Browsing by Author "Tsvuura, Zivanai."

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Aardvark and people: can a shy species be widely known in a localised area?
(2022) Makwati, Nolutho.; Kraai, Manqhai.; Tsvuura, Zivanai.
The increase in human populations has led to humans sharing space with wild animals even in the natural habitats of the animals. Conflicts may arise when people and wildlife attempt to fulfill their needs which can be detrimental to one or both parties, and this type of conflict is called human-wildlife conflict (HWC). The human needs include people hunting wild animals for consumption of the animal and trading in animal body parts.Hunting is one of the factors that decreases populations of numerous animal species, and it occurs in many parts of the world e.g. in Africa, Asia and South America, where it contributes to extinction of species. The conservation and management of burrowing animals is a major challenge due to their elusive and nocturnal behaviour. The aardvark is an African medium-sized, burrowing mammal whose conservation status has not been updated recently due to the difficulties associated with studying nocturnal animals. Aardvarks may play a significant ecological role in the ecosystems in which they occur, such as by changing the landscape through their digging activities, or through affecting the dispersal of seeds. Therefore, the aim of this study was to explore the influence of humans on population trends and activity patterns of aardvarks outside protected areas, and to determine people’s perceptions about the animal. The study was conducted in Ncunjane village in Msinga Local Municipality, KwaZulu-Natal Province of South Africa. To understand people’s perceptions about aardvark in their community, I used a semistructured questionnaire survey. I asked personal information of the participants (sex, level of education and age), and questions related to people’s perceptions about the aardvark, such as people’s knowledge, myths, and their uses of the animal or its body parts. To determine activity patterns of the animal, I focused on aardvark foraging activities in a semi- arid savanna ecosystem that is also used as a communal rangeland over eight months between 2020 and 2021. I measured and quantified aardvark foraging holes using 53 50 m × 10 m transects where there was evidence of aardvark activity. In addition, I quantified aardvark burrowing of dens in the dry, wet and early dry seasons using walking transects guided by a research assistant who knows the area. I found that people have different perspectives about aardvark with the majority (78%) of respondents having strongly positive perceptions. The positive perceptions arise from aardvark not causing physical harm to people, and fleeing away upon sighting people. I found that aardvarks were mainly hunted for meat while some animal body parts were sold to traditional healers for traditional medicine. All seasons consisted of a greater number (> 51%) of old than new and very old foraging holes.The surface area of new, old, very old holes differed significantly with season (P < 0.0001) and the depth of new, old and very old holes also varied with season (P < 0.0001). In addition, the contents of foraging holes varied with age of the hole and season in that new holes lacked evidence of plant life across seasons. Aardvark dens were used by other animals such as spiders, wild cats, Cape porcupines and snakes. Hence, an increase in aardvark holes can be associated with significant landscape heterogeneity for vegetation and animal life. Aardvarks in Ncunjane fed close to their dens presumablyto mitigate against human predation through hunting threats, which may directly affect the extent of aardvark digging activities. These results show that aardvarks may be categorised as ecosystem engineers as the burrows provide shelter for other animals, also, their effects on other animals are disproportionate to their abundance. These results highlight that aardvarks are threatened by human uses and may decline in abundance in the area. Finally, aardvarks remain poorly studied in landscapes shared with humans. Further studies to assess aardvark numbers in human-dominated landscapes are required which can raise awareness and play a significant role in conservation of aardvarks.
Assemblages of surface-active arthropods in pristine and disturbed savannah.
(2022) Mavasa, Risuna Wain.; Tsvuura, Zivanai.; Yekwayo, Inam.; Mwabvu, Tarombera.
