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Retrieving plant secondary metabolites across biomes using remotely sensed data and radiative transfer models.
(2025) Sibiya, Bongokuhle S’phesihle.; Mutanga, Onisimo.; Odindi, John Odhiambo.; Cho, Moses Azong.; Masemola, Cecilia Ramakgahlele.
Secondary metabolites are diverse defence organic chemical compounds produced by plants against biotic and abiotic environmental stresses. Examples of secondary metabolites include terpenes, phenolic and nitrogenous compounds. Because these metabolites absorb electromagnetic energy in specific wavelengths within the 400 to 2500 nm spectral range, they can be detected non-destructively using remote sensing. Methods for quantifying plant secondary metabolites are generally divided into empirical and physical approaches. Empirical methods rely on finding the statistical relationship between plant attributes and remote sensing. Although they have been praised for producing desirable results over the past decades, they are trained and tested on a specific geography or dataset, sensor-specific, hence tend to lack generalization and transferability. On the other hand, physical models, such as radiative transfer models (RTMs) simulate the interactions of light with plant canopies, making them more robust across different seasons, locations, and sensor types. Despite their potential, most RTM applications focus on retrieving more common plant attributes like Leaf Area Index (LAI) and chlorophyll, particularly in agricultural, grassland, and forest landscapes. There is a notable gap in the literature regarding the use of RTMs to directly estimate secondary metabolites such as flavonoids and carotenoids, especially in ecosystems rich in phenolic compounds like the fynbos biome. Hence, this study aimed to address this gap by exploring how remotely sensed data and RTMs can be used to retrieve plant secondary metabolites across various biomes. The first objective examined the application of RTMs on different terrestrial ecosystems for estimating both biophysical and biochemical properties. The review highlights that most studies have employed 1D models such as PROSPECT and PROSAIL, while for more complex 3D models they have used DART and FLIGHT. Furthermore, most of the existing research has utilized sensors like MODIS and Landsat on parameters like LAI and chlorophyll through inversion techniques such as look-up tables (LUT). However, research efforts are concentrated mainly in the Global North, with limited studies conducted in regions like Africa. The review reveals that PROSPECT and PROSAIL have remained the dominant RTMs over the past twenty years.Building upon this, the second objective used the PROSPECT-5 model to estimate secondary metabolites such as carotenoid content using different wavelengths at the leaf level across three datasets (i.e., savanna, tropical forest, and a combination). Results showed that the green spectral region (510–580 nm) provided the best performance for estimating carotenoids, with R² values up to 0.90 and RMSE of 0.71 in the tropical forest dataset. Wavelengths selected by the Random Forest algorithm, particularly in the green, yellow, and red-edge regions, improved estimation accuracy, especially in the savanna dataset, with R² values exceeding 0.80. The visible spectrum (400–700 nm) also played a crucial role in the detection, emphasizing targeted wavelength selection for better model performance. These findings highlight the importance of focusing on specific wavelengths rather than the full spectrum. The third objective, also at the leaf level, restricted the wavelengths in the form of vegetation indices to study the relationship between fire and secondary metabolites like phenolics and flavonoids in the phenolic-rich fynbos biome. The data revealed that areas burned in2015, 2016, and 2021 had higher phenolic levels, compared to recently burned areas, indicating fire’s role in stimulating secondary metabolite production and ecosystem regeneration. Spectral techniques such as continuum removal identified significant signals around 1660 nm for phenols and 415 nm for flavonoids. Vegetation indices like FI415,710 and FI420,710 showed correlations (R² ≈ 0.55) with phenolic content, highlighting the importance of specific wavelengths. The fourth objective tested whether including secondary metabolites in the PROSAIL model improves canopy-level estimates of plant cover in the phenolic-rich fynbos region. The results demonstrated that the PROSAIL-D model, which accounts for secondary metabolites, outperformed the traditional PROSAIL-4 model, achieving R² values around 0.72–0.78 and lower NRMSE errors (approximately 3.86–3.99%) when using AVIRIS and field spectral data dataset. This emphasizes the importance of secondary metabolites in the PROSAIL-D model to effectively simulate areas rich in phenolic compounds. Finally, the fifth objective used the PROSAIL-D model to estimate flavonoid content using AVIRIS hyperspectral data. The vegetation index FI417,693 yielded the highest accuracy, with an R² of 0.63 and RMSE of 0.24 mg CAE/g. This demonstrated the potential of using narrow spectral bands and targeted indices for reliable retrieval of flavonoids, even within complex canopies. The study underscores that focusing on specific spectral features enhances the capacity of remote sensing to effectively quantify plant biochemical traits. In conclusion, this thesis demonstrates that RTMs, especially when incorporating secondary metabolites such as carotenoids and anthocyanins, are valuable tools for monitoring plant biochemical and biophysical properties across diverse ecosystems. Targeted spectral band selection and advanced modelling approaches can significantly improve the accuracy of remote sensing estimates. While most studies are concentrated in developed regions, expanding research into underrepresented areas like Africa is essential for global ecology.
