Relating vegetation distribution to cycles of erosion and deposition in the Kromme River wetlands
- Authors: Jarvis, Samuel Cameron
- Date: 2023-10-13
- Subjects: Biogeomorphology South Africa Kromme Estuary (Eastern Cape) , Earth observation , Remote sensing , Niche construction , Wetland ecology , Geomorphology , Ecological succession , Optical radar , Prionium serratum
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424582 , vital:72166
- Description: The role of geomorphic disturbance has been increasingly recognized as fundamental in the creation and functioning of wetlands. This is true of the Kromme River wetland which has been formed through repeated cycles of erosion and deposition. However, the response – and influence – of wetland plants to these sorts of disturbance has not been investigated. This study sought to fill this knowledge gap by classifying vegetation communities over a range of hydrological and geomorphic disturbance regimes that have happened over the last few decades, and relating those vegetation communities to environmental factors. The study identified seven vegetation communities based on their species composition and abundance, which were related to geomorphic disturbance events. A conceptual model that accounts for vegetation distribution in the Kromme wetland was developed. Soil saturation was the most important factor explaining vegetation community distribution, which, in turn, is influenced by cycles of erosion and deposition. Following an erosional event on the valley floor, Prionium serratum dominated wetland is converted to a number of other vegetation communities. On the floodplain surface adjacent to the eroded gully, the Prionium serratum dominated wetland is transformed over time to Cynodon dactylon and Sporobolus fimbriatus communities. Prionium serratum clumps immediately adjacent to the recently incised gullies are able to persist, having sufficient access to water. Within the newly formed gullies, Juncus lomatophyllus colonizes the gully beds flooded to a shallow depth, Miscanthus capensis colonizes the gully bars and Setaria incrassata colonizes the exposed gully banks. Localised depositional features close to the thalweg in the gully are colonized by Prionium serratum seedlings and vegetative propagules. These plants represent the regenerating phase of Prionium serratum wetland, which also colonizes depositional floodouts downstream of the newly-formed gully. The Stenotaphrum secundatum community dominates drier, more elevated areas of the floodout. Over time, as the gully fills, Prionium serratum expands beyond the gully onto the valley floor, to replace the floodplain communities Cynodon dactylon and Sporobolus fimbriatus. Over time, Prionium serratum is thought to colonize the valley floor as the gully fills, stabilising it and promoting diffuse flow. Many restoration efforts in damaged palmiet wetlands have been focused on the preservation of intact palmiet communities upstream of erosional headcuts, with limited understanding of vegetation dynamics associated with the cut-and-fill cycles that naturally occur in these wetlands. Understanding the regeneration of Prionium serratum following erosional events is thus important for wetland restoration, as it should focus more attention on promoting palmiet restoration on depositional floodouts downstream of eroded gullies. A secondary aim of this study was to explore the possibility of mapping palmiet communities in Kromme River wetland using remote sensing techniques. Using a combination of ground-truthed data from this and previous studies in the Kromme River wetland, together with raster layers derived from a LiDAR survey, an overlay analysis was developed to effectively map the distribution of the Prionium serratum dominated community. The overlay was created using a machine learning library in RStudios known as Rpart. The results found that the model were 91% effective in classifying the distribution of the Prionium serratum community. A secondary finding was that the inclusion of a Relative Elevation Model in the overlay analysis allowed for the identification of Prionium serratum communities vulnerable to degradation following previous geomorphic disturbance events and those Prionium serratum communities that are likely to persist following a geomorphic disturbance event. , Thesis (MSc) -- Faculty of Science, Geography, 2023
- Full Text:
- Date Issued: 2023-10-13
- Authors: Jarvis, Samuel Cameron
- Date: 2023-10-13
- Subjects: Biogeomorphology South Africa Kromme Estuary (Eastern Cape) , Earth observation , Remote sensing , Niche construction , Wetland ecology , Geomorphology , Ecological succession , Optical radar , Prionium serratum
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/424582 , vital:72166
- Description: The role of geomorphic disturbance has been increasingly recognized as fundamental in the creation and functioning of wetlands. This is true of the Kromme River wetland which has been formed through repeated cycles of erosion and deposition. However, the response – and influence – of wetland plants to these sorts of disturbance has not been investigated. This study sought to fill this knowledge gap by classifying vegetation communities over a range of hydrological and geomorphic disturbance regimes that have happened over the last few decades, and relating those vegetation communities to environmental factors. The study identified seven vegetation communities based on their species composition and abundance, which were related to geomorphic disturbance events. A conceptual model that accounts for vegetation distribution in the Kromme wetland was developed. Soil saturation was the most important factor explaining vegetation community distribution, which, in turn, is influenced by cycles of erosion and deposition. Following an erosional event on the valley floor, Prionium serratum dominated wetland is converted to a number of other vegetation communities. On the floodplain surface adjacent to the eroded gully, the Prionium serratum dominated wetland is transformed over time to Cynodon dactylon and Sporobolus fimbriatus communities. Prionium serratum clumps immediately adjacent to the recently incised gullies are able to persist, having sufficient access to water. Within the newly formed gullies, Juncus lomatophyllus colonizes the gully beds flooded to a shallow depth, Miscanthus capensis colonizes the gully bars and Setaria incrassata colonizes the exposed gully banks. Localised depositional features close to the thalweg in the gully are colonized by Prionium serratum seedlings and vegetative propagules. These plants represent the regenerating phase of Prionium serratum wetland, which also colonizes depositional floodouts downstream of the newly-formed gully. The Stenotaphrum secundatum community dominates drier, more elevated areas of the floodout. Over time, as the gully fills, Prionium serratum expands beyond the gully onto the valley floor, to replace the floodplain communities Cynodon dactylon and Sporobolus fimbriatus. Over time, Prionium serratum is thought to colonize the valley floor as the gully fills, stabilising it and promoting diffuse flow. Many restoration efforts in damaged palmiet wetlands have been focused on the preservation of intact palmiet communities upstream of erosional headcuts, with limited understanding of vegetation dynamics associated with the cut-and-fill cycles that naturally occur in these wetlands. Understanding the regeneration of Prionium serratum following erosional events is thus important for wetland restoration, as it should focus more attention on promoting palmiet restoration on depositional floodouts downstream of eroded gullies. A secondary aim of this study was to explore the possibility of mapping palmiet communities in Kromme River wetland using remote sensing techniques. Using a combination of ground-truthed data from this and previous studies in the Kromme River wetland, together with raster layers derived from a LiDAR survey, an overlay analysis was developed to effectively map the distribution of the Prionium serratum dominated community. The overlay was created using a machine learning library in RStudios known as Rpart. The results found that the model were 91% effective in classifying the distribution of the Prionium serratum community. A secondary finding was that the inclusion of a Relative Elevation Model in the overlay analysis allowed for the identification of Prionium serratum communities vulnerable to degradation following previous geomorphic disturbance events and those Prionium serratum communities that are likely to persist following a geomorphic disturbance event. , Thesis (MSc) -- Faculty of Science, Geography, 2023
- Full Text:
- Date Issued: 2023-10-13
Uncoupling the exploitation and climate change effects on the biology of Cape monkfish, Lophius vomerinus Valenciennes 1837 in Namibia
- Authors: Erasmus, Victoria Ndinelago
- Date: 2021-10-29
- Subjects: Lophius Namibia , Lophius Climatic factors Namibia , Lophius Effect of human beings on Namibia , Lophius Food Namibia , Lophius Reproduction Namibia , Lophius Age Namibia , Lophius Growth Namibia , Lophius Habitat Namibia , Lophius Conservation Namibia , Fisheries Namibia , Overfishing Namibia , Fishery management Namibia , Lophius vomerinus (Valenciennes, 1837) , Cape monkfish
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/188329 , vital:44744 , 10.21504/10962/188329
- Description: Cape monkfish, Lophius vomerinus Valenciennes 1837, has supported the Namibian fishing industry for decades, historically as by-catch and recently as a target species. This species is also an important predator in this region. With increasing levels of exploitation and unprecedented climate change, an understanding of the changes in the long-term biological parameters of this species is critical. To date, there has been a scarcity of spatio-temporal studies that have examined and compared the biological aspects of Cape monkfish in relation to climate change and exploitation pressure. Investigations into changes in feeding habits, reproduction strategy, age and growth can provide valuable information for the sustainable management and conservation of this species. This thesis aimed to improve our understanding of the impacts of exploitation and climate variability on the biological parameters of Cape monkfish in the Namibian marine waters, thereby contributing to efforts directed at sustainable harvest and management of this resource. This was achieved through temporal and spatial comparisons of feeding, reproductive scope, age and growth, and catch statistics. The study used data collected during the monkfish swept-area biomass surveys of 2001–2005 and for 2007–2018, hake (deep-water hake Merluccius paradoxus Franca 1960 and shallow-water hake M. capensis Castelnau 1861) swept-area biomass surveys of 2017 and 2019, port sampling programme data collected from April 2014 to December 2019, and monkfish commercial fishing activities collected between April 2001 and December 2019. Based on historical feeding data (1986 – 1987) and contemporary feeding data (2015-2018), Cape monkfish feeds on a variety of prey species from seven groups: Teleost, Cephalopoda, Crustacea, Echinoidea, Elasmobranchii, Gastropod and Porifera. The diet was characterised by a high prevalence of empty stomachs (43.9%), showing low feeding intensity, but most prevalent in juveniles (52.9%). Although the diet composition varied at different life stages, Teleosts (especially deep-water hake Merluccius paradoxus Franca 1960) were the main constituents of the diet for all size classes as per the Index of Relative Importance (%IRI). The results highlight the particular importance of the deep-water hake M. paradoxus (by %IRI) in the diet of Cape monkfish across all size classes. There is a clear dominance of hake in both studies, which means that any overexploitation or climate-driven population decline in hake will most likely have an impact on Cape monkfish. Feeding composition was dependent on the season (p < 0.05), with the type and quantity of prey ingested changing seasonally, showing the ability of Cape monkfish to adjust its diet, depending on possible environmental parameters which consequently influence prey availability. In general, the spatial and temporal variability of the main prey items suggests that the species is highly opportunistic with a broad trophic adaptability. Comparison of historical and contemporary stomach content data indicates that Cape monkfish appear to have changed their diet, probably reflecting the availability of forage species over time and space, possibly due to climate change, fishing pressure, or both. The broad trophic adaptability for Cape monkfish highlights their adaptive potential to increasing anthropogenic stressors such as climate change. However, the dominance of the commercially important deep-water hake, M. paradoxus, in the diet during contemporary times highlights that complex trophic interactions may play a role in altering the northern Benguela fisheries. The general male to female sex ratio was measured at 1:1.67, with significant variation across depth, size class, and year (p < 0.05). Comparison of length at 50% maturity (L50) for Cape monkfish between historical (2004–2006) and contemporary time (2015–2019) showed no significant differences in both sexes, with no significant changes in the L50 for females (χ2 = 1.53, df = 1, p = 0.2154), and males (χ2 = 0.41, df = 1, p = 0.5204) between the two periods. The monthly gonadosomatic index (GSI) showed that Cape monkfish spawn throughout the year with peaks between July and September for females and August for males, similar to those observed 20 years ago. Spawning hotspot areas were identified and were consistently located between 22⁰ and 25⁰S in deeper water (> 250 m) for the 2001–2018 time series. Comparison of the contemporary (2015–2019) proportions of developing, ripe and spent gonads to the historical study data (1996 – 2000) show minimal differences. Ripe ovaries capable of spawning (Stage IV) were dominant in July (23.8%) and August (26.2%), while ripe testes were prevalent in April (52.5%) and November (28.5%). The discovery of the veil (a gelatinous, flat ribbon structure containing individual eggs) off Namibia for the first time (during this study) is a significant because this result provides important reproduction activities information of this species, which were never recorded off Namibia. The location where the veil was discovered, off Swakopmund (22⁰30'S, 13⁰25'E), provides further evidence of the identified spawning hotspot areas, this location is also identified as a monkfish consecutive hotspot fishing area. The ages, growth rates, and length-weight relationships were compared between fish collected during monkfish commercial fishing activities between 1996 and 1998 (Period 1) and during monkfish routine monitoring surveys from 2014 to 2016 (Period 2). A total of 607 (size range: 9–96 cm total length (TL)) and 852 (size range: 9–96 cm TL) Cape monkfish were aged by reading sectioned illicia, during Periods 1 and 2, respectively. The length-weight relationships were W = 0.012L3.035 (r2 = 0.98) and W = 0.014L 2.989 (r2 = 0.98) for females and males, respectively, during Period 1, and W = 0.01L2.97 (r2 = 0.98) and W = 0.01L 3.03 (r2 = 0.98) for females and males, respectively, in Period 2. The growth of Cape monkfish (in cm) for combined sexes was described by Lt = 94(1 − e(−0.10(t−(-0.31))) in Period 1 and Lt = 98(1 − e(−0.10(t−(-0.33))) in Period 2. Females grew significantly faster during Period 1 (LRT results from Maartens et al., 1999), while male and female growth was not significantly different during Period 2 (F = 0.65, p = 0.58). There were no significant differences between the male and female growth curve in Period 2 (F = 0.65, p = 0.58). Although the growth curves are similar between Period 1 and Period 2, the larger fish are in Period 2 are lighter than those in Period 1. This finding is important to the monkfish fishing industry because fish is sold by weight. This finding may suggest that although the fish grow similarly by length, changes in the environmental conditions may have resulted in a reduced condition of the fish. In terms of mean age, the historical Period 1 had a slightly lower mean age of 4.40 compared with a mean age of 5.49 during Period 2. Slight differences were also observed in the age structure between the two periods, with 2-year-olds (20.3%) the most abundant age class in the historical period while 5-year-old fish (18.3%) were most abundant in Period 2. Although the spatial distribution of the catch was not available for Period 1, 0-year-old fish were distributed from 22⁰ to 24⁰S, and 25⁰ to 26⁰S in shallower waters of 166–290 m during Period 2. Only fish between 5 and 16 years old were found off the documented historical nursery area off 28º S. The similar growth curves and spatial overlap of nursery habitats between Period 1 and Period 2 suggest that Cape monkfish may be fairly resilient to the rapid environmental change reported in this region and to the extensive levels of exploitation for the species. However, the recent spatial shifts in the nursery areas are sensitive to disturbance and may indicate that these changes could be having an impact on the early life stages of the species. Continued monitoring may be necessary to understand the consequences of these spatial shifts for the age and growth and resilience of the species. Analysis of the overall spatial and temporal catches of monkfish (both Cape monkfish and shortspine African monkfish) off Namibia