Savannahs are structurally complex ecosystems rich in biodiversity, and the conversion of savannahs into human-modified landscapes poses a significant risk to organisms with limited dispersal abilities. Surface-active arthropods have limited dispersal abilities and are sensitive to changes in their environment; as a result, they are restricted to specific habitats with the resources that they need. Surface-active arthropods are essential in ecosystem processes, such as playing a direct or indirect role in water infiltration into the soil and its storage, decomposition of plant and animal matter, nutrient cycling, humification and biological pest control. Many landscapes of natural vegetation in South Africa have been transformed into croplands, residential and commercial areas. In Mpumalanga province, croplands (including fruit plantations) dominate the landscape where savannah vegetation occurred previously. This study investigated the influences of disturbance (transformed savannah vs pristine savannah) and season on the diversity of four groups of surface-active arthropods (ants, beetles, millipedes and spiders) in the savannah biome in Mpumalanga province. The objectives of the study were to determine 1) whether flightless arthropod assemblages differ between disturbed and pristine savannah, and 2) whether functional guilds of flightless arthropod assemblages differ between summer and winter. Field sampling using pitfall traps was done to collect the surface-active arthropods in pristine and disturbed savannah during summer and winter. All samples were sorted into morphospecies and identified into family or genus where possible and then assigned into functional guilds. Functional guilds were allocated based on the feeding habits of the surface-active arthropods, resulting in three distinct functional guilds (detritivores, herbivores and carnivores) being identified. Surface-active arthropods with diverse feeding habits were lumped to form a fourth functional guild, the “diverse functional guild”. I found significant differences in the species composition of ants, beetles and spiders between disturbed and pristine savannahs. The species richness and abundance of ants was significantly greater in the disturbed than pristine savannah, while beetles and spiders had similar species richness and abundance between the two habitat types. The number of unique species of the surface-active arthropods in the disturbed savannah were two times more than those in the pristine savannah. The species richness and composition of all functional guilds of the surface-active arthropods differed between summer and winter, with greater species richness in summer than in winter. Herbivorous and carnivorous arthropods had significantly higher abundance in summer than in winter, while the abundance of detritivores and the “diverse functional guild” was similar between the two seasons. This study shows that different vegetation types support different compositions of surface-active arthropods and that there may be a positive relationship between vegetation structure and the assemblages of surface-active arthropods in the savannah. Furthermore, the study highlights a potentially positive relationship between the assemblages of herbivorous and carnivorous arthropods. I recommend that it may be essential to consider both disturbed and pristine habitat types in the conservation of surface-active arthropods, especially in South Africa where most of the land is outside of formal conservation areas. This assertion is supported by the greater number of unique species of surface-active arthropods found in the disturbed than in the pristine savannah. My study provides relevant baseline information because little is known about the assemblages of surface-active arthropods in savannah landscapes dominated by croplands. Furthermore, my study gives some insight on how the assemblages of surface-active arthropods may respond to disturbance in the savannah.
Assessment of spatial and temporal variation in water quality of the Pienaars River, Limpopo water management area.
(2018) Mlotshwa, Lungile Wendy.; Tsvuura, Zivanai.; Ndhlala, Ashwell Rungano.; Ncube, Bhekumthetho.
Abstract available in pdf.
Community diversity and composition of ground-dwelling arthropods in major habitat types of the KwaZulu-Natal Sandstone Sourveld.
(2023) Mhlongo, Nokukhanya.; Tsvuura, Zivanai.; Munyai, Thinandavha Caswell.
Grasslands constitute over 25% of the global land surface and close to one-third of southern Africa. Natural and semi-natural grasslands are recognized globally for their high biodiversity value and their important contribution to the provision of ecosystem services, including provisioning services such as carbon sequestration, water catchments, and grazing for livestock and wildlife. Nonetheless, grasslands are consistently reduced and threatened by anthropogenic activities and invasive alien plants. Invasive alien plants may hinder the growth of natural vegetation by overconsumption of resources. The impact of invasive alien plants on natural vegetation may indirectly affect plant-to-animal interactions such as specialized pollination and seed dispersal syndromes which may ultimately disturb ecosystem processes. The Sandstone Sourveld in KwaZulu-Natal province of South Africa is a threatened grassland ecosystem as a result of various anthropogenic disturbances. Knowledge of arthropod response to differences in habitat types may be essential for an improved understanding of the structure and functioning of ecosystems, which is relevant for informing conservation practice. The aim of this study was to investigate the composition and diversity patterns of ground-dwelling arthropods (ants, beetles, Orthopterans, and spiders) in three habitat types (forest, intact grassland, and disturbed grassland) at Springside and Tanglewood Nature Reserves, which occur in the KwaZulu-Natal Sandstone Sourveld (KZNSS). The objectives were: (i) to document the response of the ground-dwelling arthropod community in different habitat types, (ii) to determine the impacts of seasonal change on the abundance and richness of ground-dwelling arthropods at the two sites, and (iii) to determine the correlation between the distribution of ground-dwelling arthropods and soil characteristics in the KZNSS. Ground-dwelling arthropods were sampled in Springside and Tanglewood Nature Reserves using pitfall traps in each habitat type. Soil parameters in the habitats were also assessed. Analysis of variance was used to test for differences in arthropod morphospecies richness and abundance viii across the habitat types and between seasons. The Shannon-Weiner diversity index was computed and used to compare the diversity of ground-dwelling arthropods between the two sites and among habitat types. Ground-dwelling arthropods showed varying patterns in response to habitat characteristics and the disturbance gradient at Springside and Tanglewood. Intact grassland was the most diverse habitat in both Springside and Tanglewood. In Tanglewood, the abundance of ants was greater in disturbed grassland which consisted of a variety of alien invasive shrubs, the high abundance was explained by the “intermediate disturbance hypothesis”. However, alien invasion showed more negative than positive impacts on the abundance and composition of ground-dwelling arthropods when there was a significant decrease in the abundance and composition of ants, beetles and spiders. Species richness of ants and beetles was higher in the wet than dry season whereas Orthopterans and spiders showed no significant difference between seasons. In all arthropod groups, a greater number of species were correlated to soil potassium, soil pH, and soil bulk density. Overall, the intact grassland had the highest species richness and abundance followed by the forest and lastly the disturbed grassland. The greater abundance of ants, beetles, and spiders in the pristine grasslands of KZNSS shows that there is still a need to conserve the remnants of the KZNSS vegetation. Therefore, the conservancy management is urged to consider the eradication of alien invasive plants. Future studies are recommended to consider the volant and vegetation canopy arthropods as they are all interdependent with ground-dwelling arthropods to form a whole community of arthropods in an ecosystem.