Where the crawdads sing as an eco-Künstlerinroman.
(2026) Devdhat, Nisha.; Rossmann, Jean.
This dissertation situates Delia Owens’s Where the Crawdads Sing (2018) as an eco-Künstlerinroman: a contemporary reconfiguration of the artist’s novel in which female artistic formation emerges through intimacy with nature. While previous scholars classify the novel as a murder mystery and coming-of-age novel, I argue it inherits and revises the Künstlerroman tradition by situating the protagonist Catherine “Kya” Clark’s artistic apprenticeship within the North Carolina marshland. I explore how the marsh functions as a maternal refuge, teacher, moral guide, and artistic muse. As the marsh meets Kya’s physical and psychological needs, it enables her development as an artist, while her recognition of nature’s own artistry becomes a catalyst for self-discovery. The novel’s central concern is the formation of Kya’s artistic subjectivity under conditions of precarity: parental neglect, gender-based abuse, social exclusion, and environmental degradation. This dissertation thus reads Kya’s development — especially her emergence as a nature artist — as the narrative’s organising arc, one that invites analysis through the genre lens of the eco-Künstlerinroman. The analytical chapters follow Kya’s development across three stages: her childhood formation through the marsh’s tutelage and nurturing presence; her adolescence and young adulthood, during which sexual awakening and romantic betrayal deepen her commitment to artistic creation, authorship, and ecological responsibility; and her maturity, where she embraces her identity as nature artist, poet, and public authority on the marsh. This study builds on Jerome Buckley’s (1974) account of the Künstlerroman, while extending feminist approaches to the genre developed by Linda Huf (1985), Kathleen Hankins (1991), and Evy Varsamopoulou (2019). It also draws on Bracha Ettinger’s (2006a) feminist theories of the maternal nexus and matrixial borderspace to interpret Kya’s development as a motherless daughter and emerging artist, and on Cathy Caruth’s (1996) literary trauma theory to elucidate how Kya’s poetry becomes a medium through which the unspeakability of trauma is translated. Through this composite framework, the study makes a unique contribution to genre theory, arguing for an ecological and feminist variant of the artist’s novel in which nature and art are mutually constitutive forces: while nature serves as a catalyst for aesthetic education, artistic creation in turn becomes a means of healing and flourishing and eco-consciousness.
Impression management observation through textual characteristics in annual reports of South African state-owned entities.
(2024) Ngcizela, Andiswa.; Phesa, Doctor Masibulele.
The study sought to investigate the existence of impression management strategies in nonfinancial information, also known as narrative disclosures, of the annual report of South African state-owned enterprises (SOEs), with a specific focus on the Board chairperson’s report. These narrative disclosures are normally voluntary and prone to impression management. The focus of the study was to examine whether the SOEs engage in impression management tactics as a way of concealing and withholding information about their poor governance and maladministration. These SOEs are expected to contribute to the economic development of South Africa, yet the downward trend in performance is alarming, which has resulted in this study being undertaken. The study used secondary data in the form of annual reports that were extracted from the websites of sampled SOEs. A quantitative content analysis approach was followed to analyse the data and conclude on the findings, the Mann-Whitney U test tool was used to assess the extent of the variation between profitable and non-profitable SOEs. Signalling theory was used to interpret the results. Textual characteristics of the chairperson’s report linked to impression management tactics were analysed by measuring some key variables, namely length of the chairperson’s report, use of the positive disclosure tone through analysing positive and negative sentiments, use of personal reference words, and use of passive language for profitable and unprofitable SOEs. The results showed that profitable and non-profitable SOEs engage in impression management tactics. Profitable SOEs proved to have 1 page more and average 608 number words more than non-profitable SOEs. However, the difference in the length is considered insignificant. . Profitable SOEs also proved to use 22 more personal references than non-profitable ones, while the difference is considered marginal. The results further revealed that both profitable and non-profitable SOEs use 70% percentage of positive tone and that they used more positive tone than negative tone. Equally, non-profitable SOEs used 3% more passive voice than profitable ones, which difference was however considered marginal. The study contributed towards understanding the use of accounting theories, particularly signalling theory in the corporate disclosures of public sector entities. Moreover, this study aimed to help users of annual reports of SOEs in better understanding impression management tactics that can be engaged in for these entities to stay relevant despite their ongoing dismal performance.