between 1998 and 2018 identified noticeable spatio-temporal trends. The pattern of fishing activities for Cape monkfish is heterogeneous, with identified ‘hotspots’ in specific areas. Of particular importance is the consecutive hotspot, between 1998 to 2018 for monkfish fishing activities between 25⁰ and 26⁰ S. The kernel density analysis indicated that the area around 24⁰S, and between 26º and 27 ⁰S, between Walvis Bay and Lüderitz, had the highest total catch densities (~300 kg/km2), suggesting that this is the core of the stock abundance. Annual monkfish catches have fluctuated since the inception of the fishery in 1994, with a drastic decline in the catch recorded after 2003 through to 2018. Generally, there has been an underutilisation of the total allowable catch (TAC) for most of the years. The decrease in catches and the underutilisation of the TAC might be indicative of the reduction in the stock abundance. However, external factors such as lack of capacity of the fishing industry and the administration can contribute to underutilisation of TAC. Basic regression analysis between total monthly catches and monthly sea surface temperature (SST) yielded low r-squared values indicate that in all three grids, only ~ 1% of the variation is explained between SST and total monkfish catches in these areas. The most prominent points to consider from this study are the results of the comparative feeding study (Chapter 3), reproductive indicators (Chapter 4) and age and growth (Chapter 5). Certainly, there have been changes in feeding, demography, and distribution of the species in the last two decades – climate-driven changes were recorded in the feeding habits of Cape monkfish, spatially and temporally – but despite the changes in prey species composition, distribution and abundance in various habits and periods, Cape monkfish was able to switch prey species, reflecting wide trophic adaptability. The dominance of M. paradoxus at all size classes in all analysed habitats is a significant result because. The peak spawning period has remained the same between July and September, as previously reported in Period 1. The consecutive spawning hotspots were identified in the areas between 22º and 25ºS. From a fisheries management perspective, the spawning ground and spawning season should be protected (by means of closure). The evidence of changes in length at 50% maturity presented in this study hints at both climate change and extensive exploitation pressure. The discovery of the veil for the first time in this study is very important; however, it might be sampling related and not driven by climate or exploitation pressure. Finally, the change in the Cape monkfish distribution discussed in Chapter 6 may be attributed to a shift in the distribution or fishing effort as a consequence of shallow water depletion. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Erasmus, Victoria Ndinelago
- Date: 2021-10-29
- Subjects: Lophius Namibia , Lophius Climatic factors Namibia , Lophius Effect of human beings on Namibia , Lophius Food Namibia , Lophius Reproduction Namibia , Lophius Age Namibia , Lophius Growth Namibia , Lophius Habitat Namibia , Lophius Conservation Namibia , Fisheries Namibia , Overfishing Namibia , Fishery management Namibia , Lophius vomerinus (Valenciennes, 1837) , Cape monkfish
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/188329 , vital:44744 , 10.21504/10962/188329
- Description: Cape monkfish, Lophius vomerinus Valenciennes 1837, has supported the Namibian fishing industry for decades, historically as by-catch and recently as a target species. This species is also an important predator in this region. With increasing levels of exploitation and unprecedented climate change, an understanding of the changes in the long-term biological parameters of this species is critical. To date, there has been a scarcity of spatio-temporal studies that have examined and compared the biological aspects of Cape monkfish in relation to climate change and exploitation pressure. Investigations into changes in feeding habits, reproduction strategy, age and growth can provide valuable information for the sustainable management and conservation of this species. This thesis aimed to improve our understanding of the impacts of exploitation and climate variability on the biological parameters of Cape monkfish in the Namibian marine waters, thereby contributing to efforts directed at sustainable harvest and management of this resource. This was achieved through temporal and spatial comparisons of feeding, reproductive scope, age and growth, and catch statistics. The study used data collected during the monkfish swept-area biomass surveys of 2001–2005 and for 2007–2018, hake (deep-water hake Merluccius paradoxus Franca 1960 and shallow-water hake M. capensis Castelnau 1861) swept-area biomass surveys of 2017 and 2019, port sampling programme data collected from April 2014 to December 2019, and monkfish commercial fishing activities collected between April 2001 and December 2019. Based on historical feeding data (1986 – 1987) and contemporary feeding data (2015-2018), Cape monkfish feeds on a variety of prey species from seven groups: Teleost, Cephalopoda, Crustacea, Echinoidea, Elasmobranchii, Gastropod and Porifera. The diet was characterised by a high prevalence of empty stomachs (43.9%), showing low feeding intensity, but most prevalent in juveniles (52.9%). Although the diet composition varied at different life stages, Teleosts (especially deep-water hake Merluccius paradoxus Franca 1960) were the main constituents of the diet for all size classes as per the Index of Relative Importance (%IRI). The results highlight the particular importance of the deep-water hake M. paradoxus (by %IRI) in the diet of Cape monkfish across all size classes. There is a clear dominance of hake in both studies, which means that any overexploitation or climate-driven population decline in hake will most likely have an impact on Cape monkfish. Feeding composition was dependent on the season (p < 0.05), with the type and quantity of prey ingested changing seasonally, showing the ability of Cape monkfish to adjust its diet, depending on possible environmental parameters which consequently influence prey availability. In general, the spatial and temporal variability of the main prey items suggests that the species is highly opportunistic with a broad trophic adaptability. Comparison of historical and contemporary stomach content data indicates that Cape monkfish appear to have changed their diet, probably reflecting the availability of forage species over time and space, possibly due to climate change, fishing pressure, or both. The broad trophic adaptability for Cape monkfish highlights their adaptive potential to increasing anthropogenic stressors such as climate change. However, the dominance of the commercially important deep-water hake, M. paradoxus, in the diet during contemporary times highlights that complex trophic interactions may play a role in altering the northern Benguela fisheries. The general male to female sex ratio was measured at 1:1.67, with significant variation across depth, size class, and year (p < 0.05). Comparison of length at 50% maturity (L50) for Cape monkfish between historical (2004–2006) and contemporary time (2015–2019) showed no significant differences in both sexes, with no significant changes in the L50 for females (χ2 = 1.53, df = 1, p = 0.2154), and males (χ2 = 0.41, df = 1, p = 0.5204) between the two periods. The monthly gonadosomatic index (GSI) showed that Cape monkfish spawn throughout the year with peaks between July and September for females and August for males, similar to those observed 20 years ago. Spawning hotspot areas were identified and were consistently located between 22⁰ and 25⁰S in deeper water (> 250 m) for the 2001–2018 time series. Comparison of the contemporary (2015–2019) proportions of developing, ripe and spent gonads to the historical study data (1996 – 2000) show minimal differences. Ripe ovaries capable of spawning (Stage IV) were dominant in July (23.8%) and August (26.2%), while ripe testes were prevalent in April (52.5%) and November (28.5%). The discovery of the veil (a gelatinous, flat ribbon structure containing individual eggs) off Namibia for the first time (during this study) is a significant because this result provides important reproduction activities information of this species, which were never recorded off Namibia. The location where the veil was discovered, off Swakopmund (22⁰30'S, 13⁰25'E), provides further evidence of the identified spawning hotspot areas, this location is also identified as a monkfish consecutive hotspot fishing area. The ages, growth rates, and length-weight relationships were compared between fish collected during monkfish commercial fishing activities between 1996 and 1998 (Period 1) and during monkfish routine monitoring surveys from 2014 to 2016 (Period 2). A total of 607 (size range: 9–96 cm total length (TL)) and 852 (size range: 9–96 cm TL) Cape monkfish were aged by reading sectioned illicia, during Periods 1 and 2, respectively. The length-weight relationships were W = 0.012L3.035 (r2 = 0.98) and W = 0.014L 2.989 (r2 = 0.98) for females and males, respectively, during Period 1, and W = 0.01L2.97 (r2 = 0.98) and W = 0.01L 3.03 (r2 = 0.98) for females and males, respectively, in Period 2. The growth of Cape monkfish (in cm) for combined sexes was described by Lt = 94(1 − e(−0.10(t−(-0.31))) in Period 1 and Lt = 98(1 − e(−0.10(t−(-0.33))) in Period 2. Females grew significantly faster during Period 1 (LRT results from Maartens et al., 1999), while male and female growth was not significantly different during Period 2 (F = 0.65, p = 0.58). There were no significant differences between the male and female growth curve in Period 2 (F = 0.65, p = 0.58). Although the growth curves are similar between Period 1 and Period 2, the larger fish are in Period 2 are lighter than those in Period 1. This finding is important to the monkfish fishing industry because fish is sold by weight. This finding may suggest that although the fish grow similarly by length, changes in the environmental conditions may have resulted in a reduced condition of the fish. In terms of mean age, the historical Period 1 had a slightly lower mean age of 4.40 compared with a mean age of 5.49 during Period 2. Slight differences were also observed in the age structure between the two periods, with 2-year-olds (20.3%) the most abundant age class in the historical period while 5-year-old fish (18.3%) were most abundant in Period 2. Although the spatial distribution of the catch was not available for Period 1, 0-year-old fish were distributed from 22⁰ to 24⁰S, and 25⁰ to 26⁰S in shallower waters of 166–290 m during Period 2. Only fish between 5 and 16 years old were found off the documented historical nursery area off 28º S. The similar growth curves and spatial overlap of nursery habitats between Period 1 and Period 2 suggest that Cape monkfish may be fairly resilient to the rapid environmental change reported in this region and to the extensive levels of exploitation for the species. However, the recent spatial shifts in the nursery areas are sensitive to disturbance and may indicate that these changes could be having an impact on the early life stages of the species. Continued monitoring may be necessary to understand the consequences of these spatial shifts for the age and growth and resilience of the species. Analysis of the overall spatial and temporal catches of monkfish (both Cape monkfish and shortspine African monkfish) off Namibia between 1998 and 2018 identified noticeable spatio-temporal trends. The pattern of fishing activities for Cape monkfish is heterogeneous, with identified ‘hotspots’ in specific areas. Of particular importance is the consecutive hotspot, between 1998 to 2018 for monkfish fishing activities between 25⁰ and 26⁰ S. The kernel density analysis indicated that the area around 24⁰S, and between 26º and 27 ⁰S, between Walvis Bay and Lüderitz, had the highest total catch densities (~300 kg/km2), suggesting that this is the core of the stock abundance. Annual monkfish catches have fluctuated since the inception of the fishery in 1994, with a drastic decline in the catch recorded after 2003 through to 2018. Generally, there has been an underutilisation of the total allowable catch (TAC) for most of the years. The decrease in catches and the underutilisation of the TAC might be indicative of the reduction in the stock abundance. However, external factors such as lack of capacity of the fishing industry and the administration can contribute to underutilisation of TAC. Basic regression analysis between total monthly catches and monthly sea surface temperature (SST) yielded low r-squared values indicate that in all three grids, only ~ 1% of the variation is explained between SST and total monkfish catches in these areas. The most prominent points to consider from this study are the results of the comparative feeding study (Chapter 3), reproductive indicators (Chapter 4) and age and growth (Chapter 5). Certainly, there have been changes in feeding, demography, and distribution of the species in the last two decades – climate-driven changes were recorded in the feeding habits of Cape monkfish, spatially and temporally – but despite the changes in prey species composition, distribution and abundance in various habits and periods, Cape monkfish was able to switch prey species, reflecting wide trophic adaptability. The dominance of M. paradoxus at all size classes in all analysed habitats is a significant result because. The peak spawning period has remained the same between July and September, as previously reported in Period 1. The consecutive spawning hotspots were identified in the areas between 22º and 25ºS. From a fisheries management perspective, the spawning ground and spawning season should be protected (by means of closure). The evidence of changes in length at 50% maturity presented in this study hints at both climate change and extensive exploitation pressure. The discovery of the veil for the first time in this study is very important; however, it might be sampling related and not driven by climate or exploitation pressure. Finally, the change in the Cape monkfish distribution discussed in Chapter 6 may be attributed to a shift in the distribution or fishing effort as a consequence of shallow water depletion. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2021
- Full Text:
- Date Issued: 2021-10-29
The effects of aspect, directional heating and depth on bedrock temperatures and the potential relationship with thermal fatigue weathering
- Authors: Breytenbach, Izak Johannes
- Date: 2021-04
- Subjects: Weathering -- South Africa -- Karoo , Shields (Geology) -- South Africa -- Karoo , Shields (Geology) -- Thermal properties , Tillite -- South Africa -- Karoo
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/177688 , vital:42847 , 10.21504/10962/177688
- Description: Geomorphological weathering processes and their relationship with temperature fluctuations are frequently researched. These research efforts are mostly restricted to surface conditions where soils, loose-lying rocks or rock outcrops are assessed. However, there is a shortcoming in the understanding of the thermal properties in a rock mass, particularly in the upper metres below the surface, as this has not been investigated or researched in any great detail. The research reported here is unique in this regard as it exploited the use of rotary core boreholes in tillite bedrock in the Karoo (Western Cape, South Africa) which were drilled as part of an invasive materials investigation for a proposed new hard rock quarry to supply road stone. Temperature data were captured on a bedrock ridge hosting tillite outcrop with a strong east to west orientation. The site work was done in two separate phases. The initial phase of research saw data being captured for one year on two aspects (i.e. north and south) at a depth of 0.3 m. This was followed by the second (more detailed) phase, where three aspects were assessed (i.e. north, south and a flat crest), but at depths of 0.3 m, 2.0 m and 6.0 m, totalling nine data acquisition points. The second investigation phase gathered data for seven months. Supplementary weather data were also captured for the site. Subsequent data analyses revealed that there is much to learn about the thermal behaviour of bedrock in the upper metres below the surface, and that the temperature properties or thermal regimes are not as simple as often assumed. Temperature differences related to aspect are not only surficial, but are transmitted to underlying bedrock, and notable temperature differences were measurable to a depth of at least 6.0 m. Seasonal temperature fluctuations also have a pronounced effect on the rock mass temperatures and it was proven that deeper parts of the bedrock accumulate and dissipate heat at different (i.e. retarded) rates compared with shallower parts of the rock mass, creating suitable thermal conditions to induce thermal fatigue. Thermal properties were also proven to be non-linear. During analyses, the concept of temperature inversions was proven, whereby one part of the bedrock becomes hotter or cooler relative to another/adjacent part of the bedrock, compared with its earlier temperature state. It was argued that these temperature inversions may exacerbate thermal fatigue. This research proved that aspect (i.e. directional heating) and depth need to be considered when analysing thermal regimes in a rock mass, as these have a distinct influence. The effects which manifest themselves create suitable conditions for thermal fatigue, not only near the surface but also at depth in the bedrock. Lastly, the effects of meteorological conditions on shallow bedrock temperatures were assessed. Preliminary findings suggest that boundary conditions and meteorological processes may indeed affect shallow bedrock temperatures, but only under certain circumstances and not to the same extent as reported in the literature for conditions researched at the surface. Wind temperature relative to the rock temperature, as well as a combination of wind and rain were found to be the most significant factors. , Thesis (PhD) -- Faculty of Science, Geography, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Breytenbach, Izak Johannes
