Thesis (MSc)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: The systematics of the southern African members of the genus Oxalis L. (Oxalidaceae) is in a state of flux. The bulbs of these species contain potential taxonomically important characters and therefore require detailed study (Salter, 1944). A pilot study assessed the homology of bulbs among southern African Oxalis species (Gebregziabher, 2001), and found that they are all homologous structures. This pilot study also emphasized the range of potentially informative characters from different bulb parts. The aim of the present study was to assess the taxonomic significance of bulb morphology in selected southern African Oxalis species. As far as possible, efforts were made to represent both the taxonomic (Salter, 1944) and palynological diversity (Dreyer, 1996) present in the genus. Detailed bulb morphological studies of 30 species of southern African Oxalis species revealed 41 potentially informative characters. Different bulb-types were identified based on these characters. Bulb-type affinities of taxa included in this study, as well as bulb descriptions from the pilot study (Gebregziabher, 2001), were discussed. Comparison with the current taxonomic classification (Salter, 1944), palynological classification (Dreyer, 1996) and a preliminary phylogeny based on the non-coding plastid trnL-trnF DNA region (Oberlander, 2003), were also made. Bulb morphology conflicted with the current taxonomic classification (Salter, 1944), but showed greater congruence with both the palynological groupings and the trnL-trnF based phylogeny. Based on this study, bulb morphology is found to be taxonomically significant. Further studies on the bulb morphology and anatomy of southern African Oxalis species are merited. Key words: bulb morphology, Oxalis, informative characters, basal plates, fleshy leaves, tunics / AFRIKAANSE OPSOMMING: Die sistematiek van die suider Afrikaanse lede van Oxalis L. (Oxalidaceae) is labiel. Die bolle van hierdie spesies sluit potensieel taksonomies belangrike kenmerke in, en behoort daarom in detail bestudeer te word (Salter, 1944). In Loodsstudie het die homologie van die bolle van die suider Afrikaanse Oxalis spesies ge-evalueer (Gebregziabher, 2001), en gevind dat hulle homoloë strukture is. Resultate van hierdie loodsstudie het ook die reeks van potensieel informatiewe kenmerke van verskillende boldele beklemtoon. Die doel van hierdie studie was om die taksonomiese belang van boImorfologie in geselekteerde suider Afrikaanse Oxalis spesies te ondersoek. Pogings is aangewend om, sover moontlik, beide die taksonomiese (Salter, 1944) en die palinologiese (Dreyer, 1996) diversiteit van die genus in die studie in te sluit. Gedetailleerde bol-morfologiese studies van 30 suider Afrikaanse Oxalis spesies het 41 potensieel informatiewe kenmerke uitgewys. Gebaseer op hierdie kenmerke, is verskillende bol-tipes geïdentifiseer. Verwantskappe tussen die bol-tipes van die spesies ingesluit in hierdie studie, sowel as beskrywings van bolle volgens die loodsstudie (Gebregziabher, 2001), word bespreek. Vergelykings met die huidige taksonomiese klassifikasie (Salter, 1944), palinologiese klassifikasie (Dreyer, 1996) en In voorlopige filogenie gebaseer op die niekoderende plastied trnL-F DNA-streek (Oberlander, 2003) is ook getref. BoImorfologie weerspreek die huidige taksonomiese klassifikasie (Salter, 1944), maar toon groter ooreenstemming met beide die palinologiese groeperings en die trnL-F gebaseerde filogenie. Hierdie studie het bevind dat bolmorfologie van taksonomiese waarde is. Verdere studies op die bolmorfologie en -anatomie van die suider Afrikaanse Oxalis spesies word aanbeveel.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The Cape Floristic Region (CFR) of South Africa is well-recognised for exceptionally high plant species diversity and endemism. However, little attention has been bestowed on the pests and pathogens in this region, even though these may greatly influence plant distribution and evolution. In this study we identify various arthropods and fungi as pests and diseasecausing organisms of the ecologically and economically important CFR-endemic tree taxa of Virgilia. We isolated, identified and determined the pathogenicity of key fungal taxa from diseased Virgilia trees throughout the CFR. In addition we evaluated the role of possible pest arthropod taxa, including bark beetles, phoretic mites, larvae of a cerambycid beetle and larvae of the endemic Leto venus (ghost moth), in the death of Virgilia trees. Key fungal taxa were identified by comparisons of the internal transcribed spacer rDNA regions of the isolated taxa with those available on GenBank. Pathogenicity of the most commonly encountered fungal taxa was determined both in the field and under greenhouse conditions. Five different disease symptoms were observed on Virgilia trees throughout the CFR. At Table Mountain, Virgilia oroboides subsp. oroboides showed symptoms of: (1) several small cankers on stems, seemingly caused by a Fusarium acuminatum-like fungus, (2) a root rot disease caused by Armillaria mellea and (3) small bracket fungi on stems associated with Schizophyllum commune. Virgilia oroboides from the Harold Porter National Botanical Garden was diagnosed with a root disease consistently associated with an un-described Phomopsis species. Virgilia oroboides subsp. ferruginea and V. divaricata from Knysna and the Tsitsikamma area often showed symptoms of rapid wilting and death. The Virgilia stems were damaged by the tunnelling larvae of the ghost moth and those of an unidentified cerambycid beetle. Galleries and the surrounding wood tissues often housed the ophiostomatoid fungi Ceratocystis tsitsikammensis and Ophiostoma plurianulatum. These seem to originate from nitidulid beetles found feeding on gum exudate. Pathogenicity trials confirmed the virulence of the undescribed Phomopsis species, the F. acuminatum-like fungus, S. commune and C. tsitsikammensis to Virgilia. All four morpho-species of bark beetles found in this study, together with phoretic mites on two of the beetle morphospecies, were only collected from dead and dying Virgilia hosts and were classified as secondary pests. Both beetle taxa and mites commonly carried spores of various Geosmithia spp. These are not pathogenic to Virgilia trees, but may be an important food source for the bark beetles, as it dominated the fungal community in galleries. The phoretic mites were unable to feed on their Geosmithia associates, but have been observed to feed on dead bark beetle larvae within galleries. This suggests that the relationship of bark beetles, mites and their associated Geosmithia species in this system is complex and in need of further study. Our results show that natural populations of Virgilia play host to numerous destructive pathogens, some of which are non-native (e.g. A. mellea) and a cause for special concern. Additionally, the isolation of the undescribed Phomopsis species and A. mellea from botanical gardens, with A. mellea now spreading to natural areas, calls for stricter control over the movement of organic material from these areas. / AFRIKAANSE OPSOMMING: Die Kaapse Floristiese Streek (KFS) van Suid-Afrika is bekend vir buitengewoon hoë plantspesie-diversiteit en endemisme. Min aandag is egter tot dusver geskenk aan die peste en patogene in hierdie streek, al mag hulle plantverspreiding en evolusie dramaties beinvloed. In hierdie studie identifiseer ons verskeie geleedpotige diere en fungi as peste en organismes wat siektes veroorsaak in die ekologies en ekonomies belangrike, KFS-endemiese boom genus Virgilia. Ons het die sleutel fungi vanaf Virgilia oor die hele KFS geisoleer, geidentifiseer en hulle patogeniteit bepaal. Addisioneel het ons ook die rol van moontlike pes geleedpotiges, insluitende baskewers, cerambycid kewerlarwes en die endemiese Leto venus (spookmot) in die dood van Virgilia bome geevalueer. Sleutel fungi taksa is geidentifiseer deur die interne getranskribeerde spasieerder rDNS streke van die geisoleerde taksa met