Theses and Dissertations

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Open Access
Activity patterns, species composition and dietary analysis of bats on two macadamia farms in Levubu, South Africa
(2017-09-18) Mphethe, Vusani; Taylor, P. J.; Steyn, J. N.; Schoeman, M. C.
See the attached abstract below
Open Access
Adsorption of oxyanions of As, B, Cr, Mo and Se from coal fly ash leachates using A1/Fe modified bentonite clay
(2014-01-10) Masindi, Vhahangwele; Gitari, Wilson Mugera; Tutu, Hlanganani
Open Access
Alternative practices for optimising soil quality and crop protection for macadamia orchards, Limpopo Province, South Africa.
(2019-09-30) Steyn, Jakobus Nicolaas; Crafford, J. E.; Gliessman, S. R.; v. d. M. Louw, S.
The main aim of the research was to contribute means for converting conventional, high-input production systems to more sustainable ecological systems, thereby improving the sustainability of macadamia production and ultimately contributing to food security. This was achieved by a) investigating the potential use of cover crops and compost to enhance soil quality in macadamia orchards and b) investigating the potential use of use of cover crops and orchard heterogeneity to control stinkbug pests that target macadamia crops. Field experiments were conducted in three phases: phase one tested the potential of six cover crops for crop protection (as trap crops) and simultaneously for soil restoration or fertility enhancement purposes in macadamia orchards. Phase two repeated the trials of phase one (both soil restoration and trap crops) but with modifications to both categories. Soil restoration treatments were conducted with trees which were growing in what appeared to be healthy soils, and then repeated with trees in the same orchard where the topsoil had been degraded (totally removed) by agricultural operations. The third phase repeated the trap crop trials only, but this time on three different study areas (all commercial farms) with the single cover crop which performed the best as a trap crop during phase two. Trials were modified from the first to the last phase to overcome practical implementation problems encountered along the way and to adapt to local conditions experienced in the commercial macadamia farming systems which served as research sites. Diversity of natural orchard vegetation was enhanced in phase three to improve conditions for natural predators as part of the trap crop treatments in the last phase and cover crops were finally first composted and then returned to the root zones of the macadamia trees as part of the soil quality enhancement treatments in the second phase. The results from the trap crop trials shows a significant effect of trap crops combined with increased orchard diversity in reducing unsound kernel percentages caused by stinkbug pests and demonstrate that trap crops combined with an increase in orchard diversity could be utilized in macadamia orchards as a more sustainable alternative to inorganic pesticides against the stinkbug complex. The most notable changes in the soil that took place with soil quality enhancement treatments were the significant increases in soil phosphorous content and pH which resulted not in an improvement in soil quality in terms of these two indicators but revealed an important issue about the use of compost containing animal manure originating from dairies or feedlots. In summary however, it was clear that although not all the soil quality indicators that were employed to assess changes in the soil with compost treatments improved significantly, a holistic consideration of all indicators portrays an overall improvement which was particularly significant in the degraded soil plots where the topsoil had been removed by prior agricultural activities.
Embargo
An evaluation of flood control mechanisms to withstand and adapt to flooding in Vhembe District, Limpopo Province
(2024-09-06) Munzhedzi, Lily; Nethengwe, N. S.; Mugari, M. E.
The Vhembe district is currently grappling with a rising prevalence of flooding, a phenomenon attributed to a combination of natural elements, such as heavy rainfall, and human-induced activities like deforestation and inadequate infrastructure management. The resultant damages encompass infrastructure destruction, loss of life, crop and soil damage, and environmental harm, with implications extending to human health, housing, livelihoods, government resources, and significant economic consequences. Consequences vary based on the resources and development levels of different areas, emphasising the need to understand each community's unique aspects for the development of resilient flood control strategies. The aim of this study is to evaluate the flood control mechanisms to determine if they can withstand and adapt to flooding in the selected study areas of Musina, Duthuni, and Sane in the Vhembe District. The study pursues two objectives: investigating trends in extreme rainfall and its relationship to flood occurrences, and characterising the nature, effectiveness, and adaptability of flood control mechanisms in the Vhembe district area. Employing a mixed-methods approach, the research design integrates both quantitative and qualitative methods to gain comprehensive insights. The data collection process involved the administration of in-depth questionnaires to participants, coupled with observational analyses of flood control mechanisms. This multifaceted approach allowed for a qualitative assessment of the nature, effectiveness, and adaptability of these mechanisms. Additionally, daily rainfall data sourced from the NASA POWER website was utilised. This data facilitated the computation of an average seasonal precipitation table, the generation of monthly precipitation figures, and tables displaying the count of days when precipitation exceeded the 95th percentile. The findings reveal a recurring pattern of precipitation throughout the seasons, with the highest average precipitation consistently occurring from December to February, and January emerging as a critical month for flood risk. The analysis of flood events spanning from 2000 to 2020 establishes a connection between daily rainfall exceeding 20 mm and instances of flooding, particularly evident in Duthuni, where nearly annual flooding has been observed. The study identified diverse flood control mechanisms linked to the level of development and community traditions. Natural and traditional measures, such as furrows and vegetation-based flood control mechanisms, dominate the rural village of Sane. In contrast, the urbanised Musina prefers engineered solutions like culverts and concrete channels, while Duthuni integrates both approaches. Furrows are popular at the household level across all the study areas, although their effectiveness is considered to be lower in comparison to other household flood control mechanisms. The field observational analysis emphasises the construction of flood control mechanisms using reinforced materials and underscores the importance of regular maintenance. The study underscores the importance of region-specific flood control solutions tailored to local conditions and preferences, considering climate patterns and community traditions. By adopting this approach, the Vhembe district can enhance its readiness and adaptive capacity for flooding. The study's results provide a foundation for well-informed decision-making and policy development, emphasising the necessity for initiatives to align flood management with the distinct challenges and preferences of local communities.