- Date: 2021-04
- Subjects: Weathering -- South Africa -- Karoo , Shields (Geology) -- South Africa -- Karoo , Shields (Geology) -- Thermal properties , Tillite -- South Africa -- Karoo
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/177688 , vital:42847 , 10.21504/10962/177688
- Description: Geomorphological weathering processes and their relationship with temperature fluctuations are frequently researched. These research efforts are mostly restricted to surface conditions where soils, loose-lying rocks or rock outcrops are assessed. However, there is a shortcoming in the understanding of the thermal properties in a rock mass, particularly in the upper metres below the surface, as this has not been investigated or researched in any great detail. The research reported here is unique in this regard as it exploited the use of rotary core boreholes in tillite bedrock in the Karoo (Western Cape, South Africa) which were drilled as part of an invasive materials investigation for a proposed new hard rock quarry to supply road stone. Temperature data were captured on a bedrock ridge hosting tillite outcrop with a strong east to west orientation. The site work was done in two separate phases. The initial phase of research saw data being captured for one year on two aspects (i.e. north and south) at a depth of 0.3 m. This was followed by the second (more detailed) phase, where three aspects were assessed (i.e. north, south and a flat crest), but at depths of 0.3 m, 2.0 m and 6.0 m, totalling nine data acquisition points. The second investigation phase gathered data for seven months. Supplementary weather data were also captured for the site. Subsequent data analyses revealed that there is much to learn about the thermal behaviour of bedrock in the upper metres below the surface, and that the temperature properties or thermal regimes are not as simple as often assumed. Temperature differences related to aspect are not only surficial, but are transmitted to underlying bedrock, and notable temperature differences were measurable to a depth of at least 6.0 m. Seasonal temperature fluctuations also have a pronounced effect on the rock mass temperatures and it was proven that deeper parts of the bedrock accumulate and dissipate heat at different (i.e. retarded) rates compared with shallower parts of the rock mass, creating suitable thermal conditions to induce thermal fatigue. Thermal properties were also proven to be non-linear. During analyses, the concept of temperature inversions was proven, whereby one part of the bedrock becomes hotter or cooler relative to another/adjacent part of the bedrock, compared with its earlier temperature state. It was argued that these temperature inversions may exacerbate thermal fatigue. This research proved that aspect (i.e. directional heating) and depth need to be considered when analysing thermal regimes in a rock mass, as these have a distinct influence. The effects which manifest themselves create suitable conditions for thermal fatigue, not only near the surface but also at depth in the bedrock. Lastly, the effects of meteorological conditions on shallow bedrock temperatures were assessed. Preliminary findings suggest that boundary conditions and meteorological processes may indeed affect shallow bedrock temperatures, but only under certain circumstances and not to the same extent as reported in the literature for conditions researched at the surface. Wind temperature relative to the rock temperature, as well as a combination of wind and rain were found to be the most significant factors. , Thesis (PhD) -- Faculty of Science, Geography, 2021
- Full Text:
- Date Issued: 2021-04
The role of open government data in the repurposing of land administration in postapartheid South Africa : an exploration
- Authors: Manona, Siyabulela Sobantu
- Date: 2021-04
- Subjects: Transparency in government -- South Africa , Land reform -- South Africa , Qualitative research -- Methodology , Postcolonialism -- South Africa , Post-apartheid era -- South Africa , South Africa -- Economic conditions -- 1991- , South Africa -- Social conditions -- 1994- , South Africa -- Politics and government -- 1994- , Open Government Data (OGD)
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/178397 , vital:42936 , 10.21504/10962/178397
- Description: Almost three decades after the official end of the apartheid, South Africa has been on a sturdy path that is characterised by deepening spatial economic inequalities. A plethora of policy instruments unleashed since 1994 had not only failed to stem the tide of poverty and inequality, but had deepened them. As part of this, South Africa’s most ambitious social engineering programme – land reform -- had disappointing outcomes. Premised on a view that these apartheid continuities were embedded in South Africa’s land administration system – which was incoherent and fragmented and requiring a systemic overhaul -- the study sought to explore the potential role of Open Government Data (OGD) in the repurposing of land administration system in the post-apartheid South Africa. To achieve this goal, the study was guided by the following objectives: to explore the ontology and the state of land governance and administration in the context of the post-apartheid South Africa; to undertake an evaluation or assessment of South Africa’s land data ecosystem; and to explore the potential role of OGD in the repurposing of land administration system in the postapartheid of South Africa. This study was steeped in qualitative research methods, underpinned by primary and secondary literature review. While the study was primarily pitched on a national scale – the combination of the systems and multiple scales approaches – yielded results which dislodges solutions that are required outside of the domain of a single state. This is one glaring example of land governance complexities that straddle beyond national scale – specifically in respect of new policy trajectories on trans-national boundaries and governance of water resources. Based on the holistic ontology of land, this study concludes that land administration and land governance overarching conceptual orientation -- concerned with land use decisions made by humans at various scales from a praxis and policy perspective –constitute two sides of the same coin, the former steeped towards practice and the latter steeped towards policy. Drawing from decolonial theories the study concludes that land does not only have multiple dimensions, but it also has multiple meanings, in a manner that calls for an ontological shift away from the western ontology, towards an inclusive and holistic conceptualisation. Historiography that is anchored in de-colonial thinking of South Africa’s land governance helps us understand how and why – colonial/apartheid norms acrimoniously found their way into the post-apartheid order -- the post-apartheid institutions of modernity rest on the same hierarchies of identities, classification and pathologisation. The study concludes that, while the colonial/apartheid administration may be gone, it’s underlying power matrices continue -- i.e. capitalism/European/patriachal/white – in a manner which explains the continuities of South Africa’s spatial inequalities and the associated economic inequalities. The organising principle for land relations (including opportunities) continues to be underpinned by gender, race and class, in ways that expose the mythical dimensions of the 'post-apartheid' underbelly. While identifying the need for homogenisation and rationalistion of colonial, apartheid and post-apartheid institutions (on a national scale) that is insufficient for the transformation of the colonial situation of what is in essence a part of the global system, the study advocates for the ‘repurposing of land governance and administration’ – underpinned by de-colonial thinking. Repurposing is seen as political imaginary that would entail uncoupling thought processes and praxis from the colonial matrices of power. The study goes on to conclude that there is a definite role for Open Government Data in repurposing of land administration in the post-apartheid South Africa – as a necessary, though in and of it’s own it is an insufficient condition to achieve that ideal -- but presents an opportunity to enhance transdisciplinarity approaches and efficiencies in internal government functioning and evidence-based decision making and policy formulation processes. , Thesis (PhD) -- Faculty of Science, Geography, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Manona, Siyabulela Sobantu
- Date: 2021-04
- Subjects: Transparency in government -- South Africa , Land reform -- South Africa , Qualitative research -- Methodology , Postcolonialism -- South Africa , Post-apartheid era -- South Africa , South Africa -- Economic conditions -- 1991- , South Africa -- Social conditions -- 1994- , South Africa -- Politics and government -- 1994- , Open Government Data (OGD)
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/178397 , vital:42936 , 10.21504/10962/178397
- Description: Almost three decades after the official end of the apartheid, South Africa has been on a sturdy path that is characterised by deepening spatial economic inequalities. A plethora of policy instruments unleashed since 1994 had not only failed to stem the tide of poverty and inequality, but had deepened them. As part of this, South Africa’s most ambitious social engineering programme – land reform -- had disappointing outcomes. Premised on a view that these apartheid continuities were embedded in South Africa’s land administration system – which was incoherent and fragmented and requiring a systemic overhaul -- the study sought to explore the potential role of Open Government Data (OGD) in the repurposing of land administration system in the post-apartheid South Africa. To achieve this goal, the study was guided by the following objectives: to explore the ontology and the state of land governance and administration in the context of the post-apartheid South Africa; to undertake an evaluation or assessment of South Africa’s land data ecosystem; and to explore the potential role of OGD in the repurposing of land administration system in the postapartheid of South Africa. This study was steeped in qualitative research methods, underpinned by primary and secondary literature review. While the study was primarily pitched on a national scale – the combination of the systems and multiple scales approaches – yielded results which dislodges solutions that are required outside of the domain of a single state. This is one glaring example of land governance complexities that straddle beyond national scale – specifically in respect of new policy trajectories on trans-national boundaries and governance of water resources. Based on the holistic ontology of land, this study concludes that land administration and land governance overarching conceptual orientation -- concerned with land use decisions made by humans at various scales from a praxis and policy perspective –constitute two sides of the same coin, the former steeped towards practice and the latter steeped towards policy. Drawing from decolonial theories the study concludes that land does not only have multiple dimensions, but it also has multiple meanings, in a manner that calls for an ontological shift away from the western ontology, towards an inclusive and holistic conceptualisation. Historiography that is anchored in de-colonial thinking of South Africa’s land governance helps us understand how and why – colonial/apartheid norms acrimoniously found their way into the post-apartheid order -- the post-apartheid institutions of modernity rest on the same hierarchies of identities, classification and pathologisation. The study concludes that, while the colonial/apartheid administration may be gone, it’s underlying power matrices continue -- i.e. capitalism/European/patriachal/white – in a manner which explains the continuities of South Africa’s spatial inequalities and the associated economic inequalities. The organising principle for land relations (including opportunities) continues to be underpinned by gender, race and class, in ways that expose the mythical dimensions of the 'post-apartheid' underbelly. While identifying the need for homogenisation and rationalistion of colonial, apartheid and post-apartheid institutions (on a national scale) that is insufficient for the transformation of the colonial situation of what is in essence a part of the global system, the study advocates for the ‘repurposing of land governance and administration’ – underpinned by de-colonial thinking. Repurposing is seen as political imaginary that would entail uncoupling thought processes and praxis from the colonial matrices of power. The study goes on to conclude that there is a definite role for Open Government Data in repurposing of land administration in the post-apartheid South Africa – as a necessary, though in and of it’s own it is an insufficient condition to achieve that ideal -- but presents an opportunity to enhance transdisciplinarity approaches and efficiencies in internal government functioning and evidence-based decision making and policy formulation processes. , Thesis (PhD) -- Faculty of Science, Geography, 2021
- Full Text:
- Date Issued: 2021-04
An investigation into the fire regimes of the upper Tsitsa River catchment
- Authors: Snyman, Gareth
- Date: 2020
- Subjects: Prescribed burning -- Environmental aspects -- South Africa , Fire ecology -- South Africa , Tsitsa River catchment (South Africa) , Soil erosion -- South Africa , Grasslands -- Management -- South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/145256 , vital:38422
- Description: South African grasslands are rich in flora and fauna and are a dominant vegetation cover in many of the water catchment areas, while providing a multitude of services to local communities and the environment. Fires have been the primary tool used to manage grasslands for livestock production for many years. However, there is debate about how they impact and alter landscapes and there are two schools of thought throughout literature. One argument is that fires are detrimental to landscapes; altering hydrological processes by causing excess soil erosion and changing soil properties. The other opinion is that fires are beneficial to ecosystems; maintaining vegetation structure, preventing bush encroachment, cycling nutrients and allowing for new plant growth. This study focused on the effects of fire regimes on soil properties in order to better understand the role that fire plays in geomorphic processes in the upper Tsitsa River catchment. The catchment falls under two land management types- commercial and communal, with the latter being severely degraded. Fire regimes were determined using a combination of Landsat and MODIS remotely sensed data and testing was carried out on soils exposed to different Fire Return Intervals (FRI). It was found that soils that were exposed to a high fire frequency (1-2-year FRI) exhibited a significantly higher degree of water repellency (p< 0.001) and surface hardness (p< 0.001) than soils that were exposed to a low fire frequency (3-4 year FRI), which indicates increased erosion potential. However, whilst a higher fire frequency resulted in altered soil characteristics, it contributed to landscape degradation as suggested in the literature, and soils are able to return to their previous state in over a short period of time. Further investigation into factors affecting fire regimes found that geology influenced vegetation type, resulting in differences in biomass in the two land management areas. The commercially managed land supported a high biomass, which resulted in a more natural fire regime with frequent fires, whilst the communally managed land supported less biomass. Smaller fuel loads and increased landscape fragmentation through overgrazing and road networks resulted in an altered fire regime with less frequent fires. Although the communally managed land has an altered fire regime, this research suggests that fires are not influencing the severe degradation present in these areas, and this is rather a function of geology and mismanagement of land. Whilst fire and grazing management plans can be implemented to alter the modified fire regime in the communal areas back to its natural state, this would take a long time and an increase in fires would pose a threat to surrounding communities. Overall the fire regimes in the upper Tsitsa River catchment are being altered by human influence and land management type, and whilst fire frequency is negatively altering soil properties, these soils can return to their natural state. The severe land degradation present in the communally managed areas are not a function of fire frequency and rather of geology and land management.