The contribution of goats to household food security in selected communities of KwaZulu-Natal, South Africa.
(2021) Khowa, Anele Aurelia.; Kraai, Manqhai.; Tsvuura, Zivanai.
The growth of the human population in the world has been occurring at a rapid rate. This presents a challenge of how the world food demands will be met. These challenges are always felt the most in developing countries, and result in a lot of people in developing countries turning to alternative sources of income other than employment to manage their food situation. One of the alternatives includes a reliance on animal husbandry in order to meet and improve their livelihoods particularly with respect to food. Furthermore, small-scale farming of animals such as goats, sheep, pigs and chickens has also been an income source when the animals are sold. In developing countries, pastoralism and agro-pastoralism frequently occur among disadvantaged communities, who are often found in arid or semi-arid regions. As a result, goats have been shown to be an important type of livestock that can be kept in such conditions without financially stressing their owner by requiring constant care of supplementary feeds and medication. Goats are known for their resilience which allows them to cope with stressful conditions while being able to reproduce. This resilience and productivity of goats allows their owners to be able to liquidate them for cash if there is a need and also be able to slaughter them for their household consumption. Here, I investigated the contribution of small-scale goat farming to household food security in rural and peri-urban areas in KwaZulu-Natal (KZN), South Africa. The study was carried out in rural and peri-urban areas of Msinga, Kokstad, Howick and Pietermaritzburg in KZN. I used structured questionnaire surveys to determine the contribution of goats to household food security from the farmers’ responses. The questions asked related to the sale of goats (number, sex, age and sale value of the animal) and how the money generated from goat sales was spent. The study also determined goat sales from 27 households in three villages occurring in Msinga over a 2- year period of 2017 to 2018. I also assessed the participation of small-scale farmers in two livestock auctions, which took place in 2019 and 2020 by recording the age, sex, and coat-colour of the animals taken to auctions. The results obtained from the study showed that goats played a role in household food security as a source of cash as well as consumption in strenuous times. These findings of the study highlight that smallscale goat farming provides an alternative food source and income source for disadvantaged farmers. These findings were more prevalent in the rural areas, which kept more goats than those found in the peri-urban areas. Goats in rural areas ranged from 5 to 150 goats in a herd, and 5 to 50 goats in a herd while in periurban areas. Goats were a source of cash in numerous ways including sale of skins after slaughter that are used to craft household items such as stools that can be sold for cash. Adult goats were sold more at the farmers’ homesteads than auctions where buyers opted for younger goats. My results also showed that small-scale farmers use all possible avenues to sell their goats, as they sold a high number of animals from home and did not depend on infrequent livestock auction events. However, there were benefits derived from participating in auctions in terms of the relatively higher prices obtained there. For example, female and male goats sold for R2 177 and R1 268, respectively at auctions. The price was similar for females (R1 083) and males (R1 065) in homesteads. At auctions, female and male goats sold for R2 177 and R1 268, respectively. From homesteads, female and male goats sold for R1 083 and R1 065, respectively. Colour of goats proved to be an important trait at auctions as light-coloured goats were in higher demand than black goats. Homestead sales also remain a useful practice as farmers generate income to assist in day-to-day household expenses instead of waiting for infrequent auction events. Furthermore, small-scale farmers who plan to participate in auctions should pay attention to the characteristics (age, colour, and sex) of their animals when populating their herds. Sub-adult, light-coloured and female goats were the animals that were highly sought after at auctions.
Controlling woody plant encroachment in a southern African savanna.
(2021) Monegi, Piet.; Tsvuura, Zivanai.; Ward, David Mercer.; Tjelele, Julius Tlou.