die wat op GenBank beskikbaar was te vergelyk. Patogenisiteit van die mees algemeen geisoleerde fungi taxa is beide in die veld en onder glashuis-toestande bepaal. Vyf verskillende siekte simptome is by Virgilia bome regdeur die KFS waargeneem. By Tafelberg het Virgilia oroboides subsp. oroboides simptome getoon van: (1) verskeie klein kankers op stamme, blykbaar veroorsaak deur ‘n Fusarium acuminatum-agtige fungus, (2) ‘n wortelvrot siekte veroorsaak deur Armillaria mellea en (3) klein rakswamme op stamme geassosieer met Schizophyllum commune. Virgilia oroboides in die Harold Porter Nationale Botaniese Tuin is gediagnoseer met ‘n wortelvrot siekte wat altyd met ‘n onbeskryfde Phomopsis spesie geassosieer is. Virgilia oroboides subsp. ferruginea and V. divaricata van Knysna en die Tsitsikamma area het dikwels simptome getoon van vinnige verwelking en dood. Die Virgilia stamme is deur die tonnelende larwes van die spookmot en dié van ‘n ongeidentifiseerde cerambycid kewer beskadig. Galerye en die omringende houtweefsel het dikwels die ophiostomatoid fungi Ceratocystis tsitsikammensis en Ophiostoma plurianulatum gehuisves. Dit lyk asof hierdie fungi van nitidulid kewers afkomstig is wat op die gomuitskeidings gevoed het. Patogeniteitsproewe het die kwaadaardigheid van die onbeskryfde Phomopsis spesie, die F. acuminatum-agtige fungus, S. commune en C. tsitsikammensis teenoor Virgilia bevestig. Al vier morfo-spesies baskewer wat in hierdie studie gevind is, sowel as die foretiese myte op twee van die kewer morfo-spesies, is slegs van dooie of sterwende Virgilia gashere versamel, en is as sekondêre peste geklassifiseer. Beide kewerspesies en myt taksa het algemeen spore van verskeie Geosmithia spesies (Geosmithia pallida, G. flava, G. microcorthyli, G. sp. 1 en G. sp. 2) gedra. Die Geosmithia spesies is nie patogenies teenoor Virgilia bome nie, maar mag ‘n belangrike voedselbron vir die baskewers wees, aangesien dit die fungus-gemeenskap in die galarye gedomineer het. Die foretiese myte was nie instaat om op Geosmithia-assosiate te voed nie, maar is waargeneem om op dooie baskewer larwes te voed binne die galerye. Dit stel voor dat die verhouding van die baskewers, myte en hulle geassosieerde Geosmithia spesies in die sisteem kompleks is, en verdere studie benodig. Ons resultate dui aan dat natuurlike populasies van Virgilia gashere is vir verskeie destruktiewe patogene, sommige waarvan nieinheems (bv. A. mellea) wat ‘n bron van groot kommer is. Verder noodsaak die isolasie van die Phomopsis spesie en A. mellea, wat beide wortelvrot siektes in botaniese tuine veroorsaak, strenger kontrole oor die verskuiwing van organiese materiaal uit hierdie areas, veral gegewe dat A. mellea reeds na natuurlike areas versprei het. / The Centre of Excellence In Tree Health Biotechnology for a bursary and funding the research conducted in this study

Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Invasive alien plant species have devastating effects on the environments that they invade. Australian Acacias, a group of plants that has been planted globally for a range of uses, but has escape plantation areas and became invasive in many countries, are particularly problematic. Acacia mearnsii is one of these invasive alien plant species and in South Africa it is also an important forestry species. It is currently the fifth most widespread invasive alien plant in South Africa, only restricted by the very arid Karoo, thus it is important to assess the different habitats that it enters. The Afromontane forest complex in South Africa is highly fragmented and is one of the most threatened Biomes in the country. The widespread forest margin tree Virgilia divaricata occurs within these forest margins. It is ecologically similar to A. mearnsii as these two species share many characteristics (nodulating legumes, forest pioneer species, fast growing and fire adapted). These species occur sympatrically within invaded forest margins and within these sites, there is a potential for biological exchanges of associated pests and pathogens in the form of arthropods and fungal species. We hypothesize that these two species have different interactions with their pests and pathogens in accordance with the Enemy Release Hypothesis (ERH) and the Biotic Resistance Hypothesis (BRH), respectively. We first compared arthropod associates between these two tree species and found that they share many arthropod species. The native tree did, however, have much higher abundances of herbivores and overall arthropod associates than the invasive tree species, which supports the predictions of the ERH. The distribution of these two species also had an effect on their arthropod assemblages. We assessed their ophiostomatoid fungal associates and herbivore loads and then determined how these pests and pathogens were influenced by environmental conditions along a water gradient. We also compared the effect of plant nutrient content of the two tree species on pest and pathogen loads. A. mearnsii was unaffected by water limitation along this gradient, while δ12C/ δ13C analyses showed that V. divaricata trees experienced drought within drier sites. V. divaricata also had higher herbivore loads in drier sites. A. mearnsii had higher herbivore loads on nutrient deficient trees and higher disease development in trees with sufficient nutrient levels. Comparisons of the nutrient economies of the two legume trees showed that they had similar leaf nutrient contents and resorption efficiencies, but they differed in the use of Biological Nitrogen Fixation (BNF). The native tree utilized BNF more than the invasive. We also tested the physiological effects of a native fungal species on the two tree species. We found the infection elicited more response from the invasive, while the native plant was almost non-responsive. Both plants had significantly longer lesions on infected seedlings than on control plants after inoculation with this pathogen. This difference in response offers a measure of support to the BRH, as the invasive may be more vulnerable to infection. The importance of using related, ecologically similar species in the assessment of the impacts of invasive alien plants is highlighted here. This may provide more information on the actual ecological interaction between native and invasive species within invaded ranges. Forest margins are very vulnerable and dynamic habitats. The influx of a new species into this habitat in the form of an invasive alien plant may therefore have much negative effects. We found support for the exchange of pest and pathogens where these two tree species co-occur. The two host species were very similar in their nutrient economies, creating a potential for competition for similar resources between A. mearnsii and V. divaricata. The environment had an influence on how these plants responded to pest and pathogens and this may be important under the predicted scenario of future climate change. / AFRIKAANSE OPSOMMING: Uitheemse indringer plant spesies het vernietigende effekte op die omgewings waarbinne hulle indring. Australiese Acacias, ‗n groep plante wat reg oor die wêreld aangeplant is vir ‗n reeks gebruike, maar wat uit plantasie areas ontsnap het en indringers geword het in baie lande, is besonder problematies. Acacia mearnsii is een van hierdie indringer uitheemse plant spesies, en in Suid Afrika is ook ‗n belangrike bosbou spesie. Dit is tans die vyfde mees wydverspreide uitheemse indringer plant in Suid Afrika, en word slegs beperk deur die baie droë Karoo, so dit is belangrik om die verskillende habitatte wat dit binnedring te ondersoek. Woudrandte, the grense van die Afromontane woudkompleks in Suid Afrika, is hoogs gefragmenteerd en is dus een van die mees bedreigde Biome in die land. Die wydverspreide woudrand boom Virgilia divaricata kom in hierdie woudrandte voor. Dit is ekologies eenders aan A. mearnsii, aangesien hierdie twee spesies baie kenmerke deel (wortelknop-vormende peulplante, woudpionier spesies, vining groeiend, aangepas tot brande). Hierdie spesies kom simpatries voor binne