This study investigated the vegetation and soil characteristics in relation to distance from water points under different land management systems in semi-arid rangelands of South Africa. Six study sites, two each from communal grazing, commercial farming and game reserves were selected. Two watering points were selected in each study site. Two 500 m transects were laid from the selected watering points. Each transect was divided into sub-transects at 25 m, 50m, 100m, 200m, 300m and 500m from water points. A 100 m2 plot was marked in each sub-transect to record grass biomas, species composition, structure and distribution of woody vegetation and physical and chemical soil properties. Data were collected for two seasons 2012/13 (winter and summer). Thirty and 41 grass and woody species respectively were identified in all study areas. The most common and dominating grass species include Cynodon dactylon, Digitaria eriantha, Eragrostis obtusa, Setaria sphacelata and Sporobolus fimbriatus. Cynodon dactylon and S. sphacelata occurred more abundantly (p < 0.05) in the game reserves than in the other land management catergories. All the grass species had similar (p > 0.05) abundance along distance gradient from water points. Grass dry matter (GDM) showed significant differences (p < 0.05) between and within land management systems. However, GDM was not significantly affected by season, location of water point within each farm or reserve and distance along water points. Acacia karoo, Coddia rudis and Ehretia rigida were the most dominant woody species. Tree equivalent (TE) density of all encroaching woody plants combined was significantly (p < 0.05) higher on the communal area (1732 TE ha-1) than the commercial ranches (1136 TE ha-1) and game reserves (857 TE ha-1), but with no marked variations along distance from water points under all the land management systems. The electric conductivity (EC) was significantly (P < 0.01) higher in game reserves than in communal grazing areas and ranches. Soil organic matter percentage showed greatest and lowest values in the game reserves and commercial respectively. Soil pH and bulk density did not vary but soil organic matter (SOM), EC, bulk density and soil compaction were significant different with no increasing or decreasing trends. Soil properties were affected by herbivore pressure and trampling around water points with inconsistence magnitude and direction. In conclusion, grass species composition and GDM did not respond to distance from water points because either grazing gradient was absent or the length of transects was not enough to explain the absence or presence of gradients. High proportion of A. karoo and high densities of seedlings and saplings would seem as very good indicators of the woody vegetation changes in the different land management systems and distance from water points. The soil quality indicators around the water-points showed that livestock and game affected soil parameters.

MENVSC / Department of Ecology and Resource Management

Text in Afrikaans, abstract in Afrikaans and English / Lineere plantegroeipatrone bestaande uit afwisselende grasryke mikrotrog- en boomryke- kruinbane wat parallel met die helling georienteer is, kom voor op die voetbang van die Baviaansberg, in die Warmbadgebied, Noordelike Provinsie. Die hoofdoelwitte van die studie was om uit 'n landskapekologiese benadering die verskynsel te probeer verklaar, om die vertikale en horisontale variasie van eienskappe te kwantifiseer en om die impak van die mens daarop te benadruk. Die differensiasie in die Tukulu- en Etoshagrondvorms in onderskeidelik mikrotroe en -kruine is die gevolg van grondprosesse soos illuviasie van klei, loging en ferrolise.Granulometriese analise dui daarop dat die moedermateriaal van gronde van een bron afkomstig is. Kolluviasie en afsetting van moedermateriaal op die voethang was waarskynlik die beginpunt van landskapontwikkeling waar verdeelde oppervlakvloei van water oenskynlik die mikrostrukture geinisieer het. Na aanleiding hiervan het die ontwikkeling van grondverskille en waterregimeverskille tot plantegroeiverskille gelei. Faktore wat die patroon geaksentueer het is termietaktiwiteite, brand en beweiding. / A linear vegetation pattern consists of alternating grassland micro troughs and woody micro crests lanes which were orientated parallel to the slope occurred on the foot slope of the Baviaansberg, in the Warmbaths area, Northern Province. From a landscape ecological approach the principal aims of the study was to explain the phenomenon, to quantify the vertical and horizontal variation of features and to accent the impact of man on it. The differentiation in Tukulu and Etosha forms in micro troughs and micro crests respectively were the effect of several soil processes. Granulometric analyses showed that the parent material of soil was derived from one source. Colluviation and deposit of parent material was probably the starting-point of landscape development where the divided surface flow of water apparently initiated the micro structures. As a result of this the development of soil and water regime differences lead to vegetation differences. / Geography / M. Sc. (Geografie)