- Full Text:
- Date Issued: 2020
- Authors: Snyman, Gareth
- Date: 2020
- Subjects: Prescribed burning -- Environmental aspects -- South Africa , Fire ecology -- South Africa , Tsitsa River catchment (South Africa) , Soil erosion -- South Africa , Grasslands -- Management -- South Africa
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/145256 , vital:38422
- Description: South African grasslands are rich in flora and fauna and are a dominant vegetation cover in many of the water catchment areas, while providing a multitude of services to local communities and the environment. Fires have been the primary tool used to manage grasslands for livestock production for many years. However, there is debate about how they impact and alter landscapes and there are two schools of thought throughout literature. One argument is that fires are detrimental to landscapes; altering hydrological processes by causing excess soil erosion and changing soil properties. The other opinion is that fires are beneficial to ecosystems; maintaining vegetation structure, preventing bush encroachment, cycling nutrients and allowing for new plant growth. This study focused on the effects of fire regimes on soil properties in order to better understand the role that fire plays in geomorphic processes in the upper Tsitsa River catchment. The catchment falls under two land management types- commercial and communal, with the latter being severely degraded. Fire regimes were determined using a combination of Landsat and MODIS remotely sensed data and testing was carried out on soils exposed to different Fire Return Intervals (FRI). It was found that soils that were exposed to a high fire frequency (1-2-year FRI) exhibited a significantly higher degree of water repellency (p< 0.001) and surface hardness (p< 0.001) than soils that were exposed to a low fire frequency (3-4 year FRI), which indicates increased erosion potential. However, whilst a higher fire frequency resulted in altered soil characteristics, it contributed to landscape degradation as suggested in the literature, and soils are able to return to their previous state in over a short period of time. Further investigation into factors affecting fire regimes found that geology influenced vegetation type, resulting in differences in biomass in the two land management areas. The commercially managed land supported a high biomass, which resulted in a more natural fire regime with frequent fires, whilst the communally managed land supported less biomass. Smaller fuel loads and increased landscape fragmentation through overgrazing and road networks resulted in an altered fire regime with less frequent fires. Although the communally managed land has an altered fire regime, this research suggests that fires are not influencing the severe degradation present in these areas, and this is rather a function of geology and mismanagement of land. Whilst fire and grazing management plans can be implemented to alter the modified fire regime in the communal areas back to its natural state, this would take a long time and an increase in fires would pose a threat to surrounding communities. Overall the fire regimes in the upper Tsitsa River catchment are being altered by human influence and land management type, and whilst fire frequency is negatively altering soil properties, these soils can return to their natural state. The severe land degradation present in the communally managed areas are not a function of fire frequency and rather of geology and land management.
- Full Text:
- Date Issued: 2020
Seasonal trends of rainfall intensity, ground cover and sediment dynamics in the Little Pot River and Gqukunqa River catchments, South Africa
- Authors: Herd-Hoare, Sean
- Date: 2020
- Subjects: Land degradation -- Control -- South Africa -- Eastern Cape , Vegetation mapping -- South Africa -- Eastern Cape , Rain and rainfall -- South Africa -- Eastern Cape , Gqukunqa River catchment (South Africa) , Little Pot River catchment (South Africa) , Tsitsa River catchment (South Africa)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/146288 , vital:38512
- Description: Natural rangelands provide a variety of ecosystem services including livestock production which occurs on land under freehold land tenure and on land under communal tenure. There is an ongoing debate around the extent to which land degradation is occurring on these rangelands under different land management and land tenure systems and what the main degradation drivers are. Over-grazing, rainfall and soil type are key drivers of rangeland dynamics and the resultant sediment yield in the river systems, however, over-grazing is an outcome of land management while rainfall and soil type are natural drivers. This study explores the relationship between rainfall and daily sediment flux as well as the seasonal trends of vegetation cover and the study is part of a greater research effort called the Tsitsa Project which is based in the Tsitsa River catchment (near Maclear, Eastern Cape, South Africa). The Tsitsa Project aims at developing and managing both land and water in a sustainable way by improving the land, water and lives of people living in the Tsitsa River catchment. The restoration efforts of the Tstisa Project will aid in extending the lifespan of both the proposed dams on the Tsitsa River. The Tsitsa River catchment is characterised by grasslands, steep topography, highly erodible soils with many large gullies present and a very high sediment yield in the Tsitsa River which allowed for the exploration of some of the system drivers of sediment yield in this catchment. The study involved two sub-catchments of the Upper Tsitsa River catchment of different land management strategies: one dominated by commercial livestock farms (Little Pot River catchment) and one dominated by communal rangelands (Gqukunqa River catchment). The aim of this study was to determine the seasonal trends of rainfall intensity, ground cover and sediment dynamics in the Little Pot River and Gqukunqa River catchments. The purpose of the findings was to improve management strategies in degraded areas and catchments. In order to achieve this aim a variety of field and desktop methods were used. Field methods involved measuring variables including: vegetation biomass, vegetation cover, soil surface hardness, biocrust cover and slope angle for a range of Normalized Difference Vegetation Index (NDVI) values from the Sentinel-2A sensor. The study assessed the system response of the field variables in both catchments over one rainfall season (2018-2019). Desktop methods included various NDVI analyses as well as analyses of trends and relationships between vegetation dynamics, rainfall and sediment. The relationship between erosive rainfall events, daily rainfall, antecedent rainfall and daily sediment flux was explored over the time period of January 2016 to January 2019 and October 2015 to January 2019 for the Little Pot River catchment and the Gqukunqa River catchment respectively. NDVI was explored as a proxy for vegetation cover to extrapolate across the catchments and monitoring period. NDVI was found to have a weak positive relationship with vegetation cover and biomass (R2 values ranged from 0,04 to 0,525). Mean monthly catchment NDVI values, biomass and vegetation cover increased throughout the wet season of 2018-2019 in both catchments. Mean monthly NDVI values increased from 0,26 to 0,55 in the Little Pot River catchment and from 0,29 to 0,53 in the Gqukunqa River catchment over the course of the 2018-2019 wet season. NDVI, biomass and vegetation cover was found to be higher on south-facing slopes than north-facing slopes in both catchments for the majority of the wet season. The Gqukunqa River has significantly higher daily sediment fluxes than the Little Pot River despite similar NDVI and rainfall intensities which is owed to the dispersive soils in the Gqukunqa River catchment. Soil surface hardness results were inconclusive due to rainfall before or during every field trip which changed the properties of the soil. The largest erosive rainfall, daily rainfall and daily sediment events occurred from January to March each wet season in both catchments. Rainfall intensity and sediment fluxes were found to have a weak relationship, however, there was a stronger relationship found between antecedent rainfall and sediment flux. The larger daily sediment fluxes in each catchment often did not result from an erosive rainfall event on the same day but rather from multiple days of rainfall which can result in saturated soils and runoff leading to surface and sub-surface erosion. The possibility of sub-surface erosion via chemical processes contributing to the larger sediment events was also explored to explain the stronger relationship between antecedent rainfall and daily sediment flux.
- Full Text:
- Date Issued: 2020
- Authors: Herd-Hoare, Sean
- Date: 2020
- Subjects: Land degradation -- Control -- South Africa -- Eastern Cape , Vegetation mapping -- South Africa -- Eastern Cape , Rain and rainfall -- South Africa -- Eastern Cape , Gqukunqa River catchment (South Africa) , Little Pot River catchment (South Africa) , Tsitsa River catchment (South Africa)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/146288 , vital:38512
- Description: Natural rangelands provide a variety of ecosystem services including livestock production which occurs on land under freehold land tenure and on land under communal tenure. There is an ongoing debate around the extent to which land degradation is occurring on these rangelands under different land management and land tenure systems and what the main degradation drivers are. Over-grazing, rainfall and soil type are key drivers of rangeland dynamics and the resultant sediment yield in the river systems, however, over-grazing is an outcome of land management while rainfall and soil type are natural drivers. This study explores the relationship between rainfall and daily sediment flux as well as the seasonal trends of vegetation cover and the study is part of a greater research effort called the Tsitsa Project which is based in the Tsitsa River catchment (near Maclear, Eastern Cape, South Africa). The Tsitsa Project aims at developing and managing both land and water in a sustainable way by improving the land, water and lives of people living in the Tsitsa River catchment. The restoration efforts of the Tstisa Project will aid in extending the lifespan of both the proposed dams on the Tsitsa River. The Tsitsa River catchment is characterised by grasslands, steep topography, highly erodible soils with many large gullies present and a very high sediment yield in the Tsitsa River which allowed for the exploration of some of the system drivers of sediment yield in this catchment. The study involved two sub-catchments of the Upper Tsitsa River catchment of different land management strategies: one dominated by commercial livestock farms (Little Pot River catchment) and one dominated by communal rangelands (Gqukunqa River catchment). The aim of this study was to determine the seasonal trends of rainfall intensity, ground cover and sediment dynamics in the Little Pot River and Gqukunqa River catchments. The purpose of the findings was to improve management strategies in degraded areas and catchments. In order to achieve this aim a variety of field and desktop methods were used. Field methods involved measuring variables including: vegetation biomass, vegetation cover, soil surface hardness, biocrust cover and slope angle for a range of Normalized Difference Vegetation Index (NDVI) values from the Sentinel-2A sensor. The study assessed the system response of the field variables in both catchments over one rainfall season (2018-2019). Desktop methods included various NDVI analyses as well as analyses of trends and relationships between vegetation dynamics, rainfall and sediment. The relationship between erosive rainfall events, daily rainfall, antecedent rainfall and daily sediment flux was explored over the time period of January 2016 to January 2019 and October 2015 to January 2019 for the Little Pot River catchment and the Gqukunqa River catchment respectively. NDVI was explored as a proxy for vegetation cover to extrapolate across the catchments and monitoring period. NDVI was found to have a weak positive relationship with vegetation cover and biomass (R2 values ranged from 0,04 to 0,525). Mean monthly catchment NDVI values, biomass and vegetation cover increased throughout the wet season of 2018-2019 in both catchments. Mean monthly NDVI values increased from 0,26 to 0,55 in the Little Pot River catchment and from 0,29 to 0,53 in the Gqukunqa River catchment over the course of the 2018-2019 wet season. NDVI, biomass and vegetation cover was found to be higher on south-facing slopes than north-facing slopes in both catchments for the majority of the wet season. The Gqukunqa River has significantly higher daily sediment fluxes than the Little Pot River despite similar NDVI and rainfall intensities which is owed to the dispersive soils in the Gqukunqa River catchment. Soil surface hardness results were inconclusive due to rainfall before or during every field trip which changed the properties of the soil. The largest erosive rainfall, daily rainfall and daily sediment events occurred from January to March each wet season in both catchments. Rainfall intensity and sediment fluxes were found to have a weak relationship, however, there was a stronger relationship found between antecedent rainfall and sediment flux. The larger daily sediment fluxes in each catchment often did not result from an erosive rainfall event on the same day but rather from multiple days of rainfall which can result in saturated soils and runoff leading to surface and sub-surface erosion. The possibility of sub-surface erosion via chemical processes contributing to the larger sediment events was also explored to explain the stronger relationship between antecedent rainfall and daily sediment flux.