Open Access
Analysis of drought incidence, gendered vulnerability and adaptation in Chivi South, Zimbabwe
(2016) Chineka, Jestina; Musyoki, A.; Kori, E.; Chikore, M. R. H.
Climate change has brought about a number of global environmental challenges and the worst, climatic disasters such as floods and droughts. In Zimbabwe, particularly in the semi-arid Chivi District, droughts have become more frequent. At the household level, there are a multiplicity of vulnerability and coping mechanisms to this scourge, which have gender dimensions. This study analysed the vulnerability of the Chivi South community to drought and its adaptation with specific consideration to the gender dynamics. The specific objectives for this dissertation were to establish the characteristics and extent of drought occurrences in Chivi District in the last 30 years, assess Chivi South‟s vulnerability to drought, evaluate levels of gender vulnerability to drought, and analyse gendered adaptation to drought. Subsequently, a strategy for drought adaptation in the rural areas of Zimbabwe was drawn. The research was based on the mixed methods approach, as it employed both qualitative and quantitative approaches. Data collection methods included a review of official documents, key informant interviews with community leaders, Non-Governmental Organisations and government officials working in the area, household questionnaires and focus group discussions. The Standardized Precipitation Index was used to determine drought severity. Data was analysed using the SPSS 22.0 software. Capabilities such as Chi-square and cross tabulation were used to effectively analyse data. The Household Vulnerability Index was employed to infer vulnerability and adaptation of the community to drought. Research findings were illustrated using charts, graphs, tables and photographs. The study established the occurrence of droughts in Chivi, with a high prevalence of low magnitude droughts. A decrease in crop food production closely related to drought patterns was noted. Drought vulnerability cuts across the whole gender spectrum, with a sizable number of female headed households being severely exposed. However females adapt better to the effects of drought than males. A holistic approach which seeks to integrate both men and women in decision-making and to improve the community‟s adaptation to drought and other disasters was proposed
Open Access
Analysis of land use and land cover change and its impact on soil erosion in Nzhelele Valley, Limpopo Province, South Africa
(2022-07-15) Mavhuru, Blessing; Nethengwe, N. S.; Odhiambo, B. D.O.; Chikoore, H.
Globally, the rate of land use and land cover changes has affeceted the magnitude of soil eroion. Strategies to combat soil erosion can give assistance as solutions to provide food security in many agricultural areas. Although some changes are caused by natural factors, anthropogenic factors and an increase in population are major drivers of soil erosion. This study analyses land use and land cover change and its impact on soil erosion in Nzhelele Valley. To attain this goal, the objectives of this study are to classify land use and land cover change using GIS from 2005 to 2019 in Nzhelele Valley; assess the human influence of soil management strategies on soil erosion; determine the impact of soil fertility of different land use on soil erosion, and model soil erosion on different land-use areas of Nzhelele Valley. To select farmers, study used a stratified random sampling technique by dividing groups based on their villages. A systematic sampling technique was used to select 392 farmers. To collect 78 soil samples from Nzhelele Valley, the study used the Sampling Design Tool of ArcGIS 10.The study used supervised classification in Geographic Information System (GIS) to classify land use and land cover types. Semi-structured questionnaires were used to solicit data on human influence on soil management strategies on soil erosion. The study draws a systematic sample using Slovin’s formula to determine the size of the sample from the Nzhelele Valley, and with a target population size of 657 farmers from the village, 398 farmers were selected for the study. The study also measured soil organic matter, soil pH, phosphorus, and nitrogen from collected soil samples to determine the impact of soil fertility on soil erosion. To collect soil samples from Nzhelele Valley, the study used the Sampling Design Tool of ArcGIS 10. The tool assisted in selecting the soil sample points within the study area and a total of 78 soil samples were collected for the study. The Soil and Water Assessment Tool (ARCSWAT) with an interface of ArcView Geographic Information System software modelled soil erosion within Nzhelele Valley. In terms of LULCC, results show that from 2005 up to 2019, forest increased significantly by 5%, agricultural land cover significant decrease by 11% from 36% to 25% land use/cover, bare land built-up land increase by 3% from 14% to 17%, as well as grassland increase by 3% from 19% to 22%. The results also show a significant correlation (p < 0.05) between land use management strategies and economic support systems. The physical characteristics (slope and terrace) significantly correlate (p< 0.05) with soil management strategies that limit soil erosion. The results illustrate significant variation (p ≤ 0.0002) in nitrogen among different land-use classes. Significant variation was observed (p ≤ 0.0001) in soil pH, phosphorus, and organic matter among the different land-use areas. Changes in LULC are more likely to have an effect on soil erosion in the grassland and bare land/built-up areas where infiltration is very limited. The recorded decrease in agricultural land use and an increase in forest cover are likely to reduce the impact of soil erosion. Using SWAT to model soil erosion, 26-sub basin and 301 hydrological response units were delineated. The statistical elevation of the watershed obtained a minimum elevation of 384 m, maximum elevation of 1680 m with a minimum elevation of 808.81 m. Sub basins 13, 23, and 25 demonstrated high erosion-prone classes with average sediment yield of 15.3%, 11.26%, and 11.5% respectively. The lowest sediment yield (2.1 t/ha-1yr-1) in the study area was observed in sub-basin 3. Overall synthesis of the findings illustrates that research into land-use changes and type of land use activities factors were key aspects in addressing soil erosion challenges. These findings vibrate strongly on the need to develop a systematic land management system that can solve unplanned land cover and land-use change. Based on the results, fostering better management investments through collaborative land management in Nzhelele Valley might improve the dissemination of information. Farmer to farmer training can improve the skills of the individual, which might allow smooth dissemination of information vital for land management. The problem of soil nutrient deficiency can be a central issue put forward to the local government, which needs to be addressed with specific sectors of the government to create a better environment for agriculture and food security especially in the marginalized community of South Africa. Sediment output based on the land use classes is potentially influenced by cropland with the study. This allows for further solutions on the type of land use activities to be narrowed to understand the levels of soil erosion based on the activities. The study findings from this area can be used for comparison to other areas with the same characteristics to gain insight into possible solutions to the challenges of soil erosion.