Representative democracy and voting: an ethico-political interrogation of the vote market in Ghana.
(2026) Abraham, Kow Kwegya Amissah.; Okyere-Manu, Beatrice Dedaa.
Voting in elections is considered crucial to practising representative democracy. It is seen as the means by which citizens legitimise political office holders and participate in governance. The treatment of votes as a commodity or resource has been gaining recognition in some democracies over the years. This study examined the phenomenon of buying and selling votes, also known as the vote market, through an ethico-political lens. The key objective, which also served as the key research question, was to ascertain whether moral and political obligations play a role in the decision to participate in the Ghanaian vote market. The study employed the qualitative research methodology and further adopted grounded theory as a method of enquiry. On this basis, the study used two theories: egoism and deontology as descriptive theories and interrogated data gathered through interviews and focus group discussions within the adopted theories. Furthermore, the study analysed the data in line with the objectives and research questions. The analysis found that the vote market is prevalent in Ghana, with the main participation considerations being a lack of trust in politicians, personal interests, among others. There were also reasons for nonparticipation, such as patriotism, moral cognition and civil duty. The outcome then provided an avenue to develop a framework for the ethics of voting anchored in Afrocommunitarian theory. The fulcrum of the ethics of voting is that votes have intrinsic value and cannot be commoditised. This is because such a trade-off not only affects the value of votes but also prevents voters from demanding public accountability and enables political office-holders to fail in their public duties.
The impact of firm performance and carbon emissions on the cost of capital for the Johannesburg Stock Exchange (JSE) listed firms.
(2024) Motalingoane, Lieketseng.; Rajaram, Rajendra.
The study investigated the impact of firm performance and carbon emissions on the cost of capital for the Johannesburg Stock Exchange (JSE) listed firms. The mining firms listed on the JSE were selected as the sample, and they were observed for a period of 5 years starting from 2018 to 2022, which amounted to 75 observations. A quantitative methodology, which used panel data and the Panel Least Squares regression model, was employed, using both fixed and random specifications. The study focused on a historical analysis, which made use of quantitative secondary data through secondary analysis. Sources of relevant secondary data include firms that gather information on climate change, carbon reporting, and financial performance on listed firms. The study employed two independent variables (carbon emissions and firm performance) and one dependent variable (cost of equity capital). Carbon emissions were calculated as an inverse value of carbon intensity (scope 1 & 2 emissions). Firm performance was indicated by return on assets (ROA), return on equity (ROE) and firm size. Financial leverage, book to market ration and market beta were employed as control variables. The study found that carbon emissions have a nonstatistically significant negative relationship with the cost of capital, which implies that the higher the carbon emissions intensity, the lower the cost of equity capital. Furthermore, it showed that firm performance also has a non-statistically significant negative impact on the cost of capital, which implies that the greater the firm performance, the lower the cost of equity capital. The findings further indicate that carbon emissions influenced return on assets and firm size negatively. This is because firms that are capital intensive tend to have higher carbon emissions, which results in lower return on assets. In addition, leverage also has a negative association with return on assets because leverage increases the risk of bankruptcy and default, thus affecting firm profitability/performance. This study provides insight into how carbon emissions and firm performance affect how much investors are willing to invest in a company (cost of equity capital) and how environmental issues such as climate change affect the cost of equity of listed firms.