Thicket expansion in a vachellia karroo-dominated landscape and its effect on herbaceous communities
- Authors: Khoza, Marina Rindzani
- Date: 2022-04-06
- Subjects: Savanna ecology South Africa , Forbs South Africa , Grasslands South Africa , Herbaceous plants South Africa , Vegetation dynamics South Africa , Forest canopies South Africa
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/291015 , vital:56808
- Description: Grass and forb species found in savannas are highly diverse, contributing to the structure and function of the savanna system. Where mean annual rainfall is seasonal and high enough to support closed canopy vegetation such as forests or thickets, savannas can exist as an alternative stable state maintained by disturbances such as fire and browsing. Biotic and abiotic processes act on savanna and forest (or thicket) systems maintaining both their tree and herbaceous cover at levels that ensure their persistence in those states. Studies have shown that many semi-arid rangelands in South Africa have undergone a rapid increase in tree cover (of both native and non-native species) over the past several decades. This process of increasing tree cover in semi-arid savannas, termed bush encroachment, results in a biome shift, changing landscapes that were once grasslands with few trees to ones dominated by broad-leaved trees with fewer sun-adapted forbs and grasses. The aim of this study was to investigate the impact of changing woody cover and its associated changes in tree composition, tree canopy structure, light dynamics in the understory and herbaceous community composition on Endwell farm in the Eastern Cape. Canopy cover changes between the years 1949 and 2019 were analysed at 51 sites on the farm and related to historical rainfall patterns. There had been a general increase in tree cover over the past several decades on the farm, and many sites showed a change from open (0-15%) in 1949 to low (1635%), moderate (36-50%) and high (51-100%) canopy cover in 2019. In earlier years most sites had a canopy cover below 50%, and the higher canopy cover values (>65%) occurred in more recent decades. Canopy cover of ~ 50% was found to be rare in each decade. This suggests that ~50% canopy cover maybe a transient, unstable state. The period with the highest rate of canopy cover increase was 2002-2013, and this increase coincided with a high mean annual rainfall 10 years prior to 2002 and a high mean annual rainfall in most years between the 20022013 period. The period between 2002 and 2013 also had the highest number of sites transitioning from lower to higher tree canopy cover classes, indicating that rainfall may have been a factor driving bush encroachment during the past several decades. An increase in canopy cover (a decrease in light transmittance) was accompanied by changes in woody species composition during thicket formation. The low canopy cover (high light transmittance) sites were dominated by Vachellia karroo and Scutia myrtina trees, while high tree cover sites had fewer V. karroo and S. myrtina trees and were rather characterised by an abundance of thicket tree species. Species proportion, NMDS and dendrogram plots indicated that sites with a light transmittance range between 50-100% had similar tree species compositions, different from sites with light transmittances <50%. An increase in tree density was strongly correlated to an increase in canopy cover (from 2019 satellite imagery), density of trees > 3m, maximum height reached by trees, diversity of trees, total canopy volume, total canopy area and leaf area index (LAI), and a decrease in light transmittance. A structural equation model (SEM) was used to explore the relationships between canopy characteristics (maximum canopy area, canopy volume, tree diversity, density of trees, density of trees >3m, individual trees and maximum canopy height), aerial canopy cover in 2019, and light transmittance. The model explained 73% of the variation in light transmittance, mostly via the direct effect of canopy characteristics. Canopy characteristics had a strong influence on both aerial cover in 2019 and directly on light transmittance, but canopy cover in 2019 had a weak influence on light transmittance. The herbaceous layer was rich and dominated by C4 grasses such as Eragrostis plana, Sporobolus fimbriatus, Themeda triandra and Digitaria eriantha) and forbs including Hibiscus aethiopicus, Helichrysum dregeanum, Helichrysum nudifolium and Gerbera viridifolia at low canopy cover sites with high light transmittance. In contrast, high tree cover sites had fewer herbaceous species in general. Grass and forb species characteristic of these sites high canopy cover sites were Panicum maximum, Loudetia flavida, Pellaea viridis and Cyperus spp. Different sites with low light transmittance (<50%) had similar herbaceous species composition. Basal cover, richness, abundance and diversity of herbaceous plants decreased significantly with an increase in tree density, density of trees >3 m, canopy volume, canopy area, canopy cover, LAI, and increased significantly with increasing light transmittance. Most grasses had their highest densities at LAI <0.5, which was estimated to correspond to ~75% light transmittance and ~38% canopy cover and then started to decline thereafter. Herbaceous species basal cover was also highest at LAI <0.5. An SEM model indicated that herbaceous diversity, basal cover and richness responded both to light availability and to the structure of the woody vegetation directly (R2 = 0.53). While the