Thesis (MSc (Botany and Zoology)--University of Stellenbosch, 2006. / Parts of the West Coast Strandveld and adjacent Succulent Karoo on the arid coast of Namakwaland in the Western Cape of South Africa are subject to surface mining. An understanding of mycorrhizal association of plants in the natural vegetation of this area could contribute to the improvement of post-mining re-vegetation of the area. This study investigated mycorrhizal association of plants in the West Coast Strandveld, and compared mycorrhizal infection rates of soils taken from natural vegetation to soils from post-mined rehabilitated vegetations. The study was divided into two components. In the first component a pot experiment was conducted in the greenhouse to assess vesicular-arbuscular mycorrhiza (AM) infectivity of post-mined rehabilitated areas of Brand se Baai in Namakwa Sands mining areas. Rehabilitated areas used in this study included sites that has been strip mined for heavy minerals and then progressively backfilled with sub-soil sand remaining after mineral extraction (tailings), topsoil and translocated plants in an effort to restore the structure and functional aspects of the mined site to its original (pre-mining) ecosystem. Rehabilitated sites 1 assessed in this study included sites backfilled with: tailings + translocated plants (TP); tailing + topsoil + translocated plants (TSP) and tailings + topsoil only (TS). Natural sites (N) were also assessed to serve as reference points. AM infection was evaluated as percent root colonization on wheat planted as bioassay on sterilised sand and inoculum from rehabilitated sites in the ratio of 3:1 respectively. Results of this study component showed that mycorrhiza infectivity of rehabilitated soils was high on TSP and TS because mining disturbance has been remedied by topsoil with or without translocated plant replacement. The structural and chemical components of topsoil used as rehabilitation material favoured re-establishment of microbial activities. Infectivity was however low on soils rehabilitated with tailings and translocated plants (TP) because this treatment lacked topsoil which is a major source of infective mycorrhizal propagules. Infectivity was also low in soils from undisturbed sites (N) probably high phosphorus concentration or presence of perennial vegetation led to low mycorrhiza infection. Results showed that there was no significant effect of mycorrhiza on plant growth rate, nutrient uptake or carbon cost of mycorrhizal plants when related to non-mycorrhizal plants, instead the biomass production and nutrient contents of plants were determined by chemical properties of treatment soils. The second component of the study investigated presence of mycorrhiza on randomly selected common indigenous species of Aizoaceae, Asparagaceae, Asteraceae, Chenopodiaceae, Fabaceae, Lamiaceae, Mesembryanthemaceae, Restionaceae, families growing on unmined areas of the study site. Total mycorrhiza infection was recorded on 85% of the assessed species with percent infection level ranging from 8% in Atriplex lindleyi and Drosanthemum hispidum to 98% in Salvia lanceolata. Functional mycorrhizal association with arbuscule structures were however only observed on 15% of all species assessed. Low arbuscules infection observed in indigenous species assessed in this study could be associated with the timing of mycorrhiza infection assessment and root competition in the soil. There was no infection observed on four species belonging to Chenopodiaceae, Zygophyllaceae, Sterculiaceae, and Asteraceae families, which represented 15% of all species assessed. Most species belonging to Chenopodiaceae and Zygophyllaceae have been reported as non-mycorrhizal in other studies, absence of mycorrhiza on the remaining three families species observed in this study require further confirmation.

Thesis (MSc)--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: Erica is a genus of about 860 species world wide, with 700 of these found in South Africa’s southwestern and southern Cape, making it by far the most speciose genus in the Cape Floristic Region. This poses a particular challenge in the construction of a molecular phylogeny of the genus. The choice of suitably variable gene regions is a crucial decision on which the successful phylogenetic reconstruction of this important genus is critically dependent. The aim of this project was therefore to determine which DNA regions, both chloroplast and nuclear, would be sufficiently variable to give adequate informative characters that may be useful at the species level phylogenetic reconstruction. A subset of 30 species, representing the range of morphological diversity and pollinator preference within Erica, was selected for study. For each of these species the variability in eight chloroplast regions (trnL-F, matK, trnS-G, rps12- rpl20, psbAtrnH, trnC-D, rps4-trnT and trnT-L) and the nuclear ITS region was investigated. The psbA-trnH, trnC-D, rps4-trnT and trnT-L chloroplast regions were found to be problematic to amplify and to possess too few Parsimony Informative Characters to be of use in phylogenetic reconstruction. Four of the chloroplast regions, trnS-G, trnL-F, matK and rpS12-rpL20 and the nuclear ITS region could be amplified and sequenced with success. The ITS region was found to be reasonably variable, with the chloroplast genes showing less variability. The DNA extraction method employed showed itself to be of critical importance in the success of the study. Two DNA extraction protocols, both modified from the original Doyle and Doyle (1987) method, were tested. The one included double the amount of β-mercaptoethanol and Polyvinylpyrrolidone (PVP) and the other included an extended phenol: chloroform: isoamylalcohol step. These variables, together with the effectiveness of these methods on fresh vs. silica dried plant samples, were investigated to determine which of the two would yield high quantities and qualities of DNA and result in the best method for the extraction of DNA from Erica species. / AFRIKAANSE OPSOMMING: Erica is ‘n genus van omtrent 860 spesies wêreldwyd, met 700 van hierdie spesies aanwesig in die suidwes en suid Kaap van Suid Afrika, wat dit by verre die mees spesieryke genus in die Kaapse Floristiese Streek maak. Dit stel ’n besondere uitdaging in die konstruksie van ’n molekulêre filogenie van die genus. Die keuse van geskikte variërende geen-areas is ‘n belangrike besluit waarvan die suksesvolle filogenetiese rekonstruksie van hierdie belangrike genus krities afhanklik sal wees. Die doel van hierdie projek was dus om te bepaal watter DNS areas, buide chloroplas en kern, genoegsaam varieer om voldoende informatiewe kenmerke te lewer om bruikbaar te wees in ’n spesie-vlak molekulêre rekonstruksie. ’n Subgroep van 30 spesies, wat die