woudrandte wat deur A. mearnsii ingedring is, en in hierdie lokaliteite bestaan daar die potensiaal vir biologiese uitruiling van geassosieerde peste en patogene in die vorm van geleedpotiges en fungi spesies. Ons stel die hipotese dat hierdie twee spesies verkillende interaksies met hulle peste en patogene het, in ooreenstemming met die Vyand-Vrystellingshipotese (VVH) en die Biologiese-Weerstandshipotese (BWH), onderskeidelik. Ons het eers die geleedpotige assosieasie tussen hierdie twee boom spesies vergelyk en het bevind dat hulle baie geleedpotige spesies deel. Die inheemse boom het egter baie hoër getalle herbivore en algehele geleedpotige-assosiasies gehad as die indringer boom spesie, wat die voorspellings van die VVH ondersteun. Die verspreiding van hierdie twee spesies het ook ‗n effek gehad op hulle geleedpotige samestellings. Ons het ook hulle geassosieerde ophiostomatiede fungus assosiate en hulle herbivoor ladings bestudeer, en het bepaal hoe hierdie peste en patogene deur omgewingstoestande beinvloed is langs ‗n water gradient. Ons het ook die effek van hierdie peste en patogene op die voedingstof-inhoud van hierdie twee spesies vergelyk. A. meansii is nie geaffekteer deur waterbeperkings langs hierdie gradient nie, terwyl δ12C/ δ13C analises aangedui het dat V. divaricata bome droogte stres in droër lokaliteite ervaar het. V. divaricata het ook hoër herbivoorladings gehad in die droër lokaliteite. A. meanrsii het hoër herbivoorladings gehad op voedingstof-beperkte bome, en daar was verhoogde siekte-ontwikkeling in bome met genoegsame voiding. Vergelykings van die voedingstof-ekonomië van die twee peulplant bome het aangedui dat hulle eenderse blaarvoedingstof-inhoude en resorpsie effektiwiteite het, maar het verskil in die gebruik van Biologiese Stikstof Fiksasie (BSF). Die inheemse boom het meer van BSF gebruik gemaak as die indringer. Ons het ook die fisiologiese effekte van ‗n inheemse fungus spesie op die twee boomspesies getoets. Ons het bevind dat infeksie ‗n sterker reaksie in die indringer ontlok het, terwyl die inheemse plant feitlik glad nie op infeksie gereageer het nie. Beide plante het beduidend langer wondmerke in geinfekteerde saailinge ontwikkel as in kontrole plante na innokulasie met die patogeen. Hierdie verskil in reaksie verleen ‗n mate van ondersteuning aan die BWH, aangesien die indringer meer vatbaar mag wees teen infeksie. Die belang daarvan om verwante, ekologies soortgelyke spesies te gebruik in die bepaling van die effekte van uitheemse indringer spesies word hier beklemtoon. Dit mag meer inligting verskaf oor die werklike ekologiese interaksie tussen inheemse en indringer spesies binne verspreidings wat binnegedring is. Woudrandte is baie weerlose en dinamiese habitatte. Die invoer van nuwe spesies in hierdie habitat in die vorm van ‗n uitheemse indringer plant mag daarom baie negatiewe effekte hê. Ons het ondersteuning gevind vir die uitruiling van peste en patogene waar hierdie twee spesies saam voorkom. Hierdie spesies was baie eenders in terme van hulle voedingstof-ekonomië, wat die potensiaal skep vir kompetisie tussen A. mearnsii en V. divaricata. Die omgewing het ‗n effek gehad op hoe hierdie plante gereageer het op peste en patogene, en dit mag belangrik wees onder die huidig voorspelde senarios van toekomstige klimaatsverandering.

Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: To estimate nutrient budgets and model nutrient cycling at a whole ecosystem level on sub-Antarctic Marion Island requires information on the spatial variability of plant nutrient concentrations on the island. The complexity of constructing budgets and models will also be reduced if, instead of considering each plant species individually, the species can be grouped on the basis of their similarities/differences in nutrient concentrations. This thesis presents the results of an investigation into both these aspects. Altitude and distance from the sea are highly correlated with each other and thus influence the concentrations of all the nutrients considered (N, P, K, Ca, Mg and Na) very similarly. Concentrations of N, P and Na in living leaves, dead leaves, stems and roots decrease going inland, due to a decline in the influence of animal manuring and of sea spray. Ca concentration increases going inland, away from the organic peats characteristic of the lowland regions toward the mineral rawmark inland soils. Declining sea spray and increasing soil minerality going inland both affect plant Mg concentration; the net effect is a slight decrease in Mg concentration going away from the coast. K concentration in living leaves and roots did not change going inland; dead leaf and stem K concentrations showed a weak decline. Bryophyte shoot nutrient concentrations do not show such marked patterns of change going inland. Considering the bryophyte species as a whole, the only significant effect is that shoot Na concentration decreases, and Ca concentration increases, going inland. Although information on nutrient concentrations in all plant organs from all four (N, E, W and S) sides of the island was available for only a few species, and in many instances the between-side effect was not significant for individual species, the pattern of between-side differences is quite clear. Living leaf N, P and Mg concentrations are higher in west side than east side plants, with south and north side plants having intermediate concentrations. Leaf K concentrations are highest on the north and lowest on the west side, with east and south side concentrations being intermediate. Leaf Ca concentrations are highest on the south side and lowest on the north side, with east and west side Ca concentrations being intermediate. Leaf Na concentration declines more sharply with distance inland on the island's western and southern sides than on its eastern and northern sides, so that closer than 450 m from the shore leaf Na concentration is higher on the west and south than on the east or north sides, but further inland than that the difference lessens. There was sufficient information for dead leaf, stem and root nutrient concentrations only for the west and east sides of the island. West-east differences in nutrient concentrations of dead leaves are the same as for living leaves. Stem and root west-east concentration differences are also similar to those for living leaves, except for P and Mg concentrations, which were similar on the two sides. All organs showed the same steeper decline in Na concentration on the west than on the east side of the island. Bryophytes show somewhat different between-side nutrient concentration patterns to the vascular plants. South side (not west) bryophytes have highest N and P concentrations but, like for the vascular plants, east side bryophytes have the lowest N and P concentrations. Also similar to the vascular plants, bryophyte K concentration is highest on the north side and lowest on the west side, although south side concentrations are nearly as high as the north side ones. Unlike the vascular plant leaves, bryophyte Mg concentration is highest on the south (not west) side and lowest on the north (not east) side, with east and west side concentrations being intermediate. South side bryophytes have highest Ca and Na concentrations, similar to the vascular plant pattern. Ordination and clustering analyses of leaf nutrient concentrations suggested five nutrient type clusters amongst the island's plant species. The clusters differ in the amount (low, moderate or high) of N, P, K and Na versus the amount of Ca and Mg. Species membership of the clusters is strongly related to what major taxonomic group (bryophyte, pteridophyte, monocot or dicot) the species belongs to, but habitat factors, especially the intensity of animal manuring, also play a role. Plant guilds compiled previously for the island and which have been suggested might prove useful for modeling nutrient standing stocks on a whole island basis associate poorly with the clusters. Where a particular guild does associate closely with a cluster it is mostly an effect of taxonomic