Open Access
An analysis of patterns and trends of road traffic injuries and fatalities in Vhembe District, Limpopo Province, South Africa
(2016) Osidele, Olujimi Agbolahan; Nethengwe, N. S.; Dondofema, F.
Road transport safety is challenging globally, especially in developing countries, where it affects both road users and governments. The aim of road traffic safety is to ensure a reduction or total eradication of road fatalities and other injuries that are related to road accidents resulting from public road usage. In South Africa, one of the major problems faced by the Department of Roads and Transport is the issue of road traffic accidents. Between 2004 and 2010 the annual road traffic accidents increased to over 500,000 and 28,000 or more are fatal, which has led to serious injuries, as reported by the Department. This study analysed patterns and trends of road traffic injuries and fatalities in Vhembe District Municipality from January 2011 to August 2015. It also mapped road accident hotpots using Getis hotspot analysis and linear referencing in ArcGIS 10.2 spatial statistics extension. The research further established correlation between accidents spots and road design geometry. Factors that are responsible for road traffic accidents leading to fatalities, injuries, and loss of property were also examined. Pedestrian behavioural attitude towards adhering to road safety measures was studied using systematic random sampling, field observation and questionnaires. Finally, the study investigated if there has been any significant reduction in the road traffic injuries and fatalities occurrence rate within the last five years in Vhembe District since the commencement of World Health Organisation; Decade of Action for Road Safety 2011-2020. It was found out that most of the accidents occurred as a result of changes in human social behaviour, negligence and indulgence. The passenger road users category is the worst affected followed by drivers and pedestrians. It was found out that road crashes have decreased by 35% since the commencement of decade of action for road safety. The composition of road traffic injuries and fatalities since 2011 shows a reduction in the numbers of victims recorded. An average of 86 fatalities, 326 serious injuries and 701 minor injuries occurred per annum within the study period. There was high significant value (p  0.05) among all the categories of road users understudied. The differences observed were real and did not occurred by chance for the 5year period (2011 – 2015).
Open Access
Analysis of Peri-Urban Household Solid Waste Management System: A Case of Lwamondo Village
(2022-07-15) Nelwamondo, Fhumulani; Mudau, N. V.; Mokgoebo, M. J.
Peri-urban solid waste management has become a challenge caused by population growth, urbanization which increases the volume of waste generated into bulk quantities and change in the waste composition of solid waste generated, and neglect from a local municipality. It condones illegal disposal of household solid waste and improper use of waste management hierarchy which negatively affects the environment. The overall study examined the current peri-urban solid waste management system at Lwamondo village, with the specific objectives of the study include analysing the waste composition of solid waste generated; examine current solid waste management practices and analyse factors influencing current solid waste management, to achieve the objective of the study. Various quantitative and qualitative techniques were employed. Simple Random Sampling (SRS) technique was used as a sampling method, and 10% of the households in each sub-village were sampled for questionnaire distribution. The study also incorporated convenience sampling as a method for sampling households within 500m proximity to the illegal open dumping spots to conduct interviews. Using the designed checklist, field observation was undertaken for both households and illegal open dumping spots to identify waste composition. The study adopted a mixed-method integrating both qualitative and quantitative techniques. Using the field observation and checklist designed, findings confirmed that most of the waste generated are plastics and tin waste, rubble from demolition and construction activities, dead domestic pets, and metals waste. Due to lack of proper waste management plan, the community practice dockyard disposal, dumping, and burning waste which later have an empirical negative effect on the environment and their health. The study found that villages around the area lack waste management by-laws enforcement, lack of access roads, rapid population growth and urbanisation are the main identified factors influencing solid waste management. Based on the findings, the study recommends a nearby transfer facility and communal skin bins to cover residents, solid waste education and awareness to the community, recycling and reuse initiatives, establishment of formal buy-back centre, and waste composting.
Open Access
Analysis of soil erodability and rainfall erosivity on the Soutpansberg Range, Limpopo Province, South Africa
(2023-10-05) Kori, Edmore; Odhiambo, B. D. O.; Chikoore, H.; Van den Heever, S. C.