effect of light transmittance on herbaceous communities was strong (0.41), there was little difference between the effect of light transmittance and canopy characteristics (-0.35) on herbaceous communities. Two possible threshold points, relating to two types of transitions in vegetation structure, could be deduced from this study. The first threshold occurred at canopy cover ~ 40% (LAI < ~ 0.5, light transmittance ~ 75%), at which point many of the common herbaceous species, including the dominant C4 grasses, began to decline in abundance while the composition remained characteristic of the savanna state. A canopy cover of less than ~ 40% at a site provides a suitable state for a high abundance of grass and forb species which help maintain an open system by facilitating fires. The second threshold marked a compositional shift between savanna and closed-canopy vegetation states. Savanna species (trees, grasses and forbs) dominated at high light transmittances (>50%) and were significantly reduced at low light transmittances (< 50%), indicating a possible species composition threshold at ~50% light transmittance at which a savanna state switches to a thicket (LAI ~ 1 and canopy cover ~70%). This point indicated the point where there was a significant difference in both tree and herbaceous plant compositions, with a marked reduction in the occurrence of C4 grasses at light transmittance <50%. Fire is supressed when the C4 grass layer is lost, and further thicket encroachment will take place causing complete canopy closure. Land managers in this system should start becoming concerned about a reduction in grass biomass when canopy cover reaches about 40% and would have to reduce tree cover before the threshold of 50% light transmittance (70% canopy cover from aerial photos) is reached to maintain a savanna system. , Thesis (MSc) -- Faculty of Science, Botany, 2022
- Full Text:
- Date Issued: 2022-04-06
Thicket expansion in a vachellia karroo-dominated landscape and its effect on herbaceous communities
- Authors: Khoza, Marina Rindzani
- Date: 2022-04-06
- Subjects: Savanna ecology South Africa , Forbs South Africa , Grasslands South Africa , Herbaceous plants South Africa , Vegetation dynamics South Africa , Forest canopies South Africa
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/291015 , vital:56808
- Description: Grass and forb species found in savannas are highly diverse, contributing to the structure and function of the savanna system. Where mean annual rainfall is seasonal and high enough to support closed canopy vegetation such as forests or thickets, savannas can exist as an alternative stable state maintained by disturbances such as fire and browsing. Biotic and abiotic processes act on savanna and forest (or thicket) systems maintaining both their tree and herbaceous cover at levels that ensure their persistence in those states. Studies have shown that many semi-arid rangelands in South Africa have undergone a rapid increase in tree cover (of both native and non-native species) over the past several decades. This process of increasing tree cover in semi-arid savannas, termed bush encroachment, results in a biome shift, changing landscapes that were once grasslands with few trees to ones dominated by broad-leaved trees with fewer sun-adapted forbs and grasses. The aim of this study was to investigate the impact of changing woody cover and its associated changes in tree composition, tree canopy structure, light dynamics in the understory and herbaceous community composition on Endwell farm in the Eastern Cape. Canopy cover changes between the years 1949 and 2019 were analysed at 51 sites on the farm and related to historical rainfall patterns. There had been a general increase in tree cover over the past several decades on the farm, and many sites showed a change from open (0-15%) in 1949 to low (1635%), moderate (36-50%) and high (51-100%) canopy cover in 2019. In earlier years most sites had a canopy cover below 50%, and the higher canopy cover values (>65%) occurred in more recent decades. Canopy cover of ~ 50% was found to be rare in each decade. This suggests that ~50% canopy cover maybe a transient, unstable state. The period with the highest rate of canopy cover increase was 2002-2013, and this increase coincided with a high mean annual rainfall 10 years prior to 2002 and a high mean annual rainfall in most years between the 20022013 period. The period between 2002 and 2013 also had the highest number of sites transitioning from lower to higher tree canopy cover classes, indicating that rainfall may have been a factor driving bush encroachment during the past several decades. An increase in canopy cover (a decrease in light transmittance) was accompanied by changes in woody species composition during thicket formation. The low canopy cover (high light transmittance) sites were dominated by Vachellia karroo and Scutia myrtina trees, while high tree cover sites had fewer V. karroo and S. myrtina trees and were rather characterised by an abundance of thicket tree species. Species proportion, NMDS and dendrogram plots indicated that sites with a light transmittance range between 50-100% had similar tree species compositions, different from sites with light transmittances <50%. An increase in tree density was strongly correlated to an increase in canopy cover (from 2019 satellite imagery), density of trees > 3m, maximum height reached by trees, diversity of trees, total canopy volume, total canopy area and leaf area index (LAI), and a decrease in light transmittance. A