Thesis (MSc)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The Cape Floristic Region (CFR) is situated at the southern tip of Africa and possesses a flora that is unique amongst the floras of the rest of the world, both in terms of its incredibly high species richness, and its high levels of endemism. Proteaceae, the family to which Serruria belongs, is widely distributed amongst the landmasses of the southern hemisphere, with its centres of diversity occurring in Australia and southern Africa. Previous molecular and morphological analyses performed on the South African subfamily Proteoideae have shown Serruria, a CFR endemic, to form a well-supported monophyletic group. Based upon the strong monophyly of Serruria, DNA sequence data were collected for 53 of the 55 species from the plastid (rps16 intron, atpB-rbcL intergenic spacer, trnL-F region and psbA-trnH intergenic spacer) and nuclear (internal transcribed spacer region or ITS) genomes in order to investigate evolutionary relationships within the genus. Spatalla taxa were used as the outgroup. Both parsimony and Bayesian analyses were carried out on each of these data sets. The resulting trees were reasonably well resolved. All the Serruria taxa grouped together in a well-supported clade, except for S. f1ava, which emerged well within the Serruria clade in the analyses of the nuclear genome, but outside the clade in the plastid analyses. It was therefore proposed that this taxon represents a hybrid. Apart from this case, there was widespread agreement between the trees reconstructed using data from the two genomes. The plastid and nuclear data were therefore combined in order to analyse the data sets together. The molecular data does not support most of the groupings proposed by previous authors based on morphological data. Additionally, in some cases, multiple representatives of species do not group together. These specimens probably do not represent monophyletic taxa. Current ideas about relationships within Serruria are based predominantly on floral characters, and it is suggested that pollinator pressures have led to plasticity in the floral characters. Consequently, it is evident from this study that relationships within Serruria need to be re-examined in order to determine the patterns of evolution within the genus. / AFRIKAANSE OPSOMMING: Die Kaapse Floristiese Streek is aan die suiderpunt van Afrika geleë, en beskik oor 'n unieke flora relatief tot ander wêreldfloras, beide ten opsigte van die ongelooflike hoë spesie diversiteit en die hoë vlakke van endemisme. Proteaceae, die familie waaraan Serruria behoort, kom wydverspreid tussen die vastelande van die Suidelike Halfrond voor, en het diversiteitsentrums in Australië en suider Afrika. Vorige molekulêre sowel as morfologiese analises wat op die Suid-Afrikaanse subfamilie Proteoideae uitgevoer is, dui aan dat Serruria (wat endemies is tot die Kaapse Floristiese Streek) 'n goed ondersteunde monofiletiese groep is. Gebaseer op die sterk monofilie van Serruria, is DNA-volgorde-data vir 53 van die 55 spesies vanuit die plastied (rps16 intron, atpB-rbcL intergeniese spasie, trnL-F area en psbA-trnH intergeniese spasie) en kern (intern getranskribeerde spasie area, ook ITS genoem) ingewin om die evolusionêre verwantskappe binne die genus te ondersoek. Spatalla is as die buitegroep gebruik. Beide parsimonie en Bayesian analises is op elk van hierdie datastelle uitgevoer. Die resulterende bome het redelike hoë resolusie getroon. AI die Serruria-taxa het in 'n goed ondersteunde klade saam gegroepeer, behalwe vir S. f1ava, wat binne die Serruria klade val vir die kern genoom, maar buite die klade vir die plastied analise. Dit is dus voorgestel dat hierdie taxon as 'n hibried beskou mag word. Behalwe vir hierdie geval, was daar wydverspreide ooreenstemming tussen die bome wat verkry is vanaf data van die twee genome. Die plastied- en kern-data is derhalwe gekombineer om die datastelle saam te kan analiseer. Die molekulêre data ondersteun nie die meerderheid van morfologiese groeperings wat deur verskeie outeurs voorgestel is nie. Verder, in sommige gevalle, groepeer verskillende monsters van dieselfde spesies nie bymekaar nie. Dit is derhalwe voorgestel dat hierdia taxa nie monofileties is nie. Huidige idees omtrent die verwantskappe binne Serruria is grotendeels op blommorfologiese kenmerke gebaseer, en dit word voorgestel dat bestuiwing-druk gelei het tot plastisiteit van die blommorfologiese kenmerke. Verskille tussen die bome wat uit plastied- en kern-data gerekonstrueer is word aan vroeëre hibridisasie gebeure toegeskryf. Op grond van hierdie studie is dit duidelik dat die verhoudings binne Serruria verder ondersoek moet word om die patrone van evolusie binne die genus te bepaal.

Thesis (M.Sc.)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: It is well known that smoke and aqueous smoke solutions promote the germination of certain seeds. This has considerable practical implications for restoration in fire prone areas like the Cape fynbos. The aqueous smoke solution (more commonly known as smoke water) can be used in restoration projects to stimulate seeds to germinate faster so that a wide diversity of plants can be established rapidly. Smoke water is made using different methods and different plant materials. This inevitably results in different concentrations of smoke water. Although made in different ways, different smoke waters may all have an enhancing effect on seed germination. In this study, the germination of Grand Rapids lettuce seed was used to determine the differences between five different types of smoke water. Germination was done in a controlled environment, using through-flow germination boxes (patent no. ZA2000/1832, registered 1114/2000) instead of traditional petri dishes. The differences in the concentrations were determined using bioassays. A very strong concentration of smoke water damaged the seed and a very weak concentration did not have any enhancing effect on germination. The concentrations of the different smoke waters were compared to a standard smoke solution (the first smoke solution ever made, that of De Lange & Boucher (1990». The different concentrations of the smoke solutions were determined by comparing them to the standard, using a best fit line on the germination graphs. Each of the smoke solutions tested is given a "delb" rating (after De Lange & Boucher), with the standard smoke water being 1 delb. The delb value is used to determine the dilution factor for each smoke solution. It is concluded that the five smoke solutions tested all differed from each other emphasizing the need for quality control in commercial and experimental applications. / AFRIKAANSE OPSOMMING: Dit is wel bekend dat rook en vloeibare rook oplossings (rookwater) die ontkieming van sekere sade bespoedig. Dit het groot praktiese implikasies vir hervestiging in gebiede met gereelde vuur, soos die Kaapse fynbos. Die rookwater kan in hervestiginsprojekte gebruik word om sade te stimuleer om vinniger te ontkiem om sodoende 'n groot diversiteit van plante vinnig te vestig. Rookwater word op verskillende maniere en met verskillende materiaal vervaardig. Dit kan lei tot verskillende konsentrasies rookwater, alhoewel al die verskillende rookwaters 'n stimulerende effek op saadontkieming kan bewerkstellig. In hierdei studie is Grand Rapids slaai saad gebruik om die verskille tussen vyf verskillende rookwaters te ondersoek. Ontkieming was in 'n beheerde atmosfeer gedoen en deurvloei ontkiemingsbakke (patent nr. ZA2000/1832, geregistreer 11/4/2000) is gebruik, i. p. v. traditionele petri bakkies. Die verskille in konsentrasies is gemeet m. b. v. biotoetse. 'n Baie serk konsentrasie het die sade beskadig en 'n baie flou konsentrasie het geen stimulerende effek op ontkieming gehad nie. Die konsentrasie van die verskillende rookwaters is vergelyk teenoor 'n standaard rookwater (die eerste rookwater ooit gemaak, die van De Lange en Boucher (1990». Die verskillende rookwater konsentrasies is bepaal deur dit met die standaard te vergelyk m. b. v. 'n regressie lyn op die ontkiemingsgrafieke. Elke rookwater getoets kry dan 'n "delb" waarde (n. a. v. De Lange & Boucher), met die standard gelyk aan 1 delb. Die delb waarde word gebruik om die optimale verdunning van elke rookwater te bepaal. Daar word opgesom dat al die rookwaters getoets wel van mekaar verskil en dit beklemtoon die waarde van kwaliteits beheer in kommersiële en eksperimentele toepassings.