Soil erosion is a global challenge that threatens ecological functionality. The need for better soil conservation practices keeps growing due to the twin challenges of climate change and population growth. However, effective soil erosion management solutions remain elusive to practitioners due to the complexity of the soil erosion process. This is especially true for mountainous tropical regions which experience rainfall as high intensity thunderstorms accompanied by gusts of wind. Therefore, the aim of this research was to analyse soil erodibility and rainfall erosivity on the Soutpansberg range to establish the characteristics of the factors that influence soil erosion. The specific objectives were to classify geomorphic features of the Soutpansberg range; to characterise the spatial-temporal aspects of potentially erosive rainfall; to assess the influence of topography on wind speed and rainfall erosivity; and to compare rainfall erosivity derived from the USLE and the SLEMSA incorporating WDR erosivity. The classification of geomorphic features needed soil, hydrology, slope, geology and land-use-land-cover data. Soil data were obtained from the Harmonised World Soil Database (HWSD v 1.21) layer downloaded from The International Institute for Applied Systems Analysis (IIASA) online database. Additional soil data were obtained from field samples and splash cups. Hydrological data were downloaded from Department of Water Affairs, Forestry and Fisheries (DWAFF) website. Slope data were derived from the 30m pixel size SRTM DEM obtained from National Geo- Spatial Information (NGI). Geological data were downloaded from South African Geosciences online database. Land-use-land-cover were extracted from the South African National Land Cover 2018 dataset accessed online on the Department of Forestry, Fisheries and Environment website. Rainfall and wind speed data for the spatial-temporal characterisation of rainfall from 2000 to 2019 were obtained from the South African Weather Services. The data analysis followed different tools. Erodibility was assessed using GIS tools to combine the five factors to create a final soil erodibility map. Potentially erosive rainfall spatial-temporal characterisation section was done using spatial GIS interpolation and spatial autocorrelation. Spatial interpolation was achieved through co-kriging. Spatial autocorrelation was determined by the fusion of the coefficient of variation and the Moran’s I. The influence of topography on wind speed and rainfall erosivity was analysed through a Likert scale, simple linear regression and MANOVA. Finally, simple regression analysis and simple comparison were employed to establish the influence of wind on rainfall erosivity. This was treated from the wind free rain (WFR) and wind driven rain (WDR) perspective. The analysis produced the following results. The geomorphic classification for erodibility was based on intrinsic erodibility, landform position, slope position, geological setting as well as rain exposure. The factors operate on fourteen soil types found on the Soutpansberg range that fall into five granulometric groups. The erodibility maps for both USLE and SLEMSA, a result of a weighted sum overlay of all the erodibility factors, show high to very high erodibility on the south facing slopes of the mountain range. A large part of the range Analysis of Soil Erodibility and Rainfall Erosivity on the Soutpansberg Range, Limpopo Province, South Africa on the western part of the mountain range is classified as of very low erodibility in the SLEMSA method. The spatial-temporal characterisation indicates that rainfall on the Soutpansberg Range is very highly variable. The potentially erosive rainfall distribution is spatially dependent on the mountain range and the spatial variation mostly simple. Most rainfall is concentrated in the central areas of the south facing slope. The epicentre is located at elevations above 1200 m.a.s.l. However, rain days are dominated by medium spatial variability. The spatio-temporal characterisation mapping indicates that flash flood hotspots are in low to very low rainfall regions. This implies that high erosion areas are not defined by total rainfall amounts only because the temporal distribution of the rainfall is also important. Furthermore, the simple linear regression analysis revealed that elevation influences erosivity. In addition, hypothesis tests showed that wind speed and topography increase rainfall erosivity. Empirical data confirm that WFR and WDR erosivity are different. Wind Driven Rain computations where wind is above 2 m/s1 produce results similar to samples collected from splash cups. The research concludes that a deep understanding of the factors controlling soil erodibility is the foundation of effective erosion control. The soils’ intrinsic characteristics and raindrop exposure (represented by land use and land cover) explains more of variation in soil loss on the Soutpansberg mountain range. Furthermore, the mountain setting causes rainfall to be concentrated on the central south facing slopes at elevations above 1000 m.a.s.l. sending the very low potentially erosive rain zone to the western region of the mountain range. However, the highest peak of the mountain is in the western region. Erosion hazard potential is not confined to high rainfall zones only. Potentially erosive rainfall hotspots are located in low and very low rainfall zones. Furthermore, rainfall erosivity is not a function of rainfall amount only because topography increases both wind speed and rainfall erosivity. However, rainfall amount and wind speed are not correlated, and wind speed is not implied in rainfall amount. Nonetheless, wind speed is correlated with rainfall erosivity. Wind speed above 2m/s-1 increases rainfall erosivity. therefore, wind driven rain (WDR) erosivity is a better representation of rainfall energy than wind free rain (WFR). The research recommends soil erosion management approaches that also consider rainfall temporal distribution. In addition, further studies on rainfall spatial distribution need to be done using satellite-based rainfall data for more accuracy. Additional research on rainfall erosivity considering rainfall temporal distribution is necessary to identify erosion hazard zones. Intensive and extensive research on incorporating wind speed in the computation of rainfall erosivity can improve soil erosion estimation models. Analysis of Soil Erodibility and Rainfall Erosivity on the Soutpansberg Range, Limpopo Province, South Africa
Open Access
Ant diversity across an elevational gradient; functional versus taxonomic perspectives in the Soutpansberg Mountains, South Africa
(2015-05) Munyai, Thinandavha Caswell; Foord, Stefan H.; Baxter, Roderick M.
See the attached abstract below
Embargo
Assessing climatic and non-climatic impacts on smallholder maize production in Tshimapha Irrigation Scheme, Limpopo Province.
(2024-09-06) Mudzanani, Ntsemeni Rainah; Murungweni, F. M.; Chikoore, H.
