio- economic and ethnic variability (living near natural open space), the complex relational values with nature, and nuanced interpretations of how natural open space delivers ecosystem services were explored. Non-material services (relational benefits) were impacted by exploitative material uses, access concerns, and (mis)management. Management of natural open space also has significant implications for intra and inter-generational equity in respect of the benefits of ecosystem services, and the experience of ecosystem disservices, which require explicit consideration in municipal planning, budgeting and management. Innovative collaborative management and stewardship interventions with ecological and socio-economic benefits should be prioritised to protect the natural open space system. In the Global South the benefits of urban nature in terms of the supply and provision of ecosystem services are inequitably distributed and intertwined in complex socio-political processes. The degree to which the ecosystem services provided by natural open space are valued by local government officials, planned for, prioritised, and incorporated in decision- making, in terms of temporal and spatial implications, need to be understood. Institutional constraints of many local governments in the Global South, such as data and resource capacity, inhibit the appropriate consideration and incorporation of ecosystem services into urban planning. In such instances, expert (scientific) knowledge should be used to contribute to understanding the context-specific diverse ecosystem services provided by natural open space, and the implications of land cover changes on ecosystem service provision associated with rapid urbanisation. This expert understanding then needs to be incorporated with other knowledge systems. The research has emphasised the collective role of community members, civil society and the private sector; city officials and decision-makers; and scientists and researchers in the effective integration of ecosystem services into urban planning, in steering cities towards a sustainable trajectory. There is no panacea for effectively integrating ecosystem services into urban planning. Instead, advancing ecosystem services in urban planning requires various context-specific initiatives and approaches, which allow for collaborative governance and innovative nature-based solutions, and which give due consideration to intra and inter- generational equity. The research identifies opportunities for how to incorporate and catalyse stewardship for natural open space systems and contextually appropriate interventions that could be employed in other cities. It also highlights the need to understand the implications of trade-offs associated with the socio-economic drivers of land transformation over ecosystem service retention as cities in the Global South continue to grow and develop. The methodology followed in this research shows that an understanding of urban ecosystem services is possible without expensive and / or data-intensive decision-making tools, and similar approaches could be followed in other under-resourced cities in the Global South, which can then be used to enhance urban planning.