structural equation model (SEM) was used to explore the relationships between canopy characteristics (maximum canopy area, canopy volume, tree diversity, density of trees, density of trees >3m, individual trees and maximum canopy height), aerial canopy cover in 2019, and light transmittance. The model explained 73% of the variation in light transmittance, mostly via the direct effect of canopy characteristics. Canopy characteristics had a strong influence on both aerial cover in 2019 and directly on light transmittance, but canopy cover in 2019 had a weak influence on light transmittance. The herbaceous layer was rich and dominated by C4 grasses such as Eragrostis plana, Sporobolus fimbriatus, Themeda triandra and Digitaria eriantha) and forbs including Hibiscus aethiopicus, Helichrysum dregeanum, Helichrysum nudifolium and Gerbera viridifolia at low canopy cover sites with high light transmittance. In contrast, high tree cover sites had fewer herbaceous species in general. Grass and forb species characteristic of these sites high canopy cover sites were Panicum maximum, Loudetia flavida, Pellaea viridis and Cyperus spp. Different sites with low light transmittance (<50%) had similar herbaceous species composition. Basal cover, richness, abundance and diversity of herbaceous plants decreased significantly with an increase in tree density, density of trees >3 m, canopy volume, canopy area, canopy cover, LAI, and increased significantly with increasing light transmittance. Most grasses had their highest densities at LAI <0.5, which was estimated to correspond to ~75% light transmittance and ~38% canopy cover and then started to decline thereafter. Herbaceous species basal cover was also highest at LAI <0.5. An SEM model indicated that herbaceous diversity, basal cover and richness responded both to light availability and to the structure of the woody vegetation directly (R2 = 0.53). While the effect of light transmittance on herbaceous communities was strong (0.41), there was little difference between the effect of light transmittance and canopy characteristics (-0.35) on herbaceous communities. Two possible threshold points, relating to two types of transitions in vegetation structure, could be deduced from this study. The first threshold occurred at canopy cover ~ 40% (LAI < ~ 0.5, light transmittance ~ 75%), at which point many of the common herbaceous species, including the dominant C4 grasses, began to decline in abundance while the composition remained characteristic of the savanna state. A canopy cover of less than ~ 40% at a site provides a suitable state for a high abundance of grass and forb species which help maintain an open system by facilitating fires. The second threshold marked a compositional shift between savanna and closed-canopy vegetation states. Savanna species (trees, grasses and forbs) dominated at high light transmittances (>50%) and were significantly reduced at low light transmittances (< 50%), indicating a possible species composition threshold at ~50% light transmittance at which a savanna state switches to a thicket (LAI ~ 1 and canopy cover ~70%). This point indicated the point where there was a significant difference in both tree and herbaceous plant compositions, with a marked reduction in the occurrence of C4 grasses at light transmittance <50%. Fire is supressed when the C4 grass layer is lost, and further thicket encroachment will take place causing complete canopy closure. Land managers in this system should start becoming concerned about a reduction in grass biomass when canopy cover reaches about 40% and would have to reduce tree cover before the threshold of 50% light transmittance (70% canopy cover from aerial photos) is reached to maintain a savanna system. , Thesis (MSc) -- Faculty of Science, Botany, 2022
- Full Text:
- Date Issued: 2022-04-06
Composition portfolio
- Authors: Lemmer, Elizabeth Kate
- Date: 2022-04
- Subjects: Composition (Music) , Music South Africa , COVID-19 (Disease) and the arts , Emotions in music , Violin music Scores , String quartets Scores , Chamber music Scores
- Language: English
- Type: Master's thesis , text , sheet music
- Identifier: http://hdl.handle.net/10962/232624 , vital:50008
- Description: In this portfolio I reflect on issues Covid-19 has brought to our communities and the possibilities of creating a brighter future. My music reflects the struggle that most people have faced in the last two years, the emotions and the conspiracies surrounding the experience, and the effect of solitude. In a time such as this it is almost inevitable that the music being composed is connected to the struggle in society at large. For ma composition is a journal of the heart. The pandemic has created a situation where most are out of touch with each other, have lost all previous routine and structure, where relationships are broken due to lack of personal contact, and almost everyone has unwillingly (or unwittingly) been thrust into self-reflection. Every day sees a new struggle to squeeze in all those pre-pandemic ideals so that some normalcy can be obtained, but this is not a time to be looking back. It’s a time to understand what we are going through, build new joy and excitement for this different life and learn to live the best we can with the opportunities we are given. There has not been a more important time to foster some form of connection with friends and family, and to be as strong and supportive as possible. The portfolio begins with a solo violin piece, Unwelcome Solitude, which exemplifies the loneliness