- Full Text:
- Date Issued: 2020
Ground thermal regimes in Western Dronning Maud Land, Antarctica in 2016
- Authors: Masebe, Consliah Tebogo
- Date: 2019
- Subjects: Climatic changes -- Antarctica , Frozen ground -- Research -- Antarctica , Frozen ground -- Thermal properties -- Antarctica , Queen Maud Land , Earth temperature -- Antarctica , Soil temperature -- Antarctica -- Measurement
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/95581 , vital:31173
- Description: Research shows that the climate of Antarctica is changing and, it is vital that the change is monitored to understand how it will affect global ecosystems. Since the International Polar Year (IPY) 2007-2008, research in permafrost studies has grown. However, there are still existing gaps that impede complete understanding of Antarctic cold environments and landscape processes. Permafrost has been noted as one of the major controlling factors of the terrestrial ecosystem dynamics in Antarctica. However, the understanding of Antarctic permafrost, when compared to other cryospheric components, is limited, especially its thermal and physical properties, evolution, as well as links to pedogenesis, hydrology, geomorphic dynamics, and responses to global change. This project provided an understanding and insight to over-arching research that evaluates the state and status of permafrost and the active layer in Dronning Maud Land (DML) through examining short-term variations on ground thermal regimes. The main focus is on understanding the influence of synoptic, diurnal and seasonal events on the active layer in 2016. Analysis of available data shows that ground thermal regimes are influenced by variations in air temperature, pressure, wind speed and to some extent, relative humidity. Subsequently, ground thermal regimes also depend on soil physical characteristics including sediment particle size and bulk density. Furthermore, sediment particle size and bulk density have been found to have a great influence on thermal propagation rates as well as active layer depth; the higher the bulk density, the higher the thermal propagation rate and the lower the bulk density, the lower the thermal propagation rate. Conversely, a large proportion of bigger sediment particle size in soil corresponds with a higher thermal propagation rate and a large proportion of smaller sediment particle size in soil corresponds with a lower thermal propagation rate. Also, ground thermal regimes vary according to seasons. Ground temperatures are more variable in summer, while air temperatures are more variable in winter. The variability according to different seasons shows that the active layer responds to seasonal climatic variations. Additionally, the active layer also responds to synoptic and diurnal weather events.
- Full Text:
- Date Issued: 2019
- Authors: Masebe, Consliah Tebogo
- Date: 2019
- Subjects: Climatic changes -- Antarctica , Frozen ground -- Research -- Antarctica , Frozen ground -- Thermal properties -- Antarctica , Queen Maud Land , Earth temperature -- Antarctica , Soil temperature -- Antarctica -- Measurement
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/95581 , vital:31173
- Description: Research shows that the climate of Antarctica is changing and, it is vital that the change is monitored to understand how it will affect global ecosystems. Since the International Polar Year (IPY) 2007-2008, research in permafrost studies has grown. However, there are still existing gaps that impede complete understanding of Antarctic cold environments and landscape processes. Permafrost has been noted as one of the major controlling factors of the terrestrial ecosystem dynamics in Antarctica. However, the understanding of Antarctic permafrost, when compared to other cryospheric components, is limited, especially its thermal and physical properties, evolution, as well as links to pedogenesis, hydrology, geomorphic dynamics, and responses to global change. This project provided an understanding and insight to over-arching research that evaluates the state and status of permafrost and the active layer in Dronning Maud Land (DML) through examining short-term variations on ground thermal regimes. The main focus is on understanding the influence of synoptic, diurnal and seasonal events on the active layer in 2016. Analysis of available data shows that ground thermal regimes are influenced by variations in air temperature, pressure, wind speed and to some extent, relative humidity. Subsequently, ground thermal regimes also depend on soil physical characteristics including sediment particle size and bulk density. Furthermore, sediment particle size and bulk density have been found to have a great influence on thermal propagation rates as well as active layer depth; the higher the bulk density, the higher the thermal propagation rate and the lower the bulk density, the lower the thermal propagation rate. Conversely, a large proportion of bigger sediment particle size in soil corresponds with a higher thermal propagation rate and a large proportion of smaller sediment particle size in soil corresponds with a lower thermal propagation rate. Also, ground thermal regimes vary according to seasons. Ground temperatures are more variable in summer, while air temperatures are more variable in winter. The variability according to different seasons shows that the active layer responds to seasonal climatic variations. Additionally, the active layer also responds to synoptic and diurnal weather events.
- Full Text:
- Date Issued: 2019
The remote sensing of fires and their effects on soil properties in the uKhahlamba Drakensberg Park
- Authors: Moore, Natasha Jade
- Date: 2019
- Subjects: Remote sensing -- South Africa -- KwaZulu-Natal , Soil ecology -- South Africa -- KwaZulu-Natal , Grassland fires -- South Africa -- KwaZulu-Natal , Grassland fires -- Remote sensing -- South Africa -- KwaZulu-Natal , Soils -- Effect of fires on -- South Africa -- KwaZulu-Natal , uKhalamba Drakensberg Park (South Africa)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/94400 , vital:31042
- Description: Fires are a common and natural occurrence globally and specifically on the African continent. The Drakensberg Mountains are home to southern Africa’s high-altitude fire-climax grasslands, where fire is the dominant management tool. Fire is used to maintain the grasslands in the uKhahlamba Drakensberg Park (UDP) World Heritage Site, located on the eastern escarpment of the KwaZulu-Natal Drakensberg. This study aimed to investigate the spatial and temporal frequency of fires using remote sensing, and to investigate the effect of fire frequency on soil properties in the UDP. Remote sensing offers a set of supportive tools for the management of this sensitive vegetation and specifically to assess the frequency and spatial extent of fires. Field assessments can then be used to assess the impact of fires. Remotely sensed data were used to determine fire frequency and the spatial extent of fires in the UDP. The Moderate Resolution Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS) active fire detection point data were processed to investigate the temporal resolution of fires. Landsat 5 and 8 imagery were utilised for conducting Normalised Burn Ratios (NBR) to determine the spatial extent of the burn scars of fires. The results from the remotely sensed data were used to select study sites for accessing the effects of fire frequency on soil properties. The remote sensing results showed the main fire season in the UDP was from May to October, and annual burn scars from the available Landsat data for 1998 to 2017 ranged from 22.5% to 57.67% of the UDP. Remote sensing was shown to be an effective tool for monitoring fires in the UDP, with a combination of satellite data producing the best results. Soil properties were highly varied across the UDP. Environmental factors were shown to have a more significant influence on soil properties than fire frequency. This study highlighted the complex nature and diversity of fires and soils across the UDP.
- Full Text:
- Date Issued: 2019
- Authors: Moore, Natasha Jade
- Date: 2019
- Subjects: Remote sensing -- South Africa -- KwaZulu-Natal , Soil ecology -- South Africa -- KwaZulu-Natal , Grassland fires -- South Africa -- KwaZulu-Natal , Grassland fires -- Remote sensing -- South Africa -- KwaZulu-Natal , Soils -- Effect of fires on -- South Africa -- KwaZulu-Natal , uKhalamba Drakensberg Park (South Africa)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/94400 , vital:31042
- Description: Fires are a common and natural occurrence globally and specifically on the African continent. The Drakensberg Mountains are home to southern Africa’s high-altitude fire-climax grasslands, where fire is the dominant management tool. Fire is used to maintain the grasslands in the uKhahlamba Drakensberg Park (UDP) World Heritage Site, located on the eastern escarpment of the KwaZulu-Natal Drakensberg. This study aimed to investigate the spatial and temporal frequency of fires using remote sensing, and to investigate the effect of fire frequency on soil properties in the UDP. Remote sensing offers a set of supportive tools for the management of this sensitive vegetation and specifically to assess the frequency and spatial extent of fires. Field assessments can then be used to assess the impact of fires. Remotely sensed data were used to determine fire frequency and the spatial extent of fires in the UDP. The Moderate Resolution Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS) active fire detection point data were processed to investigate the temporal resolution of fires. Landsat 5 and 8 imagery were utilised for conducting Normalised Burn Ratios (NBR) to determine the spatial extent of the burn scars of fires. The results from the remotely sensed data were used to select study sites for accessing the effects of fire frequency on soil properties. The remote sensing results showed the main fire season in the UDP was from May to October, and annual burn scars from the available Landsat data for 1998 to 2017 ranged from 22.5% to 57.67% of the UDP. Remote sensing was shown to be an effective tool for monitoring fires in the UDP, with a combination of satellite data producing the best results. Soil properties were highly varied across the UDP. Environmental factors were shown to have a more significant influence on soil properties than fire frequency. This study highlighted the complex nature and diversity of fires and soils across the UDP.
- Full Text:
- Date Issued: 2019
Chemical weathering on selected nunataks in western Dronning Maud Land, Antarctica
- Authors: Knox, Jenna Tracy
- Date: 2018
- Subjects: Glacial climates -- Antarctica -- Queen Maud Land , Glaciology -- Antarctica -- Queen Maud Land , Chemical weathering -- Antarctica -- Queen Maud Land , Atmospheric carbon dioxide -- Environmental aspects , Climatic changes -- Antarctica -- Queen Maud Land , Nunataks -- Antarctica -- Queen Maud Land
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/61658 , vital:28046
- Description: High latitude areas are sensitive to the impacts of climate change, and it is expected that the impact of greenhouse warming will be much higher in the polar regions than in any other climatic zones, with the most highly affected area being that of the Antarctic rim (Barsch, 1993). Weathering and pedogenic processes respond to variations in climate, with models predicting that chemical weathering may increase synchronously with global carbon dioxide levels increase, due to dissolution rates and the erosional impact of hydrological cycles in warming climates (Anderson & Anderson, 2010). As liquid water becomes more available in Antarctica the potential for chemical weathering, due to a less moisture-limited environment and increased temperatures, increases (Convey et al., 2009). Weathering processes are important for soil formation and the production of fine-grained material, with chemical weathering being an active constituent of this. Increased rates of soil formation are likely to occur, with global climate changes resulting in greater chemical weathering occurring in Antarctica. Opportunistic sampling was conducted during the Austral summer of 2016/2017, whereby rock, snow and meltwater samples were taken at various sites within the western portion of Dronning Maud Land of Antarctica. Rock samples were placed in resin, and cut with a diamond saw to create thin sections. Optical microscopy and scanning transmission electron microscopy (STEM) were used to analyse mineral weight percentage with depth. Twelve soil samples were dried and weighed, sieved and statistically represented according to particle size. Inductively coupled plasma mass spectrometry (ICP-MS) determined the geochemical analysis for 10 water and snow samples. Rock hardness was inferred through the use of an Equotip, with rebound values recorded for multiple rock faces and samples. Thermal regimes of rock temperature was further recorded using a FLIR infrared camera, and documented for each rock face over a 24 hour period at 2 hourly intervals. The products of increased chemical weathering were evident from particle size analysis; samples were very poorly sorted in nature, and undergo in situ weathering, whereby products were not removed by erosional processes. Weathering rinds were found to be siliceous and ferric, depending on parent lithology. Ferric ratios increased in wt.% from the substrate rock to the external surface, creating the red, iron rich crusts noted on the hand specimens. The observable chemical weathering was found adjacent to intrusions through Precambrian dolerites. Geochemical analysis revealed thin, carbonaceous features, with impurity-rich layers, characteristic of speleothem formation. Carbonaceous layers did not follow underlying substrate features, rather deposited at the external surface, upon which, further precipitation growth could occur, creating karst features. Extensive gypsum coatings (>2mm) under BSE imagery were identified, with the abundance of gypsum salts (below surface level) and rock coatings indicating active sulphuric acid weathering, in western Dronning Maud Land, Antarctica. Were mechanical processes faster than chemical, weathering rinds and solution features on silicate rocks would be uncommon in the Antarctic, periglacial landscape. However, this is not the case as the existence of these landforms implies that chemical weathering may occur faster than mechanical weathering processes (Pope et al., 1995). In a changing world, one needs to monitor these processes at a micro-scale in order to fully understand how periglacial environments react to global climatic changes, and the subsequent impacts on these sensitive environments.
- Full Text:
- Date Issued: 2018
- Authors: Knox, Jenna Tracy
- Date: 2018
- Subjects: Glacial climates -- Antarctica -- Queen Maud Land , Glaciology -- Antarctica -- Queen Maud Land , Chemical weathering -- Antarctica -- Queen Maud Land , Atmospheric carbon dioxide -- Environmental aspects , Climatic changes -- Antarctica -- Queen Maud Land , Nunataks -- Antarctica -- Queen Maud Land
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/61658 , vital:28046
- Description: High latitude areas are sensitive to the impacts of climate change, and it is expected that the impact of greenhouse warming will be much higher in the polar regions than in any other climatic zones, with the most highly affected area being that of the Antarctic rim (Barsch, 1993). Weathering and pedogenic processes respond to variations in climate, with models predicting that chemical weathering may increase synchronously with global carbon dioxide levels increase, due to dissolution rates and the erosional impact of hydrological cycles in warming climates (Anderson & Anderson, 2010). As liquid water becomes more available in Antarctica the potential for chemical weathering, due to a less moisture-limited environment and increased temperatures, increases (Convey et al., 2009). Weathering processes are important for soil formation and the production of fine-grained material, with chemical weathering being an active constituent of this. Increased rates of soil formation are likely to occur, with global climate changes resulting in greater chemical weathering occurring in Antarctica. Opportunistic sampling was conducted during the Austral summer of 2016/2017, whereby rock, snow and meltwater samples were taken at various sites within the western portion of Dronning Maud Land of Antarctica. Rock samples were placed in resin, and cut with a diamond saw to create thin sections. Optical microscopy and scanning transmission electron microscopy (STEM) were used to analyse mineral weight percentage with depth. Twelve soil samples were dried and weighed, sieved and statistically represented according to particle size. Inductively coupled plasma mass spectrometry (ICP-MS) determined the geochemical analysis for 10 water and snow samples. Rock hardness was inferred through the use of an Equotip, with rebound values recorded for multiple rock faces and samples. Thermal regimes of rock temperature was further recorded using a FLIR infrared camera, and documented for each rock face over a 24 hour period at 2 hourly intervals. The products of increased chemical weathering were evident from particle size analysis; samples were very poorly sorted in nature, and undergo in situ weathering, whereby products were not removed by erosional processes. Weathering rinds were found to be siliceous and ferric, depending on parent lithology. Ferric ratios increased in wt.% from the substrate rock to the external surface, creating the red, iron rich crusts noted on the hand specimens. The observable chemical weathering was found adjacent to intrusions through Precambrian dolerites. Geochemical analysis revealed thin, carbonaceous features, with impurity-rich layers, characteristic of speleothem formation. Carbonaceous layers did not follow underlying substrate features, rather deposited at the external surface, upon which, further precipitation growth could occur, creating karst features. Extensive gypsum coatings (>2mm) under BSE imagery were identified, with the abundance of gypsum salts (below surface level) and rock coatings indicating active sulphuric acid weathering, in western Dronning Maud Land, Antarctica. Were mechanical processes faster than chemical, weathering rinds and solution features on silicate rocks would be uncommon in the Antarctic, periglacial landscape. However, this is not the case as the existence of these landforms implies that chemical weathering may occur faster than mechanical weathering processes (Pope et al., 1995). In a changing world, one needs to monitor these processes at a micro-scale in order to fully understand how periglacial environments react to global climatic changes, and the subsequent impacts on these sensitive environments.