Thesis (MSc (Microbiology))--Stellenbosch University, 2008. / Penicillium is a well‐known cosmopolitan genus with more than 225 accepted species. Species from this diverse genus, in general, are considered to primarily be soil fungi, with decomposition as its main function. Therefore, together with its ubiquitous nature, these species are of great importance in ecosystems, agriculture and biotechnology. However, in South Africa, very little research has been done on this complex genus, as species identification were often found to be problematic, even for experienced taxonomists. This lead to a number of South African studies only mentioning that a Penicillium spp. were isolated, without making any attempt of showing the extent of diversity within the genus from the unique habitats. The present study set out to explore the extent of the species diversity in Penicillium isolated from the Cape Floristic Region, specifically focusing on coastal fynbos soil. Soil samples were collected from this region, at sites situated outside Malmesbury. Four hundred and thirty four Penicillium strains were isolated from soil‐dilutions. The strains were characterized using morphological characters and subsequently placed into 24 morphological groups. There were, also, more or less 40 strains that could not be grouped with any other isolates. Groupings were made according to conidiophore branching patterns which divided the strains into their respective subgenera. Eight species from subgenus Aspergilloides, seven from subgenus Furcatum, eight from subgenus Biverticillium and one from subgenus Penicillium were isolated. The species were further characterized in subsequent chapters. In the second chapter of this thesis, one of the taxonomic groups in subgenus Biverticillium, isolated from coastal fynbos soil, Protea infructescences and on moth‐damaged Riesling grapes in Canada, was examined. This species was characterized using morphology and were found to have several unique characters, such as the very short synnema produced after prolonged incubation. These characters did not conform to descriptions of previously described species. Its novelty was confirmed by an ITS phylogeny and the strains were subsequently described as Penicillium ramulosum prov. nom. with P. cecidicola and P. dendriticumas its sister taxa. In chapter three, a further seven groups belonging to Penicillium subgenus Biverticillium were characterized. These strains were identified as P. minioluteum, P. verruculosum and P. rugulosum‐like, respectively. Four of the groups showed unique morphological characters, with the ITS phylogeny resolving the fynbos strains separate from all previously described species. The strains were, therefore, considered to be new to science and described as P. solicola prov. nom., P. ptychoconidium prov. nom., P. occultum prov. nom. and P. chloroloma prov. nom., respectively. A key to species from subgenus Biverticilliumcluded. is also inPenicillium subgenus Furcatum was the subject of the fourth chapter of this thesis. Our survey found that although the species diversity in this group was not as high as for the other subgenera, it was the group most often isolated in this study. Species were identified as P. janczewskii, P. canescens, P. melinii, P. corylophilum and P. citrinum using morphological characters. One species belonging to subgenus Penicillium, P. expansum, was also isolated and compared to species recorded during a previous survey. Amongst the identified species, were two groups that could not be identified using published keys, with their novelty confirmed by an ITS phylogeny. They are, therefore, described here as P. subturcoseum prov. nom. and P. hemitrachum prov. nom. A key to species in this subgenus is also provided. In Chapter 5 the presence of Penicillium subgenus Aspergilloides, which is characterized by monoverticillate conidiophores, were investigated. Species were identified as P. roseopurpureum, P. restrictum, P. hirayamae and P. toxicarium. Amongst the identified species, were four groups that did not conform to previously described species and are described here as P. brachycaulon prov. nom., P. malacosphaerula prov. nom., P. cumulacinatum prov. nom. and P. vulgaris prov. nom., respectively. The newly described species have been included in a key, together with closely related species and the other species of subgenus Aspergilloides from the fynbos soil. Species identifications in Penicillium is often problematic and South African taxonomists have often not attempt to identify strains down to species level. During this study, Penicillium was found to be well represented in the soil, with a large proportion being previously undescribed. For this reason, a dichotomous and synoptic key to species isolated during this study are provided in the final chapter. This study should thus serve as a basis for further explorations into the diversity and ecological role of this group of organisms in this ecologically mportant biome.

Thesis (MScAgric)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Botrytis cinerea Pers.: Fr., a pathogen of grapevine (Vitis vinifera L.), moves mainly through conidia by air currents in vineyards which are deposited intermittently on the surfaces of leaves, inflorescences and bunches. Little is known about the relationship between the inoculum dosage in air and incidence of Botrytis bunch rot, and how the relationship is influenced by environmental and host factors. To better understand this relationship, information is needed on the period over which conidia have accumulated, the time they are able to survive and remain infectious, time of symptom expression in relation to conidium arrival at the infection court and host surface wetness. The aims of this study were (i) to estimate the amount of viable B. cinerea occurring in air in vineyards, and at different positions on leaves, inflorescences and bunches of grape at different phenological stages, (ii) to determine the relationships between the number of B. cinerea colonies recorded on spore traps placed in the bunch zone of vines and the incidence of B. cinerea recorded from the different tissues, and (iii) to compare the efficacy of fenhexamid on leaves and inflorescences carrying natural B. cinerea inoculum with those inoculated with