Thesis (MSc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: This investigation was undertaken to determine whether elevated concentrations of dissolved inorganic carbon (DIC) supplied to plant roots could improve plant growth and alleviate the effects of salinity stress on tomato plants infected with arbuscular mycorrhizae. Lycopersicon esculentum cv. FI44 seedlings were grown in hydroponic culture (pH 5.8) with 0 and 75 mM NaCI and with or without infection with the fungus Glomus mosseae. The root solution was aerated with ambient CO2 (360 ppm) or elevated CO2 ( 5 000 ppm) concentrations. The arbuscular and hypha I components of mycorrhizal infection as well as the percentages total infection were decreased or increased according to the variation in seasons. The plant dry weight of mycorrhizal plants was increased by 30% compared to non-mycorrhizal plants at elevated concentrations of CO2, while the dry weight was decreased by 68% at ambient CO2 concentrations. Elevated CO2 also stimulated the growth of the mycorrhizal fungus. Elevated CO2 increased the plant dry weight and stimulated fungal growth of mycorrhizal plants possibly by the provision of carbon due to the incorporation of HCO)- by PEPc. Plant roots supplied with elevated concentrations of CO2 had a decreased CO2 release rate compared to roots at ambient CO2. This decrease in CO2 release rate at elevated CO2 was due to the increased incorporation of HC03- by PEPc activity. Under conditions of salinity stress plants had a higher ratio of N03-: reduced N in the xylem sap compared to plants supplied with 0 mM NaCI. Under salinity stress conditions, more N03- was transported in the xylem stream possibly because of the production of more organic acids instead of amino acids due to low P conditions under which the plants were grown. The N03· uptake rate of plants increased at elevated concentrations of CO2 in the absence of salinity because the HCO)- could be used for the production of amino acids. In the presence of salinity, carbon was possibly used for the production of organic acids that diverted carbon away from the synthesis of amino acids. It was concluded that mycorrhizas were beneficial for plant growth under conditions of salinity stress provided that there was an additional source of carbon. Arbuscular mycorrhizal infection did not improve the nutrient uptake of hydroponically grown plants. / AFRIKAANSE OPSOMMING: In hierdie studie was die effek van verhoogde konsentrasies opgeloste anorganiese koolstof wat aan plant wortels verskaf is, getoets om te bepaal of dit die groei van plante kan verbeter asook of sout stres verlig kon word in tamatie plante wat met arbuskulêre mikorrhizas geïnfekteer was. Lycorpersicon esculentum cv. FJ44 saailinge was in water kultuur gegroei (pH 5.8) met 0 en 75 mM NaCI asook met of sonder infeksie met die fungus Glomus mosseae. Die plant wortels was bespuit met normale CO2 (360 dele per miljoen (dpm)) sowel as verhoogde CO2 (5 000 dpm) konsentrasies. Die arbuskulere en hife komponente, sowel as die persentasie infeksie was vermeerder of verminder na gelang van die verandering in seisoen. Die plant droë massa van mikorrhiza geïnfekteerde plante by verhoogde CO2 konsentrasies was verhoog met 30% in vergelyking met plante wat nie geïnfekteer was nie, terwyl die droë massa met 68% afgeneem het by gewone CO2 konsentrasies. Verhoogde CO2 konsentrasies het moontlik die plant droë massa en die groei van die fungus verbeter deur koolstof te verskaf as gevolg van die vaslegging van HCO)- deur die werking van PEP karboksilase. Plant wortels wat met verhoogde CO2 konsentrasies bespuit was, het 'n verlaagde CO2 vrystelling getoon in vergelyking met die wortels by normale CO2 vlakke. Die vermindering in CO2 vrystelling van wortels by verhoogde CO2 was die gevolg van die vaslegging van HC03- deur PEPk aktiwiteit. Onder toestande van sout stres, het plante 'n groter hoeveelheid N03- gereduseerde N in die xileemsap bevat in vergelyking met plante wat onder geen sout stres was nie, asook meer NO)- was in die xileemsap vervoer moontlik omdat meer organiese sure geproduseer was ten koste van amino sure. Dit was die moontlike gevolg omdat die plante onder lae P toestande gegroei het. Die tempo van NO.; opname was verhoog onder verhoogde CO2 konsentrasies en in die afwesigheid van sout stres omdat die HCO)- vir die produksie van amino sure gebruik was. In die teenwoordigheid van sout was koolstof moontlik gebruik om organiese sure te vervaardig wat koolstof weggeneem het van die vervaardiging van amino sure. Daar is tot die slotsom gekom dat mikorrhizas voordelig is vir die groei van plante onder toestande van sout stres mits daar 'n addisionele bron van koolstof teenwoordig is. Arbuskulere mikorrhiza infeksie het 'n geringe invloed gehad op die opname van voedingstowwe van plante wat in waterkultuur gegroei was.