Globally, climatic extremes and non-climatic factors are a major concern due to their emerging and expected impacts on maize production. Climatic extremes come through drought and floods, whilst non-climatic factors include lack of education, poor management, and lack of support. The study evaluated the impacts of climatic extremes and non-climatic factors on the production of maize yield and further examined measures for sustainable production of maize yield in Tshimapha Irrigation Scheme, Limpopo Province of South Africa. The irrigation scheme was established in the 1960s, and today has 115 smallholder farmers, each having 1.5 hectares. Climate data was obtained from the Agricultural Research Council (ARC), South African Weather Services (SAWS) and from literature. Questionnaires were administered among the 115 smallholder farmers. The key informant interviews were conducted among the farmer’s leaders, community leaders and extension officers. The extension officer and smallholder farmers assisted with generating maize yield data. For the first objective, rainfall data was analysed using Mann- Kendall test analysis in R-Studio. Furthermore, Sen’s slope was also done to determine the magnitude of the trend of the rainfall, monthly, seasonal, and yearly and questionnaires were analysed using Microsoft Excel Version 2310. For the second objective, the Standardized Precipitation Index (SPI) was analysed using rainfall data in Microsoft Excel, and the last objectives were analysed using Statistical Package for the Social Sciences (SPSS) by looking at the percentage distribution. The findings of this study indicated an increase in the intensity and amount of rainfall received during flood years, with floods peaking in January and February. The SPI indicated that the area is not prone to severe drought as it is mountainous. The highest production of maize yield was 3.4 tons, with the least being 1 ton per year (based on the available data). Water and land for farming in the scheme were sufficient before the establishment of the Mutshedzi dam, which restricts access to dam water, and the land taken for some of the farmers during the establishment of the dam. This study is in response to national, regional, and global demand for knowledge on how smallholder farmers can adapt to erratic climates and in support of achieving the Sustainable Development Goal (SDG) Number 2. This study can be useful the in working towards alleviating challenges experienced by smallholder farmers in South Africa to ensure sustainability in smallholder production.
Open Access
Assessing the contribution of agroforestry technologies to poverty alleviation in Thulamela Municipality Limpopo Province, South Africa
(2013-02-26) Muhoni, Lina Hazyviyemurwe; Ojungu, O; Mwihomeke, S.
Open Access
Assessing the effects of invasive and native leaf litter decomposition dynamics in agricultural water impoundments
(2020-02) Mutshekwa, Thendo; Dalu, Tatenda; Wasserman, Ryan J.; Murungweni, Florence M.
Leaf litter contributes to the functioning of aquatic ecosystems through allochthonous inputs of carbon, nitrogen and other elements. In many freshwater ecosystems, leaf litter inputs are among the most important cross-ecosystem nutrient contributions. However, native plant communities are under threat from invasive plant species, with largely unexplored consequences for recipient aquatic ecosystems. Broadly, ecological impacts of invasive alien species can be unpredictable and simultaneously span multiple habitat types and taxonomic groups. Invasive alien plants can have particularly severe ecological impacts, and plant inputs into aquatic environments can alter abiotic and biotic aquatic dynamics. Lakes and reservoir ecosystems are regarded as heterotrophic detritus-based habitats which are dependent upon allochthonous organic matter for the majority of energy inputs. Allochthonous detritus is extremely important for the trophic dynamics of the microbial organisms, macroinvertebrates and benthic plants in lakes and reservoirs. In the present study, leaf litter nutrient inputs, decomposition and colonisation associated with four plant species was examined using a combination of mesocosm and field experimental approaches. Native sycamore fig Ficus sycomorus L., and silver cluster–leaf Terminalia sericea Burch. ex DC. decomposition dynamics were compared to invasive tickberry Lantana camara L and guava Psidium guajava L., whereby phosphate, nitrate, nitrite, silicate and ammonium releases were quantified over time. Leaf inputs significantly reduced pH, with reductions most marked by invasive L. camara. Conductivity was heightened by all leaf input treatments, excepting native T. sericea. Leaf inputs significantly affected all nutrient levels monitored in the water over time, except for silicate. In particular, leaf litter from invasive L. camara drove significantly increased nutrient concentrations compared to other native plant species, whilst effects of invasive P. guajava were less statistically clear. The end weights of the leaf litter demonstrated decomposition differences among the species types, following a decreasing order of P. guajava > T. sericea > F. sycomorus > L. camara, further suggesting high organic inputs from invasive L. camara. Furthermore, ex-situ larval mosquito colonisation of with the above-mentioned native and invasive species leaves were assessed. Larval mosquito abundances differed significantly accordingly to leaf treatment, whilst no mosquitoes colonised leaf-free controls. Leaf litter from the invasive L. camara, invasive P. guajava and native F. sycomorus drove significant increases in mosquito abundances relative to native T. sericea. In situ macroinvertebrate colonisation, and quantify decomposition rates, of four species of native and invasive terrestrial plants was also assessed. Leaf treatments had a significant, group-specific effect on abundances and composition among focal macroinvertebrates. Invasive leaves reduced Physidae and Oligochaeta abundances, yet Ostracoda were significantly more abundant in the presence of invasive P. guajava. Chironomidae relative abundances increased under invasive L. camara treatments, whilst differences among leaf treatment effects on Coenogrionidae abundances were not statistically clear. In turn, macroinvertebrate diversity did not differ significantly among plant treatment groups, but the contributing taxa varied. The decomposition rate of the leaf litter demonstrated differences among the species types, following a decreasing order of L. camara > F. sycomorus > T. sericea > P. guajava. The study results highlight that differential leaf litter decomposition rates of invasive and native plant types play a significant role in nutrient release, thereby potentially supporting increased aquatic ecosystem productivity. The study highlights that shifting terrestrial plant communities following invasion may alter aquatic nutrient availability and how insect communities may utilise such resources. In addition, the study highlights that even semi-aquatic organisms such as mosquitos are affected by differing leaf-litter inputs and this may have broader societal implications through vectoring of mosquitoborne disease. While the study showed that invasive leaf litter generally decomposes faster than native litter, the overall findings suggest that plant species-specific, rather than invasive versus native, considerations were important for colonization and nutrient release dynamics. As such, future studies should continue to assess characteristics of other dominant native and invasive plant species within the context of leaf litter allochthonous inputs into recipient aquatic ecosystems. Larger datasets will hopefully prove useful in developing a predictive framework for how riparian plant community shifts will impact on aquatic ecosystem functioning.