dry, airborne conidia. Different techniques were used to detect viable Botrytis cinerea in air currents and on plant material obtained from table (cultivars Dauphine and Waltham Cross in Paarl- and Worcester-district) and wine grape (cultivars Chardonnay, Sauvignon Blanc and Merlot in Stellenbosch- and Malmesbury district) vineyards in the Western Cape province during 2001-02 and 2002-03. For four consecutive days during prebloorn, bloom, pea-size, bunch closure, veraison and harvest, sets of Petri dishes with freshly prepared Kerssies' B. cinerea selective medium (spore traps) were left overnight in the bunch zone of vines. Plant material was collected from the vines on the fourth day. Leaves, infloresence and bunches were treated with paraquat to terminate host resistance and to promote the development of the pathogen on the tissues. The B. cinerea inoculum dosage in air, and the incidence at which the pathogen was detected at various positions on leaves and in bunches normally differed between vineyards. However, the various tests revealed that the pathogen generally occurred in a consistent pattern in air in the bunch zone of vines, on leaves and in bunches from all vineyards. The inoculum dosage in air in the bunch zone of the vine was generally highest during prebioom or during bloom, it decreased at pea size and mostly remained at a very low level at the later growth stages. The estimations of viable B. cinerea residing naturally on leaves and in bunches, showed that their amounts depicted levels occurring in air in the bunch zone of the vine. Necrotic leaves occurring early season in vineyards were identified as an important source of secondary inoculum for dispersal to the developing bunches. Latent infections at the various positions in bunches were few at véraison and harvest. However, due to the necrotrophic ability of the pathogen, extensive berry rot (due to berry-to-berry contact) and thus severe bunch rot developed from a single berry that become symptomatic at the base of the pedicel/berry attachment zone. The B. cinerea occupation pattern explains why Botrytis bunch rot develops mostly from the inner bunch and why disease management strategies should concentrate on the bloom to pre-bunch closure stage and on inhibiting B. cinerea development in the inner bunch during the early part of the season. Thus, to effectively reduce B. cinerea in grapevine, preventative applications are recommended to reduce two primary infection events: (a) between budding and pre-bloom to counteract primary leaf infection; (b) during late bloom or early pea size stage, to reduce the amount of the pathogen on leaves and infloresences and to prevent colonisation of floral debris. A third spray can be applied at bunch closure to reduce the amount of B. cinerea at various positions of the inner bunch, especially for cultivars with tight bunches. The efficacy of fenhexamid on leaves and inflorescences carrying natural B. cinerea inoculum was compared with those inoculated with dry, airborne conidia. Shoots were obtained during late bloom from a vineyard (wine grape cultivar Merlot) in the Stellenbosch region. The shoots were divided into two main groups. One group of shoots was left uninoculated, the other shoots were inoculated by dusting with dry B. cinerea conidia in a settling tower. Before inoculation, equal numbers of shoots in each main group was sprayed with fenhexamid, or left unsprayed. Following inoculation and incubation, shoots of each treatment were divided in two equal groups. The one lot of shoots were rinsed in water. The other lot of shoots were immersed in paraquat solution to terminate host resistance and to promote the development of the pathogen from the tissues. For both uninoculated and inoculated shoots, irrespective of fungicide treatment, leaves remained asymptomatic at both the blade and petiole position for the water rinse treatment. No symptom of B. cinerea decay developed at any of the positions on leaves from shoots sprayed with fenhexamid. Spraying of shoots with fenhexamid completely suppressed B. cinerea infection and symptom expression on both uninoculated and inoculated inflorescens. For inoculated shoots, B. cinerea developed from approximately 50% of the laterals in the water rinse treatment. However, inflorescences rinsed in water remained asymptomatic. The laboratory studies showed that fungicides, if applied properly to shoots and bunches under controlled conditions, effectively reduced the amount of B. cinerea at the various positions on leaves and inflorescence, and prevented infection and symptom expression at bloom. However, these goals are not achieved in vineyards where the fungicides are applied by conventional spraying methods. Therefore, more work is needed to evaluate fungicide application techniques by conventional spraying methods for proper fungicide coverage, and the reduction of B. cinerea in bunches. / AFRIKAANSE OPSOMMING: Botrytis cinerea Pers.: Fr., 'n patogeen van druiwe (Vilis vinifera L.), beweeg hoofsaaklik deur middel van konidia in lugstrome deur die wingerd, en word dan afwisselend op die oppervlakte van die blare, bloeiwyses en trosse gedeponeer. Daar is nog min bekend oor die verhouding tussen die hoeveelheid inokulum in die lug en die voorkoms van Botrytis op die trosse, en hoe die verhouding deur omgewings- en gasheerfaktore beïnvloed word. Ten einde hierdie interaksie beter te verstaan, word inligting benodig oor die tydperk waarin die konidia akkumuleer, die tyd wat hulle oorleef en virulent bly, en die tyd van simptoom-uitdrukking in verhouding tot die verspreiding van die konidia by die infeksie-setel en benatbaarheid van die gasheer-oppervlakte. Die doel van hierdie studie was (i) om die hoeveelheid lewensvatbare