and sadness during the various lockdowns over the last two years, with hints of the past and the difficulties in trying to resurrect pre-Covid-19 times. There are some unusual expressive markings to add to the descriptive effect within the piece. This is followed by The Pandemic, two serialism works: Panic and Pain scored for a string quartet. Both of these pieces apply a flexible use of serialism to emphasize out the emotional aspects of the music, and quite simply; the panic and the pain caused by Covid-19 and the country’s response to the pandemic as a whole. Finally there is a three movement chamber piece titled A Storm Series which quite literally represents the series of events that occur from the upcoming to the closure of a typical Highveld storm. Further than this, these pieces represent the series of events that occurred in South Africa from the first rumour of the Covid-19 virus starting to circle around the world, through the various lockdowns and progression of events in our country and abroad. The final movement of this series, Re-awakening, ends on a positive note representing the rainbow at the end of the storm, and the positive outlook for South Africa to keep persevering through the pandemic. , Thesis (MMus) -- Faculty of Humanities, Music and Musicology, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Lemmer, Elizabeth Kate
- Date: 2022-04
- Subjects: Composition (Music) , Music South Africa , COVID-19 (Disease) and the arts , Emotions in music , Violin music Scores , String quartets Scores , Chamber music Scores
- Language: English
- Type: Master's thesis , text , sheet music
- Identifier: http://hdl.handle.net/10962/232624 , vital:50008
- Description: In this portfolio I reflect on issues Covid-19 has brought to our communities and the possibilities of creating a brighter future. My music reflects the struggle that most people have faced in the last two years, the emotions and the conspiracies surrounding the experience, and the effect of solitude. In a time such as this it is almost inevitable that the music being composed is connected to the struggle in society at large. For ma composition is a journal of the heart. The pandemic has created a situation where most are out of touch with each other, have lost all previous routine and structure, where relationships are broken due to lack of personal contact, and almost everyone has unwillingly (or unwittingly) been thrust into self-reflection. Every day sees a new struggle to squeeze in all those pre-pandemic ideals so that some normalcy can be obtained, but this is not a time to be looking back. It’s a time to understand what we are going through, build new joy and excitement for this different life and learn to live the best we can with the opportunities we are given. There has not been a more important time to foster some form of connection with friends and family, and to be as strong and supportive as possible. The portfolio begins with a solo violin piece, Unwelcome Solitude, which exemplifies the loneliness and sadness during the various lockdowns over the last two years, with hints of the past and the difficulties in trying to resurrect pre-Covid-19 times. There are some unusual expressive markings to add to the descriptive effect within the piece. This is followed by The Pandemic, two serialism works: Panic and Pain scored for a string quartet. Both of these pieces apply a flexible use of serialism to emphasize out the emotional aspects of the music, and quite simply; the panic and the pain caused by Covid-19 and the country’s response to the pandemic as a whole. Finally there is a three movement chamber piece titled A Storm Series which quite literally represents the series of events that occur from the upcoming to the closure of a typical Highveld storm. Further than this, these pieces represent the series of events that occurred in South Africa from the first rumour of the Covid-19 virus starting to circle around the world, through the various lockdowns and progression of events in our country and abroad. The final movement of this series, Re-awakening, ends on a positive note representing the rainbow at the end of the storm, and the positive outlook for South Africa to keep persevering through the pandemic. , Thesis (MMus) -- Faculty of Humanities, Music and Musicology, 2022
- Full Text:
- Date Issued: 2022-04
Recruitment disruptors: an exploratory study on the perception of artificial intelligence amongst selected Eastern Cape Province recruiters
- Authors: Sobekwa, Sinazo
- Date: 2022-04
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/232238 , vital:49974
- Description: Thesis (MA) -- Faculty of Humanities, Psychology, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Sobekwa, Sinazo
- Date: 2022-04
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/232238 , vital:49974
- Description: Thesis (MA) -- Faculty of Humanities, Psychology, 2022
- Full Text:
- Date Issued: 2022-04
Representations of adult women who have experienced 'absent' fathers: a thematic analysis of True Love magazine
- Authors: Moola, Lubayna Codelia
- Date: 2022-04
- Subjects: Absentee fathers South Africa , Fathers and daughters South Africa , Fathers and daughters in literature South Africa , Mass media and families South Africa , Mass media and women South Africa , Families Psychological aspects , Self-actualization (Psychology) in women South Africa , True Love magazine , Thematic analysis
- Language: English
- Type: Master's thesis , text
- Identifier: http://hdl.handle.net/10962/232568 , vital:50003