Thesis (MSc)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The effects of regulated deficit irrigation on the production and fruit quality of peaches were investigated. A field trial was carried out in a twelve-year-old Neethling peach orchard at Robertson Experiment Farm. Treatments consisted of five different soil water depletion levels applied during five different growth stages. Irrigation was applied at the five soil water depletion levels of which T1 was regarded as relatively wet (irrigation was applied when the average soil matric potential reached ca. -50 kPa). T2 was regarded as normal (irrigation applied at ca. -100 kPa) and three different deficit irrigation regimes T3, T4 and T5, irrigated at soil matric potentials of ca. -200, -400 and -800 kPa respectively. The five growth stages were Stage 1 (cell growth), Stage 2 (slow fruit growth), Stage 3 (rapid fruit growth), Stage 4 (ripening) and Stage 5 (post-harvest). The soil water content was monitored and irrigation was scheduled by means of a neutron probe. Vegetative and fruit growth, fruit mass and production were measured. Fruit were examined for bruises and firmness. Fruit size, fruit mass, fruit quality, as well as production, were not sensitive to water deficits during the different growth stages with a normal crop load. However, a tendency to reduced shoot growth with decreasing soil matric potentials was observed during the slow fruit growth, rapid fruit growth as well as the ripening stages. The application of deficit irrigation during the slow fruit growth or post-harvest stages can save substantial amounts of water with a normal crop load, provided that normal irrigation is applied during the other growth stages. A combination of water deficits during the ripening stage and high crop load resulted in smaller fruit and lower production. Fruit size, fruit mass, fruit quality, as well as production, were not sensitive to water deficits during either the cell growth, slow fruit growth or post harvest growth stages, provided that normal irrigation is applied in the other growth stages. Irrespective of crop load, soil matric potentials up to -200 kPa can be applied during anyone of the growth stages without seriously affecting the final fruit size, fruit mass, fruit quality or production. However, this soil water deficit may then only be applied in one of the growth stages and normal irrigation must be applied in the other four stages. Although deficit irrigation reduced seasonal water consumption, it could not be justified as water saving with a heavy crop load. / AFRIKAANSE OPSOMMING: Die effekte van gereguleerde tekort besproeiing op die produksie en vrugkwaliteit van perskes is ondersoek. 'n Veldproef is in 'n twaalf-jaar-oue Neethling perskeboord te Robertson Proefplaas uitgevoer. Die behandelings het bestaan uit vyf grondwater-ontrekkingspeile wat gedurende vyf verskillende groeistadiums toegepas is. Besproeing is toegedien by vyf verskillende grondwaterontrekkingsvlakke waar T1 beskou is as redelik nat (besproeiing is toegedien wanneer gemiddelde grondmatrikspotensiale ca. -50 kPa bereik het). Behandeling T2 is as normaal beskou (besproeiing toegedien by ca. -100 kPa en drie verskillende regimes van tekort besproeiing naamlik T3, T4 en T5 wat onderskeidelik by ca. -200, -400 en -800 kPa besproei is. Die vyf groeistadiums was onderskeidelik Stadium 1 (selgroei), Stadium 2 (stadige vruggroei), Stadium 3 (vinnige vruggroei), Stadium 4 (rypwording) en Stadium 5 (na-oes). Die grondwaterinhoud is gemonitor en die besproeiing is met behulp van 'n neutronpeiler geskeduleer. Vegetatiewe groei, vruggroei, vrugmassa en produksie is gemonitor. Vrugte is ook ondersoek vir kneusbaarheid en fermheid. Geen negatiewe effek as gevolg van watertekorte is ten opsigte van vruggrootte, -massa, -kwaliteit sowel as produksie waargeneem gedurende die verskillende groeistadiums waar 'n normale vruglading gehandhaaf is nie. 'n Afnemende tendens in lootgroei met afnames in grondwatermatrikspotensiale is egter gedurende die stadige- en vinnige vruggroei-stadiums, asook in die vrugrypwordingstadium, waargeneem. 'n Aansienlike hoeveelheid water kan bespaar word deur gereguleerde tekort besproeiing gedurende die stadige vruggroei- of na-oes-stadiums toe te pas, mits 'n normale vruglading gehandhaaf word en normale besproeiing in die ander groeifases toegedien word. 'n Kombinasie van watertekorte en 'n hoë vruglading gedurende die rypwordingstadium het tot kleiner vrugte en laer produksies gelei. Vruggrootte, -massa, -kwaliteit en produksie is egter nie gevoelig vir watertekorte gedurende die selgroei-, stadige vruggroei- en na-oes-stadiums nie. Tekort besproeiing by 'n grondwatermatrikspotensiaal van tot -200 kPa kan egter met 'n normale en hoë vruglading in enige van die fases toegepas word, sonder om die finale vruggrootte, -massa, - kwaliteit of produksie nadelig te beïnvloed. Hierdie tekort besproeiingsregime mag egter slegs in een van die groeistadiums toegedien word en normale besproeiings moet in die ander groeistadiums toegedien word. Alhoewel tekort besproeiing die seisoenale waterverbruik verminder het, kan dit nie geregverdig word as 'n waterbesparende praktyk indien 'n hoë vruglading gehandhaaf word nie.