B. cinerea wat in die lug voorkom, asook by verskeie posisies op blare, bloeiwyses en trosse by verskillende fenologiese stadiums te kwantifiseer, (ii) om die verhouding tussen die aantal aangetekende B. cinerea kolonies op spoorvangers wat in die trossone van die wingerd geplaas is, en die voorkoms van B. cinerea, aangeteken van verskeie weefsels, te bepaal, en (iii) om die effektiwiteit van fenhexamid op blare en bloeiwyses wat natuurlike B. cinerea inokulum dra, te vergelyk met dié wat met droë, luggedraagde konidia geïnokuleer is. Verskillende tegnieke is gebruik om lewensvatbare Botrytis cinerea in lugstrome en op plantmateriaal van tafeldruiwe (kultivars Dauphine en Waltham Cross In Paarl- en Worcester-distrik) en wyndruiwe (kultivar Chardonnay, Sauvignon Blanc en Merlot in Stellenbosch- en Malmesbury distrik) in wingerde van die Wes-Kaap provinsie gedurende 2001-02 en 2002-03 te kwantifiseer. Petri bakkies met vars voorbereide Kerssies medium, selektief vir B. cinerea (spoorvangers), is vir vier agtereenvolgende dae gedurende vóórblom, blom, ertjiekorrel, trostoemaak, kleurbreek en oes, oornag in die trossone van wingerdstokke in betrokke wingerde, gelaat. Plantmateriaal is op die vierde dag versamel. Blare, bloeiwyses en trosse is met paraquat behandel ten einde die gasheerweerstand af te breek en ontwikkeling van die patogeen op die weefsel te bevorder. B. cinerea inokulum in die lug, en die frekwensie waarby die patogeen op verskeie posisies op blare en in die trosse voorgekom het, het normaalweg tussen wingerde verskil. Die verskeie toetse het getoon dat die patogeen normaalweg in 'n vaste patroon in die lug en die trossones van wingerde, asook op blare en in trosse van alle wingerde voorkom. Die inokulumkonsentrasie in die lug in die trossones van wingerdstokke was normaalweg die hoogste gedurende vóórblom of gedurende blom. Die inokulumdruk het by ertjiekorrel verminder en meestal by 'n 'n baie lae vlak tydens die latere groeistadia gebly. Die bepaling van lewensvatbare B. cinerea wat natuurlik op blare en in trosse gedeponeer is, het getoon dat hul hoeveelhede ooreenstem met vlakke wat in die lug in die trossone van die wingerd voorkom. Nekrotiese blare vroeg in die seisoen is 'n belangrike bron van sekondêre inokulum en speel dus 'n belangrike rol by die verspreiding van Botrytis tussen die ontwikkelende trosse. Latente infeksies by die verskeie posisies in trosse was laag by kleurbreek en oes. Weens die saprofitiese vermoëns van die patogeen, kan uitgebreide korrelvrot (a.g.v. korrel-tot-korrel kontak) en dus ernstige trosvrot, ontwikkel. 'n Enkele korrel kan by die basis van die pedisel/korrel vashegtingsone simptomaties raak, en vandaar na aangrensende korrels versprei. Die B. cinerea kolonisasiepatroon verduidelik waarom Botrytis trosvrot meestal vanaf die binneste tros ontwikkel en waarom siektebeheerstrategieë op die vóórblom- tot blomstadium gekonsentreer moet word, en op die inhibering van B. cinerea ontwikkeling in die binneste tros gedurende die vroeë stadia van die seisoen. Dus, om B. cinerea effektief tydens die twee primêre infeksie stadiums in wingerde te verminder, kan voorkomende toedienings aanbeveel word: (a) tussen knopvorming en vóórblom om primêre blaarinfeksie te verhoed; (b) gedurende láátblom en vroeë ertjiekorrel om die hoeveelheid inokulum op die blare en bloeiwyses te verminder, en die kolonisasie van blomdebris te voorkom. 'n Derde toediening kan tydens trostoemaak aangewend word om B. cinerea by verskeie posisies in die binneste tros te verminder, veral by kultivars met digte trosse. Die effektiwitiet van fenhexamid op blare en bloeiwyses waarop natuurlike B. cinerea inokulum voorkom is vergelyk met dié wat met droë, luggedraagde konidia geïnokuleer is. Lote is vanaf 'n wingerd (wyndruif kultivar Merlot) in die Stellenbosch distrik tydens láátblom verkry en in twee hoofgroepe verdeel. Die een groep lote is geïnokuleer deur droë B. cinerea konidia in 'n afsettingstoring te strooi, terwyl die ander groep nie geïnokuleer is nie. Vóór inokulasie, is die helfte van die lote in elke groep met fenhexamid behandel, terwyl die ander helfte onbehandeld gelaat is. Ná inokulasie en inkubasie, is lote van elke behandeling verder in twee eweredige groepe verdeel. Die een groep lote is in water gespoel, terwyl die ander groep lote in 'n paraquatoplossing gedompel is om die gasheerweerstand te verwyder, en die ontwikkeling van die patogeen vanuit die weefsels te bevorder. Vir die waterspoelbehandeling van beide ongeïnokuleerde en geïnokuleerde lote, ongeag van die fungisiedbehandeling, het die blare asimptomaties by beide die bladoppervlakte en blaarsteelposisie gebly. Geen simptome van B. cinerea verrotting het by emge van die blaarposisies van die lote, met fenhexamid gespuit, ontwikkel nie. Die spuit van die lote met fenhexamid het die B. cinerea infeksie en die simptoomontwikkeling op beide die ongeïnokuleerde en geïnokuleerde bloeiwyses heeltemalonderdruk. By die geïnokuleerde lote, het B. cinerea vanaf ongeveer 50% van die laterale in die waterspoelbehandeling ontwikkel, alhoewel, bloeiwyses wat in water afgespoel is, heeltemal asimptomaties gebly het. Laboratoriumstudies het getoon dat fungisiedes, indien korrek toegedien op lote en trosse onder gekontroleerde toestande, tot effektiewe vermindering van B. cinerea getalle by die verskillende posisies op blare en bloeiwyses lei, en infeksie en simptoomuitdrukking tydens blom voorkom. Weens die feit dat die doelwitte nie behaal kan word in wingerde waar die fungisiede deur konvensionele spuitmetodes toegedien is nie, moet meer studies gedoen word om fungisied toedieningstegnieke, by konvensionele spuitmetodes, VIr deeglike fungisiedbedekking en die vermindering van B. cinerea in trosse, te evalueer.