group (the guild members are all from a single taxonomic group) or habitat (the guild members are typical for a particular habitat). It is suggested that in order to reduce the complexity and arduousness of constructing whole island plant nutrient standing stock budgets, the species should be grouped according to their taxonomy – as bryophytes, dicots, monocots, club mosses or pteridophytes (the ferns proper). Subgroups of these taxonomic groups can be constructed on the basis of habitat. Mostly, this will be necessary to distinguish plants from manured habitats from plants of the same species from unmanured ones. / AFRIKAANSE OPSOMMING: Ten einde die voedingstofvoorrade en modelvoedingstofsiklus op die sub-Antarktiese Marioneiland op 'n algehele ekosisteemvlak te raam, word inligting oor die ruimtelike variasie in plantvoedingstofkonsentrasies op die eiland benodig. Die raming van voorrade en die konstruksie van modelle sal ook minder ingewikkeld wees indien plantspesies op grond van hul ooreenkomste/verskille in voedingstofkonsentrasies gegroepeer word eerder as om elke spesie individueel te beskou. Hierdie tesis bied 'n uiteensetting van die ruimtelike variasie (hoogte, afstand van die see én kant van die eiland) in die chemiese samestelling (N, P, K, Ca, Mg en Na) van plante, en probeer die plantspesies op grond daarvan in voedingstoftipes klassifiseer. Hoogte en afstand van die see is nou verwant en beïnvloed dus voedingstofkonsentrasies op feitlik dieselfde manier. N-, P- en Na-konsentrasies in lewende blare, dooie blare, stingels en wortels neem af in die rigting van die binneland weens 'n afname in die invloed van dierebemesting en seesproei. Ca-konsentrasies styg weer namate daar vanaf die organiese veengrondkenmerke van die laagliggende streke na die mineraalryke binnelandse grond beweeg word. Sowel die afname in seesproei as die toename in grondmineraalgehalte in die rigting van die binneland beïnvloed die Mg-konsentrasie in plante; die netto uitwerking is 'n effense afname in Mg-konsentrasie namate daar wegbeweeg word van die kus. Die K-konsentrasie in lewende blare en wortels verander nie in die rigting van die binneland nie, terwyl dié in dooie blare en stingels 'n geringe afname toon. Die voedingstofkonsentrasies in briofietspruite toon egter nie dieselfde merkbare veranderingspatrone in die rigting van die binneland nie. Wat die briofietspesie in die geheel betref, is die enigste beduidende uitwerking dat die Na-konsentrasie in spruite afneem en die Ca-konsentrasie toeneem namate daar na die binneland beweeg word. Die N-, P- en Mg-konsentrasies in lewende blare is hoër by plante in die weste as in die ooste van die eiland, en plante in die suide en noorde toon tussenkonsentrasies. K-konsentrasies in blare is die hoogste in die noorde en die laagste in die weste, met tussenkonsentrasies in die ooste en suide. Ca-konsentrasies in blare is weer die hoogste in die suide en die laagste in die noorde, met tussenkonsentrasies in die ooste en weste. Aan die weste- en suidekant van die eiland toon Na-konsentrasies in blare 'n skerper afname namate daar verder van die see beweeg word as aan die ooste- en noordekant. Verskille in die voedingstofkonsentrasies van dooie blare in die weste en ooste is dieselfde as vir lewende blare. Konsentrasieverskille in stingels en wortels in die weste en ooste is ook soortgelyk aan dié in lewende blare, buiten P- en Mg-konsentrasies, wat dieselfde was aan albei kante. Alle plantorgane toon dieselfde skerper afname in Na-konsentrasies in die weste as in die ooste van die eiland. Die voedingstofkonsentrasiepatrone tussen die verskillende kante van die eiland was ietwat anders vir briofiete as vir vaatplante. Briofiete in die suide (nie die weste nie) het die hoogste N- en P-konsentrasies. Soos die vaatplante, het die briofiete in die ooste die laagste N- en P-konsentrasies. Óók soortgelyk aan die vaatplante, is die K-konsentrasie van briofiete die hoogste in die noorde en die laagste in die weste, hoewel konsentrasies in die suide bykans so hoog is as dié in die noorde. In teenstelling met die blare van vaatplante, is die Mg-konsentrasie van briofiete die hoogste in die suide (nie die weste nie) en die laagste in die noorde (nie die ooste nie), met tussenkonsentrasies in die ooste en weste. Briofiete in die suide het die hoogste Ca- en Na-konsentrasies, wat weer ooreenstem met die vaatplantpatroon. Ordinasie- en trosvormingsontledings van voedingstofkonsentrasies in blare dui op vyf voedingstoftipes onder die plantspesies op die eiland, op grond van die (klein, matige of groot) hoeveelheid N, P, K en Na teenoor die hoeveelheid Ca en Mg. Die klas waartoe 'n spesie behoort, hou sterk verband met sy hoof- taksonomiese groep (briofiet, pteridofiet, monokotiel of dikotiel), hoewel habitatfaktore (veral die intensiteit van dierebemesting) ook 'n rol speel. Die plantgildes wat voorheen vir die eiland opgestel is, toon weinig ooreenkoms met die klasse wat uit hierdie studie na vore kom.

Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Responding appropriately to anthropogenic climate change presents a considerable challenge to humankind. Projected changes in climate are anticipated to affect the world's natural systems, human health and economies in many ways. Consequently, there is an urgent need to implement climate change mitigation and adaptation measures that are appropriate and efficient. This dissertation focuses on aspects of risk and feasibility associated with land use based climate change mitigation. First, it reviews policy, implementation and incentive issues that are key to promoting permanence and reducing the risk of leakage associated with reducing emissions from deforestation and forest deforestation (REDD1) in sub-Saharan Africa. Secondly, it assesses the transaction costs associated with the implementation of avoided deforestation and reforestation activities and their effect on the financial feasibility of ventures located in woodland and rangeland systems. Thirdly, it explores the potential impact of biophysical risk factors (such as fire) on the outcome of REDD activities in two chapters. The first risk chapter introduces the notion of biophysical risk and reviews the risk of fire to REDD activities located in important African vegetation types. The second chapter on risk uses the Century Ecosystem Program and published climate projection data to assess the effect of projected changes in temperature, rainfall and atmospheric carbon dioxide on the outcome of REDD activities. The results indicate that, among the biophysical risk variables assessed, fire may not present a major risk to REDD activities located in African woodland, savanna and grassland systems. In contrast, fire may present a significant risk in moist forests where unprecedented dry periods may allow fire to occur in a system where it has previously been absent. The analysis of the affect of climate change found that changes in climate are generally predicted to lead to an increase in carbon stocks and sequestration rates for the vegetation types assessed. Exceptions do occur, such as the modeled effect on nutrient-rich savannas, which require further investigation. The analysis of transaction costs associated with REDD activities illustrated that such costs may inhibit the feasibility of smaller-scale activities, especially in ecosystems outside of moist forests with relatively low carbon stocks and associated revenues. Whereas the proposed creation of national-scale capacity may reduce some transaction costs to a certain extent, there is a clear need to better understand the true cost of REDD activities. In terms of required supporting policy and implementation capacity, it is noted 1) that multi-criteria land use planning is particularly important in reducing permanence risk, 2) that the scope of recognized land use activities that reduce atmospheric GHG needs to be expanded if the benefits of REDD are to be fully realised and 3) that informal land tenure may not require transformation prior to successful, sustainable implementation. A review