On t.p.: Systematics and Biodiversity Science. / Thesis (MSc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Pollen grains of the southern African genus Heliophila L. (Brassicaceae), were examined using light microscopy (77 taxa), scanning electron microscopy (82 taxa) and transmission electron microscopy (IOtaxa). The present study emanates from a pilot study by Kose (200 I) in which palynology was identified as one of the taxonomically informative data sources that can be used in the classification and subdivision of the genus Heliophila. The aim of this study was to assess the taxonomic significance of palynological data in the genus Heliophila. All pollen grains of Heliophila taxa are prolate in shape and tricolpate. The exine surface sculpture varies and two main groups are identified. In the majority of the taxa the sculpture is psilate or psilate micro-perforate with suprateetal spinules (Pollen Type A), whereas in the remaining taxa the sculpture is micro-reticulate to reticulate with or without suprateetal spinules (Pollen Type B). Pollen Type B may be divided further into three subgroups based on the shape of the lumina and the position of the suprateetal spinules. TEM results also confirm the two main groups as proposed by the SEM. The structural and sculptural features of the exine proved important in the demarcation of the pollen grains into two distinctively different pollen types and the other pollen morphological data such as pollen grain sizes, pollen grain shape are discussed in relation to the groups/subgroups of pollen types. The sculpturing types are discussed with regard to their evolution and pollination discussed with regard to plant habit and pollen size. Cluster analysis, based on vegetative and reproductive characters, excluding palynological characters, was performed only after the pollen types were identified. These groups were well supported by plant habit, life form, leaf type, presence or absence of appendages on the filaments, indumentum of filaments and presence of the stipe on the ovary and divided the genus Heliophila into two main clades. It was observed that this division followed a sim ilar pattern as the species arrangement in the classification by Marais (1970). AIthough the two main pollen types occur in both clusters proposed by the morphological analysis, the specific pollen types are restricted to distinct subclusters. In conclusion, pollen data reveals that Heliophila is a heterogeneous genus. The present study also reveals that it is difficult to subdivide the Heliophila taxa into infrageneric units on the basis of palynological evidence alone. In conjunction with other data sources, it does, however appear to have systematic significance. Therefore, the results of the present palynological study can be used as an additional source of evidence to support the subdivision of the Heliophila taxa into infrageneric units in the near future if a better understandinz and classification of the zenus is to b b be achieved. / AFRIKAANSE OPSOMMING: Stuifmeelkorrels van die suider Afrikaanse genus Heliophila L. (Brassicaceae) is met behulp van ligmikroskopie (77 taksons), skandeerelektronmikroskopie (82 taksons) en transmissie-elektronmikroskopie (IOtaksons) bestudeer. Die huidige studie is 'n uitvloeisel van 'n lootsprojek deur Kose (200 I) waarin palinologie geïdentifiseer is as een van die taksonomies-belangrike data-bronne wat in die klassifikasie en subdivisie van die genus Heliophila gebruik kan word. Die doel van die studie was om die taksonomiese waarde van palinologiese data van die genus Hettophila te bepaal. Alle stuifmeelkorrels van Heliophila taksons is prolaat in vorm en trikolpaat. Die oppervlak-skulptuur van die eksien varieer en twee hoofgroepe word onderskei. In die meerderheid van die taksons is die skulptuur psilaat of psilaat-mikroperforaat met supratektale uitsteeksels (stuifmeeltipe A), terwyl die skulptuur in die oorblywende taksons rnikro-retikulaat tot retikulaat met of sonder supratektale uitsteeksels (stuifmeeltipe B) is. Stuifmeeltipe B kan verder in drie subgroepe, gebaseer op die vorm van die lumens en die posisie van die supratektale uitsteeksels, verdeel word. Resultate verkry vanaf die TEM bevestig die twee hoofgroepe soos voorgestel deur die SEM-studies. Die strukturele en skulpturele kenmerke van die eksien blyk belangrik te wees in die verdeling van die stuifmeelstruktuur in twee duidelike stuifmeeltipes en ander morfologiese kenmerke, byvoorbeeld die grootte en vorm van die stuifmeelkorrels word bespreek in hul verhouding tot die groepe / subgroepe van die stuifmeeltipes. Die tipes stuifmeel-skulptuur word bespreek ten opsigte van hul evolusie en bestuiwing word bespreek ten opsigte van groeiwyse en stuifmeelgroottes. Groepanalise, gebaseer op vegetatiewe en reproduktiewe kenmerke, uitsluitend palinologiese kenmerke, is saamgestel nadat die stuifmeeltipes geïdentifiseer is. Die groepe word gevorm op grond van groeiwyse, groeivorm, blaartipe, aan- of afwesigheid van aanhangsels aan die helmdrade, die indumentum van die helmdrade en die aanwesigheid van 'n stipe op die vrugbeginsel en verdeel die genus Heliophila in twee hoofgroepe. Daar is waargeneem dat hierdie analise 'n soortgelyke patroon volg as die spesie-rangskikking in die klassifikasie van Marais (1970). Alhoewel die twee stuifmeeltipes in beide die morfologiese hoofgroepe aanwesig is, stem die stuifmeeltipes duidelike ooreen met die sub-groepe wat deur die morfologiese analise gevorm is. Ten slotte, stuifmeeldata dui daarop dat Heliophila 'n heterogene genus is. Die huidige studie dui ook daarop dat' n onderverdeling van Heliophila in infrageneriese eenhede op grond van palinologiese kenmerke alleen ook baie moeilik is, maar saam met ander kenmerke kan stuifmeeldata wel van taksonomiese waarde wees. Dus, die resultate van hierdie studie kan as 'n aanvullende bron van data gebruik word om 'n onderverdeling van die genus te steun en 'n klassifikasie van die genus daar te stel.