Woody plant encroachment is considered one of the most extensive forms of degradation affecting savannas in arid and semi-arid ecosystems. Thus, reactive interventions such as chemical and mechanical controls, as well as fire application remains the norm in management of woody plant encroachment. I conducted a series of woody plant control experiments at the Agricultural Research Council’s Roodeplaat experimental ranch, situated in Gauteng Province, South Africa. The first experiment was a tree-thinning study at two savanna sites that differ in soil texture and woody species. Site 1 was on previously cultivated clay-dominated soils characterized by severe soil erosion and was encroached by Vachellia tortilis. Site 2 has never been cultivated and was on sandy soils with several woody species. At each site, 24 30 m × 30 m plots separated by 5 m wide fire breaks were established. Trees were removed to the approximate equivalents of 0% (control-no removal), 10%, 20%, 50%, 75% and 100% (complete removal of trees), followed by herbicide application on half of the stumps for each plot. I also investigated the effectiveness of Tree Poppers® (weed wrench) as a low-cost mechanical control tool to physically uproot seedlings and saplings of woody plants. To examine the effectiveness of the Tree Popper®, I used eight dominant tree species that were grouped into three height classes (0-49 cm, 50-99 cm, 100-150 cm) of ten seedlings and saplings per species per height class. In addition, investigated the effects of five years of annual burning on vegetation dynamics in a Vachellia karroo woodland. To determine the effects of annual burning on vegetation dynamics, plots (0.25 ha) established in 2013 were used. These studies are summarized below: (1) I determined the combined effects of tree species, tree thinning, stump diameter and herbicide application on resprouting patterns of woody plant species (Dichrostachys cinerea, Ehretia crispa, E. rigida, Gymnosporia buxifolia, Pappea capensis, Searsia lancea, S. caffra, Vachellia karroo, V. nilotica, V. robusta, V. tortilis and Ziziphus mucronata) that encroach study site 1. All the tree species in this study resprouted after cutting. Herbicide application significantly reduced the resprouting ability of D. cinerea, E. rigida, V. robusta and Z. mucronata. Tree removal positively influenced the resprouting ability and vigour of E. crispa only. The diameter of stumps was an important factor in determining resprouting ability, with shoot production decreasing with increasing stump diameter. The findings from this study suggest that woody plants are more likely to resprout and survive as juveniles than as adults after cutting. (2) I found no significant differences in the number of seedlings and saplings uprooted by Tree Popper®. However, there were significant differences in the number of juveniles uprooted using a Tree Popper® with a few individuals of Vachellia species uprooted. The effectiveness of the Tree Popper® may be due to differences in plant morphological structure, particularly the root system. The Tree Popper® is not an effective tool for controlling the Vachellia species used in this study. However, communal ranchers may mechanically control shallow-rooted tree seedlings with the Tree Popper® but not deep-rooted ones, specifically Vachellia species. (3) In the tree thinning experiment, I determined the effects of different tree thinningintensities on grass species-richness, composition, cover, β diversity, and soil fertility. I found that tree thinning did not have any significant effects on grass species-richness in either study site. However, we found a clear separation of different grass species among the treatments over the study period. Different levels of tree thinning increased the abundance of two dominant grass species (i.e. Digitaria eriantha and Panicum maximum) in both study sites, particularly in moderate (50%) and high removal (75% and 100%) treatments. However, the nitrophilous grass (i.e. P. maximum) will likely decline in abundance with time, particularly in the 100% thinning treatment because the ecological process that is responsible for N-fixation is no longer existent. Contrastingly, I found no evidence that tree thinning affects the amunt of soil cover. In addition, tree thinning did not have a significant impact on soil fertility in either study site. I recommend maintaining a stand density of 50% in rangeland affected by woody plant encroachment. In this study, 50% thinning created an opportunity for different palatable grass species to increase in abundance, which may help to increase forage production. (4) I determined the effects of different tree removal-intensities on grass production, tree-seedling establishment and growth, and the growth of the remaining large trees. In site 1, tree-removal treatments (i.e. 75 and 100%) significantly reduced grass biomass production after the first growing season, with no effect after the second season. In site 2, tree removal significantly increased grass biomass production. I found no significant effect of tree removal on tree seedling establishment in site 1. In site 2, tree removal had a significantly negative effect on overall tree seedling establishment. In both sites, there were no significant differences in tree seedling growth. Moderate (50%) to high (75%) removal of trees had a positive effect on the growth of remaining large trees in both study sites. I found that increased and/or diminished grass biomass production plays a vital role on tree seedling recruitment. Reduced tree competition facilitates the growth of the remaining large trees. An implication of these findings is that regardless of the substantial costs of woody plant control, the recovery of key ecosystem services such as an increased forage production may not be realised. However, this may be system-specific. In other systems, the absence of management interventions such as tree removal may compromise provision of ecosystem services and ecosystem functioning. (5) In the fire experiment, I investigated the effects of five years of annual burning on the density of young and adult Vachellia karroo plants. This study also aimed to investigate the effects of annual burning on tree growth (i.e. height, stem diameter and canopy size). The results supported the “fire-trap” paradigm by demonstrating substantially higher densities of young plants in the burned plots than in the unburned plots. In addition, the recruitment of young plants and saplings into adult trees was significantly higher in the unburned plots than in the burned plots. V. karroo populations substantially increased in growth (height and basal diameter) in the unburned plots. Different grass species changed in abundance in response to annual burning. However, I found no significant changes in grass species diversity and richness between the treatments. I found that the removal of the grass layer by fire and repeated topkill increased the number of young V. karroo individuals. Annual burning limited V. karroo juveniles and saplings from reaching an adult size class that may have detrimental effects on the herbaceous layer. I demonstrated that grass species composition is more prone to fireinduced changes than species diversity and richness in our study area. In conclusion, I show that managers of savanna rangelands may use annual burning to achieve specific vegetation structural objectives. This thesis demonstrated that mechanical- and chemical -control, as well as fire application influences the structure and functioning of savannas. By creating gaps that promote grass production, these management practices may assist increase the economic viability of savanna ecosystems. However, despite the popular belief that reduced tree densities promote ecosystem functions, this thesis demonstrates that the impact of control techniques (especially tree thinning) on forage production vary across savanna sites. This thesis also shows that management with prescribed annual fire reduced woody plant encroachment across the 5-year study, suggesting that fire management can be beneficial and should be explored as a management method.