- Full Text:
- Date Issued: 2018
On high-altitude and high- latitude frost environments
- Authors: Hansen, Christel Dorothee
- Date: 2018
- Subjects: Frost -- Drakensberg Mountains , Frost -- Prince Edward Islands -- Marion Island , Frost -- Antarctica -- Queen Maud Land , Climatic geomorphology -- Southern Hemisphere , Permafrost -- Southern Hemisphere , Periglacial processes -- Southern Hemisphere , Frost environments -- Southern Hemisphere
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/62383 , vital:28169
- Description: Frost environments occur throughout the world, with associated processes occurring across climatic zones. Climatic geomorphology proposes that climatic zones, largely derived from annual average air temperature and precipitation values, have specific landforms and processes active within that zone. This study offers unique insights into the frost environments of three locations in the Southern Hemisphere, namely the Eastern Cape Drakensberg of South Africa, sub-Antarctic Marion Island, and Dronning Maud Land of Antarctica. The Drakensberg ranges from temperate to alpine, Marion Island is hyper-maritime, and Dronning Maud Land a polar desert. Drivers and forcings on the ground frost regime are identified, as are future climatic scenarios. Altitude and latitude were identified as the most important locational drivers, while air temperature showed highest correlation with freezing events. The initiation of a freeze event correlated strongly with maximum ground temperatures. Vegetation cover was found to ameliorate frost cycles, thereby increasing ground temperatures. Dronning Maud Land of Antarctica is characterised by annual frost (permafrost), with limited seasonal thaw in summer. Thawing cycles reflected the depth of the active layer, which ranged from just under 60 cm for Robertskollen (at lowest altitude) to less than 15 cm on Slettfjell (at greatest altitude). Marion Island had the most active frost environment, exhibiting both seasonal frost, and ubiquitous shallow diurnal frost cycles. The Drakensberg were largely frost-free, with limited seasonal frost and few diurnal freeze- thaw events. Diurnal frost processes were found to be azonal, and present at all three study locations. Evidence of landforms derived from diurnal frost processes were evident in each zone. Equifinality/convergence of form was present to a degree. The presence of patterned ground, which was not wholly derived from frost processes, suggests a measure of equifinality. Furthermore, openwork block deposits, of which not all are either blockstreams nor blockfields, are not necessarily the result of frost processes. The periglacial environment is poorly defined and methods to delineate this environment, as well as other climatic zones, should include additional parameters. Delineating zones on annual (and limited) monthly averages based on predominantly temperature, is not sufficient. While concepts of climatic geomorphology may be applied in a general sense, this framework is not suited to working at smaller scales. Specifically, periglacial environments should be delineated using ground moisture, as well as air temperature. Furthermore, vegetation and snow cover are important, as are soil textural properties.
- Full Text:
- Date Issued: 2018
- Authors: Hansen, Christel Dorothee
- Date: 2018
- Subjects: Frost -- Drakensberg Mountains , Frost -- Prince Edward Islands -- Marion Island , Frost -- Antarctica -- Queen Maud Land , Climatic geomorphology -- Southern Hemisphere , Permafrost -- Southern Hemisphere , Periglacial processes -- Southern Hemisphere , Frost environments -- Southern Hemisphere
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/62383 , vital:28169
- Description: Frost environments occur throughout the world, with associated processes occurring across climatic zones. Climatic geomorphology proposes that climatic zones, largely derived from annual average air temperature and precipitation values, have specific landforms and processes active within that zone. This study offers unique insights into the frost environments of three locations in the Southern Hemisphere, namely the Eastern Cape Drakensberg of South Africa, sub-Antarctic Marion Island, and Dronning Maud Land of Antarctica. The Drakensberg ranges from temperate to alpine, Marion Island is hyper-maritime, and Dronning Maud Land a polar desert. Drivers and forcings on the ground frost regime are identified, as are future climatic scenarios. Altitude and latitude were identified as the most important locational drivers, while air temperature showed highest correlation with freezing events. The initiation of a freeze event correlated strongly with maximum ground temperatures. Vegetation cover was found to ameliorate frost cycles, thereby increasing ground temperatures. Dronning Maud Land of Antarctica is characterised by annual frost (permafrost), with limited seasonal thaw in summer. Thawing cycles reflected the depth of the active layer, which ranged from just under 60 cm for Robertskollen (at lowest altitude) to less than 15 cm on Slettfjell (at greatest altitude). Marion Island had the most active frost environment, exhibiting both seasonal frost, and ubiquitous shallow diurnal frost cycles. The Drakensberg were largely frost-free, with limited seasonal frost and few diurnal freeze- thaw events. Diurnal frost processes were found to be azonal, and present at all three study locations. Evidence of landforms derived from diurnal frost processes were evident in each zone. Equifinality/convergence of form was present to a degree. The presence of patterned ground, which was not wholly derived from frost processes, suggests a measure of equifinality. Furthermore, openwork block deposits, of which not all are either blockstreams nor blockfields, are not necessarily the result of frost processes. The periglacial environment is poorly defined and methods to delineate this environment, as well as other climatic zones, should include additional parameters. Delineating zones on annual (and limited) monthly averages based on predominantly temperature, is not sufficient. While concepts of climatic geomorphology may be applied in a general sense, this framework is not suited to working at smaller scales. Specifically, periglacial environments should be delineated using ground moisture, as well as air temperature. Furthermore, vegetation and snow cover are important, as are soil textural properties.
- Full Text:
- Date Issued: 2018
Periglacial landforms of the Ahlmannryggen and Jutulsessen areas of western Dronning Maud land, Antarctica
- Authors: Wilmot, Nicola Frances
- Date: 2018
- Subjects: Periglacial processes Antarctica Queen Maud Land , Geomorphology Antarctica Queen Maud Land , Permafrost Antarctica Queen Maud Land , Freezes (Meteorology) Antarctica Queen Maud Land , Thawing Antarctica Queen Maud Land
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/61535 , vital:28034
- Description: Periglacial landforms are a common occurrence in Ahlmannryggen and Jutulsessen areas of western Dronning Maud land (WDML). Classification and formation of these landforms were disputed in literature. In Antarctica information on periglacial landforms is limited or confined to a specific landform. Thus a holistic approach was taken when investigating the periglacial landforms found in WDML. An overview of the existing knowledge base on periglacial landforms in WDML was given which was coupled with the analysis of archival data. The landforms found in this area were patterned ground, openwork block deposits (OBD), rock glaciers, terraces, a pronival rampart and lake ice blisters. With patterned ground being the common periglacial landform in WDML, heave monitoring was used where time-lapse videos were used to investigate the formation processes in patterned ground. From consolidating existing knowledge as well as adding new knowledge on the formation of periglacial landforms, it is clear that the landforms in Antarctica should not be compared to other examples, especially examples from the northern hemisphere. Further research in the formation of periglacial landforms is needed and can be further enhanced with more extensive use of the heave monitoring method in future research.
- Full Text:
- Date Issued: 2018
- Authors: Wilmot, Nicola Frances
- Date: 2018
- Subjects: Periglacial processes Antarctica Queen Maud Land , Geomorphology Antarctica Queen Maud Land , Permafrost Antarctica Queen Maud Land , Freezes (Meteorology) Antarctica Queen Maud Land , Thawing Antarctica Queen Maud Land
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/61535 , vital:28034
- Description: Periglacial landforms are a common occurrence in Ahlmannryggen and Jutulsessen areas of western Dronning Maud land (WDML). Classification and formation of these landforms were disputed in literature. In Antarctica information on periglacial landforms is limited or confined to a specific landform. Thus a holistic approach was taken when investigating the periglacial landforms found in WDML. An overview of the existing knowledge base on periglacial landforms in WDML was given which was coupled with the analysis of archival data. The landforms found in this area were patterned ground, openwork block deposits (OBD), rock glaciers, terraces, a pronival rampart and lake ice blisters. With patterned ground being the common periglacial landform in WDML, heave monitoring was used where time-lapse videos were used to investigate the formation processes in patterned ground. From consolidating existing knowledge as well as adding new knowledge on the formation of periglacial landforms, it is clear that the landforms in Antarctica should not be compared to other examples, especially examples from the northern hemisphere. Further research in the formation of periglacial landforms is needed and can be further enhanced with more extensive use of the heave monitoring method in future research.
- Full Text:
- Date Issued: 2018
A meteorological analysis of extreme flood events in the southern parts of the Eastern Cape, South Africa
- Authors: Jacobs, Tennielle Lindsay
- Date: 2017
- Subjects: Floods -- South Africa -- Eastern Cape , Floods -- South Africa -- Eastern Cape -- Cast studies , Lows (Meteorology) -- South Africa -- Eastern Cape , Rain and rainfall -- South Africa -- Eastern Cape , Rainfall anomalies -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/50525 , vital:25996
- Description: Extreme flood events have been found to occur in the Eastern Cape Province of South Africa. The southern and south-eastern coastal regions are particularly susceptible to floods with daily rainfall records of up to 490 mm having been recorded here. In order to gain a better understanding of these floods, historical floods in the southern parts of the Eastern Cape have been analysed in this study. This study aimed to investigate the most extreme flood events in the history of the area and to analyse the surface observational data during the heavy rainfall events found, to contribute to the understanding of these heavy rainfall events. Seven case studies were investigated using NCEP/NCAR Reanalysis 1 data and surface observational data, to analysis the synoptic circulation and surface data tendencies during heavy rainfall events. All of the case studies that had synoptic data available showed to have a COL system present with the upper air low lying westward of the flood area. The surface synoptic situation presented an intense high pressure system lying south west or south of the country in the Atlantic Ocean between 35-45°S. Another key factor was a surface trough over the interior of the country, due to the COL, extending southwards to protrude off of the south or south eastern coastline east of the flood areas. The combination of these three systems colloquially referred to as a “Black South-Easter”, produced dangerous rainfall intensities when the winds were perpendicular to the coast. The results of the surface observations revealed temperatures increasing at night (against diurnal cycles) with increasing relative humidity preceding the heavy rainfall events. The pressure showed both increasing and decreasing trends during heavy rainfall events however in five of six cases a tight pressure gradient was present producing an influx of moist air into the flood area. Onshore winds were found to be of high importance in heavy rainfall events to bring moist air into the area. Wind speeds greater than 5m/s occurred during times of high rainfall intensities.
- Full Text:
- Date Issued: 2017
- Authors: Jacobs, Tennielle Lindsay
- Date: 2017
- Subjects: Floods -- South Africa -- Eastern Cape , Floods -- South Africa -- Eastern Cape -- Cast studies , Lows (Meteorology) -- South Africa -- Eastern Cape , Rain and rainfall -- South Africa -- Eastern Cape , Rainfall anomalies -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/50525 , vital:25996
- Description: Extreme flood events have been found to occur in the Eastern Cape Province of South Africa. The southern and south-eastern coastal regions are particularly susceptible to floods with daily rainfall records of up to 490 mm having been recorded here. In order to gain a better understanding of these floods, historical floods in the southern parts of the Eastern Cape have been analysed in this study. This study aimed to investigate the most extreme flood events in the history of the area and to analyse the surface observational data during the heavy rainfall events found, to contribute to the understanding of these heavy rainfall events. Seven case studies were investigated using NCEP/NCAR Reanalysis 1 data and surface observational data, to analysis the synoptic circulation and surface data tendencies during heavy rainfall events. All of the case studies that had synoptic data available showed to have a COL system present with the upper air low lying westward of the flood area. The surface synoptic situation presented an intense high pressure system lying south west or south of the country in the Atlantic Ocean between 35-45°S. Another key factor was a surface trough over the interior of the country, due to the COL, extending southwards to protrude off of the south or south eastern coastline east of the flood areas. The combination of these three systems colloquially referred to as a “Black South-Easter”, produced dangerous rainfall intensities when the winds were perpendicular to the coast. The results of the surface observations revealed temperatures increasing at night (against diurnal cycles) with increasing relative humidity preceding the heavy rainfall events. The pressure showed both increasing and decreasing trends during heavy rainfall events however in five of six cases a tight pressure gradient was present producing an influx of moist air into the flood area. Onshore winds were found to be of high importance in heavy rainfall events to bring moist air into the area. Wind speeds greater than 5m/s occurred during times of high rainfall intensities.