Thesis (MSc)--Stellenbosch University, 1959. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming

Thesis (MSc)--Stellenbosch University, 1968. / Please refer to full text for abstract

Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Species’ seasonal behaviour is of paramount importance in understanding community functioning and dynamics. Recently, plant phenology has further gained significance as a reliable indicator of climate change impacts. Despite the importance of understanding plant dynamics, there are relatively few plant phenological records for the sub-Antarctic region, and where records exist they are often not extensive. Sub-Antarctic Marion Island, typical of Southern Ocean Islands, offers a useful setting for addressing these knowledge gaps. This study documented the vegetative and reproductive phenologies (or aggregate phenological patterns) of twelve indigenous and three alien vascular plant species on the island. The phenological differences among the species and distinct seasonal groupings (e.g. early, intermediate and late species) were examined. I also investigated the phenological differences among the indigenous and alien plant species. Furthermore, the onset of selected reproductive phenophases from the current records was compared with historical records for determining the extent of climate change-related alterations in phenology. Phenological data were collected fortnightly on five, 5 m x 5 m permanent plots per species (except for a few species) for a full growing season. Thus the sample size is n = 5 for all plant species except for Crassula moschata (n = 4), Juncus effusus (n=4) and Rumex acetosella (n=1). Sites of the same species were separated by at least 500 m except for the alien plant, Juncus effusus, where all four known populations were selected despite two of these populations being < 500 m apart. This study indicated that Marion Island plants grow throughout the year with no major peaks except in Azorella selago and Acaena magellanica which showed winter dormancy. However, reproduction in most plant species predominately occurred in spring and summer months. Pringlea antiscorbutica and Poa cookii were the first two species to set flower buds in September while most species dispersed their seeds in summer except for Agrostis magellanica and Crassula moschata which dispersed in early autumn. Distinct from most temperate systems, the reproductive seasonality displayed by Marion Island plant species is explained more by daylength than by temperature, perhaps due to the region’s typical thermal aseasonality. Interestingly, many cooccurring species and/or clades across the Falkland, Kerguelen, Macquarie and South Georgia Islands also showed similar flowering onset date to the Marion Island plants, further confirming their daylength sensitivity. However, other external factors seem to come into play at later events of reproduction. Consequently, fruit maturation time of similar species across the sub-Antarctic islands varied substantially despite the plants having flowered in the same month. Although plant species showed similar reproductive seasonality, there were significant differences among species phenologies i.e. phenophase timing, duration and peak occurrence dates. However, using 95% confidence intervals of Generalized Linear Models weighted means, and/or one-way ANOVA (Tukey post hoc test), three homogenous sets of species (early, late, or intermediate onsets) were identified based on flower bud, flowering and seed dispersal phenophase onset dates. The homogenous species groupings observed for flower buds also remained unchanged during flowering onset except for Cotula plumosa and Callitriche antarctica which switched groups. As for the seed dispersal timing, the pattern was not consistent with that of the flower bud and flowering onset homogenous groupings, except for Acaena magellanica and Agrostis magellanica which remained in the early and late groups, respectively. Conversely, in the case of the timing of other phenophases (pollen release, fruit set and fruit ripening), entire phenophase durations, and peak occurrence dates, species overlapped greatly, resulting in an unbroken progression or continuum of phenology among species. Similarly, the three alien plant species investigated here (Cerastium fontanum, Juncus effusus and Rumex acetosella) showed no consistent phenological differences from the rest of the species. However, a widespread alien plant species on Marion Island, C. fontanum, reproduced for most of the year, although its reproduction peak was in summer months as was the case for the rest of the species. This study also indicated that indigenous plant species have altered their reproductive phenologies since 1965. Although the response was species-specific, the majority of plant species significantly delayed the onset of reproductive activities in 2007 by comparison with 1965. However, it is not clear if the observed species response was caused by the now drier and warmer Marion Island climate or by discrepancies in reporting in the earlier studies and/or sampling differences between the recent and historical records. Therefore, these results should be taken with caution. In conclusion, this research provided a detailed phenological dynamics record for vascular plant species on the island. Over time these records may be used as a basis for monitoring and modelling the impact of climate on plant phenology on the island. / AFRIKAANSE OPSOMMING: Spesies se seisoenale gedrag is van die allergrootste belang in die begrip van gemeenskapsfunksionering en dinamika. Meer onlangs het plant fenologie verdere betekenis verwerf as ‘n betroubare indikator vir die impakte van klimaatsverandering. Ondanks die belangrikheid om plant dinamika te verstaan, is daar relatief min plant fenologiese rekords vir die sub-Antarktiese streek en waar rekords wel bestaan is dit dikwels nie omvangryk nie. Sub- Antarktiese Marion Eiland, tipies van Suidelike Oseaan Eilande, bied ‘n nuttige ligging om hierdie kennis gapings aan te spreek. Hierdie studie het die vegetatiewe en voorplantingsfenologieë (of gesamentlike fenologiese patrone) van elf inheemse en drie uitheemse vaatplantspesies op die eiland gedokumenteer. Die fenologiese verskille tussen die spesies en duidelike seisoenale groeperings (bv. vroeë, intermediêre en laat spesies) is ondersoek. Ek het ook die betekenisvolle fenologiese verskille tussen die inheemse en uitheemse plantspesies ondersoek. Voorts, die aanvang van gekose voortplanting feno-fases van huidige rekords is vergelyk met historiese rekords om die mate van klimaatsverandering verbandhoudende veranderings in die fenologie te bepaal. Fenologiese data is twee weekliks ingesamel op vyf, 5 m x 5 m permanente plotte per spesie (behalwe vir ‘n paar spesies) vir ‘n volle groei seisoen. Dus, die insamelings grootte is n = 5 vir al die plantspesies behalwe vir C. moschata (n = 4), Juncus effusus (n=4) en Rumex acetosella (n=1). Persele vir dieselfde spesies is geskei deur ten minste 500 m, behalwe