of the appropriateness of community-based forest carbon monitoring found that such an approach presents significant cost savings while providing local employment and incentive opportunities. Exposure to such initiatives to date indicated that the quality of data collected is adequate and sufficiently robust to fulfill project and national-scale reporting and verification requirements. / AFRIKAANSE OPSOMMING: Antropogeniese klimaatsverandering hou daadwerklike uitdagings vir die mensdom in. Huidige voorspellings dui daarop dat klimaatsverandering natuurlike sisteme, gesondheid en die ekonomie op 'n verskeidenheid van vlakke gaan beinvloed. Daar is dus 'n dringende nood aan korrekte en effektiewe aanpassings- en mitigasie maatstawwe wat geimplementeer kan word. Hierdie proefskrif fokus op die risiko en lewensvatbaarheid van grondgebruiksgebaseerde klimaatsverandering mitigasie. Eerstens gee dit 'n oorsig van die beleids en implementasie dryfvere wat noodsaaklik is vir die bevordering van permanentheid en die verlaging van die risiko van lekkasie wat geassosieer word met verlaagde emissies vanwee degradasie en ontbossing (VEDO2) in sub-Sahara Afrika. Tweedens analiseer dit die transaksiekoste wat geassosieer word met die vermyding van ontbossing en herbebossing en die effek daarvan op die finansiele lewensvatbaarheid van sulke aktiwiteite in bosveld en weiveld. Derdens ondersoek die proefskrif die biofisiese risiko faktore (soos vuur) op die uitslag van VEDO aktiwiteite in twee hoofstukke. Die eerste hoofstuk word ingelei deur 'n ontleding en verklaring van biofisiese risiko en gee dan 'n oorsig oor die risiko van vuur op VEDO projekte in belangrike plantegroei-tipes in Afrika. Die tweede hoofstuk maak gebruik van die Century Ekostelsel Program om die impak van voorspelde veranderings in temperatuur, reenval en atmosferiese koolstofdioksied op VEDO aktiwiteite te evalueer. Die resultate dui aan dat onder die biofisiese risiko faktore wat ondersoek is, vuur nie so „n belangrike risiko inhou vir VEDO projekte in die bosveld, savanna en grasveld plantegroeitipes in Afrika nie. In teenstelling hou vuur 'n groot risiko in vir nat woude waar ongekende droeë tydperke kan veroorsaak dat vuur wel mag voorkom in „n stelsel waar dit voorheen afwesig was. Die analise op die effek van klimaatsverandering het bevind dat veranderinge in klimaat tipies sal lei tot a toename in koolstof voorrade en verhoogde sekwestrasie tempos vir die plantegroeitipes wat geevalueer is. Daar was egter uitsonderings, soos byvoorbeeld die gemodeleerde impakte op nutrientryke savannas wat verdere ondersoek benodig. Die analise ten opsigte van die transaksiekoste wat gepaardgaan met VEDO aktiwiteite illustreer dat sulke kostes dalk die lewensvatbaarheid van kleinerskaal projekte mag benadeel, veral in ekostelsels anders as nat woude met relatief lae koolstof voorrade en geassosieerde inkomste. Die voorgestelde skepping van kapasiteit op 'n nasionale vlak mag dalk transaksie koste verlaag tot 'n mate, maar daar is duidelik 'n behoefte om beter insigte te verkry oor die ware kostes van VEDO aktiwiteite. Wat betref die vereiste ondersteunende beleid en implimentasie kapasiteit is daar bevind dat 1) multi-kriteria grondgebruik beplanning uiters belangrik is in die verlaging van permanentheidsrisiko, 2) die omvang van erkende grondgebruiks aktiwiteite moet uitgebrei word om ten volle voordeel te trek uit VEDO, 3) dat informele grondbesit dalk nie transformasie vereis voor suksesvolle, volhoubare implementasie nie. „n Oorsig oor die aanvaarbaarheid van gemeenskapsgebaseerde woudkoolstofmonitering het gevind dat so 'n benadering tot groot kostebesparings lei terwyl dit ook plaaslike werkskepping bevorder en dien as dryfveer vir projekte. Blootstelling aan sulke inisiatiewe tot op hede dui aan dat die kwaliteit van die data wat ingesamel is voldoen aan projek- sowel as nasionale vlak verslaggewingsvereistes.

Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Invasive alien species are widely considered to be the second most significant threat to biodiversity globally following direct habitat destruction. The invasion of riparian systems worldwide by alien plants has contributed to profound changes in biodiversity and ecosystem functioning. In South Africa, river banks and river beds are amongst the most severely invaded landscapes, with the most damaging invaders, especially in the Fynbos Biome, being trees and shrubs of the Australian genera Acacia and Eucalyptus. Although large-scale management operations are underway to clear invasive trees and restore ecosystems, little is known regarding opportunities and constraints of native species recovery after alien clearing. The core aim of this thesis is to consider whether key aspects of two widely cited restoration models (successional and alternative-state models) are useful for guiding effective management of severely-invaded riparian vegetation. As a study system, I used the Berg River in the Western Cape, South Africa which is severely impacted by invasive trees, especially Eucalyptus camaldulensis. By linking the studies of constraints for restoration and opportunities for native species recovery, the aim was to provide new possibilities for restoration in riparian zones. The thesis starts by examining constraints to restoration following alien invasion, in particular allelopathy which is one of the factors that exacerbate the impacts of Eucalyptus invasion and inhibit recovery of natural vegetation after clearing. I further assess opportunities for both passive (based on the successional model) and active restoration (based on the alternative-state model) following different strategies for removing invasive trees. The aim is to determine the effectiveness of the different models for sustainable, goal-directed management. Finally, I investigate soil-related properties namely water repellency, soil moisture and infiltration that benefit from alien clearing and subsequent recovery of native vegetation. Work on allelopathy as a restoration constrain showed that the presence of E. camaldulensis along the Berg River negatively affects the recovery of native species. Eucalyptus camaldulensis is allelopathic and induces soil water repellency. I recommend the removal of E. camaldulensis from riparian systems as this has the potential to restore soils to a non-allelopathic and non-repellent state that can pave way for native vegetation recovery. Native vegetation recovery showed mixed results. Restoration based on the successional model was generally efficient, whereas restoration based on tenets of the alternative-state model was inefficient mainly due to the several constraints active restoration faced. Native species recovery was successful on both completely cleared and thinned sites that were treated four years ago. Cover of native trees and shrubs was higher in both completely cleared and thinned sites compared to invaded sites, indicating that both methods promote indigenous vegetation recovery and set the ecosystem on a trajectory towards recovery. To improve recovery through thinning, I propose a new four-stage process to guide management in ensuring good recovery of key native species. Numerous challenges associated with active restoration following fell & stack burning and fell & removal were observed on sites that were treated one year ago. Germination of introduced native species was low in both fell & removal and fell & stack burning sites. Secondary invasion of alien herbs and graminoids, dry summer conditions and low seed germination hindered early native species establishment and recovery. Therefore, for active restoration to achieve its goals, effective recruitment and propagation strategies need to be established. Recruitment of native species was non-existent in the sites that were not seeded; this is attributed to the dominance of alien herbaceous species and graminoids and the depletion of native species in the soil seed bank. Reduction of water repellency of soils after removal of the invasive trees is important as it has the potential to affect the success of native vegetation recovery. On sites where native vegetation was recovering well, soil water repellency ranged from moderately repellent in thinned sites to non-repellent in completely cleared sites. Therefore, successful native species recovery has the potential to improve soil-related ecosystem functions, which will possibly help towards restoring indigenous vegetation. I conclude that the invasive alien tree E. camaldulensis negatively affects the native riparian ecosystem and that strategies to remove the species are needed. Recovery of native vegetation composition, structure and ecosystem function depends on the degree of ecosystem degradation and remaining ecosystem resilience. Besides having clear and effective restoration goals, restoration efforts should also develop realistic solutions to overcome numerous challenges and constraints, before any restoration plan is implemented. Successfully restored riparian ecosystems have potential to increase river flow and may lead to increased availability of water to agriculture, recreation, conservation and for domestic use, resulting in significant water security in South Africa. Both the successional model and the alternative-state model emphasize the need to identify restoration constraints. This study identified allelopathy as an important constrain for restoration and recommends measures to address it so as to facilitate restoration. Recovery based on the successional model was more effective than recovery based on the alternative-state model, which faced several constraints. Models of alternative-states incorporate system thresholds and feedbacks that might explain why the degraded system faced recovery challenges and remained resilient to restoration. / AFRIKAANSE OPSOMMING: Naas habitatverlies word indringer spesies as die grootste bedreiging vir biodiversiteit beskou. Die indringing van riviersisteme wêreldwyd deur uitheemse plante dra by tot groot veranderinge in die biodiversiteit en ekosisteem funksie. In Suid-Afrika, veral in die Fynbos Bioom, is rivieroewers en -beddings van die landskappe wat die meeste ingedring word, meestal deur skadelike indringers soos bome en struike van Australiese genera soos bv. Acacia en Eucalyptus. Alhoewel grootskaalse bestuursoperasies besig is om die indringers te verwyder en ekosisteme te herstel, is min bekend omtrent die geleenthede en beperkinge vir die herstel van inheemse spesies na die verwydering van indringers. Die hoofdoel van hierdie tesis is om die nut te bepaal van die sleutel faktore van twee wyd aangehaalde restorasie modelle (suksessie en alternatiewe-toestand modelle) om die effektiewe bestuur van hewig ingedringde oewers te lei. Die Berg Rivier in die Wes Kaap, Suid-Afrika, is gebruik as studie area. Die Berg Rivier is hewig geimpakteer deur indringers, veral deur Eucalyptus camaldulensis. Die doel was om nuwe geleenthede vir restorasie in rivier areas te voorsien, deur die studies oor beperkinge vir restorasie en geleenthede vir inheemse spesie herstel te verbind. Hierdie tesis begin deur die beperkinge van restorasie na indringing te ondersoek, veral allelopatie wat een van die faktore is wat die impakte van Eucalyptus indringing verhoog en die herstel van natuurlike plantegroei na verwydering van indringer inhibeer. Verder bepaal ek die geleenthede vir beide passiewe (gebaseer op die suksessie model) en aktiewe restorasie (gebaseer op die alternatiewe-toestand model) wat volg op verskillende strategieë van verwydering van indringer bome. Die doel is om die effektiwiteit van die verskillende modelle vir volhoubare, doel georiënteerde bestuur te bepaal. Laastens het ek die grond verwante eienskappe ondersoek naamlik, water terugdrywing, grondvog en infiltrasie wat voordeel trek uit indringer verwydering en die daaropvolgende herstel van inheemse plantegroei. Resultate van allelopatie as ʼn restorasie beperking het getoon dat die teenwoordigheid van E. camaldulensis langs die Berg Rivier die herstel van inheemse spesies negatief beïnvloed. Eucalyptus camaldulensis is allelopaties en gee aanleiding tot grondwater terugdrywing. Ek beveel aan die verwydering van E. camaldulensis vanuit rivier sisteme omdat dit die potensiaal het om grond na nie-allelopatiese en nie-terugdrywende toestand te herstel wat die weg kan baan vir die herstel van inheemse plante groei. Die herstel van inheemse plantegroei het gemengde resultate gewys. Restorasie gebaseer op die suksessie model was oor die algemeen meer doelmatig, teenoor restorasie gebaseer op die idee van ʼn alternatiewe-toestand model, hoofsaaklik as gevolg van verskeie beperkinge wat aktiewe restorasie in die gesig staar. Inheemse spesie herstel was suksesvol op beide die totaal indringer verwyderde en uitgedunde areas, wat vier jaar vantevore behandel is. Dekking van inheemse bome en struike was hoër in beide heeltemal skoongemaakte en uitgedunde areas wanneer die vergelyk word met ingedringde areas. Dit dui daarop dat beide metodes inheemse plantegroei herstel promoveer en die ekosisteem op ʼn baan na herstel plaas. Om herstel deur uitdunning te verbeter stel ek ʼn vier-stadium proses voor om bestuurders te lei vir goeie herstel van sleutel inheemse spesies. Verskeie uitdagings geassosieer met aktiewe restorasie wat volg op val-en-stapel brand en val-en-verwyder is geobserveer in areas wat ʼn jaar van te vore behandel is. Ontkieming van aangeplante inheemse spesies se sade was laag in beide die val-en-verwyder en die val-en-stapel brand areas. Sekondêre indringing van uitheemse kruie en graminoiede, droë somers toestande en lae saad ontkieming hinder die vroeë inheemse spesie vestiging en herstel. Dus, vir aktiewe restorasie om sy doel te bereik moet effektiewe werwing en verspreidings strategieë in plek wees. Daar was geen werwing van inheemse spesies in die areas wat nie gesaai was nie. Dit kan toegeskryf word in die dominansie van uitheemse kruie spesies and graminoiede en die uitputting van inheemse spesies in die grond saadbank. Vermindering van water terugdrywing van grond ná verwydering van indringer bome is belangrik aangesien dit die potensiaal het om die sukses van inheemse plantegroei herstel te affekteer. Die areas waar inheemse plantegroei goed herstel het, het grondwater terugdrywing gevarieer van gemiddeld afstootlik in die uitgedunde areas na nie-afstootlik in die heeltemal skoongemaakte areas. Dus, suksesvolle inheemse spesie herstel het die potensiaal om die grondverwante ekosisteem funksies te verbeter, wat moontlik sal bydra tot die herstel van inheemse plantegroei. Ek kom tot die gevolgtrekking dat die indringer boom E. camaldulensis die inheemse rivier ekosisteem negatief affekteer en dat strategieë om hierdie spesie te verwyder nodig is. Herstel van inheemse plantegroei samestelling, struktuur en ekosisteem funksie hang af van die graad van ekosisteem verval en die oorblywende ekosisteem weerstandigheid. Behalwe die verwyderings en effektiewe restorerings doelwitte, moet restorasie pogings ook realistiese oplossings vir die oorkombaarheid van verskeie uitdagings en beperkinge ontwikkel voor enige restorasie plan geïmplementeer kan word. Suksesvolle herstel van rivier ekosisteme het die potensiaal vir verhoogde rivier vloei en mag moontlik lei tot ʼn verhoogde beskikbaarheid van water vir landbou, ontspanning, natuurbewaring en vir huishoudelike gebruik, en kan dus ʼn beduidende bydrae kan lewer tot water sekuriteit in Suid Afrika. Beide die suksessie model en die alternatiewe-toestand model beklemtoon die noodsaaklikheid om restorasie beperkinge te identifiseer. Hierdie studie identifiseer allelopatie as ʼn belangrike beperking tot restorasie en maak aanbevelings om dit aan te spreek en om restorasie te fasiliteer. Herstel gebaseer op die suksessie model was meer effektief as herstel gebaseer op die alternatiewe-toestand model wat verskeie beperkings in die gesig staar. Die alternatiewe-toestand modelle inkorporeer sisteemdrumpels en terugvoer wat moontlik kan verduidelik waarom gedegradeerde sisteme herstel uitdagings getoon het en weerstandig teenoor restorasie gebly het.

Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Biofuels are being promoted as a global necessity to meet climate change targets through the replacement of fossil fuels. Many countries have identified biofuels as a potential mechanism to meet these challenges, with policy directives driving biofuel production. The South African government has proposed that biofuels form part of the country’s future renewable energy and has proposed a draft biofuel strategy. This study aims to investigate appropriate approaches to determine potential biodiversity impacts from biofuel production. Since biofuels are not currently grown to any large extent in South Africa, impact was modelled using future scenarios of converting available land within the Eastern Cape Province of South Africa. Suitable species were identified using the species distribution modelling programme MaxEnt. Some of the proposed biofuel crops were considered as invasive (i.e. they spread from sites where they are cultivated) or are very likely to be invasive in South Africa. This study also highlighted the considerable overlap between suitable growing areas and areas considered important for future biodiversity conservation. The biodiversity intactness index (BII), a broad based biodiversity indicator, was used to assess the biodiversity implications of transforming available land to biofuels. The BII indicates losses of biodiversity between 17.6% and 42.1% for the land use scenarios identified. An important finding was that excluding important biodiversity areas that occur outside of protected areas can reduce biodiversity losses by as much as 13% and maintain an overall intactness of ~70%. Currently the BII does not account for fragmentation or landscape configuration. This was addressed by developing a revised biodiversity intactness index (R-BII) which included the effect of patch-size and habitat fragmentation on biodiversity intactness. This study found that although the original BII reported on the biodiversity trends of large-scale shifts in land-use across multiple scales it could not detect changes in landscape configuration which was reflected by the R-BII. Land-use change can impact on ecosystem processes that underpin the provisioning of ecosystem services by changing the combinations of species and the plant functional traits within communities. The impacts of cultivating potential biofuel species (Acacia mearnsii, Sorghum halepense and Eucalyptus species) were investigated using a plant functional traits approach. These species were shown to affect the leaf nitrogen content, leaf phosphorous content and leaf dry matter content associated with important ecosystem functions within an ecosystem service hotspot in the Eastern Cape. A decline in functional diversity was reported for all transformed land-uses by as much as ~40%. These shifts may be used to identify potential changes to ecosystem services associated with natural vegetation. The methods used in this thesis highlight the overall relevance of this work and its importance to minimising biodiversity resulting from biofuel production. Some of the key findings address resolving spatial conflict, using biodiversity indicators, assessing impacts of potential invasive species and planning for ecosystem services. New drivers of change to land-use, such as biofuel production, are a major challenge to conservation biologists and planners and the insights derived in from this study can be successfully applied to guide biofuel production. / AFRIKAANSE OPSOMMING: Biobrandstof word internasionaal beskou as 'n noodsaaklike komponent in die bereiking van klimaatsverandering doelwitte deur fossielbrandstowwe daarmee te vervang. Daarom word biobrandstof deur verskeie lande geïmplementeer as 'n potensiële meganisme om aan hierdie uitdaging te voldoen. Die Suid-Afrikaanse regering het voorgestel dat biobrandstof deel vorm van die land se hernubare energie toekoms en het daarom 'n konsep biobrandstofstrategie voorgestel. Die aanvaarding van so 'n strategie sal waarskynlik ‘n aantal verreikende gevolge inhou. Hierdie studie gebruik verskeie benaderings ten einde die impak van biobrandstof produksie op biodiversiteit te bepaal. Aangesien biobrandstof nie tans ‘n beduidende bydra maak tot tradisionele brandstofproduksie in Suid-Afrika nie, word die impak daarvan geskoei op die omskakeling van beskikbare grond. Die Oos-Kaap provinsie van Suid-Afrika speel a sleutelrol in hierdie opsig en vorm daarom die fokus van hierdie analise. Geskikte spesies is geïdentifiseer deur die sagtewareprogram, MaxEnt, waardeur spesiesverspreiding gemodelleer word. Hierdie studie beklemtoon die aansienlike oorvleueling wat daar bestaan tussen geskikte aanplantingsgebiede en belangrike biodiversiteitsareas wat nie tans formeel bewaar word nie. Sommige van die voorgestelde biobrandstofgewasse is tans indringers, of het die potensiaal om indringerplante te word en daarom is daar toenemende kommer oor die kweek van biobrandstof gewasse in Suid-Afrika. Die “Biodiversity Intactness Index” (BII), 'n algemene biodiversiteitsaanwyser, is gebruik om die implikasies van grondomskakeling na biobrandstof op biodiversiteit te evalueer. Die BII dui op verliese van tussen 17,6% en 42,1% vir die grondgebruikscenario's wat geïdentifiseer is. 'n Belangrike bevinding was dat die uitsluiting van belangrike biodiversiteitsareas buite beskermde gebiede die verlies van biodiversiteit met soveel as 13% kan verminder en biodiversiteit eenheid van ~ 70% kan behou. Die BII maak egter nie tans voorsiening vir landskap fragmentasie nie. ‘n “Revised-Biodiversity Intactness Index” (R-BII) is ontwikkel wat die effek van kol-grootte en habitat op biodiversiteit eenheid insluit. Hierdie studie het bevind dat alhoewel die oorspronklike BII grootskaalse verandering in die grondgebruik op verskeie skale aandui, dit egter nie verandering in landskapsamestelling kon opspoor soos die R-BII nie. Ten slotte, die impak van die aanplanting van potensiële biobrandstofspesies (Acacia mearnsii, Sorghum halepense en Eucalyptus spesies) op biodiversiteit is ondersoek deur ‘n plant funksionele eienskappe benadering te gebruik. Daar is bevind dat hierdie spesies die stikstof, fosfor en droë materiaal inhoud van blare verander wat geassosieer word met belangrike ekosisteem funksies binne 'n biodiversiteit brandpunt in die Oos- Kaap. ‘n Vermindering van funksionele diversiteit van soveel as ~ 40% is binne alle omgeskakelde grondgebruike gevind. Hierdie skuiwe kan gebruik word om potensiële veranderinge van ekosisteemdienste te identifiseer en benadruk ook die potensiële impak van uitheemse spesies. Die metodes wat gebruik word in hierdie studie beklemtoon die relevansie van die werk asook die belangrikheid daarvan om die nadelige uitwerking van biobrandstofproduksie op biodiversiteit te minimaliseer. Verskeie benaderings tot die oplossing van ruimtelike konflik, die gebruik van biodiversiteitaanwysers, die beoordeling van die impak van die potensiële indringerspesies en die beplanning vir ekosisteemdienste. Nuwe dryfvere van grondgebruikverandering soos biobrandstof is 'n groot uitdaging en die insigte wat uit hierdie studie verkry is dra by tot die vermindering van die potensiële impak van biobrandstofproduksie op biodiversiteit.

PhD / Thesis (PhD (Botany and Zoology))—University of Stellenbosch, 2009. / An intriguing biogeographic area that lies in northwestern Namibia and southwest Angola is known for having numerous endemic taxa. It had, however remained vaguely defined because of the complex flora, the arid environment and confusing and inconsistent use of biogeographic terminology. This thesis redefined the area as a centre of endemism based on recurrent patterns of plant distributions by shared species. The end result is a well-defined entity with regard to, not only geographic boundaries and floristic elements, but also to its history and floristic relationships. A vast amount of information on the plants of the area, their affinities and their distributions is required for a study of this nature and this was undertaken through literature surveys and field work. All the relevant information on Namibia and the southwestern Angolan flora, i.e. the region and the study area, were incorporated into a database which formed the bases for numerical analysis and GIS studies. The database also brought together a wide range of information from literature sources that included facts and theories about the past and present physical environment. The structure of the database permitted querying this electronic data in many different ways. To accommodate the wide variety of subjects in a logical way, the thesis was divided into two sections. Section A concentrated on the region and provided background information and context. The theory, terminology and phytogeographic studies in the region were evaluated as a first step. A large amount and variety of palaeo-environmental and palaeo-ecological information, pertinent to the region was incorporated. Secondly the flora was assessed. Besides the diversity, distribution patterns of the plants within and outside the region, including disjunct distributions, phylogenies were assessment. Finally taxa with similar geographic ranges were grouped. These entities were mapped and both the taxa and their environments were evaluated Section B focused on the core area, namely the Kaokoveld Centre of Endemism, which was delimited by numerical techniques, and then investigated further with regard to its floristic components, relationships and origins. The flora and endemic components are described in detail. The result is a well-defined centre of endemism which comprises one endemic family, 10 endemic genera and nearly 300 endemic species. The flora of the Centre includes about 1600 species in nearly 550 genera in 130 families. Three floristic Groups, identified in section A, that have a remarkable number of endemics are found in the Centre. Historical explanations for the distribution patterns were suggested and the Group that includes Welwitschia mirabilis Hook.f., has been shown to be linked to the Arid Corridor. The demand for accurate knowledge about biodiversity has been highlighted by the Convention of Biological Diversity and there are a remarkable number of users with different requirements today. This study provides a much needed alternate look at the plants of the region, as well as a summation of the principle phytogeographic elements of the Namibian flora. It also includes a new phytogeographic classification and map of the floristic Groups of Namibia, which will contribute to defining floristic areas in the region.

Thesis (MSc )--Stellenbosch University, 2010. / ENGLISH ABSTRACT: The patterns of spread of non-indigenous species and the factors influencing their distribution have been studied infrequently on Southern Ocean Islands, where the prevention and control of biological invasions is a priority for conservation management. Owing to its remoteness and relatively small size, sub-Antarctic Marion Island provides an ideal opportunity to investigate the patterns of spread of invasive species and the factors likely influencing the distribution of alien species. Therefore, this study provides a spatially explicit documentation of the alien and invasive vascular plant species on Marion Island, the change in their distribution patterns through time, an assessment of the correlates of the current distributions, documentation of species rich areas, and provides recommendations for control based on these data and life history data available for each species. To ensure comprehensive coverage for the current estimate of distributions, a combination of a systematic (spatially explicit) survey and an ad hoc data collection method was used to examine the abundance and occupancy of each alien plant species across the island. The spatially explicit survey was used to identify sampling sites on a ½ minute by ½ minute scale (926 m × 926 m) which resulted in 348 sites across the island, whereas 2356 additional presence records were added during the ad hoc sampling. The residence time of each species was also estimated from the first records reported in various literature. While it has been documented in many studies that residence time is an important factor explaining species distribution, this study showed that distribution of alien species on Marion Island is not explained by residence time. The alien plant species on Marion Island differ markedly in their occupancy, distribution and rate of expansion. Agrostis stolonifera, Cerastium fontanum, Poa annua and Sagina procumbens are all expanding their ranges, whereas the range of Stellaria media appears to be contracting. Cerastium fontanum is the most widespread species on Marion Island while Sagina procumbens is the most abundant (number of records) and most rapidly expanding species on both Marion and Prince Edward Islands. Generalized linear models demonstrated that altitude, distance to human disturbed sites, and nearest neighbour presence are all significant and often strong correlates of spatial variation in alien vascular plant species richness and individual species presences on Marion Island. In particular, alien species richness on Marion Island declines sharply with increasing elevation, and that the distribution of the most widespread species is spatially aggregated. The surroundings of the Meteorological station and Mixed Pickle hut exhibit high richness and a high likelihood of the presence of individual species. None of the models developed for this study resulted in habitat type being significant explanatory variable for the distribution of any of the alien plant species, although from the records alone it is clear that the salt spray vegetation type is avoided. Together with assessments of the life history of the species, the current distribution data suggest that few alien plant species can be easily eradicated. Most are already too widespread already for cost effective eradication. Moreover, given the current rate of spread of Agrostis stolonifera, Cerastium fontanum, Poa annua and Sagina procumbens, and their apparent lack of habitat preference, it seems likely that within the next few decades many lowland habitats will be dominated by these species. By contrast, Rumex acestosella, Agrostis gigantea, Agropyron repens, Juncus effusus, Luzula cf. multiflora and the newly established shrub species should be the subject of control or eradication efforts. This thesis provides comprehensive baseline data on alien vascular plant distributions as a benchmark for future assessments. / AFRIKAANSE OPSOMMING: Die verspreidingspatrone van uitheemse spesies en die faktore wat hulle verspreiding beïnvloed is selde op Suidelike Oseaan Eilande bestudeer, waar die voorkoming en beheer van biologiese indringing ‘n prioriteit is vir bewaringsbestuur. Te danke aan sy afgeleëndheid en relatiewe klein grootte, voorsien sub-Antarktiese Marion Eiland ‘n ideale geleentheid om die patrone van verspreiding van indringer spesies en die faktore wat moontlik die verspreiding van uitheemse spesies beïnvloed te ondersoek. Daarom voorsien hierdie studie ‘n ruimtelik eksplisiete dokumentering van die uitheemse en indringer vaatplant spesies op Marion Eiland, die verandering in hulle verspreidingspatrone oor tyd, ‘n bepaling van die korrelasies van die huidige verspreidings, dokumentering van spesiesryke areas, en voorsien aanbevelings vir beheer gebasseer op hierdie data en die lewensloopdata beskikbaar vir elke spesie. Om omvattende dekking vir die huidige skatting van vespreidings te verseker, is ‘n kombinasie van sistematiese en ad hoc metodes gebruik om die talrykheid en besetting van elke uitheemse spesie oor die eiland te ondersoek. Die ruimtelik eksplisiete opname is gebruik om moniteringsplotte op ‘n ½ minuut by ½ minuut skaal (926 m × 926 m), met die resultaat van 348 plotte oor die eiland, terwyl 2356 addisionele voorkomsrekords bygevoeg is tydens die ad hoc versameling. Die verblyftyd van elke spesie is ook beraam vanaf die eerste rekords in die literatuur. Terwyl dit aangeteken is dat verblyftyd ‘n belangrike faktor is om spesie verspreiding te verduidelik, wys hierdie studie dat verspreiding van uitheemse spesies op Marion Eiland nie verduidelik word deur verblyftyd nie. Die uitheemse spesies op Marion Eiland verskil aansienlik in hulle besetting, verspreiding en tempo van uitbreiding. Agrostis stolonifera, Cerastium fontanum, Poa annua en Sagina procumbens brei almal hulle areas uit, terwyl die area van Stellaria media bleik te krimp. Cerastium fontanum is die mees wydverspreide spesie op Marion Eiland, terwyl Sagina procumbens die oorvloedigste (aantal rekords) en die vinnigste uitbreidende spesie is op beide Marion en Prince Edward Eiland. Veralgemeende lineêre modelle het aangetoon dat hoogte, afstand na menslike versteurde plotte, en naaste buurman teenwoordigheid almal betekenisvol is en gereeld sterk korreleer met ruimtelike variasie in uitheemse vaatplant spesierykheid en individuele spesie voorkoms op Marion Eiland. Uitheemse spesierykheid op Marion Eiland neem in besonder sterk af met ‘n toename in hoogte en die verspreiding van die mees wyduitgebreide spesies is ruimtelik saamgesteld. Die omgewing om die Weerstasie en Mixed Pickle hut toon hoë rykheid en ‘n hoë waarskynlikheid van die voorkoms van individuele spesies. Nie een van die modelle wat vir hierdie studie ontwikkel is toon ‘n belangrikheid in habitat tipe as ‘n verduidelikbare veranderlike vir die verspreiding van enige van die uitheemse plant spesies nie, alhoewel vanuit die rekords alleen is dit duidelik dat soutsproei plantegroei nie verkies word nie. Tesame met ondersoeke oor die lewensloop van die spesies, stel die huidige verspreidingsdata voor dat min uitheemse plant spesies maklik uitgeroei kan word. Die meeste is eenvoudig te wydverspreid vir koste effektiewe uitroeiing. Voorts, gegewe die huidige tempo van uitbreiding van Agrostis stolonifera, Cerastium fontanum, Poa annua en Sagina procumbens en hulle skynbare gebrek aan habitat voorkeur, is dit hoogs waarskynlik dat baie van die laerliggende habitatte binne die volgende paar dekades gedomineer sal word deur hierdie spesies. In teenstelling, Rumex acestosella, Agrostis gigantea, Agropyron repens, Juncus effusus, Luzula cf. multiflora en die nuutgevestigde struik spesie moet die fokus wees van beheer/uitroeiing pogings. Hierdie tesis voorsien omvattende basislyn data oor uitheemse vaatplantverspreidings as ‘n standaard vir toekomstige ondersoeke. / This project was funded by the South African National Antarctic Programme of the National Research Foundation (NRF – SANAP). Additional funding was provided by The Prince Edward Islands book fund.

Thesis (MSc (Botany and Zoology))--University of Stellenbosch, 2005. / South Africa is one of the most biodiverse countries in the world and even with conservation initiatives in place continues to face biodiversity loss. There is a need to prioritise areas for conservation as resources for conservation purposes are limited in South Africa. From prioritisation methods reviewed it was found that prioritisation indices normally use one or a combination of variables that measure stock; and/or variables that measure threat.