reeks van morfologiese diversiteit en bestuiwer voorkeure in Erica verteenwoordig, is dus vir die studie geselekteer. Vir elk van hierdie spesies is die variasie in agt chloroplast areas (trnL-F, matK, trnS-G, rps12- rpl20, psbA-trnH, trnC-D, rps4-trnT en trnT-L) en die kern ITS area ondersoek. Dit was problematies om die psbA-trnH, trnC-D, rps4-trnT en trnT-L chloroplast areas te amplifiseer, en daar is gevind dat hulle te min Parsimonie Informatiewe Kenmerke besig om bruikbaar te wees in filogenetiese rekonstruksie. Vier van die chloroplas areas, trnS-G, trnL-F, matK en rpS12-rpL20 en die kern ITS kon suksesvol geamplifiseer word en die basisvolgordes kon suksesvol bepaal word. Daar is gevind dat die ITS area redelik variërend is, terwyl chloroplas areas minder variasie getoon het. Die DNS ekstraksie metode wat gebruik is het die kritiese belang van die ekstraksie metode in die sukses van die studie bewys. Twee DNS protokolle, beide gemodifiseer van die oorspronklike Doyle en Doyle (1987) metode, is getoets. Die een het dubbel die hoeveelheid β-mercaptoetanol en Polyvinylpyrrolidone (PVP) bevat, en die het ’n uitgebruide fenol: chloroform: isoamylalkohol stap ingesluit. Hierdie veranderlikes, saam met die effektiwiteit van hierdie metodes op vars teenoor silika-gedroogde plant monsters, is ondersoek om vas te stel watter een van die twee die hoogste kwaliteit en kwantiteit DNS sou lewer en dus sal lei tot die beste DNS ekstraksie metode vir Erica spesies.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Only a limited number of systems involving anther-smut fungi have been studied, usually due to the economic significance of their crop plant hosts. A smut fungus of the genus Thecaphora has been discovered infecting Oxalis hosts in South Africa. This pathogenic fungus, Thecaphora capensis, produces dark-coloured spores in the anthers of host flowers, rendering it an anther-smut fungus. The host genus is the seventh largest plant genus in the Cape Floristic Region (CFR) and the largest geophytic genus of this region. Nine Oxalis species that host T. capensis have been identified across a wide distribution in the CFR of South Africa. A preliminary assessment of T. capensis infections of Oxalis was conducted in 2009, which provided a foundation for further research into the ecological and evolutionary consequences of hosting this fungus. In this study, a comprehensive host diversity assessment was conducted to determine the extent of infected Oxalis individuals within the CFR. Three new Oxalis host species for Thecaphora capensis were discovered. This brings the total number of known hosts to twelve. The morphological and reproductive effects of the fungus were assessed on two host species (O. incarnata and O. lanata) by comparing healthy and infected individuals of these species. Infection by Thecaphora capensis had a significantly negative effect on both of these factors. Host resources appear to be co-opted for fungal spore production, since floral morphological characters of infected individuals were reduced in size. Furthermore, infection by T. capensis ensured near-universal sterility in both hosts. Differences in floral characters and pollinator preferences for healthy Oxalis incarnata and O. lanata individuals from disease-free and diseased populations were compared to determine the evolutionary influence of Thecaphora capensis infections. It was shown that this pathogen can have a significant evolutionary influence on its hosts, showing its ability to shape flower size and pollinator activity in O. lanata, but not in O. incarnata. A need has therefore been identified to assess these evolutionary forces independently for each host and its pathogen before making erroneous assumptions for conservation practices. Plant pollinators play an integral role in plant fitness. Pollinator movements within a population are important when between-flower spore transfer by pollinators increases the likelihood of new infections. Pollinator movements may be influenced by host density and the frequency of diseased individuals, amongst other factors. Pollinators were found to mediate Thecaphora capensis spore transfers within diseased Oxalis populations. Host density and disease frequency affected the number of spores transferred under field and standardized conditions. More research is required to investigate confounding factors in these complex systems. This study highlighted the complexities of a fungal-plant-insect relationship, the evolutionary consequences of such fungal infections and the various factors influencing the likelihood of new infections. This research adds to the limited body of knowledge on multi-organismal interactions in the CFR and provides a base for more detailed future studies on this intriguing system. / AFRIKAANSE OPSOMMING: 'n Brandswam, wat deel is van die Thecaphora genus,is ontdek in 'n Oxalis blom waar dit die gasheer plant se blom gebruik om spore in te produseer. Die swam, Thecaphora capensis, produseer donker gekleurde spore in die helmknoppe van die blomme van gasheer plante, daarom word dit geklasifiseer as 'n brandswam van die helmknop. Die gasheer plante van die swam is deel van die genus Oxalis, die sewende grootste plant genus in die Kaapse Floristiese Streek (KFS) en die grootste geofitiese genus in die streek. Nege Oxalis species is al klaar identifiseer as gasheer plante van T. capensis. Hulle is versprei oor 'n groot area van die KFS van Suid Afrika. 'n Primêre ondersoek van T. capensis infeksies op Oxalis is in 2009 onderneem. Hierdie ondersoek het gelei tot meer vrae oor die sisteem en het 'n goeie fondasie geskep vir verdere navorsing rakende die ekologiese koste verbonde daaraan om as gasheer plant vir 'n swam op te tree. 'n Deeglike ondersoek is in die KFS aangepak om die Oxalis gasheer plante van die brand swam te identifiseer en om voort te bou op die basiskennis wat in die primêre ondersoek daargestel is. Drie nuwe Oxalis gasheer plante van Thecaphora capensis is ontdek. Die totale aantal gasheer plante staan nou op twaalf. Gesonde en geinfekteerde individuele gasheer plante is gebruik om die morfologiese en reproduktiewe effekte van die swam te toets in twee Oxalis spesies (O. incarnata en O. lanata). Die negatiewe gevolge om 'n gasheer plant van die brand swam te wees was duidelik toe gesonde en geinfekteerde individuele met mekaar vergelyk is. Dit kom voor asof gasheer plante se hulpbronne vir spoor produksie gebruik word, want hulle is morfologies kleiner en meestal steriel. Die evolusionêre effek van Thecaphora capensis op 'n populasie is getoets met gesonde individuele in populasies van twee Oxalis spesies. Blomkenmerke en insek bestuiwers van gesonde individue in gesonde en geinfekteerde populasies is ondersoek om die effekte van T. capensis op populasies te toets. Daar is