vir die uitheemse plant, Juncus effusus, waar al vier populasies wat bekend is gekies is, ten spyte daarvan dat twee van hierdie populasies < 500 m uitmekaar is. Hierdie studie het aangedui dat Marion Eiland plante regdeur die jaar groei, met geen belangrike spitstye nie, behalwe in Azorella selago en Acaena magellanica wat ‘n winter rusperiode wys. Hoe ookal, voortplanting in meeste van die plantspesies het hoofsaaklik voorgekom tussen die lente en somermaande. Pringlea antiscorbutica en Poa cookii was die eerste twee spesies om blomknoppe uit te stoot in September, terwyl die meeste spesies hulle sade versprei het gedurende die somer, behalwe vir Agrostis magellanica en Crassula moschata wat versprei het in vroeg herfs. Duidelik van meeste gematigde sisteme, word die voortplanting seisoenaliteit, getoon deur die Marion Eiland plantspesies, verduidelik meer deur daglengte as deur temperatuur, moontlik weens die streek se tipiese termiese a-seisoenaliteit. Interessant, baie spesies en/of afstameling-groeperings wat saam aangtref word dwarsoor die Falkland, Kerguelen, Macquarie en Suid Georgia Eilande wys ook soortgelyke bloei aanvangsdatums as die Marion Eiland plante, nog meer bevestigend van hulle dag-lengte sensitieweteit. Hoe ookal, ander eksterne faktore blyk betrokke te raak by latere gebeure van voortplanting. Gevolglik het vrug rypwordingstyd van dieselfde spesies oor die sub-Antarktiek noemenswaardig verskil, ten spyte daarvan dat die plante in dieselfde maand geblom het. Alhoewel plantspesies dieselfde voortplanting seisoenaliteit gewys het, was daar ‘n noemenswaardige veskil tussen spesie fenologieë, m. a. w. feno-fase tydsberekenning, tydsduur en spits voorkomsdatums. Hoe ookal, deur gebruik te maak van 95% betroubaarheid intervalle van Algemene Lineêre Modelle gewigte gemiddelde en/of een rigting ANOVA (Turkey post hoc toets), is drie homogene stelle van spesies (vroeë, laat en intermediêre aanvang) geïdentifiseer gebasseer op blomknop, bloei en saad verspreiding feno-fase aanvangsdatums. Die homogene spesie groeperings waargeneem op blomknoppe het ook onveranderd gebly gedurende bloei aanvang behalwe vir Cotula plumosa en Crassula antarctica wat groepe geruil het. Vir die saadverspreiding tydsberekenning was die patroon nie konstant met die van die blomknop en bloei aanvang homogene groepe nie, behalwe vir Acaena magellanica en Agrostis magellanica wat in die vroeë en laat groepe respektiewelik gebly het. Omgekeerd, in die geval van tydsberekenning van ander feno-fases (stuifmeel vrysetelling, vrugwerp, vrugrypwording), volledige feno-fase tydsduur en spits voorkomsdatums het spesies grootliks oorvleuel, wat ‘n ongebroke vordering of deurlopendheid van fenologie tussen die spesies tot gevolg het. Ooreenkomstig het die drie uitheemse spesies wat hier ondersoek is (Cerastium fontanum, Juncus effusus en Rumex acetosella) geen bestendige fenologiese verskille van die res van die spesies gewys nie. Hoe ookal, ‘n wydverspreide uitheemse spesie op Marion Eiland, Cerastium fontanum, het deur die meeste van die jaar voortgeplant, hoewel met ‘n voorplanting spits in die somer maande soos die res van die spesies. Hierdie studie dui ook aan dat inheemse plantspesies hulle voortplanting fenologieë verander het sedert 1965. Alhoewel die reaksie spesiespesifiek was, het die meerderheid van die plantspesies hulle voortplanting aanvang aansienlik vertraag gedurende 2007 in vergelyking met 1965. Hoe ookal, dis nie duidelik of die waargeneemde spesie reaksie was as gevolg van die nou droër en warmer Marion Eiland klimaat of deur teenstrydighede in verslagewing gedurende die vroëre studies en/of insameling verskille tussen die onlangse en historiese rekords. Daarom moet hierdie resultate met versigtigheid hanteer word. In samevatting, hierdie navorsing voorsien ‘n gedetaileerde fenologiese dinamieka rekord vir vaatplantspesies op die eiland. Oor tyd kan hierdie rekords gebruik word as basis vir monitering en modellering van die impak van klimaat.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The aim of this study was to determine how P nutrition affects biological nitrogen fixation (BNF) via effects on the N2-fixing bacteria in the nodules of Virgilia species native to the Cape Floristic Region (CFR), South Africa. This was evaluated in 3 separate studies: The first study aimed to determine how phosphorus deficiency affects N nutrition of two legume tree species from the Mediterranean Fynbos ecosystem. This study showed that during prolonged P deficiency, V. divaricata maintained a constant biomass, while V. oroboides showed a decreased biomass. V. oroboides showed a decrease in nutritional concentrations, which resulted in the decrease of symbiotic nitrogen fixation (SNF). Both plants utilized atmospheric N more efficiently per nodule under P deficiency. Maximum photosynthesis decreased in V. oroboides, while V. divaricata maintained its photosynthesis. Both species also had greater carbon construction costs during P deficiency. V. divaricata showed clear adaptive features during P-deficiency, as it maintained its growth respiration. The two legume species appear to have different adaptations to P deficiency, which may influence their performance and distribution in their naturally low P environment. The second study aimed to evaluate if soil environmental conditions and mineral nutrient concentration play a major role in microbial communities in plant rhizosphere and nodulation during N2 fixation in legumes. Therefore this study firstly aimed to determine the composition of the N2 fixing bacterial population in the rhizosphere and nodules of V. divaricata. Secondly, it aimed to determine the contribution of these bacteria to N2 fixation during conditions of P deficiency in the Fynbos environment. In the study, the effects of phosphate (P) nutrition on N2 fixing bacterial community structures in Virgilia divaricata rhizosphere and nodules were examined in a pot experiment. V. divaricata were germinated in Fynbos soil as natural inoculum, transferred to clean sand cultures and supplied with 500 μM P and 5 μM P. The N2 fixing bacterial communities in the rhizosphere and nodules were examined based on the PCR-DGGE banding patterns of 16S rDNA and sequencing methods. The GenBank blast results revealed that V divaricata was efficiently nodulated by a wide range of root-nodule bacterial strains, including Burkholderia phytofirmans, Burkholderia sp. and Bradyrhizobium sp. during low P supply. The 15N natural abundance data also confirmed that 40-50% of the N nutrition was acquired through symbiotic N2 fixation. This is not only evidence of nodulation, but also an indication of the adaptation of a range of N2 fixing bacterial strains / species to the nutrient poor, sandy, acidic soil of the Mediterranean-type ecosystems of the Fynbos. The third study examined the physiological effects, such as N2 fixation parameters, plant dependence on N2 fixation, N preference, legume plant growth, carbon costs and amino acid biosynthesis during P deficiency and mineral N supply as NH4NO3 in a slow-growing, Fynbos legume tree, Virgilia divaricata. Continued application of NH4NO3 to the legume plant showed a greater increase in plant dry matter compared to plants with two nitrogen sources (mineral N and atmospheric N2) or plants that relied on atmospheric N2 fixation. Carbon construction costs were more pronounced in plants supplied with two N sources and during P deficiency. Maximum photosynthetic rates per leaf area increased during prolonged P deficiency, irrespective of the N sources. Though plants nodulated, plant dependence on N2 fixation decreased with the addition of NH4NO3. Roots and nodules of the P deficient plants showed an increase in asparagine content, most strikingly so in plants treated with a single source of N. These studies reveal that different legume species of the same genus, may employ contrasting adaptations in order to maintain N nutrition under P deficiency. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was die bepaling van die wyse waarop fosfaat (P) voeding die biologiese stikstof binding (BNF) deur middel van die effek op N2-bindingsbakterië in die wortelknoppies van Virgilia spesies wat inheems tot die Kaap floraryke area (CFR), Suid Afrika is, affekteer. Drie aparte eksperimente is uitgevoer om die doel te evalueer: Die eerste studie het gepoog om te bepaal hoe 'n fosfaat tekort N voeding van twee peulplant spesies van die Mediterreense Fynbos ekosisteem affekteer. Hierdie studie het getoon dat V. divaricata 'n konstante biomassa tydens verlengde P tekort behou, terwyl V. oroboides ‟n verlaagde biomassa getoon het. V. oroboides het 'n verlaging in voedingskonsentrasies getoon, wat tot 'n verlaging in simbiotiese stikstof binding (SNF) gelei het. Beide plante benut atmosferiese N meer doeltreffend per nodule tydens P tekort. Die maksimum fotosintese in V. oroboides het afgeneem, terwyl V. divaricata sy fotosintese gehandhaaf het. Beide spesies het ook 'n groter koolstof konstruksie koste tydens P tekort gehad. V. divaricata toon duidelike aanpassingsmeganismes tydens P-tekort, aangesien hierdie species sy groei respirasie konhandhaaf. Dit wil voorkom asof die twee peulplant spesies verskillend aangepas is vir P tekort, wat hulle producksie en verspreiding in hulle natuurlike lae P omgewing mag beïnvloed. Die doel van die tweede studie was om te bepaal of grond omgewingskondisies en minerale voedingskonsentrasie 'n belangrike rol speel in die mikrobiese gemeenskappe in die plant risofeer en wortelknoppie vorming tydens N2 binding in peulgewasse. Eerstens het die studie dus gepoog om die samestelling van die N2 bindende bakteriële populasie in die risosfeer en die wortelknoppies van V. divaricata te bepaal. Ten tweede, is die bydrae van die bakterië tot N2-binding tydens P tekort kondisies in die Fynbos omgewing bepaal. In die studie is die effek van fosfaat (P) voeding op die N2-bindende bakteriële gemeenskapstrukture in die Virgilia divaricata risofeer en wortelknoppies in 'n pot eksperiment ondersoek. V. divaricata sade is in fynbos grond as 'n natuurlike inokulum ontkiem, waarna dit na skoon sand kulture oorgedra is en van 500 μM P en 5 μM P voorsien is. Die N2-bindende bakteriële gemeenskappe in die risofeer en wortelknoppies is op grond van die PCR-DGGE band patrone van die 16S rDNA en volgorde bepalingsmetodes ondersoek. Die GenBank Blast resultate het getoon dat V. divaricata doeltreffend deur 'n wye reeks wortel-wortelknoppie bakteriële stamme genoduleer is, insluitende insluitende Burkholderia phytofirmans, Burkholderia sp. en Bradyrhizobium sp. tydens lae P toediening. Die natuurlike 15N voorkoms data het ook bevestig dat 40-50% van die N voeding deur simbiotiese N2 binding bekom is. Dit dien nie net as bewys vir wortelknoppie vorming nie, maar ook 'n aanduiding van die aanpassing van 'n reeks N2 bindende bakteriële stamme/ spesies tot die voedingsarme, sanderige, suur grond van die Mediterreanse ekosisteem van die Fynbos. Die derde studie het die fisiologiese effekte soos bv. N2 fikserings faktore, die afhanklikheid van plante op N2 fiksering, N voorkeur, peulgewas groei, koolstof kostes en aminosuur biosintese tydens P tekort en minerale N toediening soos NH4NO3 in 'n stadig-groeiende, Fynbos peulgewasboom, Virgilia divaricata ondersoek. Volgehoue toediening van NH4NO3 aan die peulplant toon 'n groter toename in plant droë weefsel. Tydens P tekort is die koolstof bou koste meer verhoog in plante wat met twee N bronne voorsien is. Tydens verlengde P tekort het die maksimum fotosintese tempo per blaaroppervlakte toegeneem, ongeag die N bron. Alhoewel die plante wortelknoppies gevorm het, het die plant se afhanklikheid van N2 binding tydens die toediening van NH4NO3 afgeneem. Wortels en wortelknoppies van die P tekort plante het 'n toename in asparagien inhoud getoon, veral in die plante wat met 'n enkele bron van N behandel is. / The DST/NRF-Center of Excellence for Tree Health and Biotechnology, based at the University of Pretoria, for their financial support

Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Understanding the processes that drive the invasion of non-native species is often essential for effective management. This thesis focuses on Casuarina spp. – an economically and ecologically important tree genus with taxa that have been widely disseminated by humans. I explore the effects certain taxa can have on community dynamics in recipient environments, investigate the factors that mediate invasion of Casuarina species, and from this aim to develop recommendations for managing the group. First, I assessed the global introduction history, invasion ecology and the evolution of management approaches of Casuarina. Ten of the 14 species in the genus have been introduced outside their native ranges to over 150 countries, but only three species are recorded as naturalized or invasive. As with other groups there is a correlation between native range size and invasiveness – the three invasive species also have the largest introduced ranges. Propagule pressure explains much more of the variance in observed invasiveness between Casuarina taxa than any known combination of life-history traits. Large-scale plantings of casuarinas in some climatically suitable areas have not yet resulted in large-scale invasions; there is a substantial global Casuarina invasion debt. Experiences in Florida and the Mascarene Islands highlight that casuarinas have the potential to transform ecosystems with significant control costs. Despite modest progress with managing invasions in some areas, substantial problems remain. As with most other invasive tree taxa, complex conflicts of interest are particularly challenging. Second, I looked at mechanisms underlying naturalization and assessed invasion risk at a regional scale. Here, I examined Casuarina cunninghamiana invasions in the south-western Cape of South Africa – the part of the country with the largest contiguous area climatically similar to the native range of the species. Propagule pressure is a key driver of naturalization of