Thesis (MSc)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: This study investigated the composition of Themeda triandra Renosterveld in part of the Grootvadersbosch Conservancy and the effects of selected environmental and management variables to provide guidelines for promoting the presence of Themeda triandra in the veld. The Zürich-Montpellier phytosociological method was used to determine the composition of the Renosterveld communities. The point quadrat method was used to determine the cover of Themeda triandra at three grass dominated sites and compare cover from one site with past cover measurements at the specific site. Ordination was used to examine the effects of the environmental and management variables on the plant communities. Two community groups, five communities and five subcommunities were identified and described. The Themeda triandra – Stoebe phyllostachys Grassland Community Group consists of two communities of which one has two subcommunities. The Themeda triandra – Elytropappus rhinocerotis Shrubland Community Group consists of three communities of which one has three subcommunities. The vegetation units described in this study have not been described previously in the literature. One community belongs to Silcrete Fynbos while another subcommunity is transitional between Renosterveld and thicket and gallery forest. The rest of the plant communities fit the definition for Renosterveld (the local Renosterveld type is Eastern Rûens Shale Renosterveld). Cover of Themeda triandra did not differ significantly either between sites or between years. The comparison of Themeda triandra cover between years was done at a site that had been burnt between the last two sampling times yet the cover was not significantly different. This indicates that fire and other management practices did not have a negative impact on Themeda triandra at the site. Unconstrained ordination of the dataset in which cover/abundance values were included, grouped the relevés by moisture and disturbance but the presence/absence dataset indicates that the two community groups have a slight transitional overlap. Constrained ordination of both datasets with a) soil variables and b) management variables, both showed a tendency to separate the relevés into community groups, that did not happen with topographic and vegetation variables. Ordination did not separate the community groups into their subdivisions. The soil variables (both nutrients and texture) influence the vegetation structure and the community distribution. Under the existing grazing management regime, fire at three to five year intervals promoted the dominance of Themeda triandra by affecting the structure of the plant communities, the abundance of species other than Themeda triandra, and influencing which plant community is present. The use of fire as a management tool was regulated by the importance of the natural veld pastures to the farmers. The natural veld pastures are not suitable for dairy cattle in milk. Thus dairy farmers are less likely to burn the natural veld (no planned burns only chance fires) than those who farm with mutton or beef (planned burns on a three to five year interval). / AFRIKAANSE OPSOMMING: Die studie het die samestelling van Themeda triandra Renosterveld in ’n deel van die Grootvadersbosch-Bewaria en die uitwerking van geselekteerde omgewings- en bestuursveranderlikes ondersoek om riglyne vir die bevordering van Themeda triandra in die veld daar te stel. Die Zürich-Montpellier fitososiologiese metode is gebruik om die samestelling van die Renosterveldgemeenskappe te bepaal. Die puntkwadraat-metode is gebruik om ’n skatting van die dekking van Themeda triandra by drie gras-gedomineerde persele te bepaal en om ’n vergelyking te maak tussen die huidige en vorige dekking van ’n enkele perseel. Ordinasie is gebruik om die invloed van omgewings- en bestuursveranderlikes op die plantgemeenskappe te bepaal. Twee gemeenskapsgroepe, vyf gemeenskappe en vyf subgemeenskappe is geïdentifiseer en gedefinieer. Die Themeda triandra – Stoebe phyllostachys Grasland-gemeenskapsgroep bestaan uit twee gemeenskappe waarvan een in twee subgemeenskappe onderverdeel is. Die Themeda triandra – Elytropappus rhinocerotis Struik-gemeenskapsgroep bestaan uit drie gemeenskappe waarvan een in drie subgemeenskappe onderverdeel is. Die plantegroei-eenhede wat in die studie beskryf is, is nie voorheen in die literatuur beskryf nie. Een gemeenskap behoort aan Silkreet-fynbos en ’n ander subgemeenskap is ’n oorgangsfase tussen Renosterveld en struikbosveld of woud, terwyl die res van die plantgemeenskappe binne die definisie van Renosterveld val (die plaaslike Renosterveld tipe staan bekend as Oostelike Rûens Skalierenosterveld). Die bedekking van Themeda triandra het nie betekenisvol gevarieer tussen óf die verskillende lokaliteite óf die verskillende jare nie. Die vergelyking van Themeda triandra-bedekking oor tyd is onderneem in ’n gebied wat tussen opnames gebrand is. Die bedekking het nie betekenisvol verskil nie. Dit dui aan dat vuur en ander bestuurspraktyke nie ’n negatiewe invloed op Themeda triandra in hierdie gebied het nie. Onbeperkte ordinasie van die datastel met die vergelyking van bedekking/volopheidwaardes, groepeer die relevés volgens vogtigheid en versteuring, terwyl die datastel ten opsigte van teenwoordigheid/ afwesigheid aandui dat die twee gemeenskapsgroepe ’n effense oorgangs-oorvleueling het. Beperkte ordinasie van beide datastelle met a) grondveranderlikes en b) bestuursveranderlikes, toon albei ’n neiging om die gemeenskapsgroepe te skei, wat nie gebeur het met die topografiese- en plantegroeiveranderlikes nie. Ordinasie het nie die gemeenskapsgroepe onderverdeel in gemeenskappe of subgemeenskappe nie. Die grondveranderlikes (beide voedingstowwe en tekstuur) beïnvloed die struktuur en die verspreiding van die plantegroei. Met die bestaande weidingsbestuur bevorder brande met ’n interval van tussen drie tot vyf jaar die oorheersing van Themeda triandra deur die struktuur van die teenwoordige plantgemeenskap te beïnvloed, deur die getal van die verskillende plantsoorte te beïnvloed en selfs deur die plantgemeenskap se voorkoms te beïnvloed. Die waarde wat die boer aan die natuurlike veld as weiveld heg bepaal die mate waartoe hulle veldbrand gebruik as ’n deel van bestuur. Die natuurlike veld is nie geskik vir melkkoeie wat in die melkproduksiestadium is nie. Die melkboere is dus minder geneig om die natuurlike veld te brand (geen beplande brande nie net kans brande) as die boere wat met vleisbeeste of skape boer (beplande brande elke drie tot vyf jaar).