suksesvol gedemonstreer dat swamme sterk evolusionêre kragte uitoefen, en die vermoë het om plantpopulasies te vorm en te verander, ofskoon nie in alle gevalle ewe sterk nie. Daarom is dit belangrik om die evolusionêre kragte vir elke gasheer plant en sy patogeen onafhanklik te assesseer, sonder om algemene aannames te maak in bewaringspraktyke. Plantbestuiwers speel 'n belangrike rol in die fiksheid van plante. Hulle kan hul fiksheid verbeter deur bestuiwers te lok met blomme en deur aspekte geassosieer met blomme. Die bewegingspatrone van plantbestuiwers is baie belangrik indien hulle helmknop-geproduseerde spore van brandswamme vervoer instede van stuifmeel, want dit vergroot die kanse vir nuwe infeksies. Die bewegingspatrone van plantbestuiwers word, onder andere, beinvloed deur die digtheid en frekwensie van geinfekteerde individue. Plantbestuiwers speel 'n belangrike rol in die vervoer van Thecaphora capensis spore in geinfekteerde Oxalis populasies. Die digtheid en frekwensie van geinfekteerde blomme het die vervoer van spore geaffekteer onder veld en gestandardiseerde kondisies, alhoewel baie veranderlikes so 'n komplekse natuurlike sisteem beinvloed. Hierdie studie beklemtoon die kompleksiteit van 'n fungus-plant-insek verhouding, die gevolge van so 'n interaksie en die verskeie faktore wat die waarskynlikheid van nuwe infeksies beinvloed. Tot dusver is daar 'n beperkte aantal sisteme soos hierdie bestudeer waarin 'n brandswam van die helmknop betrokke is, en die enkele beskikbare studies is onderneem meestal as gevolg van hulle ekonomiese effekte op landboukundig belangrike gasheer plante. Hierdie studie verteenwoordig 'n belangrike byvoeging tot die inter-organismiese studies in die KFS. 'n Holistiese ekologiese oorsig soos hierdie verskaf 'n belangrike basis vir toekomstige studies en bewarings- en bestuurspraktyke.

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 (Botany and Zoology))--University of Stellenbosch, 2005. / The family Oxalidaceae has a worldwide distribution, but is most common in tropical and subtropical regions. Oxalis L. is the largest genus of the family comprising ca. 800 of the 900 species. Oxalis species are annual or perennial herbs or rarely subshrubs or trees. The current study assesses on the taxonomic placement of O. furcillata Salter. Currently this species, comprising two varieties, O. furcillata var. furcillata and O. furcillata var. caulescens Salter, is placed in section Foveolatae. Members of this section have endospermous seeds and fleshy leaflets. However, both in terms of leaf morphological and seed characters the two varieties of this species appear to be misplaced within this section. In addition O. furcillata var. caulescens has a unique pollen type, different from both the typical variety and the rest of the section. Both lines of evidence thus suggest that O. furcillata var. caulescens may be misplaced within this section. The present study thus sets out to assess the placement of O. furcillata in general, and the placement of O. furcillata var. caulescens in particular. A multi-disciplinary approach was followed, which included analyses of macro-morphological (including LM and SEM analyses), biogeographical and palynological characters. The variability of quantitative characters was assessed using the STATISTICA 6.0 software package. Leaf dimensions, plant height, bulb length, petiole length and palynology showed sufficient differences between the two taxa to confirm the separate identity of these two varieties as separate species. O. furcillata var. caulescens was thus raised to specific status as O. caulescens (Salter) Bissiengou. The results suggest two different options in terms of the taxonomic placement of the species O. furcillata and O. caulescens. They can either remain in section Foveolatae, best placed near O. senecta and O. densa or may moved to the highly variable section Latifoliolatae. But retaining them within the section Foveolatae appeared to be the better alternative. The correct position will be established both through further morphological analyses and correlation to the trnL-F and ITS sequence-based phylogeny of the southern African members of Oxalis.

Thesis (PhD (Botany and Zoology))—University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Metal pollution is a problem of increasing global concern. It could arise from industrial activities, as well as pesticide use in agriculture, among other sources. For adequate protection of the soil ecosystem from metal toxicity, the bioavailability of metals must be properly evaluated. A plethora of soil factors affect the bioavailability of metals to soil organisms. These include pH, clay and organic matter contents, salinity among others. While much is known about the influence of some of these parameters, little is known on how clay content and salinity modify the bioavailability of metals to soil organisms. This study investigated the influence of clay content and salinity on partitioning, uptake and toxicity of two essential metals (Cu and Zn) to the earthworm Eisenia fetida in separate laboratory trials. Partitioning of the metals was evaluated with 0.01 M CaCl2, DTPA (di-ethylene-triamine-penta acetic acid), and nitric acid extractions. The metal content of worms was determined by acid digestion, while growth, cocoon production, and mortality were used as endpoints showing toxicity to metals and/or salinity. To test the validity of some of the laboratory results, a field study was undertaken, using the earthworm Aporrectodea caliginosa. Further, the study assessed the effect of salinity, using a battery of laboratory tests (acute, chronic and avoidance tests) with natural and/or artificial soils on four species of organisms (a collembolan Folsomia candida, a potworm Enchytraeus doerjesi and two earthworm species E. fetida and A. caliginosa), representing different feeding patterns and ecological roles in soil. Results showed that with increased clay content, there was increased availability of Cu in the substrate, and increased toxicity to E. fetida as shown by data for mortality and growth. The situation with Zn was less significant at sub-lethal concentrations but much so at lethal concentrations. DTPA and CaCl2 extracted metals revealed changes in partitioning of Cu and Zn with changes in clay content, but this trend was not always consistent. Both DTPA and CaCl2 revealed increased availability of Zn in substrates with increased salinity. Salinity had an additive to synergistic effect with Zn in toxicity to E. fetida. When combined with Cu, salinity also increased the availability of Cu as shown by CaCl2 extracted fraction, and had additive effect on toxicity of Cu to the earthworm. The field study did not succeed in in iv confirming the results of the laboratory study due to confounding