A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. October 1990 / Problems arising from a disparity in viewpoints regarding the surface form of the Tsondab Sandstone Formation, central Namib desert, Namibia, are examined through literature review and field investigation. It is shown that large distal low-angle fans, proposed in what has been termed the Low-Angle Fan model, are absent or limited to proximal reaches of the study area. The depositional sequence identified in what has been termed the Axial Deposition Model along the Kuiseb River in the northern part of the study area is safely applicable to the rest of the study area. Further, new deposits of the Tsondab Sandstone Formation are identified. The problem of the age of the Namib desert in its fossil and active forms is discussed. The processing of satellite images is used and is shown not to be a viable technique for the identification of sedimentary bodies which are partly mantled by deposits of sediments of a similar nature. / MT2017

>Magister Scientiae - MSc / The Namib Desert is a hyper-arid, coastal desert with limited bioavailable water and nutrients; characteristics which collectively impose constraints on edaphic microbial communities. Several studies in the Namib Desert have investigated changes in soil microbial communities across space. However, the temporal variation of edaphic bacterial community in response to seasonal microenvironmental variation in the Namib Desert gravel plains has never been investigated in situ.The edaphic bacterial community dynamics were evaluated over short (57 days) and long-term (1 year) sampling intervals using an extensive sampling strategy in combination with community fingerprinting by T-RFLP analyses and microenvironmental characterization. The short-term study was conducted on three distinct locations in the Namib Desert gravel plains. Soil bacterial communities were found to be more similar within habitats than between habitats, with the differences likely shaped by soil pH. These findings are consistent with the concept of habitat filtering.Investigation of edaphic bacterial communities over 1 year in an 8100 m2 sampling site revealed seasonal patterns of variation in community structure. Soil moisture,phosphorus, potassium and magnesium were identified as significant abiotic drivers of community temporal dynamics. β diversity was found to increase over time, while the environment remained relatively static. These findings support previous observations that desert communities are likely structured by stochastic and deterministic processes.Taken together, these findings advance understanding of temporal variation of edaphic communities in the Namib Desert.

Hydrologic and material dynamics of ephemeral rivers were investigated in the Namib Desert to assess how hydrologic regimes shape the physical habitat template of these river ecosystems. An analysis of long-term hydrologic records revealed that the variation in mean annual runoff and peak discharge were nearly four times higher than the global average, rendering the rivers among the most variable fluvial systems yet described. Further, a pronounced downstream hydrologic decay characterized all of the rivers. The high spatio-temporal variability in flow was reflected in patterns of material transport. Retention of woody debris increased downstream, in contrast to patterns typically reported from more mesic systems, largely attributable to hydrologic decay. Woody debris piles were the principal retentive obstacles and played an important role in channel dynamics. They were also key microhabitats for various organisms, forming "hotspots" of heterotrophic activity analogous to patterns reported from perennial streams. Large amounts of fine particulate and dissolved organic matter (FPOM and DOM) deposited in the lower reaches of the rivers serve to fuel this heterotrophic biota. As a result of the hydrologic decay, sediment concentration (both organic and inorganic) increased downstream and the lower reaches of these rivers acted as sinks for material exported from their catchments. FPOM and DOM concentrations were among the highest reported for any aquatic system, and, contrary to patterns reported from more mesic systems, FPOM dominated the total organic load transported in these rivers. Inorganic solute concentration also increased downstream, resulting in a downstream increase in soluble salt content in floodplain soils. Soils within the river's lower reaches served as effective long-term integrators of hydrologic variability. The mean extent of floods entering the lower river was defined by an alluviation zone, evident from the convexity exhibited in the lower section of the rivers' longitudinal profiles. A downstream increase in the proportion of silt within floodplain soils is associated with increased sediment deposition. Silt deposition had a positive influence on moisture availability, plant rooting, and habitat suitability for various organisms, including fungi and invertebrates. In addition, a strong positive correlation was observed between silt, organic matter, and macronutrients. Thus, the hydrologic control of transport and deposition patterns has important implications for the structure and function of ephemeral river ecosystems. Finally, an examination of the influence of elephants upon riverine vegetation highlighted the importance of these systems as isolated resource patches interspersed in an arid and hostile landscape. Further, it illustrated that flooding was a key ecological process and that hydrologic alterations would affect the fluvial ecosystem as well as the regional landscape they drain. / Ph. D.