Thesis (MSc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: The geometric tortoise, Psammobates geometricus, found in the Western Cape, South Africa, is one of the world's rarest tortoises. At present, it is only known from five isolated geographical areas, one being the Worcester-Tulbagh Valley. The primary aims of my study were to determine the status of geometric tortoise subpopulations along the Nl highway in the Worcester Valley, to determine the population structure of these subpopulations and, if necessary, to provide recommendations for the mitigation ofNI highway-induced impacts on geometric tortoise subpopulations along the road. All Renosterveld remnants along the Nl between Du Toitskloof and Worcester were surveyed for the presence of geometric tortoises, and tortoise density and population structure were determined for each remnant that supports tortoises. Two geometric tortoise subpopulations on opposite sides of the Nl were identified. In the larger remnant of the two, females dominated both the subadult and adult classes, whereas in the other remnant male frequency was slightly higher than female frequency for the adult class only. In both remnants, adult females were significantly larger than adult males in mean carapace length. Mean body mass for adult females and males also differed significantly in both remnants. Analysis of habitat quality showed that both remnants supporting the geometric tortoise are seriously infested by encroaching indigenous and alien plants. The barrier effect of the Nl highway can be mitigated by constructing underpasses, linking the two remnants on opposite sides of the road. Furthermore, road mortality of tortoises can be avoided by erecting tortoise proof fencing along appropriate sections of the highway in the Worcester Valley. By linking the remnants, the largest single area available to the geometric tortoise in the Worcester Valley will also be formed. An additional aim of my study was to investigate the correspondence of geometric tortoise density in individual habitat remnants to the West-to-East change in vegetation composition/characteristics occurring along the Nl in the Worcester Valley. Vegetation composition/characteristics were thus determined in all remnants also surveyed for tortoises. The West-to-East change in vegetation composition/characteristics of the study area indicates that there is a transition from Renosterveld in the West to karroid veld in the East. / AFRIKAANSE OPSOMMING: Die geometriese skilpad, Psammobates geometrieus, wat in die Wes-Kaap, Suid- Afrika, voorkom, is een van die wêreld se skaarste skilpaaie. Vandag word hierdie skilpad net nog in vyf geïsoleerde geografiese streke gekry, een van hulle die Worcester-Tulbagh Vallei. Die primêre doel van my studie was om die status van geometriese skilpad subpopulasies langs die Nl snelweg in die Worcester Vallei te ondersoek en om die populasiestruktuur van hierdie subpopulasies te bepaal. Verder was die doelook, om aanbevelings te maak oor hoe die impakte van die pad op die geometriese skilpad subpopulasies langs die Nl verminder kan word. Al die Renosterveld oorblyfsels langs die Nl tussen Du Toitskloof en Worcester, en binne die bekende gebied van die geometriese skilpad, is deursoek vir geometriese skilpaaie. Populasiedigtheid en populasiestruktuur van die skilpaaie is bepaal vir elke oorblyfsel wat skilpaaie bevat. Twee geometriese skilpad subpopulasies is gekryaan teenoorgestelde kante van die Nl. In die groter oorblyfsel, het wyfies albei die onvolwasse en volwasse klasse gedomineer. In die ander oorblyfsel is gevind dat die frekwensie van mannetjies ietwat hoër was as die frekwensie van wyfies, maar vir slegs die volwasse kategorie. Binne albei oorblyfsels is gevind dat volwassse wyfies betekenisvol groter in gemiddelde doplengte is as volwasse mannetjies. Gemiddelde liggaamsgewig het ook betekenisvol verskil tussen volwasse wyfies en mannetjies in albei oorblyfsels. 'n Analise van habitatkwaliteit het gewys dat beide oorblyfsels wat die geometriese skilpad ondersteun grootliks ingeneem is deur inheemse indringers, sowel as uitheemse plante. Die versperrings effek van die Nl snelweg kan verminder word deur duikwege te skep wat die twee ooblyfsels, op teenoorgestelde kante van die pad, verbind. Bowendien, deur 'n ondeurdringbare heining langs passende dele van die snelweg in die Worcester Vallei op te rig, sal skilpadmortaliteit vermy word. Deur oorblyfsels te verbind, salook die grootste enkele area, beskibaar aan die geometriese skilpad in die Worcester Vallei, gevorm word. 'n Addisionele doel van hierdie studie was om veranderinge in vegetasie langs 'n wes-na-oos gradient binne die studie area te korreleer met die teenwoordigheid van skilpaaie langs hierdie gradient. Vegetasie samestelling/eienskappe is dus bepaal vir elke oorblyfsel wat deursoek is vir skilpaaie. Die wes-na-oos verandering in vegetasie samestelling/eienskappe binne die studie area wys dat daar 'n oorgang van Renosterveld in die weste na 'n karooagtige veld in die ooste is.