role of flooding after heavy rainfall and subsequent leaching of salts and Cu. The results of the experiment on acute and chronic toxicity tests for NaCl on E. fetida showed LC50 of 5436 mg/kg NaCl and EC50 for growth and cocoon production of 4985 and 2020 mg/kg NaCl. These values showed that earthworms might be negatively affected in many soils containing fairly moderate concentrations of salts. Similarly, A. caliginosa could not survive in natural soil containing relatively low salt concentrations (EC = 1.62 dS/m) while reproduction was severely affected at lower EC value of 0.52 dS/m. F. candida and E. doerjesi could survive in the highest salinity soil (EC = 1.62 dS/m) used in this study but their reproduction was severely affected from 1.03 dS/m. Overall, it appears that of all the taxa used, earthworm species were the most sensitive to saline stress and could proof useful in determining ‘safe levels’ of salt in contaminated soils. The results of the avoidance test showed that A. caliginosa avoided both natural and artificial saline soil containing concentrations lower than those avoided by E. fetida. The conclusion is that the influence of clay content and salinity on the bioavailability of Cu and Zn depends largely on the metal in question, but generally speaking, bioavailability and toxicity of the metals were reduced with increased clay content while the opposite was true for salinity. If the species used in this study can be seen as fairly representative of a wide range of soil organisms, the conclusion is that salinisation of soil will be detrimental to most soil organisms at relatively low saline concentrations. Given the role of beneficial soil organisms in several soil processes which in turn contribute to soil fertility and sustainable use of land, it is recommended that any farming practices that may lead to an increase in salt content of agricultural soils should be discouraged. / AFRIKAANSE OPSOMMING: Metaalbesoedeling is ‘n probleem wat toenemende globale kommer veroorsaak. Dit kan ontstaan as gevolg van industriële aktiwiteite sowel as van plaagmiddelgebruik in die landbou en ander bronne.Ten einde die grondekostelsel genoegsaam te beskerm, moet die biobeskikbaarheid van metale ge-evalueer word. ‘n Verskeidenheid van grondfaktore be-invloed die biobeskikbaarheid van metale vir grondorganismes Hulle sluit onder andere in pH, klei, organiese inhoud en soutgehalte. Hoewel heelwat bekend is oor die rol van sommige van hierdie parameters, is min bekend oor hoe klei en soutgehalte die biobeskikbaarheid van metale vir grondorganismes kan modifieer. Hierdie studie het die invloed van kleiinhoud and soutgehalte op die verdeling/partisie, opname en toksisiteit van twee essensiële metale (Cu en Zn) vir die erdwurm Eisenia fetida in afsonderlike laboratoriumproewe ondersoek. Kompartementele verdeling van die metale is geevalueer deur middel van ekstraksie-metodes met 0.01 M CaCl2, DTPA (di-etileentriamien- penta asysnsuur), en salpertersuur ekstraksies. Die metaalinhoud van wurms is bepaal deur suurverterings en spektrofotometriese analises te doen terwyl groei, kokonproduksie en mortaliteit van organismes gebruik is as gevoeligheidseindpunte om toksisiteit van metale en soutgehalte aan te toon. Om die geldigheid van somige van die laboratoriumresultate te toets, is ‘n veldstudie ook onderneem met die erdwurm Aporrectodea caliginosa. Die effek van soutgehalte is verder ondersoek deur ‘n battery van laboratoriumtoetse met vier spesies (‘n kollembool Folsomia candida,’n potwurm Enchytraeus doerjesi en twee erdwurmspesies E. fetida en A. caliginosa), wat verskillende voedingspatrone verteenwoordig. Die resultate het getoon dat met toenmende klei-inhoud was daar ‘n toename in die beskikbaarheid van Cu vir opname vanuit die substraat, asook ‘n toename in toksisiteit vir E. fetida soos deur die gegewens vir mortaliteit en groei uitgewys. Die situasie met Zn was minder betekenisvol by subletale konsentrasies en selfs baie minder so by letale konsentrasies. DTPA en CaCl2 ge-ekstraheerde metale het veranderinge in die partisie/verdeling van Cu en Zn uitgewys met verandering in klei-inhoud, maar die tendens was nie altyd konstant nie. Beide DTPA en CaCl2 ekstraksie het toenemende beskikbaarheid van Zn in substrate uitgewys met toenemende soutinhoud. Soutinhoud het ‘n additiewe/toegevoegde tot sinergistiese vi toksisiteitseffek saam met Zn vir E. fetida. In kombinasie met Cu het soutgehalte ook die geskatte biobeskikbaarheid van Cu verhoog soos uitgewys deur die CaCl2, geekstraheerde fraksie, en het ‘n additiewe effek gehad op die toksisitiet van Cu vir die erdwurm. Die veldstudie kon nie die resultate van die laboratoriumstudie bevestig nie weens die belemmerende rol van vloede na swaar reënneerslae en daaropvolgende uitloging van soute en Cu. Die resultate van die eksperimentele ondersoek na die akute en chroniese effekte van NaCl op E. fetida het ‘n LC50 van 5436 mg/kg NaCl en EC50 vir groei en kokonproduksie van 4985 en 2020 mg/kg NaCl opgelewer. Hierdie waardes het aangetoon dat erdwurms moontlik negatief beinvloed kan word in baie gronde wat ‘n redelike gemiddelde konsentrasie van soute bevat. Soortgelyk kon A. caliginosa nie oorleef in natuurllike grond wat relatief lae soutkonsentrasies bevat het (EC=1.62 dS/m) nie terwyl voortplanting sterk ge-affekteer is by ‘n lae EC waarde van 0.52 dS/m. F. candida en E. doerjesi kon oorleef in die grond met die hoogste soutgehalte (EC= 1.62 dS/m) maar hulle voortplanting is ernstig geknou vanaf 1.03 dS/m. In geheel blyk dit dat van allle taksa wat gebruik is, erdwurms die sensitiefste was vir die stres wat deur soutgehalte veroorsaak is. Die kennis kan nuttig wees in die bepaling van “veilige vlakke” van sout in gekontamineerde gronde. Die resultate van die vermydingstoetse het getoon dat A. caliginosa beide natuurlike en kunsmatig versoute gronde vermy het by konsentrasies wat heelwat laer was as dié wat deur E. fetida vermy is Die gevolgtrekking is dat die invloed van klei en soutgehalte op die biobeskikbaarheid van Cu en Zn grootliks afhanklik is van die metale wat betrokke is en dat biobeskikbaarheid en toksisiteit normaalweg verminder het met verhoogde klei-inhoud, met die teenoorgestelde wat waar was in die geval van soutgehalte. Indien die spesies wat in die studie gebruik is beskou kan word as redelik verteenwoordigend van ‘n wye reeks van grondorganismes, is die gevolgtrekking dat versouting van gronde nadelig sal wees vir meeste grondorganismes, selfs by relatief lae soutkonsentrasies. In die lig van die rol wat nuttige grondorganismes speel in verskeie grondprosesse wat bydraend is tot grondvrugbaarheid en volhoubare gebruik van gronde, word dit aanbeveel dat enige boerderypraktyk wat mag lei tot verhoging van die soutinhoud van landbougronde ontmoedig moet word.