- Description: This study explored how adult women who have experienced father 'absence' are represented in True Love magazine, a popular South African women's magazine targeting black women readers. The study examined nineteen articles published between 2016 and 2021 in True Love, featuring black women’s stories and clinical psychologists, which mentioned ‘absent’ fathers. Through the lenses of psychoanalytic, traditional African cultural, and feminist theoretical frameworks and their key concepts, the articles were examined in relation to how the effects on the adult women of complicated relationships with their fathers while they were growing up, were represented. The selected articles were analysed using Braun and Clarke's reflexive thematic analysis, and representational themes were identified guided by theoretical frameworks and familiarity with the scholarly literature on father ‘absence’ in South Africa. A wide range of childhood and young adult experiences of father-daughter relationships, and household circumstances, appeared alongside the strong maternal networks which supported these girls and women. Representations and themes of clinical psychologists involved Freudian psychoanalytic frameworks to describe the damaging psychological implications of ‘absent’ fathers, particularly affecting adult women’s capacities to form trusting intimate relationships with men. The adult women’s stories – largely successful businesswomen and/or celebrities in the arts, as represented by True Love feature writers and editors – presented themes of what the women had learnt from their mothers, and how they had overcome difficulties and obstacles. These themes included representations of resilience, and of being ‘survivors’, informed by empowerments from a feminist theoretical framework. These themes also represented the women as working psychotherapeutically to manage their past experiences and psychological distress, to transform their retriggering in adult heterosexual relationships, and to pursue healing and self-actualisation. These representations and themes are argued to have inspirational and motivating implications for girls and women in contemporary South Africa. They generate alternate stories about the longer-term effects and outcomes of father ‘absence’, rather than the prominent 'victim' stories in media and scholarly literature of young women doomed to suffer poor relationships and depression forever. , Thesis (MA) -- Faculty of Humanities, Psychology, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Moola, Lubayna Codelia
- Date: 2022-04
- Subjects: Absentee fathers South Africa , Fathers and daughters South Africa , Fathers and daughters in literature South Africa , Mass media and families South Africa , Mass media and women South Africa , Families Psychological aspects , Self-actualization (Psychology) in women South Africa , True Love magazine , Thematic analysis
- Language: English
- Type: Master's thesis , text
- Identifier: http://hdl.handle.net/10962/232568 , vital:50003
- Description: This study explored how adult women who have experienced father 'absence' are represented in True Love magazine, a popular South African women's magazine targeting black women readers. The study examined nineteen articles published between 2016 and 2021 in True Love, featuring black women’s stories and clinical psychologists, which mentioned ‘absent’ fathers. Through the lenses of psychoanalytic, traditional African cultural, and feminist theoretical frameworks and their key concepts, the articles were examined in relation to how the effects on the adult women of complicated relationships with their fathers while they were growing up, were represented. The selected articles were analysed using Braun and Clarke's reflexive thematic analysis, and representational themes were identified guided by theoretical frameworks and familiarity with the scholarly literature on father ‘absence’ in South Africa. A wide range of childhood and young adult experiences of father-daughter relationships, and household circumstances, appeared alongside the strong maternal networks which supported these girls and women. Representations and themes of clinical psychologists involved Freudian psychoanalytic frameworks to describe the damaging psychological implications of ‘absent’ fathers, particularly affecting adult women’s capacities to form trusting intimate relationships with men. The adult women’s stories – largely successful businesswomen and/or celebrities in the arts, as represented by True Love feature writers and editors – presented themes of what the women had learnt from their mothers, and how they had overcome difficulties and obstacles. These themes included representations of resilience, and of being ‘survivors’, informed by empowerments from a feminist theoretical framework. These themes also represented the women as working psychotherapeutically to manage their past experiences and psychological distress, to transform their retriggering in adult heterosexual relationships, and to pursue healing and self-actualisation. These representations and themes are argued to have inspirational and motivating implications for girls and women in contemporary South Africa. They generate alternate stories about the longer-term effects and outcomes of father ‘absence’, rather than the prominent 'victim' stories in media and scholarly literature of young women doomed to suffer poor relationships and depression forever. , Thesis (MA) -- Faculty of Humanities, Psychology, 2022
- Full Text:
- Date Issued: 2022-04