Thesis (PhDEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The interaction between moving water and the physical attributes of a river, as displayed by the channel morphology, determines the availability of physical habitat for aquatic species and thus also the condition of the ecosystem. As such, the environmental flow assessment process requires knowledge on how changes in the flow regime will affect both the morphological and hydraulic conditions within a river channel. With the increasing development of water-related infrastructure in mountain regions, knowledge of the morphological and hydraulic characteristics of rivers in the upper catchment areas is very important. Cobble and boulder bed rivers in the Western Cape are typical examples. They are characterized by steep gradients, great variability in sediment size and relatively low flow depths. The bed configuration contains a series of pools, steps, rapids, riffles and plane beds, while energy losses are high as a result of turbulence and hydraulic jumps. Due to their wideranging morphological and associated hydraulic attributes, the physical habitats within these rivers are extremely diverse, both on a spatial and temporal scale. This study addresses the interaction between moving water and the physical attributes of cobble and boulder bed rivers. Empirical, semi-empirical and theoretically based models are developed which define the hydraulic and morphological related characteristics of environmental flow components in cobble and boulder bed rivers. They cover macro scale channel deformation, the scouring of sand from the interstitial spaces between the cobbles as well as velocity-depth relationships, which prove to be key components in the assessment of environmental flow requirements in cobble and boulder bed rivers. / AFRIKAANSE OPSOMMING: Die wisselwerking tussen die vloeiende water en die fisiese eienskappe van 'n rivier, soos beskryf deur die morfologie, bepaal die beskikbaarheid van habitat vir akwatiese spesies en gevolglik ook die welstand van die ekosisteem. Kennis omtrent die impak van 'n veranderde vloei regime op beide die morfologiese en die hidrouliese toestande in 'n rivierloop is dus nodig vir die bepaling van omgewingsvloeibehoeftes. Met die toenemende ontwikkeling van water-verwante infrastruktuur in bergagtige gebiede is 'n grondige kennis van die morfologiese en hidrouliese eienskappe van riviere in hierdie bo-opvanggebiede gebiededend noodsaaklik. Spoelklip riviere in die Wes-Kaap is tipiese voorbeelde van sulke riviere. Hierdie riviere word gekenmerk deur steil hellings, 'n wye verskeidenheid sedimentgroottes, relatiewe lae vloeidieptes en hoë energieverliese as gevolg van turbulensie. Verder bevat die ri vierbed afwisselend poele en stroomversnellings en gevolglik word 'n wye verskeidenheid habitat tipes in hierdie riviere aangetref. Hierdie studie fokus op die interaksie tussen bewegende water en die fisiese eienskappe van spoelklip riviere. Met behulp van empiriese, semi-empiriese en teoretiese modelle word die morfologiese en hidrouliese eienskappe van omgewingsvloeibehoeftes in spoelklip riviere aangespreek. Dit sluit makroskaal kanaal vervorming, die uitskuur van sand tusen die spoelklippe asook die verwantskap tussen vloeisnelheid en vloeidiepte in. Hierdie aspekte kan beskou word as van die sleutel elemente vir die bepaling van omgewingsvloeibehoeftes in spoelklip riviere.