Dissertation (PhD)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Riparian vegetation has received a lot of attention in South Africa recently, mainly because of its importance in bank stabilization and its influence on flood regimes and water conservation. The upper reaches have thus far received the least of this attention because of their inaccessibility. This study mainly focuses on these reaches where riparian vegetation is still mostly in a pristine state. The study area chosen for this purpose is the Hottentots Holland Mountains in the Southwestern Cape, the area with the highest rainfall in the Cape Floristic Region, which is very rich in species. Five rivers originate in this area and the vegetation described around them covers a large range of habitats, from high to low altitude, with different geological substrates and different rainfall regimes. All of these rivers are heavily disturbed in their lower reaches but are still relatively pristine in their upper reaches. All of them are dammed in at least one place, except for the Lourens River. An Interbasin Transfer Scheme connects the Eerste-, Berg- and Riviersonderend Rivers. The water of this scheme is stored mainly in Theewaterskloof Dam. Another big dam for water storage, Skuifraam Dam, will be built on the Berg River near Franschhoek in the nearby future. In order to study the vegetation around a river, a zonation pattern on the river bank is described and several physical habitats are recognized. A primary distinction is made between a Wet Bank (flooding at least once a year) and a Dry Bank (flooding less than once a year). The Dry Bank is further subdivided into a Lower Dynamic, a Shrub/Tree and a Back Dynamic Zone. In the lower reaches these zones are very distinct, but in the upper reaches of a river they tend to blend into each other and some zones can be absent or very narrow. Vegetation has been sampled in transects across the riverbed, following the Braun-Blanquet method. Additional vegetation samples have been recorded in the bogs and mires at the sources of the rivers. Vegetation structure and physical habitat has been described to contribute to the description of the vegetation types. In order to understand the environmental processes that determine the vegetation, environmental parameters were recorded in every vegetation sample, such as, slope, aspect, rockiness and soil variables. The classification of the vegetation samples resulted in the identification and subsequent description of 26 riverine and 11 mire communities. The riverinecommunities have been subdivided into ten Community Groups, including a group of Aquatic communities and three groups of Wet Bank communities. The main distinction within the Wet Bank Zone is the importance of erosion or deposition as a driving force of the ecosystem. Three groups of Fynbos communities are identified in the Back Dynamic Zone, with Asteraceous Fynbos occurring on shales and granites, Ericaceous Fynbos occurring on Table Mountain Group sandstones and Transitional Fynbos on a variety of substrates. One community group is characterized by the dominance of Cliffortia odorata, which shows affinity with some renosterveld communities known from literature. The two final groups contain the Afromontane Forests and Riparian Scrub communities, respectively. Discharges are calculated from data recorded at existing gauging weirs. The recurrence intervals, inundation levels and stream power of several flood events are derived from these data and are extrapolated to upstream sites. It appears that most vegetation types in the zonation pattern on the riverbank can be explained by these flood events, except for the Afromontane Forests, which are dependent on other sitespecific factors including protection from fire. Constrained and unconstrained ordinations are used to relate vegetation patterns to the environment. The vegetation is determined by three environmental gradients, operating at different scales. The lateral gradient across the riverbed is mainly determined by inundation frequency and stream power, which are difficult to measure in rocky mountain situations, although variables like distance from the water’s edge, elevation above the water level and rockiness are correlated to them. The longitudinal gradient is the gradient along the length of the river, from high to low altitude. This gradient has the least influence on the riparian vegetation. The geographical gradient reflects the large-scale climatic processes across the mountain range. This gradient accounts for the biggest part of the total explained variation. Important variables are especially the ratio between the summer and winter rainfall and the geological substrate. In the Fynbos Biome, where gamma diversity is extremely high, large-scale environmental processes are important in azonal vegetation as well. The most species-rich vegetation associated with the rivers is found furthest from the water’s edge at intermediate altitudes. Knowledge about the vegetation types and environmental processes in Western Cape rivers is essential for monitoring and maintaining these special ecosystems. Specific threats are related to possible abstraction of water from theTable Mountain Group aquifer and from climate change, which might result in an overall drying of the ecosystem. / AFRIKAANSE OPSOMMING: Riviere se oewerplantegroei kry die laaste tyd baie aandag in Suid-Afrika, hoofsaaklik vanweë die belang vir die beheer van vloede, stabilisasie van die oewers en die bewaring van drinkwater. Die hoë-liggende dele van die riviere het tot dusver die minste aandag geniet omdat hulle tot ’n groot mate ontoeganklik is weens die onherbergsame terrein waarin hulle geleë is. In hierdie studie is daar veral na bergstrome gekyk waar die plantegroei nog taamlik natuurlik en onversteur is. Die studiegebied wat vir hierdie doel gekies is, is die Hottentots-Holland berge in die Wes-Kaap. Die gebied het die hoogste reënval in die Kaapse Floristiese Ryk en is ook baie ryk aan spesies. Vyf riviere het in hierdie gebied hulle oorsprong. Die plantegroei wat hier voorkom sluit ‘n wye reeks habitatte in: van hoog tot laag in hoogte bo seespieël, verskeie geologiese substrate asook verskillende reënval patrone. Al die vyf riviere wat ondersoek is, is baie versteur in hul onderlope, maar is nog grotendeels natuurlik in hul hoë-liggende dele. Almal is reeds opgedam deur een of meer damme, behalwe