- Full Text:
- Date Issued: 2017
Biogeomorphic aspects of lichen colonisation in part of western Dronning Maud Land, Antarctica
- Authors: Ayres, Gabrielle Alexzena
- Date: 2017
- Subjects: Lichen communities -- Queen Maud Land , Lichens -- Ecology -- Queen Maud Land , Polar regions , Ecology -- Polar regions , Antarctica , Ecology -- Antarctica
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/19713 , vital:22477
- Description: Ice-free regions in Antarctica provide natural laboratories for investigating and modelling change in landscapes and ecosystems. The terrestrial ecosystems in western Dronning Maud Land are potentially critical to improve current understanding of polar ecosystems, however, they remain poorly represented and under-protected. Lichen habitats were used to elucidate geomorphic-biological feedbacks that shape the landscape’s topography and biodiversity, which in turn promote environmental heterogeneity. Environmental parameters acting on two landforms were measured to determine the colonisation and growth of lichens in niche habitats. The habitats were identified and characterised, and topographic heterogeneity was found to control lichen colonisation. Micro-topographical niches provide the most stable environments for colonisation, and are preferred habitats. Lichen-habitat interactions were species specific, and closely related to insolation and moisture availability. The bidirectional relationships between rock weathering and lichen colonisation was ascertained. Results showed that lichens are good indicators of landform heterogeneity, but also promote landform heterogeneity. Given the habitat preferences of specific lichen species, they provide proxy to evaluating environmental responses, especially environmental change. The findings of this research are to be used as baseline data for future studies exploring ecosystem development in emerging landforms.
- Full Text:
- Date Issued: 2017
- Authors: Ayres, Gabrielle Alexzena
- Date: 2017
- Subjects: Lichen communities -- Queen Maud Land , Lichens -- Ecology -- Queen Maud Land , Polar regions , Ecology -- Polar regions , Antarctica , Ecology -- Antarctica
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/19713 , vital:22477
- Description: Ice-free regions in Antarctica provide natural laboratories for investigating and modelling change in landscapes and ecosystems. The terrestrial ecosystems in western Dronning Maud Land are potentially critical to improve current understanding of polar ecosystems, however, they remain poorly represented and under-protected. Lichen habitats were used to elucidate geomorphic-biological feedbacks that shape the landscape’s topography and biodiversity, which in turn promote environmental heterogeneity. Environmental parameters acting on two landforms were measured to determine the colonisation and growth of lichens in niche habitats. The habitats were identified and characterised, and topographic heterogeneity was found to control lichen colonisation. Micro-topographical niches provide the most stable environments for colonisation, and are preferred habitats. Lichen-habitat interactions were species specific, and closely related to insolation and moisture availability. The bidirectional relationships between rock weathering and lichen colonisation was ascertained. Results showed that lichens are good indicators of landform heterogeneity, but also promote landform heterogeneity. Given the habitat preferences of specific lichen species, they provide proxy to evaluating environmental responses, especially environmental change. The findings of this research are to be used as baseline data for future studies exploring ecosystem development in emerging landforms.
- Full Text:
- Date Issued: 2017
Identifying growth criteria and sediment movement mechanisms of needle ice using high-frequency environmental and visual monitoring
- Authors: Borg, Carl-Johan
- Date: 2017
- Subjects: Frazil ice , Sediment transport , Ice mechanics , Photography -- Digital techniques , Environmental monitoring
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/17656 , vital:22268
- Description: Environmental growth conditions and mechanisms involved in sediment transport by needle ice have historically been difficult to assess and are poorly documented. The spatial and temporal dynamics that relate to the environment, growth and decay of needle ice are not fully understood. This study monitored needle ice growth, melt and visually identified sediment displacement mechanisms by needle ice, with the aim of revealing environmental growth criteria, timing of growth/melt, ground-surface-air energy balance and sediment displacement mechanisms. Furthermore, the impact of needle ice displacement on vegetation and patterned ground formation was analysed. High-frequency visual monitoring, using three cameras, supplemented by high-frequency measurements of air temperature, soil moisture and wind speed was used to investigate needle ice growth and decay dynamics. Results from visual and environmental monitoring of needle ice growth, showed that the needle ice growing environment was more dynamic, especially in terms of surface temperature, than previously argued. Needle ice growth was observed to occur during surface temperatures from -2.0°C to 2.2°C, soil moisture levels from 0.4% to 37.4% and in winds speeds of 0 m/s to 12.6 m/s. Needle ice initiation was documented a few minutes to hours before or after the onset of surface temperature dropping to below 0°C. Imagery displayed that the depth of ice nucleation was variable within the soil column, possibly relating to the energy balance of radiative cooling, convective heat loss, ground conductivity and latent heat release at the air-surface-ground boundary. Heaving and resettling, toppling and rolling were identified as slope displacement mechanisms when needle ice decayed. Animal trampling and hail were additionally documented as substantial surface altering processes. Furthermore, no impact of needle ice reducing vegetation stability was identified, although a tendency to hinder vegetation expansion was noted. Also, no creation of patterned ground was observed as a result of needle ice decay.
- Full Text:
- Date Issued: 2017
- Authors: Borg, Carl-Johan
- Date: 2017
- Subjects: Frazil ice , Sediment transport , Ice mechanics , Photography -- Digital techniques , Environmental monitoring
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/17656 , vital:22268
- Description: Environmental growth conditions and mechanisms involved in sediment transport by needle ice have historically been difficult to assess and are poorly documented. The spatial and temporal dynamics that relate to the environment, growth and decay of needle ice are not fully understood. This study monitored needle ice growth, melt and visually identified sediment displacement mechanisms by needle ice, with the aim of revealing environmental growth criteria, timing of growth/melt, ground-surface-air energy balance and sediment displacement mechanisms. Furthermore, the impact of needle ice displacement on vegetation and patterned ground formation was analysed. High-frequency visual monitoring, using three cameras, supplemented by high-frequency measurements of air temperature, soil moisture and wind speed was used to investigate needle ice growth and decay dynamics. Results from visual and environmental monitoring of needle ice growth, showed that the needle ice growing environment was more dynamic, especially in terms of surface temperature, than previously argued. Needle ice growth was observed to occur during surface temperatures from -2.0°C to 2.2°C, soil moisture levels from 0.4% to 37.4% and in winds speeds of 0 m/s to 12.6 m/s. Needle ice initiation was documented a few minutes to hours before or after the onset of surface temperature dropping to below 0°C. Imagery displayed that the depth of ice nucleation was variable within the soil column, possibly relating to the energy balance of radiative cooling, convective heat loss, ground conductivity and latent heat release at the air-surface-ground boundary. Heaving and resettling, toppling and rolling were identified as slope displacement mechanisms when needle ice decayed. Animal trampling and hail were additionally documented as substantial surface altering processes. Furthermore, no impact of needle ice reducing vegetation stability was identified, although a tendency to hinder vegetation expansion was noted. Also, no creation of patterned ground was observed as a result of needle ice decay.
- Full Text:
- Date Issued: 2017
Active Layer Dynamics at Four Borehole Sites in Western Dronning Maud Land, Antarctica
- Authors: Kotzé, Camilla
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4894 , http://hdl.handle.net/10962/d1021295
- Description: Permafrost and active layer dynamics in the Antarctic play an important role within terrestrial landscapes and ecosystems and as a climate change indicator. However, they remain less thoroughly researched than their Northern-Hemispheric counterpart. Despite advancements made by ANTPAS on the permafrost and active layer monitoring network in the Antarctic, observational gaps still exist. Western Dronning Maud Land (WDML) has been identified as one of these gaps, necessitating further research on permafrost dynamics and the influence of climate parameters thereon. Such elucidation is critical to both the cryospheric and life sciences. Variations in the surface climate of Antarctica can be seen as a result of inter-annual variations in atmospheric circulation, enhancing permafrost degradation and active layer thickening which directly affects soil processes, such as sorting and cryoturbation. Ground temperatures from four permafrost boreholes from WDML were analysed from 2007 to 2014. The study sites exhibit seasonal freezing, periglacial landforms, and altitudinal variation, ranging between ca. 450masl to ca. 1300masl. Using ground thermal regime and regional climate data, the spatial and temporal variability of the active layer in the Ahlmannryggen and Jutulsessen areas of WDML were characterised. 137 Cs tracing has revealed that the active layer and associated landforms have been active over the past half century. Further results show that active layer depths at each site vary inter-annually and are particularly influenced by snow cover, altitude and distance to the ice-shelf. Moreover, a correlation between the SAO (Semi-Annual Oscillation) and measured ground temperatures was found, principally during the transitional season of the SAO in May and September. The relationship between climate and ground thermal regimes, especially the influence of teleconnections thereon, is essential to improving the understanding of permafrost dynamics and landform morphology in continental Antarctica.
- Full Text:
- Date Issued: 2016
- Authors: Kotzé, Camilla
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4894 , http://hdl.handle.net/10962/d1021295
- Description: Permafrost and active layer dynamics in the Antarctic play an important role within terrestrial landscapes and ecosystems and as a climate change indicator. However, they remain less thoroughly researched than their Northern-Hemispheric counterpart. Despite advancements made by ANTPAS on the permafrost and active layer monitoring network in the Antarctic, observational gaps still exist. Western Dronning Maud Land (WDML) has been identified as one of these gaps, necessitating further research on permafrost dynamics and the influence of climate parameters thereon. Such elucidation is critical to both the cryospheric and life sciences. Variations in the surface climate of Antarctica can be seen as a result of inter-annual variations in atmospheric circulation, enhancing permafrost degradation and active layer thickening which directly affects soil processes, such as sorting and cryoturbation. Ground temperatures from four permafrost boreholes from WDML were analysed from 2007 to 2014. The study sites exhibit seasonal freezing, periglacial landforms, and altitudinal variation, ranging between ca. 450masl to ca. 1300masl. Using ground thermal regime and regional climate data, the spatial and temporal variability of the active layer in the Ahlmannryggen and Jutulsessen areas of WDML were characterised. 137 Cs tracing has revealed that the active layer and associated landforms have been active over the past half century. Further results show that active layer depths at each site vary inter-annually and are particularly influenced by snow cover, altitude and distance to the ice-shelf. Moreover, a correlation between the SAO (Semi-Annual Oscillation) and measured ground temperatures was found, principally during the transitional season of the SAO in May and September. The relationship between climate and ground thermal regimes, especially the influence of teleconnections thereon, is essential to improving the understanding of permafrost dynamics and landform morphology in continental Antarctica.
- Full Text:
- Date Issued: 2016
Surface characteristics of rock glaciers in the Jutulsessen, Dronning Maud Land, Antarctica
- Rudolph, Elizabeth Magdalena
- Authors: Rudolph, Elizabeth Magdalena
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/2667 , vital:20314
- Description: Rock glaciers are landforms that present downslope movement of debris under the influence of ice and gravity. These landforms can be used as paleo-climate indicators as well as proxies for climate change. Rock glaciers have been investigated in a variety of climates and landscapes, however continental Antarctica, Dronning Maud Land specifically, remains understudied. This thesis aimed to investigate and classify five rock glaciers observed in the Jutulsessen, Dronning Maud Land. The surface characteristics and geomorphology were assessed and used as generic classifiers. Size, shape and landscape association was established by field surveying and GIS, whilst sediment and clast characteristics were determined from sampling. A surface temperature profile was created from short-term high frequency temperature measurements. All of the rock glaciers exhibit either undulating surfaces or patterned ground, or both, which suggests active-layer related processes. Sediment particle size analysis is inconclusive. The 137Cs-content and fabric analysis suggest movement regimes similar to other rock glaciers with higher activity at the head, and variable movement directions at the toe. Relative “activeness” is inferred from morphology: Grjotlia, Grjotøyra and Vassdalen were classified as lobate, spatulate and tongue-shaped respectively with Grjotlia the most stable. A new morphological classification of ‘crown-shaped’ is suggested for Brugdedalen and Jutuldalen, and they also appear most active. The control of local climate on rock glacier mechanics is emphasised by the findings, and thus climatic interpolation from a single weather stations is not useful. Increased spatial and temporal coverage of sediment profiles, surface topography and active-layer characteristics could be used to elucidate the processes and controls of these landforms in the Antarctic.
- Full Text:
- Date Issued: 2016
- Authors: Rudolph, Elizabeth Magdalena
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/2667 , vital:20314
- Description: Rock glaciers are landforms that present downslope movement of debris under the influence of ice and gravity. These landforms can be used as paleo-climate indicators as well as proxies for climate change. Rock glaciers have been investigated in a variety of climates and landscapes, however continental Antarctica, Dronning Maud Land specifically, remains understudied. This thesis aimed to investigate and classify five rock glaciers observed in the Jutulsessen, Dronning Maud Land. The surface characteristics and geomorphology were assessed and used as generic classifiers. Size, shape and landscape association was established by field surveying and GIS, whilst sediment and clast characteristics were determined from sampling. A surface temperature profile was created from short-term high frequency temperature measurements. All of the rock glaciers exhibit either undulating surfaces or patterned ground, or both, which suggests active-layer related processes. Sediment particle size analysis is inconclusive. The 137Cs-content and fabric analysis suggest movement regimes similar to other rock glaciers with higher activity at the head, and variable movement directions at the toe. Relative “activeness” is inferred from morphology: Grjotlia, Grjotøyra and Vassdalen were classified as lobate, spatulate and tongue-shaped respectively with Grjotlia the most stable. A new morphological classification of ‘crown-shaped’ is suggested for Brugdedalen and Jutuldalen, and they also appear most active. The control of local climate on rock glacier mechanics is emphasised by the findings, and thus climatic interpolation from a single weather stations is not useful. Increased spatial and temporal coverage of sediment profiles, surface topography and active-layer characteristics could be used to elucidate the processes and controls of these landforms in the Antarctic.