Open Access
Assessing the effects of MACADAMIA ORCHARD pesticide inputs on recipient aquatic ecosystems
(2023-10-05) Mutshekwa, Thendo; Dalu, Tatenda; Mugwedi Lutendo; Wasserman, Ryan J.
Aquatic environments, while not the target of many pesticide applications, often receive chemicals through catchment runoff dynamics. In this regard, the use of pesticides in agricultural systems may have deleterious effects on aquatic ecosystems within the same catchment area. Here using a series of in–situ and ex–situ experiments, the study assessed (a) pesticide concentrations of acetamiprid and chlorpyrifos across MACADAMIA ORCHARD and communal area reservoirs using liquid chromatography tandem mass spectrometry (LC–MS/MS), (b) the behavioural responses of Mozambique tilapia, Oreochromis mossambicus, following exposure to three commonly used macadamia pesticides (i.e., Karate Zeon 10 CS, Mulan 20 SP, Pyrinex 250 CS at different concentrations, (c) macadamia Macadamia integrifolia leaf litter decomposition and mosquito colonisation following pesticide exposure, and (d) macroinvertebrate colonisation associated with introduced stone substrates in cages within the MACADAMIA ORCHARD and control reservoirs to explore whether macadamia pesticides affected on macroinvertebrate colonisation dynamics. Firstly, analysis of acetamiprid and chlorpyrifos associated with sediments in MACADAMIA ORCHARD reservoirs revealed mean pesticide concentrations of 14.48 μg L–1 and 5.67 μg L–1, respectively, whereas, in communal area reservoirs outside of agricultural catchments, both pesticides were not detected. Acetamiprid was not detected across reservoir water, whereas the mean pesticide concentration of chlorpyrifos of 6.51 μg L–1 (MACADAMIA ORCHARD) and 0.13 μg L–1 (communal area) were detected. Secondly, O. mossambicus demonstrated different onset behavioural responses, i.e., swimming erratically, surfacing, vertical positioning, loss of equilibrium, being motionless and mortality with high mortality at increased mortality. Thirdly, macadamia leaf litter tended to decompose faster when exposed to pesticide treatments, whereas chlorophyll–a were reduced. Furthermore, pesticide treatments seemed to promote mosquito (i.e., Culex spp.) and pupal abundances. Finally, a total of 644 macroinvertebrate individuals were recorded across macadamia and communal reservoirs, mostly dominated by Chironominae (55.1 %), Ostracoda (14.4 %), Trithemis sp. (5.2 %), Anax sp. (5.2 %) and Radix natalensis (5.0 %). The results indicate that MACADAMIA ORCHARD reservoirs are highly contaminated by acetamiprid and chlorpyrifos and that these contaminants have implications for the ecological functioning of aquatic ecosystems. Reduction of species diversity adjusted community structure and altered energy flow and nutrient recycling were all demonstrated. The results of the study collectively show how common pesticides used in the macadamia plantation may be exert pressure on adjacent freshwater ecosystems. Future studies should examine effects on trophic interactions, pesticide accumulation in faunal groups and allochthonous trophic transfer dynamics to terrestrial environments. Such information would be useful for managers tasked with mitigation plans for the region.
Embargo
Assessing the effects of sampling time on the accuracy of extracting water quality indicators through geospatial techniques: A case study of Rietvlei Dam
(2024-09-06) Rabohale, Mokabolane Innocent; Malahlela, Oupa E.; Mugwedi, Lutendo
Freshwater is scarce, and the Earth’s ability to supply it is equally limited. Anthropogenic activities, urbanisation, and the effects of climate change degrade freshwater quality at a rapid rate. To design an effective water quality monitoring strategy that can respond to the rapid changes in surface water, regular sampling and analyses are essential. In developing countries, traditional methods of water sampling and laboratory analyses are adopted to generate water quality information. There is, however, a growing global adoption of optical remote satellite sensing for monitoring water quality, in conjunction with field surveys. One of the main challenges of optical remote sensing is sensitivity to cloud cover, which makes it difficult to synchronise with field surveys. This research addressed the question: “What is the effect of sampling time on the accuracy of extracting water quality indicators through remote sensing and geospatial techniques?”, using a case study of Rietvlei Dam, South Africa. The research established the correlation between laboratory-analysed water quality and the Sentinel-2 (S2) data extracted from the months before, during and after the given field sampling date. This covered four sampling periods i.e., mid-winter, late winter, early spring, and mid-spring. Through multiple regression and accuracy analyses, the study determined the efficacy of the S2 remote sensing models for the chlorophyll-a, turbidity, coloured dissolved organic matter (CDOM) and total suspended solids (TSS) water quality indicators from the different field and satellite sampling periods. The S2 remote sensing models predicted the spatial distribution of the water quality indicators and high concentration area coverage of the dam in hectares (ha). S2 models were found to be best for early spring. Chlorophyll-a was extracted five days after field sampling at R2= 0.79; for late winter CDOM was derived 44 days before the field sampling period at R2 = 0.64; for late winter turbidity was optimally extracted 36 days after field sampling season at R2= 0.54; and mid-winter TSS was extracted seven days before field sampling season at R2=0.62. The turbidity and chlorophyll-a S2 models’ spatial prediction of highly concentrated areas covered 36.14 and 28.92ha, respectively. In conclusion, the accuracies of mapping water quality indicators with remote sensing data and field observations differ based on an indicator measured and the time sampling difference between them. In general, the mapping accuracies decrease outside a seven-day sampling difference, whether before or after satellite image acquisition. This study contributes to the scientific understanding of remote sensing applications to the management of water quality in a given area, especially inland water quality.