die Lourensrivier. ’n Tussenopvanggebied-oordragskema verbind tans die Eerste-, Berg- en Riviersonderendriviere met mekaar. Die water uit hierdie riviere word tans hoofsaaklik in die Theewaterskloofdam opgegaar. ’n Verdere groot opgaardam, die sogenaamde Skuifraamdam, word binnekort in die Bergrivier te Franschhoek gebou. Al die riviere se onderlope is tot ’n mindere of meerdere mate vervuil met landbou- en rioolafvoerprodukte. Uitheemse indringerplante, wat die natuurlike oewerplantegroei verdring, skep veral probleme stroomaf van plantasies en dorpe. Om die plantegroei van die rivieroewers na te vors, te klassifiseer en te beskryf, is variasies in die fisiese omgewing bepaal en korrelasies gesoek om die verspreiding van die plantegroei te verklaar. Die belangrikste verdeling in die oewerplantegroei wat gevind is, is tussen die Nat-oewersone (dit word meer as een keer per jaar oorstroom) en die Droë-oewersone (dit word minder as een keer per jaar oorstroom). Die Droë-oewersone word verder onderverdeel in die Laerdinamiesesone, die Boom/Struiksone en die Agter-dinamiesesone. In die laer dele van die rivier is hierdie soneringspatrone baie duidelik, maar in die boonste dele van die rivier kan die onderverdelings dikwels nie van mekaar onderskei word nie omdat hulle gemeng is, of kan die sones baie smal wees of selfs heeltemal afwesig wees.Die plantegroei is gemonster in transekte wat dwarsoor die rivierloop uitgelê is. Die Braun-Blanquet monstertegniek is gevolg. Bykomende monsterpersele is opgemeet in die moerasse in die boonste dele van die berg-opvanggebiede. Om die omgewingsprosesse wat die plantegroei bepaal te verstaan, is ’n aantal omgewingsfaktore in elke monsterperseel aangeteken, wat, onder andere, helling, aspek en bedekking van rotse ingesluit het, terwyl die variasie in samestelling van die bodem ook aangeteken is. Die klassifikasie van die plantegroei het tot die beskrywing van 26 plantgemeenskappe in die riviere en 11 gemeenskappe in die moerasse gelei. Die struktuur van die plantegroei asook kenmerke van die fisiese habitat is in die beskrywing van die plantegroei-eenhede ingesluit. Die gemeenskappe in die riviere is onderverdeel in tien gemeenskapsgroepe. Daar is een gemeenskapsgroep wat die akwatiese gemeenskappe en drie wat die Nat-oewersone gemeenskappe insluit. Die belangrikste verskille tussen die verskillende Nat-oewersone gemeenskappe word bepaal deur die mate waartoe erosie of deposisie voorkom. Daar is ook drie gemeenskapsgroepe van Fynbos onderskei wat in die Agter-dinamiesesone voorkom. Dit sluit in die Aster-fynbos op die skalies en graniete, die Erica-fynbos op die sandstene en die Oorgangs-fynbos op gemengde substrate. Een gemeenskapsgroep is deur die dominansie van Cliffortia odorata gekenmerk. Dit toon verwantskap met renosterveld gemeenskappe wat reeds in die literatuur beskryf is. Die laaste twee groepe sluit die Afromontane woude en Oewerstruikbosse in. Die waterafloop is bereken deur middel van data verkry vanaf bestaande keerwal meetstasies. Die herhalings-intervalle, oorstromingsdiepte en vloei-sterkte van verskillende vloedtipes word vanaf hierdie data afgelei en stroomop geekstrapoleer. Die meeste plantegroeivariasie op die oewers kan deur die vloede verklaar word, behalwe in die geval van die Afromontane woude, wat deur ander omgewingsfaktore bepaal is. Beperkte en onbeperkte ordinasie is gebruik om die verband tussen die plantegroeipatrone en die omgewing te bepaal. Die plantegroei se verspreiding is bepaal deur drie omgewingsgradiënte, wat op verskillende skale ‘n uitwerking het. Die laterale gradiënt oor die rivierbedding is hoofsaaklik bepaal deur oorstromingsfrekwensie en stroomvloeisterkte. Hierdie veranderlikes is moeilik bepaalbaar, alhoewel ander soos, afstand vanaf die rivier, hoogte bo watervlak en bedekking van rotse, wat hieraan gekorreleer is, wel meetbaar is. Die lengte gradiënt,dit is die gradiënt wat van oorsprong na einde langs die lengte van die rivier teenwoordig is, het die minste invloed op die plantegroei. Die geografiese gradiënt weerspieel die grootskaalse klimaatsveranderinge oor die bergreeks. Deur hierdie gradiënt word die grootste deel van die totale variasie tussen die monsters verklaar. Die belangrikste veranderlikes is die verhouding van somer- teenoor winter-reënval en die geologiese substraat. Soortgelyk aan die fynbos in die Fynbosbioom, waar gammadiversiteit buitegewoon hoog is, is die grootskaalse omgewingsprosesse, ook vir asonale oewerplantegroei, baie belangrik. Die spesierykste plantegroei rondom die rivier word die verste van die oewer op gemiddelde hoogtes bo seespieël gevind. Kennis oor die plantegroei en die omgewingsprosesse in die riviere in die Wes-Kaap is belangrik vir die monitering en effektiewe beheer van hierdie besondere ekosisteem. Spesifieke bedreigings is gekoppel aan die potensiële ontginning van water uit die akwifer in die Tafelberggroep-sedimente asook deur grootskaalse klimaatsveranderinge waartydens die hoeveelheid water, volgens voorspellings, waarskynlik sal afneem in hierdie ekosisteem.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Non-native species are recognized as a major component of global environmental change. Their ecological impacts are numerous and include the alteration of whole ecosystem processes as well as the loss of native biodiversity. As such, understanding the processes that drive the invasion of non-native species is essential for the control and management thereof. Numerous research approaches have been used to provide insight on the history and ecology of non-native species invasions. However, recent approaches employing molecular techniques have greatly helped in solving taxonomic issues associated with some of these species; identifying sources of invasions; and shedding light on colonization dynamics. Lantana camara, a globally invasive and highly variable species complex, is one of the most notorious plant invaders in South Africa. The species has been associated with negative impacts in agricultural areas, decreased invertebrate diversity, livestock mortality, and where it occurs along riparian areas- decreased water quality and obstruction to accessing water sources. This project aimed to review L. camara invasions in South Africa and to unravel patterns of spread in L. camara along the Sabie-Sand catchment in South Africa’s flagship protected area, the Kruger National Park, using a molecular