>Magister Scientiae - MSc / Salt pans are a characteristic feature of many dry deserts. The microbial communities inhabiting salt pans are thought to be particularly complex and are generally dominated by halophilic microorganisms. Although saline pools are frequently found within the hyper-arid Namib Desert, the microbial communities of these saline sites have been scarcely investigated. The aim of the present study was to characterise the archaeal, bacterial and cyanobacterial diversity inhabiting these extreme saline pools using three culture independent molecular techniques (DGGE, T-RFLP and 16S rRNA clone libraries). The physiochemical results, mainly the conductivity readings recorded from the sampling sites, indicated that the Gobabeb (103.0mS/cm) region was less saline than the two Swakopmund [(Sps01) (150.0mS/cm) and Sps02 (180.0mS/cm)] sites. Results obtained from DGGE and T-RFLP data were in agreement for both bacterial and cyanobacterial analysis indicating that the Gobabeb site was more diverse than the two Swakopmund sites (Sps01 and Sps02). In comparison, the archaeal community profiles for DGGE and T-RFLP analysis were in agreement illustrating that the archaeal community were more abundant in the two extreme Swakopmund saline sites. Phylogenetic data obtained from 16S rRNA gene clone libraries identified halophilic phylotypes (Rhodothermaceae, Idiomarinaceae Puniceicoccaceae and Cyanobacteria/Chloroplast, Family VII) normally associated with salt rich sites. In addition, a large number of unclassified taxa were identified. To conclude, the study highlighted the presence of a rich microbial diversity present within the salt pans of the Namib Desert and establishes a platform for future investigations. / National Research Foundation

Desert environments are characterised by harsh conditions and possess low biodiversity largely caused by abiotic factors such as; low precipitation, soil organic matter, high temperatures, high levels of evapo-transpiration, pH and salinity. These factors significantly reduce primary production, which influences the availability of food resources for deserts organisms. The diversity and the drivers of diversity for below ground invertebrates including Collembola (springtails) are relatively unknown in the Namib Desert. Previous morphological studies have found only five species on the basis of traditional taxonomy. This study assesses the diversity of Namib Desert Collembola and determines the effect of environmental parameters on this diversity, The diversity of Namib Desert Collembola was assessed using DNA Barcoding. The sequence information of the 178 Collembola specimens, taken from mitochondrial barcoding using the Cytochrome-c oxidase subunit I (COI) gene, was analyzed and Molecular Operational Taxonomic Units (MOTUs) were defined. Collembola community responses to soil physicochemical properties were investigated by using Redundancy Analysis (RDA). MOTUs were successfully indentified to family level (Isotomidae, Neanuridae and Sminthuridae). The researcher found a total of 30 MOTUs, most of which showed limited geographical localisation. The mtDNA COI (barcode) locus revealed high levels of previously unreported genetic diversity of Collembola in the Namib Desert. The RDA indicated that none of the soil physicochemical properties significantly drove variation in Collembola community composition. However, total soil nitrogen was shown to be a strong but not significant driver of variation in community composition (p<0,054). The taxonomic identification of the Collembola specimens was also attempted using traditional morphological analysis. A total of 23 individuals, collected from pitfall traps or extracted from soil samples, were selected for identification. Available European keys were used for identification to genus level where possible. A total eight of specimens were identified to genus level (Folsomides sp), 14 to family level (Entomobryidae) and one to order level (Symphypleona). Both Symphypleona and Entomobryidae were previously unreported from the Namib Desert. The Folsomides genus and the family Entomobryidae were the most abundant groups. This research suggests that soil dwelling Collembola in the Namib Desert have a much higher level of diversity than previously known. However, the study also highlighted the need for a more comprehensive database for Namib Collembola that includes COI sequence data as well as the morphological identification of species. / Dissertation (MSc)--University of Pretoria, 2018. / National Research Foundation (NRF) / Genetics / MSc / Unrestricted

The large-scale use of artificial light throughout the night has occurred in the last 100 years and continues to increase globally. Artificial light impacts many animal and plant taxa. The effects of artificial light on bats is species specific. The Namib Desert in Namibia is still relatively dark but subject to the same drivers of increasing development and urbanization that have increased the spread of artificial light globally. This study investigated the effects of the introduction of ultraviolet, yellow and white artificial light on the activity of bats in a rural environment with minimal development in the Namib Desert. Four sites, 100 m apart, had one light and one bat detector each. The fourth light was a dark control. Each site was sampled four times by each light type. Bat activity was recorded by the bat detectors. Eight bat species were recorded during the experiment. Activity increased for open air and clutter-edge foraging species analysed. Broadband white light caused the highest increases in activity followed by yellow light when compared with the dark control site. Ultraviolet light caused the lowest increases in activity contrary to expectations. / Mengwaga ye 100 ya go feta go bile le koketšego ye kgolo ya tšhomišo ya seetša sa maitirelo bošego ka moka. Setlwaedi se se ata kudu lefaseng ka moka go feta pele, gomme se ama diphoofolo tše ntši le mehuta ya dimela. Leganata la Namib go la Namibia gabotse le sa ntše le swiswetše, eupša le ka fase ga dikgontšhi tša go oketša tlhabollo le toropofatšo tšeo di hlotšego koketšego tšhomišong ya seetša sa maitirelo lefaseng ka bophara. Dikhuetšo tša seetša sa maitirelo go memankgagane di fapana go ya ka mohuta. Nyakišišo ye e nyakišišitše dikhuetšo tša tsebagatšo ya seetša sa maitirelo sa go phadima, serolwane le se sešweu go modiro wa memankgagane ka tikologong ya nagaselegae ya go ba le tlhabollo ye nyane ka Leganateng la Namib. Seetša se setee le tithekethara e tee ya mankgagane di hlomilwe go le lengwe le le lengwe la mafelo a mane, a go arogantšhwa ka 100 m. Seetša sa bone se be se le taolo ya leswiswi. Lefelo le lengwe le le lengwe le dirilwe mohlala makga a mane ka mohuta wo mongwe le wo mongwe wa seetša. Modiro wa mankgagane e rekotilwe ka ditithekethara tša mankgagane. Mehuta ya mankgagane ye seswai e rekotilwe nakong ya eksperimente. Modiro wa mehuta ya sebakabakeng le ya go sela thobekgeng ye e sekasekilwego e oketšegile. Seetša se sešweu sa porotepente se hlotše dikoketšego tša modiro, sa latelwa ke seetša se se serolwane, ge se bapetšwa le lefelo la taolo ya leswiswi. Go fapana le ditetelo, seetša sa go phadima se hlotše dikoketšego tša fasefase modirong. / School of Environmental Sciences / M. Sc. (Nature Conservation)

Demographic, biological and behavioural knowledge, together with information on the ecological interactions and impact of a species is fundamental to effective management of most mammal species. In this study, these aspects were investigated for a population of feral horses in the Namib Naukluft Park of Namibia, which lies within a part of the Namib Desert. An attempt was made to evaluate the justification of the continued existence of this exotic species in a conservation area, as well as to provide baseline information and recommendations regarding management of these horses. The study investigated the botanical component and grazing capacity of the area inhabited by the horses, as well as the demography and quality of life of the horses. The study further examined the possible negative impact the horses may have on the natural biodiversity of the area. Finally, it looked at the historic, scientific, aesthetic and economic values of the horses. The collected data was then used as a technical basis for the development of a draft management plan during a stakeholder workshop. The study proposed a range of grazing capacity values related to the total rainfall of the preceding twelve months, based on grass production in response to rainfall in different plant communities. The horses, as well as the native large herbivores, utilized the study area according to the patchy rainfall patterns typically found in the Namib Desert. The population size of the horses fluctuated between 89 and 149 over a ten year period. The social structure of the population was more significantly influenced by artificial interference than natural disasters which had implications on natality, mortality and genetic viability. Termite activity, measured as utilization of grass provided in bait boxes, did not correlate with horse density and seems, instead, to be influenced by soil properties. The results of ant and tenebrionid beetle species composition surveys and analyses did not indicate a significant negative impact from the horses on the study area. No indication could be found that the horses threaten the survival of any native species in the area or that they change the vegetation structure. It appears as if the biodiversity of the area is subjected to large natural stresses due to the continued and frequent desiccation in the desert environment. The impact of the horses is therefore probably minor to that of the climatic stochasticity. It also became apparent that the horses have developed significant historical, scientific and tourism value. The general public opinion is that the horses should be managed as a wild population with minimal artificial interference. / Thesis (Ph.D. (Zoology))--North-West University, Potchefstroom Campus, 2006.