Ecological effects of Festuca costata on the Drakensberg grasslands.
(2018) Mwambilwa, Kabemba.; Tsvuura, Zivanai.; Kirkman, Kevin Peter.
Fire and herbivory are important in determining the vegetation structure in savannas and grasslands. In addition, anthropogenic activities have significantly contributed to alterations in the relative abundance and distribution of plant species in many grasslands through increased nitrogen deposition and elevated concentration of carbon dioxide in the atmosphere. Using a field experiment, the study explored the effect of neighbouring plants, defoliation, and fire on the ecological performance of a major C3 grass, Festuca costata, whose range is expanding in Afro-temperate grasslands of the Drakensberg Mountains in South Africa. The experiment had three factors: fire at two levels (burned, unburned), defoliation by clipping 50mm above-ground surface, at four levels (no defoliation, defoliation of focal plant, defoliation of neighbouring plant within a 300 mm radius, and defoliation of both the focal and the nearest neighbouring grass within a 300 mm radius from the focal plant). The third factor was plant neighbourhood types at three levels (the focal plant growing alone, focal plant growing with other F. costata plants, focal plant growing with any other grass species) for a total of 24 treatment combinations with five replicates. Using a pot experiment under garden conditions, the study evaluated the influence of soil nutrient amendment with 140 KgHaˉ¹ limestone ammonium nitrate in the performance of F. costata. The variables of interest in both experiments were; above-ground biomass production, tuft circumference, number of tillers and specific leaf area of the focal plant. Generalised Linear Models in SPSS were used to analyse the data from both experiments. The results showed that burning had a significant negative effect on above-ground biomass production, number of tillers and tuft circumference of the focal plant (P < 0.001), with the unburned grassland showing greater mean values for all parameters than the burned grassland. Defoliation had significant negative effects on above-ground biomass production, number of tillers, tuft circumference while it showed strong positive influence on specific leaf area of the focal plant. Neighbourhood types were significantly negative for above-ground biomass production, number of tillers and tuft size of the focal plants (P< 0.001 in all cases). Nutrient addition reduced the number of tillers of F. costata and tuft size and showed no significant effects on above-ground biomass production and specific leaf area. Defoliation significantly increased SLA, above-ground biomass production, number of tillers and tuft circumference were not affected.. Plant neighbourhood types showed significant negative influences on tuft circumference. Defoliation accounted for the most variations in reduced tuft size, above-ground biomass and number of tillers, however, it resulted in increased specific leaf area. These results suggest that defoliation by herbivores and use of fire may be complementary tools for managing high altitude grasslands under climate change. The findings of both the field and pot experiment suggest that F. costata may not be tolerant to selective herbivory. In addition, the study shows that the increase in nitrogen availability due to anthropogenic activity may have a negative influence on the performance of F. costata.
The effects of Chromolaena odorata on tree growth dynamics at Buffelsdraai Landfill site.
(2019) Ramaano, Rerani.; Tsvuura, Zivanai.; Moyo, Hloniphani Peter Mthunzi.
Ecological restoration is a process which assists the recovery of an ecosystem which was previously disturbed or degraded. Through continuous disturbances, invasive alien plants (IAPs) are able to successfully spread and establish themselves while reducing the diversity and the abundance of native plants. The IAPs invade both human and non-human modified landscapes thus causing huge threats to biodiversity conservation and ecosystem services provision. The invasion of alien plants at Buffelsdraai Landfill Site Community Reforestation Programme is a major threat to reforestation success. Buffelsdraai is under rehabilitation through a community reforestation programme that focuses on active involvement of nearby communities in propagating seedlings and planting them on site. The study was conducted in a former sugarcane field which has been planted with diverse native tree species, but invaded by dense stands of Chromolaena odorata. This study aimed to 1) determine the influence of a woody shrub C. odorata on the growth dynamics of replanted native trees at the Buffelsdraai Landfill Site, and 2) to assess the efficacy of cutting height and frequency in mechanical control of C. odorata. Over a period of 12 months, the growth responses of three native tree species (i.e., Vachellia natalitia, Brachylaena discolor and Erythrina lysistemon) were investigated by measuring stem length and diameter, trunk basal diameter, tree height and canopy diameter, under four treatments. The treatments consisted of: (i) a control, where no clearing of C. odorata or grasses was undertaken beneath the canopy of trees; (ii) clearing of C. odorata from underneath trees; (iii) clearing of grass from underneath trees; and (iv) clearing of both grass and C. odorata from trees. Measurements were undertaken on 264 trees, 88 individual trees per species, 22 individuals per species per treatment at the beginning and the end of the study. Stem, trunk and canopy length, diameter, and tree height growth data within each tree species were analysed using generalized linear models. Tree height growth comparisons among the tree species was analyzed using a non-parametric Kruskal-Wallis test since the data did not meet the assumptions of a One-way ANOVA. There were no significant differences between all four treatments across the tree species (P > 0.05). However, E. lysistemon growing where there was grass removal had significantly higher (P = 0.033) trunk basal diameter growth, than