approach. The findings of the first part of the study highlight that L. camara has successfully spread across South Africa with only four known introduction events, and this can be attributed to the species’ broad ecological tolerance, its use in the horticultural industry, and a variety of dispersal vectors (birds, humans and rivers). Furthermore, although sale of the species is prohibited in the country, it will continue to spread naturally and also has the potential to expand its distribution under changing climate scenarios. The second part of the study highlights that spread along the Sabie-Sand catchment is primarily river-driven and that the Sand tributary is the invasion source in the system. Because the Sand tributary originates outside the Kruger National Park, and only a small portion is under park management, the implications for spread are important. / AFRIKAANSE OPSOMMING: Nie-inheemse spesies word erken as 'n belangrike komponent van die globale omgewing verandering. Hulle ekologiese impak is talle en sluit in die verandering van ekosisteem prosesse asook die verlies van inheemse biodiversiteit. As sodanig, die begrip van die prosesse wat lei tot die inval van 'n nie-inheemse spesies is noodsaaklik vir die beheer en bestuur daarvan. Talle navorsingsbenaderings is gebruik om insig te gee oor die geskiedenis en ekologie van nie-inheemse spesies invalle. Onlangse benaderings soos die gebruik van molekulêre tegnieke, help in die oplossing van taksonomiese kwessies wat verband hou met 'n paar van hierdie spesies,in die identifisering van bronne van invalle, en om lig te werp op die kolonisasie dinamika. Lantana camara, 'n wêreldwye indringende en spesie kompleks, is een van die mees berugte plantindringer in Suid-Afrika. Die spesie is geassosieer met negatiewe gevolge in landbou gebiede, afgeneem ongewerwelde diversiteit, vee mortaliteit, en waar dit voorkom saam oewer gebiede - afgeneem kwaliteit van die water en obstruksie tot waterbronne. Hierdie projek is daarop gemik om om L. camara invalle in Suid-Afrika te hersien en patrone van verspreiding te ontrafel in L. camara langs die Sabie-Sand-opvanggebied in Suid-Afrika se vlagskip beskermde gebied, die Kruger Nasionale Park, met behulp van 'n molekulêre benadering. Die bevindinge van die eerste deel van die studie wys dat L. camara het suksesvol versprei oor die hele Suid-Afrika met slegs vier bekende inleiding gebeure, en dit kan toegeskryf word aan die spesie se breë ekologiese verdraagsaamheid, die gebruik daarvan in die hortologie bedryf, en 'n verskeidenheid van die verspreiding vektore (voëls, mens en riviere). Verder, hoewel die verkoop van die spesie in die land verbied word, sal dit natuurlik voortgaan om te versprei en het ook die potensiaal om uit te brui onder veranderende klimaat scenario's. Die tweede deel van die studie wys dat versprei langs die Sabie-Sandopvanggebied hoofsaaklik rivier-gedrewe is en dat die Sand sytak die inval bron is. Omdat die Sand sytak buite die Kruger Nasionale Park ontstaan, en slegs 'n klein gedeelte onder park bestuur is, is die implikasies vir verspreiding belangrik. / Financial support from the DST-NRF Centre of Excellence for Invasion Biology and the Working for Water (WfW) Programme through their collaborative project on “Research for Integrated Management of Invasive Alien Species” and Stellenbosch University’s Subcommittee B Young Researcher's Fund

Thesis (MSc)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Understanding the responses of individual plant communities to variations in near-surface water levels and to water quality is a step towards determining the critical or important factors applicable to a Rapid Wetland Assessment System. This thesis describes and discusses factors associated with wetland plant communities, with an attempt to predict changes in a wetland system. This study was initiated with a primary aim of establishing the relationship between plant communities and the variation in near-surface water levels in areas occupied by various plant communities in the Middelvlei wetland system at Stellenbosch. A second aim was to assess whether water quality had an influence on the plant communities. Seven plant communities are identified and described from this particular wetland system using standard Braun-Blanquet techniques (Typha capensis Reedswamp; Cyperus textilis Sedgeland; Pennisetum macrourum Grassland; Juncus effusus Sedgeland; Cyperus longus Sedgeland; Cliffortia strobilifera Shrubland and Populus canescens Forest). The Typha capensis Reedswamp community is found in the wettest parts of the wetlands, with a fluctuation in water table from 0.10 m above surface during the wet season to 0.43 m below surface during the dry season. The Populus canescens Forest is actively invading the wetland replacing the wetland species by modifying the wetland hydrological condition. Water samples from 35 wells, collected on a monthly basis over 11 months, are used to assess sodium, magnesium, potassium, calcium, nitrate and phosphate, pH, redoxs potencial and dissolved oxygen levels in each community, over four seasons. Both multivariate analysis (ANOVA) and regression tree analysis (CART) are applied to evaluate differences between communities or groups of plant communities on a seasonal basis. Direct gradient analysis (CCA) is used to determine the relationship between plant communities and environmental variable gradients. A wide variation in water quality condition between plant communities is present. The Typha capensis Reedswamp community is associated with low nutrient levels (phosphates and nitrates) in all seasons. The Cyperus textilis Sedgeland is associated with low levels of nitrates and high phosphate levels. The Juncus effusus Sedgeland displays the highest phosphate concentration, occurring in summer, while low nitrate levels occur in this community during all the seasons. Dissolved oxygen in the near-surface water in this wetland is at very low concentrations, and has no significant difference between communities. It plays no major role in determining the occurrence and distribution of the plant communities. Most of the water chemical constituents measured in this study are the result of multiple complex relationships, with constituent variations occurring differently between communities. A remarkable seasonal distinction in the chemical constituents in different communities is present. Despite the complex