C. cunninghamiana populations in climatically suitable areas. The species also naturalizes in regions with suboptimal bioclimatic conditions, but then only very near (<10 m) planted trees. Risk models indicate that C. cunninghamiana is likely to spread across a greater region of the Western Cape than it currently occupies. Naturalized populations of C. cunninghamiana are young and expanding. The capacity of the species to resprout and attain reproductive maturity at an early age suggests that this species could become a widespread and damaging invader in South Africa. We conclude with some recommendations for management, and argue that if particular steps are taken (e.g. the immediate removal of all female plants from proximity to dams and water-courses; all future sales and plantings to be restricted to male plants) then it might be possible to safely utilise the species in future. Third, I examined the invasion dynamics of a single Casuarina species at the landscape scale. I explored how interactions between disturbance and invasion govern successional trajectories, using the remarkable invasion of C. equisetifolia on the volcanic island of Réunion. Invasive populations of C. equisetifolia have increased substantially in extent over 40 years. Lava flows have facilitated the spread of C. equisetifolia and invasion of this species has radically changed successional trajectories, increasing the rate of succession sevenfold. This case mirrors work done on Morella faya and Falcataria moluccana on Hawa'ii, which shows the extent to which invasive species can alter ecosystem function and benefit from natural disturbances generated by volcanic lava flows. The continued spread of C. equisetifolia poses a major threat to the small area of remaining native lowland rainforests on Réunion which cover < 2 % of their original extent. The studies in this thesis have uncovered patterns, processes and invasion risks for invasive trees that are not well represented in the literature. Some insights derived from well-studied tree genera, such as Acacia and Pinus, seem to apply fairly well to tree invasions in general. However, special ecological features of Casuarina species and the ways they are used by humans call for unique considerations when piecing together changing global distributions and creating effective strategies for management. / AFRIKAANSE OPSOMMING: ‘n Deeglike begrip van die prosesse wat die indringing van uitheemse spesies fasiliteer is noodsaaklik vir effektiewe besturing. Hierdie tesis fokus op Casuarine spp. – ‘n ekonomiese en ekologiese belangrike boom genus, met menigte spesies binne hierdie genus wyd verspreid deur mense. Ek ondersoek die effekte wat sekere taksa kan hê op die gemeenskap dinamika in die ontvanger omgewing, sowel as die faktore wat Casuarina indringing bemiddel, en deur hierdie doelwitte beoog ek om aanbevelings te maak aangaande die effektiewe bestuur van hierdie groep. Eerstens evalueer ek die invoerings geskiedenis van die genus wêreldwyd, die indringer ekologie en ook die evolusie van bestuurs benaderinge ten opsigte van Casuarina. Tien van die 14 spesies binne hierdie genus is ingevoer na meer as 150 verkillende lande buite hul inheemse streek, maar slegs drie van hierdie spesies word beskou as genaturaliseerd of indringers. Soos met ander groepe is daar ‘n korrelasie tussen inheemse streeks-grote en indringerheid – die drie indringer spesie het ook die grootste ingevoerde streke. Propaguul druk verduidelik die meerderheid van die variasie in die waargeneme indringer Casuarina taksa as enige ander kombinasie van lewens geskiendenis eienskappe. Groot skaalse plantasies van casaurina taksa in sommige klimaat geskikste areas het nog nie na groot skaalse indringing gelei nie; daar is wêreldwyd ‘n aansienlike Casuarina indringer skuld. Ervarings in Florida en die Mascarene Eilande beklemtoon dat casuarinas die potensiaal het om ekosisteme te transformeer met geweldige beheer omkostes. Ten spyte van redelike vordering aangaande die besturing van indringers in sekere areas, is daar steeds aansienlike probleme. Soos met meeste ander indringer boom taksa, is die botsing van belange veral uitdagend. Tweedens, het ek die meganismes van die naturalisasie bemiddel as ook indrigner risiko op die plaaslike skaal ondersoek. In hierdie deel het ek Casuarina cunninghamiana indringers in die Suid-Wes Kaap van Suid-Afrika ondersoek – die deel van die land met die grootste aangrensende area wat ‘n ooreenstemmend klimaat het met die inheemse areas van die spesie. Propaguul druk is ‘n belangrike drywer vir die naturalisasie van C. cunninghamiana populasies in areas met ‘n geskikte klimaat. Hierdie spesie het ook genaturaliseer in areas met suboptimale klimaats kondisies, maar slegs baie naby (<10m) aan plantasies. Risiko modelle dui aan dat C. cunninghamiana die potensiaal het om te versprei na ander dele van die Wes-Kaap waar dit huidiglik afwesig is. Natuurlike populasies van C. cunninghamiana is jonk en in die proses van uitbreiding. Die kapasiteit van die spesie om te hergrooi en voortplantings volwassenheid op n vroeë ouderdom te beriek stel voor dat hierdie spesie ‘n wyd verspreide en skadelike indringer kan word. Ons sluit af met aanbevelings vir effektiewe bestuur en stel voor dat indien sekere stappe geneem word (bv. ontmiddelike verwydering van die vroulike plante naby damme en water areas; alle verdere verkope beperk word tot manklike plante), dit moontlik sal wees om hierdie spesie op ‘n omgewings-veilige manier te gebruik. Derdens het ek die indringing dinamika van ‘n enkele Casuarina spesie on landskap skaal ondersoek. Ek het verken hoe interaksies tussen versteurings en indringing plantegroei prosesse dryf, deur gebruik te maak van die merkwaardige indringing van C. equisetifolia op die vulkaniese eiland van Reunion. Indringer populasies van C. equisetifolia het aansienlik vermeerder in die afgelope 40 jaar. Lava vloei het die verspreiding van C. equisetifolia gefasiliteer en indringing van hierdie spesie het plantegroei prosesse radikaal verander, deur die tempo van opvolging sewevoudig te verhoog. Hierdie studie weerspieël werk wat op Morella faya en Falcataria moluccana in Hawa’ii gedoen is en toon tot watter mate indringer spesies ekosisteem funksies kan verander en voordeel kan trek uit natuurlike versteurings wat gegenereer word deur vulkansiese lava vloei. Die voortgesette verspreiding van C. equisetifolia hou ‘n groot bedreiging in vir oorblywende inheemse laeveld reënwoude op Reunion wat tans < 2% van hul oorspronlike area dek. Die studies in hierdie tesis het patrone, prosesse en indringer risikos vir indringer bome ontdek wat nie goed in die literatuur verteenwoodig word nie. Sommige insigte wat deur goed bestudeerde boom genera, soos Acacia en Pinus, ontdek is, blyk om redelik goed van toepassing te wees op boom indringers in geheel. Alhoewel, sekere ekologiese funksies van Casuarina spesies en die manier wat hulle deur mense gebruik word, vra vir unieke oorwegings aangaande hul wêreldwye verspreiding en effektiewe beheer.