- Full Text:
- Date Issued: 2016
Geomorphic and ambient environmental impacts on lichen distribution on two inland Nunataks in western Dronning Maud Land, Antarctica
- Authors: Dwight, Rosemary Anne
- Date: 2015
- Subjects: Lichens -- Antarctica -- Queen Maud Land , Lichen communities -- Antarctica -- Queen Maud Land , Lichens -- Climatic factors -- Antarctica -- Queen Maud Land , Lichens -- Effect of environment on -- Antarctica -- Queen Maud Land , Biotic communities -- Antarctica -- Queen Maud Land , Biotic communities -- Climatic factors -- Antarctica -- Queen Maud Land , Biodiversity -- Climatic factors -- Antarctica -- Queen Maud Land
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4889 , http://hdl.handle.net/10962/d1018189
- Description: Feedbacks between abiotic variables and community structure in Antarctica are poorly understood. Research is, therefore, required to elucidate the patterns of biodiversity that exist and the factors that influence them, particularly under changing climates. Landscape processes affect environmental heterogeneity, which in turn affect patterns of biodiversity. Two inland Antarctic nunataks, Robertskollen and the Northern Buttress of Vesleskarvet, were selected for investigation to determine the potential impact of selected environmental factors on lichen distribution and abundance, at the intra- and inter-nunatak scales. Lichens were found to prefer rock faces with dips between 1° and 45°, and northern/southern aspects. Lichen colonisation was mostly in microtopographical features that result from rock weathering. The distribution of lichens was found to be regular at the intra- and inter-nunatak scale, whereas lichen abundance was found to be mostly influenced by temperature. On the Northern Buttress, rock hardness displays a similar pattern to lichen abundance, both of which are suggested to be a function of exposure time, which is dependent on deglaciation. The two nunataks serve as excellent laboratories that can potentially be used as proxies for investigating the possible impacts of climate change
- Full Text:
- Date Issued: 2015
- Authors: Dwight, Rosemary Anne
- Date: 2015
- Subjects: Lichens -- Antarctica -- Queen Maud Land , Lichen communities -- Antarctica -- Queen Maud Land , Lichens -- Climatic factors -- Antarctica -- Queen Maud Land , Lichens -- Effect of environment on -- Antarctica -- Queen Maud Land , Biotic communities -- Antarctica -- Queen Maud Land , Biotic communities -- Climatic factors -- Antarctica -- Queen Maud Land , Biodiversity -- Climatic factors -- Antarctica -- Queen Maud Land
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4889 , http://hdl.handle.net/10962/d1018189
- Description: Feedbacks between abiotic variables and community structure in Antarctica are poorly understood. Research is, therefore, required to elucidate the patterns of biodiversity that exist and the factors that influence them, particularly under changing climates. Landscape processes affect environmental heterogeneity, which in turn affect patterns of biodiversity. Two inland Antarctic nunataks, Robertskollen and the Northern Buttress of Vesleskarvet, were selected for investigation to determine the potential impact of selected environmental factors on lichen distribution and abundance, at the intra- and inter-nunatak scales. Lichens were found to prefer rock faces with dips between 1° and 45°, and northern/southern aspects. Lichen colonisation was mostly in microtopographical features that result from rock weathering. The distribution of lichens was found to be regular at the intra- and inter-nunatak scale, whereas lichen abundance was found to be mostly influenced by temperature. On the Northern Buttress, rock hardness displays a similar pattern to lichen abundance, both of which are suggested to be a function of exposure time, which is dependent on deglaciation. The two nunataks serve as excellent laboratories that can potentially be used as proxies for investigating the possible impacts of climate change
- Full Text:
- Date Issued: 2015
On active layer processes and landforms in western Dronning Maud Land, Antarctica
- Authors: Scott, David Alan
- Date: 2015
- Subjects: Landforms -- Antarctica -- Queen Maud Land , Permafrost -- Antarctica -- Queen Maud Land , Permafrost -- Thermal properties -- Antarctica -- Queen Maud Land , Climatic changes -- Antarctica -- Queen Maud Land , Cryosphere , Drone aircraft -- Antarctica -- Queen Maud Land , 3-D modeling
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4893 , http://hdl.handle.net/10962/d1019757
- Description: Permafrost is a variable in Antarctic terrestrial ecosystems, and the role it plays in the cryosphere is not well understood. There is much still to be learnt about the thermal state, physical properties, thickness and age of permafrost in Western Dronning Maud Land (WDML). Active layer dynamics and observed change over time have the potential to improve our knowledge of climate change. Understanding the effects of a warming climate on permafrost can also be of benefit to infrastructure, especially in areas with a large amount of frozen ground such as Scandinavia, Canada and Russia. Active layer and permafrost dynamics of WDML, Antarctica, are presented and discussed using data from six study sites, namely the Robertskollen, Vesleskarvet, Flarjuven, Grunehogna, Slettjfell nunataks and the Troll research station in the Jutulsessen area. Ground and ambient air temperature, as well as ground moisture data were collected for each site. An inventory of active layer and permafrost landforms was compiled, as were the frequency of cycles over the zero-degree isotherm, and the depth of the active layer. Furthermore, 3D models, geo-referenced maps and Digital Elevation Models were created of study areas with the use of an Unmanned Aerial Vehicle (UAV). Polygonal features are the most common landscape feature and are common to most of the study sites. Robertskollen has the deepest active layer at over 66cm and Slettfjell the shallowest at 9cm. A maximum recorded air temperature of 8.76°C (10/11/2014) occurred at Troll with the second highest maximum of 6.77°C (22/12/2010) recorded at Vesleskarvet. Robertskollen has the highest observable biological growth and a maximum recorded ground temperature of 22.84°C (10/01/2014). Troll and Valterkulten, registered the second and third highest ground temperatures respectively. The high ground Temperature observed for Robertskollen may be ascribed to it being the lowest altitude site. The highest number of cycles over the zero-degree isotherm was observed at Troll (11.01%), followed by Robertskollen (10.99%). For relatively warm areas, such as Robertskollen it is recommended that two metre borehole loggers are installed in order to capture a detailed understanding of the active layer. The UAV proved to be a beneficial tool for capturing aerial photographs for post fieldwork analysis and 3D modelling.
- Full Text:
- Date Issued: 2015
- Authors: Scott, David Alan
- Date: 2015
- Subjects: Landforms -- Antarctica -- Queen Maud Land , Permafrost -- Antarctica -- Queen Maud Land , Permafrost -- Thermal properties -- Antarctica -- Queen Maud Land , Climatic changes -- Antarctica -- Queen Maud Land , Cryosphere , Drone aircraft -- Antarctica -- Queen Maud Land , 3-D modeling
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4893 , http://hdl.handle.net/10962/d1019757
- Description: Permafrost is a variable in Antarctic terrestrial ecosystems, and the role it plays in the cryosphere is not well understood. There is much still to be learnt about the thermal state, physical properties, thickness and age of permafrost in Western Dronning Maud Land (WDML). Active layer dynamics and observed change over time have the potential to improve our knowledge of climate change. Understanding the effects of a warming climate on permafrost can also be of benefit to infrastructure, especially in areas with a large amount of frozen ground such as Scandinavia, Canada and Russia. Active layer and permafrost dynamics of WDML, Antarctica, are presented and discussed using data from six study sites, namely the Robertskollen, Vesleskarvet, Flarjuven, Grunehogna, Slettjfell nunataks and the Troll research station in the Jutulsessen area. Ground and ambient air temperature, as well as ground moisture data were collected for each site. An inventory of active layer and permafrost landforms was compiled, as were the frequency of cycles over the zero-degree isotherm, and the depth of the active layer. Furthermore, 3D models, geo-referenced maps and Digital Elevation Models were created of study areas with the use of an Unmanned Aerial Vehicle (UAV). Polygonal features are the most common landscape feature and are common to most of the study sites. Robertskollen has the deepest active layer at over 66cm and Slettfjell the shallowest at 9cm. A maximum recorded air temperature of 8.76°C (10/11/2014) occurred at Troll with the second highest maximum of 6.77°C (22/12/2010) recorded at Vesleskarvet. Robertskollen has the highest observable biological growth and a maximum recorded ground temperature of 22.84°C (10/01/2014). Troll and Valterkulten, registered the second and third highest ground temperatures respectively. The high ground Temperature observed for Robertskollen may be ascribed to it being the lowest altitude site. The highest number of cycles over the zero-degree isotherm was observed at Troll (11.01%), followed by Robertskollen (10.99%). For relatively warm areas, such as Robertskollen it is recommended that two metre borehole loggers are installed in order to capture a detailed understanding of the active layer. The UAV proved to be a beneficial tool for capturing aerial photographs for post fieldwork analysis and 3D modelling.
- Full Text:
- Date Issued: 2015
The characterisation of an openwork block deposit, northern buttress, Vesleskarvet, Dronning Maud Land, Antarctica.
- Authors: Hansen, Christel Dorothee
- Date: 2014
- Subjects: Formations (Geology) -- Antarctica -- Queen Maud Land , Geology, Structural -- Antarctica -- Queen Maud Land , Weathering -- Antarctica -- Queen Maud Land , Climatic changes -- Antarctica -- Queen Maud Land , Physical geography -- Antarctica -- Queen Maud Land , Paleoclimatology -- Antarctica
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4878 , http://hdl.handle.net/10962/d1013138
- Description: Investigating openwork block accumulation has the potential to further our understanding of rock weathering, the control of geological structure on landforms, the production of substrates for biological colonisation and the impacts of climate change on landform development and dynamics. Various models for the development of these landforms have been proposed. This includes in situ weathering, frost heave and wedging. Furthermore, it has been suggested that cold-based ice has the potential to preserve these features rather than to obliterate them. Blocky deposits are also frequently used as proxy evidence for interpreting palaeoclimates. The morphology and processes acting on a blockfield located on the Northern Buttress of the Vesleskarvet Nunataks, Dronning Maud Land, Antarctica (2°W, 71°S) were investigated and characterised. Given block dimensions and orientations that closely resembled the parent material and only small differences in aspect related characteristics observed, the blockfield was found to be autochthonous with in situ block production and of a young (Holocene) age. Small differences in rock hardness measurements suggest some form of aspect control on rock weathering. South-facing sides of clasts were found to be the least weathered. In comparison, consistently low rock hardness rebound values for the north-facing aspects suggest that these are the most weathered sides. Additional indicators of weathering, such as flaking and pitting, support analyses conducted for rock hardness rebound values. Solar radiation received, slope gradients and snow cover were found to influence weathering of clasts across the study site. Furthermore, ambient temperatures and wind speed significantly influenced near-surface ground temperatures dynamics. However, the lack of a matrix and paucity of fine material in textural analyses suggest a limited weathering environment. It is suggested that the retreat of the Antarctic ice sheet during the last LGM led to unloading of the surface, causing dilatation and subsequent fracturing of the bedrock along pre-existing joints, leading to in situ clast supply. Subsequent weathering and erosion along other points or lines of weakness then yielded fines and slight edge rounding of clasts.
- Full Text:
- Date Issued: 2014
- Authors: Hansen, Christel Dorothee
- Date: 2014
- Subjects: Formations (Geology) -- Antarctica -- Queen Maud Land , Geology, Structural -- Antarctica -- Queen Maud Land , Weathering -- Antarctica -- Queen Maud Land , Climatic changes -- Antarctica -- Queen Maud Land , Physical geography -- Antarctica -- Queen Maud Land , Paleoclimatology -- Antarctica
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4878 , http://hdl.handle.net/10962/d1013138
- Description: Investigating openwork block accumulation has the potential to further our understanding of rock weathering, the control of geological structure on landforms, the production of substrates for biological colonisation and the impacts of climate change on landform development and dynamics. Various models for the development of these landforms have been proposed. This includes in situ weathering, frost heave and wedging. Furthermore, it has been suggested that cold-based ice has the potential to preserve these features rather than to obliterate them. Blocky deposits are also frequently used as proxy evidence for interpreting palaeoclimates. The morphology and processes acting on a blockfield located on the Northern Buttress of the Vesleskarvet Nunataks, Dronning Maud Land, Antarctica (2°W, 71°S) were investigated and characterised. Given block dimensions and orientations that closely resembled the parent material and only small differences in aspect related characteristics observed, the blockfield was found to be autochthonous with in situ block production and of a young (Holocene) age. Small differences in rock hardness measurements suggest some form of aspect control on rock weathering. South-facing sides of clasts were found to be the least weathered. In comparison, consistently low rock hardness rebound values for the north-facing aspects suggest that these are the most weathered sides. Additional indicators of weathering, such as flaking and pitting, support analyses conducted for rock hardness rebound values. Solar radiation received, slope gradients and snow cover were found to influence weathering of clasts across the study site. Furthermore, ambient temperatures and wind speed significantly influenced near-surface ground temperatures dynamics. However, the lack of a matrix and paucity of fine material in textural analyses suggest a limited weathering environment. It is suggested that the retreat of the Antarctic ice sheet during the last LGM led to unloading of the surface, causing dilatation and subsequent fracturing of the bedrock along pre-existing joints, leading to in situ clast supply. Subsequent weathering and erosion along other points or lines of weakness then yielded fines and slight edge rounding of clasts.
- Full Text:
- Date Issued: 2014
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