nature of the relationships between plant communities and environmental factors, the low species diversity levels through the tendency for single species dominance and the strong association of these communities with particular environmental variables, the combination of these factors all add value to the use of wetland vegetation as a good tool to indicate wetland condition. An effort to understand wetland plant communities in relation to determining environmental factors would promote the use of plant communities as user-friendly tools for wetland monitoring and assessment. / AFRIKAANSE OPSOMMING: Om die reaksies van plantgemeenskappe teenoor variasies in naby-oppervlakte watervlakke te verstaan, is die eerste krities-belangrike faktor die ontwikkeling van ‘n sisteem om vleilande vinnig te assesseer. Hierdie studie se basiese mikpunt is om verwantskappe te soek tussen plantgemeenskappe in die Middelvlei Vleilandsisteem en wisseling in naby-oppervlak watervlakke. ‘n Sekondêre doel is om te bepaal of daar enige korrelasie is tussen waterkwaliteit en die plantgemeenskappe teenwoordig in die vleiland. Sewe plantgemeenskappe is in hierdie vleilandsisteem geïdentifiseer en beskryf deur gebruik te maak van standaard Braun-Blanquet tegnieke, naamlik die Typha capensis Rietmoeras; Cyperus textilis Biesieveld; Pennisetum macrourum Grasveld; Juncus effusus Biesieveld; Cyperus longus Biesieveld; Cliffortia strobilifera Struikveld en ‘n Populus canescens Woud. Die Typha capensis Rietmoeras kom in die natste dele van die vleilande voor, met vrywater wisselling vanaf 0.10 m bo grondoppervlakte, tydens die nat-seisoen, tot 0.43 m onder grondoppervlakte tydens die droë seisoen. Die Populus canescens Woud het die grootste wisseling in watervlak vanaf die grondoppervlakte tot ten minste ‘n diepte van 1.0 m gehad. Dit blyk dat die Populus canescens Woud besig is om die vleigemeenskappe aktief binne te dring deur die vleiland uit te droog. Water is maandeliks, oor 11 maande, uit 35 geperforeerde plastiek pype, sogenaamde ‘putte’ onttrek, om natrium, magnesium, kalium, kalsium, nitrate en fosfate, pH, redokspotensiaal en opgeloste suurstof vlakke se seisoenale wisseling te bepaal. Beide veelvuldige analise (ANOVA) en regressie-analises (CART) is bereken om enige betekenisvolle verskille tussen plantgemeenskappe te bepaal. Direkte Gradiëntanalise (CCA) is gebruik om die verwantskap tussen plantgemeenskappe en gradiënte van omgewingsveranderlikes te bepaal. Groot variasies in waterkwaliteit tussen plantgemeenskappe is waargeneem. Die Typha capensis Rietmoeras-gemeenskap is geassosieer met lae voedingstofvlakke (veral van fosfate en nitrate) in alle seisoene. Die Cyperus textilis Biesieveld-gemeenskap is geassosieer met lae nitraat- en hoë fosfaatvlakke. Die Juncus effusus Biesieveldgemeenskap vertoon die hoogste fosfaatvlakke, tydens die die somermaande, terwyl die nitraatvlakke deur al die seisoene ook laag bly. Opgeloste suurstof in die naby-oppervlakte water in die vleilandsisteem het deurgaans ‘n lae konsentrasie vertoon met geen betekenisvolle verskille tussen gemeenskappe nie. Dit speel dus geen belangrike rol in die voorkoms of verspreiding van die plantgemeenskappe nie Die meeste van hierdie faktore, gemeet om die waterkwaliteit te bepaal, het veelvoudige, komplekse verhoudingsverskille, gebaseer veral op konsentrasieverskille, tussen die gemeenskappe. Ten spyte van die komplekse verwantskap tussen die plantgemeenskappe en omgewingsfaktore, is die spesierykheid laag en kom die neiging tot eensoortigedominansie algemeen in die vleiland-plantgemeenskappe voor. Die sterk assosiasie tussen die plantgemeenskappe en bepaalde omgewingsveranderlikes voeg aansienlike waarde daaraan toe om vleilandplantegroei te gebruik as indikator van vleilandtoestand. ‘n Poging om die verwantskappe tussen vleiland-plantgemeenskappe en omgewingsveranderlikes algemeen te bepaal, sal die gebruikersvriendelike nut van vleiland-plantgemeenskappe vir vleilandmonitering en assessering duidelik uitwys.

Thesis (MSc (Botany and Zoology))--University of Stellenbosch, 2005. / At present a proper systematic classification of the southern African members of Oxalis L. (Oxalidaceae) does not exist. The most recent and comprehensive revision of the genus based on macro-morphological characters is out-dated (published 60 years ago (Salter, 1944)). The external morphology of the flowers of the southern African Oxalis species is reasonably wellstudied, but little is known about the anatomy thereof. A pilot study of fruit and seed morphology and anatomy of nine selected southern African Oxalis species (Obone, 2003) already revealed some trends to demarcate two main groups. This confirmed the systematic value of some of the characters already proposed by Salter (1944). The aim of the present study was to assess the potential systematic value of fruit and seed morphology and anatomy of 32 Oxalis species. The selection was done such that the included species would represent the main sections proposed by Salter (1944), the pollen types proposed by Dreyer (1996) and the different clades revealed by the phylogenetic tree compiled by Oberlander et al. (2004). Although the species sampling was very low (20% of the southern African taxa), 35 potentially informative characters were identified in fruit and seed morphology and anatomy. These characters may be grouped into three character types, namely autapomorphic characters, randomly distributed characters and systematically informative characters. The first two character types were particularly useful in species-specific characterization. The third group of linked characters could be used to demarcate two major groups of species, those producing endospermous seeds and those producing exendospermous seeds. The three types of characters may prove to be taxonomically informative if more species-inclusive studies are performed. The cluster analysis strongly supported the demarcation of endospermous and exendospermous groups with 100% bootstrap support. Low bootstrap values were observed for subgroups within each of the major groups. This is probably due to low taxon sampling. Therefore clustering based on fruit and seed morphology should be considered with extreme caution within the two groups. Despite these limitations of sample size, fruit and seed morphological and anatomical characters have proven to be systematically informative at the infra-generic level.