Eremitalpa granti namibensis is a small blind subterranean insectivore (Chrysochloridae) endemic to the Namib Desert sand dunes. This study of the biology and ecology of the Namib mole assesses its adaptive strategies for survival in a harsh environment. Major areas of study include feeding ecology, movement patterns, home range, activity, thermoregulation and water metabolism. Diet of free-living moles was assessed through stomach content analysis while qualitative and quantitative descriptions of surface foraging paths related searching behaviour to resource abundance and distribution. Moles opportunistically fed on termites, a sedentary prey resource occurring in patches of high concentrations while non-random surface locomotion minimised foraging costs. Population density and home range utilisation were studied by following surface trails and capture mark and recapture. Population density was low but stable and home range size large. No permanent nests or burrows were found while the pattern of home range utilisation was nomadic but circumscribed. Although ranges overlapped, a system of mutual avoidance limited encounters with neighbouring animals. Activity phasing was examined in the field and in the laboratory. Free-living moles were almost exclusively nocturnal while captive moles were active day and night. These findings are discussed in relation to prey availability, predator pressure and avoidance of diurnal extremes. Light and temperature appeared to be important cues for daily onset and cessation of activity. Aspects of thermoregulation examined under laboratory and field conditions revealed high thermal conductance, a low basal metabolic rate and poor thermoregulatory abilities. Factors suggested to have selected for these traits are the gaseous regime of the sand in which moles burrow and the need to minimise energy expenditure in an energy sparse environment. Laboratory and field studies employing isotopic dilution of energy and water methods e xamined the metabolism ability of moles to survive on an insect diet without drinking water. Water independence was achieved through efficient renal function while low rates of energy usage and torpor were further effective in reducing overall water requirements. In summation, a broad overview of adaptive radiation in Namib moles compared to other subterranean mammals is discussed. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1989.

Demographic, biological and behavioural knowledge, together with information on the ecological interactions and impact of a species is fundamental to effective management of most mammal species. In this study, these aspects were investigated for a population of feral horses in the Namib Naukluft Park of Namibia, which lies within a part of the Namib Desert. An attempt was made to evaluate the justification of the continued existence of this exotic species in a conservation area, as well as to provide baseline information and recommendations regarding management of these horses. The study investigated the botanical component and grazing capacity of the area inhabited by the horses, as well as the demography and quality of life of the horses. The study further examined the possible negative impact the horses may have on the natural biodiversity of the area. Finally, it looked at the historic, scientific, aesthetic and economic values of the horses. The collected data was then used as a technical basis for the development of a draft management plan during a stakeholder workshop. The study proposed a range of grazing capacity values related to the total rainfall of the preceding twelve months, based on grass production in response to rainfall in different plant communities. The horses, as well as the native large herbivores, utilized the study area according to the patchy rainfall patterns typically found in the Namib Desert. The population size of the horses fluctuated between 89 and 149 over a ten year period. The social structure of the population was more significantly influenced by artificial interference than natural disasters which had implications on natality, mortality and genetic viability. Termite activity, measured as utilization of grass provided in bait boxes, did not correlate with horse density and seems, instead, to be influenced by soil properties. The results of ant and tenebrionid beetle species composition surveys and analyses did not indicate a significant negative impact from the horses on the study area. No indication could be found that the horses threaten the survival of any native species in the area or that they change the vegetation structure. It appears as if the biodiversity of the area is subjected to large natural stresses due to the continued and frequent desiccation in the desert environment. The impact of the horses is therefore probably minor to that of the climatic stochasticity. It also became apparent that the horses have developed significant historical, scientific and tourism value. The general public opinion is that the horses should be managed as a wild population with minimal artificial interference. / Thesis (Ph.D. (Zoology))--North-West University, Potchefstroom Campus, 2006.

Knowledge of the thermal ecology of a species can improve model predictions for temperature-induced population collapse, which in light of climate change is increasingly important for species with limited distributions. Here, we use a multi-faceted approach to quantify and integrate the thermal ecology, properties of the thermal habitat, and past and present distribution of the diurnal, xeric-adapted, and active-foraging Namibian lizard Pedioplanis husabensis (Sauria: Lacertidae) to model its local extinction risk under future climate change scenarios. We asked whether climatic conditions in various regions of its range are already so extreme that local extirpations of P. husabensis have already occurred, or whether this micro-endemic species is adapted to these extreme conditions and uses behavior to mitigate the environmental challenges. To address this, we collected thermoregulation and climate data at a micro-scale level and combined it with micro-and macroclimate data across the species' range to model extinction risk. We found that P. husabensis inhabits a thermally harsh environment, but also has high thermal preference. In cooler parts of its range, individuals are capable of leaving thermally favorable conditions-based on the species' thermal preference-unused during the day, probably to maintain low metabolic rates. Furthermore, during the summer, we observed that individuals regulate at body temperatures below the species' high thermal preference to avoid body temperatures approaching the critical thermal maximum. We find that populations of this species are currently persisting even at the hottest localities within the species' geographic distribution. We found no evidence of range shifts since the 1960s despite a documented increase in air temperatures. Nevertheless, P. husabensis only has a small safety margin between the upper limit of its thermal preference and the critical thermal maximum and might undergo range reductions in the near future under even the most moderate climate change scenarios.