Open Access
Assessing the impacts of climate change and adaptation strategies on smallholder farming in the Vhembe District, South Africa
(2020) Kom, Zongho; Nethengwe, N. S.; Mpandeli, N. S.; Chikoore, H.
One of the major challenges facing all categories of farmers globally is climate change. African smallholder farmers are the most vulnerable to changes in climate. In most parts of South Africa, empirical evidence indicates the level to which climate change has impacted negatively on agricultural production. Rising temperatures, prolonged drought and decreasing rainfall have affected local farmers’ livelihood and crop production. In the Vhembe District of South Africa’s Limpopo Province, smallholder farming predominates and its vulnerability to climate change has increased for the past decades. This study, therefore, assesses the impact of climate change and adaptation strategies on smallholder farming systems in the Vhembe District To achieve this aim, qualitative and quantitative research methodologies were employed. A questionnaire was administered to a sample of 224 smallholder farmers to elicit data on perceptions; climate change impacts, adaptation and IKS based strategies to deal with climatic shocks. Focus group discussions (FGDs), semi-structured interviews with the extension officers elicited thematic data that complemented the interview survey. Climate data were obtained from the South Africa Weather Service (SAWS) for the period 1980 to 2015. Smallholder farmers’ perceptions about climate change were validated by an analysis of climatic trends from 1980-2015. A thematic analysis of qualitative data and the Multi Nominal Logit (MNL) regression model was used based on socio-economic and biophysical attributes such as access to climate knowledge, gender, farm size, education level, and farmers’ experience, decreasing rainfall and increasing temperature as farmers’ determinants of their adaptation options to climate change. Furthermore, farmers’ perceptions tallied well with climatic trends that showed flood and drought cycles. Most of the smallholder farmers were aware of climate change and its impacts over the past decades. The study further indicated that, due to the marked climate change over this period, farmers have adopted different coping strategies at on-farm and off-farm levels. In terms of adaptation, the major adaptive strategies used by smallholder farmers included the use of drought-tolerant seeds; planting of short-seasoned crops; crop diversification; changing planting dates; irrigation and migrating to urban areas. The study recommends a framework that would include water conservation (rainfall harvesting); investment in irrigation schemes and other smart technologies that integrate indigenous knowledge systems and modern scientific knowledge to enhance crop production.
Open Access
Assessing the impacts of riparian land use on gully development and sediment load : a case study of Nzhelele River Valley, Limpopo Province, South Africa
(2015) Mavhuru, Blessing; Nethengwe, N. S.; Dondofema, F.
Human activities on land degradation have triggered several environmental problems especially in rural areas that are under developed. The main aim of this study is to analyse the contribution of different land uses to gully development and sediment load on the Nzhelele River Valley in the Limpopo Province. Data was collected using different methods such as observation, field data techniques and experiments. Satellite digital images, topographic maps, aerial photographs and the sediment load static model also assisted in determining how land use affects gully development and sediment load. For data analysis, the researcher used the following methods: Analysis of Variance (ANOVA), descriptive statistics, Pearson correlation coefficient and statistical correlation methods. The results of the research illustrates that high land use activities create negative changes especially in areas that are highly fragile and vulnerable. Distinct impact on land use change was observed within settlement area (9.6 %) within a period of 5 years. High correlation between soil organic matter and soil moisture (R=0.96) was observed. Furthermore a significant variation (p ≤ 0.6) between the soil organic matter and soil moisture was also observed. A very significant variation (p ≤ 0.003) was observed in bulk density and extreme significant variations (p ≤ 0.0001) were observed in organic matter and soil particle size. The sand mining and agricultural activities has contributed significantly to the amount of sediment load in the Nzhelele River. A high significant amount of total suspended sediment (55.3 %) and bed load (53.8 %) was observed within the agricultural area. The connection which associates the development of gullies to various land use activities determines the amount of sediment load. These results are consistent with other previous research and suggest that land use activities is likely to exacerbate the development of gullies and sediment load in the Nzhelele River Valley
Open Access
Assessing the impacts of small-holder farming activities on Wetland Area in Nzhelele Agricultural Hub in the Vhembe District; Limpopo Province, South Africa
(2023-10-05) Mapfumo, Mulisa Norah; Murungweni, F. M.; Malahlela, O. E.
Wetlands play a crucial role in supplying essential ecosystem products and services, yet they are threatened by several anthropogenic activities. Wetlands are at risk of crop production which depend on the reliability of water supply. The effects of farming on wetlands are a result of the exploitation of wetland resources and the extensive usage of fertilizers. Notwithstanding the alleged role that farming plays in the destruction and degradation of wetlands, wetland area fluctuations and anthropogenic impacts over time and across regions have not been adequately assessed. The aim of this case study research was to assess the impacts of small-holder farming activities on wetland area in Makhado Local Municipality, in Vhembe District of Limpopo Province. Data was collected through interviews and the main data collection tools were a questionnaire, Landsat 8 satellite and UAV images of 2014, 2018 and 2022. The participants of the study included a variety of individuals such as farmers, household heads, extension officer (Mulimisi) and of the community. The Statistical Package for Social Sciences (SPSS) software was used to analyze the survey data. Analysis of satellite imagery was done using Aeronautical Reconnaissance Coverage Geographic Information System (ArcGIS) (Version 10.1) and Earth Resources Data Analysis System ERDAS Imagine (version 2015) software packages. The results show that farming is the major activity within the wetland area over the years 2014 to 2022 which increased from 96 hectares to 181 hectares. Throughout the study period, there have been significant changes to the wetland region. The main contributory factors were the expansion of agriculture (cultivation), increased food demand due to population growth and local water deficit. There is insufficient assistance and mentoring provided by the government to the community and to small-holder farmers when it comes to land use reform and awareness building among villagers and farmers about the importance of wetlands. The results also show that 78.3% of the respondents are not aware that farming has impacts on wetland areas while 17.7% of the respondents are aware. Lack of knowledge has been identified as one of the major factors contributing to the environmental effects of land use change in the wetland area. This study suggested that to manage wetland resources properly, local small-holder farmers and the local community should both be targeted for awareness campaigns and initiatives.
Embargo
Assessing the potential of biochar to restore degraded lands
(2024-09-06) Shirinda, Hazel; Stam, E. M.; Mugwedi, L.
Land degradation and climate change are interlinked processes that negatively impact sustainable development. Globally, they pose a risk to human livelihoods, but their effects are even more prominent in developing nations, especially in sub-Saharan Africa. Even with land degradation and climate change currently happening, communities, especially in developing countries, still need to adapt to the changes. This may be due to the high adaptation costs and the need for more knowledge. Biochar is the product of the thermochemical conversion of biomass through pyrolysis. Using biochar as a soil ameliorant has been increasingly advocated because of its effects on soil properties, crop productivity, and carbon sequestration. Biochar has been reported to improve soil quality, crop yield, and soil carbon sequestration potential. Despite this, little is known about the effects of biochar on soil physical properties, making it difficult to recommend biochar to improve soil quality in agriculture. Thus, this study aims to assess the potential of biochar to restore severely degraded land by improving soil properties and crop productivity and mitigating climate change through carbon sequestration at the Lapalala Wilderness Reserve, Waterberg District, Limpopo Province, South Africa. For this purpose, four treatments (biochar, biochar with fertilizer, biochar without fertilizer, and control) were applied to four plots, each replicated five times. A 14-species grass mixture was sown in each of the 20 plots. Soil physical and chemical properties, plant biomass, carbon stock, species richness, and species composition were then measured. None of the four treatments had a significant effect on soil bulk density while only biochar had a significant effect on soil chemical properties of soil Total C, Na and soil pH. No treatment had a significant effect on plant biomass. The analysis of similarity showed no significant difference in species composition for all treatments at month three and month six. The species composition for both treatments and sites for months three and six was mostly similar. The effects of biochar were not significant on soil chemical and physical properties as well as plant growth and biomass. Longer-term studies with higher rates of biochar application are required to confirm the effects of biochar on soil properties, plant growth, and species composition. The biochar feedstock (e.g., agricultural residues, forestry residues, and grassland cutting), biochar properties (such as porosity, bulk density, carbon content) and soil types need to be taken into consideration before application of biochar into the soil to enhance soil properties and plant growth.
Open Access
Assessing the spatiotemporal variation of phytoplankton biomass in Nandoni reservoir in the Vhembe District (South Africa) using LANDSAT satellite imagery
(2022-07-15) Muthivhi, Fulufhelo Faith; Dalu. Tatenda; Dondofema, F.; Mokgoebo, M. J.
Chlorophyll–a (chl–a) is an optical active compound used as proxy for phytoplankton biomass to determine the trophic state of the aquatic ecosystem. Traditional approaches for monitoring aquatic system are time consuming, expensive, and non–continuous, therefore, Remote Sensing technologies are qualitative for monitoring the status for water quality in large scale and low cost. The aim of this study was to assess the spatial and temporal variation of phytoplankton biomass in Nandoni reservoir, Limpopo to examine the relationship that exist between the physico–chemical variables and chl–a concentration using readily available Landsat multispectral images. Multispectral resolution of (30 m) Landsat 7 ETM+ and Landsat 8 OLI images for June to December 2008 to 2020 were used to derive the distribution of chl–a concentration. The spatial distribution of chl–a concentration in wet and dry season of these years was obtained. By using regression techniques, in situ measured chl–a was related to construct and validate Landsat predicted chl–a to determine the distribution of chl–a in the reservoir. The results indicate that Landsat derived chl–a was similar with the observed measured chlorophyll–a (R2 = 0.91). There was a negative significant correlation among Land Use and Land Cover with water quality (P > 0.05). Using permutational multivariate analysis of variance (PERMANOVA) analysis, there was significant differences for chl–a concentration in sites, seasons, and zones. There was positive significant correlation observed on water temperature with strong negative significant with salinity and TDS. A strong perfect linear association among predicted vs measured chl–a were found. Chlorophyll–a concentration in Nandoni reservoir was derived using Landsat remote sensing images, suggesting that Landsat sensor is suitable for monitoring small reservoir in a short timescale. Remote sensing techniques can be used to control the development of an early warning system of this study and other reservoirs.