other treatments. Results from this study showed that the removal of C. odorata at the Buffelsdraai community project had no impact on the trees due to short time period of the study. Overtime we expect that tree performamce would increase with less C. odorata competition. Trees performed equally well in the presence and absence of grass and C. odorata. Young tree saplings of pioneer species were used for this study which could be a possible influence of these results. To investigate the impact of C. odorata mechanical control, 28 plots (5 m × 5 m) were established, at least 2 m apart, with one designated as the control with no cutting of the plants. The two treatment combinations were between cutting frequencies which had: (1) cutting frequency made up of single, twice and thrice cutting; and (2) stem cutting height which had 30, 100 and 200 mm cutting heights aboveground. I used 420 C. odorata plants (i.e. 3 cutting heights × 9 replicate plots × 15 plants + 15 control plants). Plants were first cut in November 2016, the coppice regrowth was cut on plants in 18 plots in February 2017, and a third cut was made on plants in the last nine plots in May 2017. Stump basal diameter, the number, length and diameter of resprouting shoots were measured at 3-month intervals. Mean number of resprouting shoots, mean shoot length and diameter of the resprouts, mean shoot length:diameter ratio (shoot taper function) of resprouts, shoot production (shoots mm-1) and mean total shoot basal area:stump basal area ratio for all treatment combinations were analysed using the Friedman’s test. The relationship between cut stem diameter and the number of resprouting shoots, resprouting shoot length, and resprouting shoot diameter were explored using correlation analysis. There was a significant difference in the number of resprouts produced across all treatment combinations (P < 0.001). The 30 mm cutting height produced the least number of resprouts with increasing cutting cycles compared to the 100 and 200 mm cutting height. Shoot length and diameter decreased with cutting frequency, with smaller shoots produced with continued cutting cycle. There were significant difference in the shoot length and diameter of shoots produced in the 30 mm cutting height in the last cutting cycle and those that were produced on 200 mm cutting height. Shoot taper function and shoot production showed significance (P < 0.001), with smaller number of shoots produced in the 30 mm cutting height over the cutting frequencies (P < 0.001). Total shoot basal area:stump basal area ratio did not differ significantly across the cutting heights and the cutting frequencies. There was a strong positive relationship (r = 0.91; P < 0.001) between the number of resprouts and stem diameter across all repeatedly cut stems in all cutting heights and the number of resprouts produced in each cutting height decreased over each cutting frequency. Repeated cutting of C. odorata at a lower cutting height of 30 mm may deplete its energy reserves, reducing the number of resprouts produced, thereby leading to death of the plants. Repeated cuttings at short-term intervals also prevents the plants from growing to reproductive maturity and seed production, leading to no seed dispersal to increase infestations
Genetic diversity of some Moringa oleifera Lam. cultivars available in South Africa.
(2020) Makgolane, Thandy Ramathetje.; Tsvuura, Zivanai.; Zishiri, Oliver Tendayi.; Ndhlala, Ashwell Rungano.
Moringa oleifera Lam. (Moringaceae) is a nutritious and high medicinal value tree. The species is native to India but grown globally due to its properties. The nutritional content of the species includes high levels of vitamins, minerals, calcium, magnesium and iron. It is now known that different cultivars of M. oleifera are grown throughout the world depending on the intended products. However, in South Africa, there is limited knowledge on the genetic variation of the cultivars most farmers and researchers are growing. In this study, a partial sequence of chloroplast atpB gene was used to determine genetic diversity of M. oleifera cultivars from different regions across the world but grown for research at the Agricultural Research Council, Vegetable and Ornamental Plants campus in Roodeplaat, Gauteng Province, South Africa. Thirteen cultivars were collected, of which three were domesticated cultivars from South Africa, eight were from Thailand, and one cultivar each was from Taiwan and the United States of America. Each cultivar consisted of six replicates. DNA extraction, PCR and gel electrophoresis were performed at the University of KwaZulu-Natal whereas DNA sequencing was done at Inqaba Biotec laboratory. DNA sequence analysis was done using BioEdit, MegaX, POPArT and DnaSP softwares. Based on the phylogenetic analysis, the average total length of the sequences was 404 nucleotides with the number of polymorphic segregating sites and mutation of 21 and 24, respectively. From the maximum likelihood tree and neighbour-joining tree, South African domesticated cultivars SH and Limpopo were more related to each other than to the domesticated cultivar, CHM (South African). The cluster which was well supported with 84% bootstrap value was between cultivars TOT 5077 (Thailand) and TOT 4100 (Taiwan). The polymorphic data indicated a nucleotide diversity of 0.01654 and average number of nucleotide difference (k) of 6.58095. The haplotype network also showed less genetic differences between the cultivars with some cultivars recorded as similar. The low genetic diversity observed in these cultivars suggests that the cultivars might have originated from a common ancestor. However, further study is necessary by collecting more cultivars of M. oleifera South Africa and other parts of the world to get a clear view on the genetic diversity. The results from this study will be an addition to the already existing knowledge of M. oleifera available in the world and new knowledge on genetic variation among South African cultivars, which may be relevant in cultivar development and conservation.
Impacts of foraging behavior [sic] by Cape porcupines and their effects on nutrient cycling in mesic savannas.
(2021) Kraai, Unathi Masiobi.; Tsvuura, Zivanai.; Kraai, Manqhai.; Mkhize, Nthuthuko Raphael.; Mgqatsa, Nokubonga.; Tjelele, Julius Tlou.
Through feeding and associated activities, herbivores play a major role in determining the structure of savannas. The Cape porcupine (Hystrix africaeaustralis) is a semi-fossorial, large (ca. 12 kg) herbivorous rodent with a generalist foraging strategy that feeds on plant parts occurring above- and below ground. Subterranean foraging by porcupine may influence biotic and abiotic processes in that area. The extent of soil and vegetation perturbation may be pervasive on the landscape so that these animals may be considered as ecosystem engineers. The digging activities of ecosystem engineers are significant as they influence soil properties (e.g. nutrient cycling) including germination of trapped seeds and establishment of seedlings. These changes may occur at small and large scale on a landscape. The utilisation of woody vegetation and ecosystem engineering by such animals, particularly by shy and nocturnal species, is understudied in African savannas. The study was aimed at: (1) quantifying the extent of herbivory by the porcupines on target trees during the wet and dry season in three mesic savanna sites, and (2) evaluating the effects of Cape porcupines’ digging on nutrient cycling (total carbon and total nitrogen) and quantify establishment of vegetation on the mounds. Sampling was undertaken at three mesic savanna sites in South Africa: (i) Roodeplaat Farm in Gauteng Province; (ii) Goss Game Farm; and (iii) Bisley Valley Nature Reserve, both in KwaZulu-Natal Province. I used 30 m × 30 m plots to quantify porcupine foraging holes and bark damage on adult trees at Roodeplaat and Goss while 10 m × 10 m plots were used at Bisley where porcupines foraged on seedlings and saplings of woody plants. I also collected porcupine dung samples over the dry and wet season for micromorphological examination of porcupine diet. I collected soil samples from the mound soil of foraging holes and from adjacent locations within 0.5 m of the hole for analysis of amounts of total carbon and total nitrogen. Measurements of foraging holes comprised of two perpendicular diameters on the soil surface and the maximum depth. Porcupines utilised different tree species of various sizes at the three sites while targeting specific parts of these trees. At Roodeplaat, porcupines targeted Vachellia robusta on which they consumed the trunk part immediately below ground, whereas at Bisley, roots and the lower trunk of V. nilotica seedlings and saplings were utilised, also through digging holes while the bark of the lower trunk (up to 0.7 m) of Spirostachys africana trees was stripped off at Goss. I found that 70% of young V. nilotica trees in or adjacent to holes in Bisley were scarred or destroyed as a result of porcupine feeding on them, while 16% of S. africana trees were wounded at Goss. Only 7% of V. robusta trees were damaged at Roodeplaat. In Bisley, I found that grasses and forbs established faster on the mound than on the surrounds, i.e. seedlings germinated first on the mound than the adjacent not disturbed soil. I also found that foraging holes provide shelter to other animals especially those from the arthropod group e.g. spiders. Amounts of total carbon and total nitrogen were similar between the mounds and undug soil. These findings are discussed in terms of nutrient cycling through digging, breaking down of plant parts and herbivore-induced mortality of main tree species. I argue that tree thinning from ringbarking by porcupine through their foraging activities ameliorates woody plant encroachment in mesic savannas.
The influence of the monocarpic herb, Isoglossa woodii, on subtropical forest tree dynamics and diversity.
(2009) Tsvuura, Zivanai.
Dominant understorey species, such as herbs, ferns, palms and shrubs may influence forest tree species diversity and dynamics. Their influence may be through shading the forest floor, thereby affecting regeneration of shade-intolerant species and reducing species diversity, or it may be through competition with seedlings for space and belowground resources, thus modifying or changing the structure of the forest. These effects may be compounded if the life cycle of the understorey species consists of synchronized reproductive and mortality events. This study examines the influence of a dominant understorey species, Isoglossa woodii (Acanthaceae), on regeneration of trees in Indian Ocean subtropical coastal dune forest in southern Africa. The species is a semiwoody herb and has population-wide synchronous reproduction at 4-7 year cycles after which it dies and regenerates from seed. In this thesis I examine three aspects of the ecology of this suppressive herb: (i) the ecological and environmental correlates of the distribution of I. woodii; (ii) the evolutionary advantages of synchronous monocarpy; and (iii) the ecological effects of the extensive cover and putative recruitment window caused by I. woodii on forest tree seedling dynamics and diversity. Isoglossa woodii covered 65–95 % of the understorey, while gaps in this understorey cover occupied the remaining 5–35 % of the area. The spatial distribution of I. woodii was strongly related to tree canopy structure, with the species excluded from sites with dense canopy cover. Woody seedling establishment was inhibited by low light availability (
Influences of bush encroachment and intensity on small mammals in a mesic savanna, Pretoria, South Africa.
(2021) Zwane, Thabile Jane.; Kraai, Manqhai.; Tsvuura, Zivanai.; Tjelele, Julius Tlou.
Abstract available in pdf.
Investigating the effectiveness of a simple water-purifying gadget made of Moringa oleifera seeds as the active beads.
(2023) Raphasha, Dineo Gladys.; Tsvuura, Zivanai.; Ndhlala, Ashwell Rungano.; Mbendana, Dambudzo.
Abstract available in PDF.
Soil phosphorus deficiency affects the microbial symbiosis, nitrogen nutrition, and growth of Vachellia nilotica and Themeda triandra growing in competition in grassland ecosystems in KwaZulu-Natal, South Africa.
(2021) Lembede, Zinhle Nokubonga.; Magadlela, Anathi.; Tsvuura, Zivanai.
Abstract available in PDF.
Use of ground-dwelling arthropods as bioindicators of ecological condition in grassland and forest vegetation at eThekwini Municipality in KwaZulu-Natal.
(2018) Hlongwane, Zabentungwa Thakasile.; Tsvuura, Zivanai.; Mwabvu, Tarombera.; Munyai, Thinandavha Caswell.
Epigaeic arthropods are among the most diverse and abundant group of animals. They are important in the functioning of terrestrial ecosystems. Assemblages of arthropods may be affected by vegetation type, seasonality and disturbances such as alien plant invasion. The aim of this study was to develop a bioindicator tool for monitoring ecological conditions of the KwaZulu-Natal Sandstone Sourveld (KZNSS), which is one of the most threatened grasslands in KwaZulu-Natal. The objectives of this study were to 1) determine species abundance and species richness of ground-dwelling arthropods; 2) determine the effect of season on ground-dwelling arthropods; 3) determine functional diversity of ground-dwelling arthropods; and 4) determine if ground-dwelling arthropods distribution differs in three vegetation types in Tanglewood and Giba Gorge nature reserves in the KwaZulu-Natal Sandstone Sourveld. Ground-dwelling arthropods were sampled during the wet and dry seasons at two sites in each of the nature reserves. At each site, pitfall trap sampling was carried out in three vegetation types, namely intact grassland, riverine or scarp forest and a disturbed grassland vegetation. The disturbed grassland vegetation was an ecotone between grassland and forest dominated by alien invasive plants. Ants, beetles, spiders, terrestrial crustaceans, sand crickets, roaches, termites, millipedes, lacewigs, hemipterans and woodlice were the sampled taxa in both reserves. A total of 6 150 specimens belonging to 60 morpho-species were sampled in Giba Gorge and Tanglewood Nature Reserve. Species abundance and richness varied among reserves as greater epigaeic arthropod abundance was observed in Tanglewood than in Giba Gorge Nature Reserve. However, Giba Gorge was the richer reserve than Tanglewood. Distribution of epigaeic arthropods varied among vegetation types, higher arthropod abundance was recorded in the forest than the disturbed and intact grassland. While higher species richness of epigaeic arthropods was recorded in an intact grassland. Ants were the most abundant and richest taxon at both sites and greater abundance of ants was recorded in the disturbed grassland which shows that ants are opportunistic organisms. Seasonality played an important role in epigaeic arthropod species abundance and richness. Higher abundance and richness was observed in the wet season. This shows that the wet season provides optimum food resources, temperature, soil moisture and diverse vegetation structure which is favourable to epigaeic arthropods. Functional diversity varied across vegetation types. Forest supported a greater abundance of decomposers and predators while the disturbed grassland supported greater abundance of generalists and herbivores. This shows that functional guilds have different food resources and niche requirements and vegetation type plays an important role in functional diversity. Generalist arthropods were more abundant in the dry season unlike the predators, herbivores and decomposers which were more abundant in the wet season. Generalists have broad diets and are able to survive under unfavourable conditions. A terrestrial crustacean, Talitriator africana occurred in all vegetation types but was more abundant in forest. An ant, Pheidole sp.02 (megacephala gp.) was the most widespread species. However, it was more abundant in disturbed grassland. These results suggest that T. africana and Pheidole sp.02 (megacephala gp.) could be useful potential indicators for monitoring ecological conditions in the KwaZulu-Natal Sandstone Sourveld. Forests and grasslands should be conserved because they supported higher numbers of epigaeic arthropods and functional guilds. Arthropods play an important role in the functioning of terrestrial ecosystems. Disturbed grassland should be managed and restored back to a grassland because grasslands play an important role in the functioning of the ecosystem by providing direct and indirect ecosystem services