Dissertation (PhD)--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: The central goal in macroecology is to determine species diversity patterns across ecological gradients. Altitudinal and latitudinal patterns in species richness are often assumed to be analogous. Furthermore, the primary mechanisms underlying richness patterns along these two gradients might be similar. To date, few studies have tested whether the hypotheses proposed to explain latitudinal richness variation apply to patterns across altitude. This study therefore tests several hypotheses proposed to explain patterns in species diversity (i.e. ambient energy, productivity, area and geometric constraints) and their underlying mechanisms using altitudinal gradients in epigaeic ant and beetle species richness in the Greater Cederberg Biodiversity Corridor (GCBC) (Western Cape, South Africa). The study was conducted across an altitudinal gradient that was laid out from sea level to the top of a mountain (approximately 2000 m above sea level) and down the other side thereof. First, it was determined how the ant and beetle assemblages differ between the main vegetation types included in the transect and which environmental variables might underlie these differences. Thereafter, the variation in species richness and range size patterns of the two groups was investigated across the full altitudinal gradient. This is the first study that tests the applicability of two mid-domain models across such an altitudinal gradient using both complete and partial assessments. The models explained large proportions of the variance in range sizes across three domains but the ranges could have been constrained to show peaks in the middle of the domains due to the way in which the boundaries of the domains were selected. By contrast, the mid-domain models were not important in explaining species richness patterns, which suggests that they cannot explain diversity across the gradient. The species richness patterns of the two groups did not show the predicted mid-altitudinal peak. Moreover, it was demonstrated that different processes structure ant and tenebrionid assemblages across the same altitudinal transect. Ant species diversity was highly correlated to contemporary climatic variables, while historical factors appear to play a more important role in structuring tenebrionid beetle assemblages. Furthermore, support was found for the species energy theory in the ant assemblages, as well as for two of its underlying mechanisms, namely the more individuals hypothesis and the niche position mechanism. These results suggest that there are likely to be substantial and complex changes to ant assemblages under the predicted climate change scenarios for the region. Given the crucial role played by this group in ecosystem functioning (e.g. myrmecochory) it is suggested that these responses are not likely to be a response solely to vegetation changes, but might also precipitate vegetation changes. This study also forms the basis of a long-term monitoring programme to establish baseline data for the epigaeic ants and tenebrionids and to monitor changes in these communities due to climate change. / AFRIKAANSE OPSOMMING: Een van die sentrale idees in makro-ekologie is om die patrone in spesies diversiteit oor ekologiese gradiënte te ondersoek. Verder word daar aangeneem dat spesie rykheidspatrone oor hoogte- en breedtegradiënte analoog is aan mekaar en dat die primêre onderliggende meganismes van die patrone dieselfde kan wees oor hierdie twee gradiënte. Tot dusver het min studies getoets of die voorgestelde hipoteses wat breedtegradiënte in spesie rykheid verduidelik van toepassing is op hoogtegradiënte. Hierdie studie toets dus verskeie van hierdie hipoteses (aanvoelbare temperatuur, produktiwiteit, area en geometriese beperkinge) en hulle onderliggende meganismes in mier en kewer spesie rykheid in die Groter Cederberg Biodiversiteits Korridor (GCBK) (Wes Kaap, Suid Afrika). Die studie is uitgevoer oor ‘n hoogtegradiënt wat vanaf see vlak tot ongeveer 2000 meter bo seevlak en weer aan die ander kant van die berg af uitgelê is. Eerstens is daar bepaal hoe die mier en kewer diversiteit verskil tussen die hoof planttipes wat oor die hoogtegradiënt voorgekom het en watter omgewingsveranderlikes daarvoor verantwoordelik is. Daarna is die variasie in spesie rykheid en area van verspreiding van die twee groepe ondersoek oor die hele hoogtegradiënt. Hierdie is die eerste studie wat die toepaslikheid van twee mid-domein modelle oor so ‘n hoogtegradiënt toets met behulp van volledige en gedeeltelike ondersoeke. Die modelle het baie van die variasie in area van verspreiding verduidelik oor drie domeine maar die areas van verspreiding kon beperk gewees het om pieke in die middel van die domeine te vorm as gevolg van die manier waarop die grense van die domeine gekies is. In teenstelling, het die modelle nie spesie rykheid verduidelik nie en dus kan hulle nie spesie diversiteit oor hierdie gradiënt verduidelik nie. Die spesie rykheidspatrone van die twee groepe het nie die verwagte piek by midhoogte gewys nie. Verder het verskillende prosesse mier en kewer groeperings oor die hoogtegradiënt gestruktureer. Mier diversiteit was hoogs gekorroleer met kontemporêre klimaatsveranderlikes, terwyl historiese faktore belangriker was vir die kewers. Die spesie-energie teorie was ondersteun deur die data, asook die meer individue hipotese en die nis posisie meganisme. Hierdie resultaat dui daarop dat daar moontlik komplekse veranderinge in mier groeperings gaan plaasvind soos die klimaat verander. Miere vervul belangrike ekologiese prosesse in ekosisteme, wat beteken dat die laasgenoemde verandering nie bloot net gaan plaasvind as gevolg van veranderinge in die plantegroei nie, maar dat hulle self ook veranderinge kan veroorsaak. Hierdie studie vorm ook die basis van ‘n langtermyn moniteringsprogram om basislyn data vir hierdie twee ekologies belangrike groepe vas te stel en om veranderinge wat in hierdie gemeenskappe plaasvind, as gevolg van klimaatsverandering, te monitor.

Thesis (DSc)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: No abstract available / AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar