Alien invasive species can have serious negative impacts on the biodiversity and functioning of ecosystems, but identifying invaders early, before they cause problems, can dramatically reduce the costs of controlling them. There is substantial research in identifying key attributes of invasive species, which can potentially be used in this regard. Many Eucalypts have formed the backbone of forestry in South Africa since the 1800s. While many other plantation species such as pines and legumes, have become serious invaders in many parts of the world, Eucalyptus species have been not been nearly as successful in invading alien environments. This is surprising considering that in their native habitat; members of this genus dominate almost all vegetation types. This project used available theory on the qualities that characterise invasive species to assess the invasive potential of one Eucalyptus species: Eucalyptus grandis (rose gum). Many alien plants take a long time to establish naturalised populations and spread through new ecosystems and this research will provide information on the likelihood that E. grandis will become a problem species in the future. A field study was used to determine whether there is any indication that it is in fact, invading from plantations in Mpumalanga, and if so, which ecological processes affect this invasion potential. Belt transects (5 by 50 metres) were used in sampling the populations growing near plantations. To determine whether frost is affecting the populations, one site was at high elevation where it is exposed to frost (near Graskop) and the other at a low elevation area with infrequent frost (near White river). Key reproductive traits such as generation time and seed viability which are known to affect invasion potential were also studied. Demographic data was used to determine the rates of establishment of E. grandis outside of plantations. The results showed that E. grandis had a short generation time and its seeds had a viability of 97%. Assessing the shape parameter (c) of the Weibull distribution function showed that both the Graskop (c=1) and White River (c=1) size class distributions had reverse j-shaped curves, characteristic of good rejuvenation. However, some Graskop sites had a monotonic function (c < 1) showing that frost is affecting the rejuvenation process. Generally the results show that rate of spread is low and this might suggest that the populations are on the establishing populations’ invasion stage. However, there is no indication that there are any environmental or life history factors that would prevent Eucalyptus from becoming invasive in the future, and I would recommend strict monitoring of its rates of spread out of plantation forests in various parts of the country.

The plant communities of the Andries Vosloo Kudu Reserve (6493 ha.; Acocks's Valley Bushveld) are classified using the Braun-Blanquet phytosociological technique. A checklist of the flowering plants is presented. The flora of the reserve displays an affinity to five phytochoria (Capensis, Karoo-Namib, Sudano-Zambezian, Afro-montane and Indian Ocean Coastal Belt 1, of which the Karoo-Namib and Indian Ocean Coastal Belt are the most extensive. The flora of the Valley Bushveld is regarded as adequately conserved, but a recommendation is made to consolidate the study area with adjacent farms. A small herbarium, containing specimens of all species listed in the checklist, has been established. The climate of the study area is classified according to the Koppen classification as Cfa. Simultaneous air temperature recording at four separate localities demonstrated that differences exist between local ities of marginally different altitude, aspect and slope. The phenology of 51 plant species, recorded at monthly intervals over a continuous period of 478 days, is presented. These species are classified according to their response to air temperature and rainfall for the initiation of new growth, flowering and fruiting. Species exhibited a spectrum of responses ranging from endogenous to exogenous control over phenological events. / KMBT_363 / Adobe Acrobat 9.53 Paper Capture Plug-in

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. 25 October 2016 in Johannesburg, South Africa. / Ecosystem services, nature’s benefit to people, contribute to human well-being. Extensive reliance on, and unsustainable use of, natural resources is typical of the rural poor in developing countries and can lead to ecosystem degradation, decreased ecosystem service provision, and increased vulnerabilities of rural populations. Most ecosystem services are intangible or difficult to quantify, but fuelwood provisioning can be measured directly and can serve as a proxy for the status of other ecosystem services (e.g. aesthetic and spiritual services, nutrient cycling, carbon sequestration). South African rural communities have a high reliance on fuelwood despite extensive access to electricity. Within this context, live wood harvesting occurring around rural settlements in increasing amounts has been deemed unsustainable. However, the ‘fuelwood crisis’ of the 1970s, and subsequent predictions of woodland collapse through fuelwood supply-demand models, has still not occurred despite substantial population growth in developing countries. Hypothesised reasons for modelled supply-demand mismatches are based on underestimation of fuelwood supply and woodland regeneration, as well as overestimation of fuelwood demand by discounting behavioural adaptability of users. It is likely that the spatial configuration of fuelwood use allows for the co-adaptability of both humans and ecosystems. A lack of understanding of the spatial configuration of these social-ecological dynamics limits our insights into current and future adaptive responses and thus, the degree of sustainability. This thesis aimed to assess woody biomass stocks and vertical structure changes, as a proxy for provisioning ecosystem services, in a spatially and temporally explicit manner, to describe the status and impact of wood extraction in semi-arid, savanna communal lands. Using repeat, airborne light detection and ranging (LiDAR) data from 2008 and 2012, we surveyed three-dimensional woodland structure in Bushbuckridge Municipality communal lands – the grazing and harvesting areas for densely populated rural settlements in former Apartheid ‘homelands’ in South Africa. Woody biomass in 2008 ranged from 9 Mg ha-1 on gabbro geology to 27 Mg ha-1 on granitic geology. Land-use pressure was associated with compensatory regrowth of savanna tree species through post-harvest coppice in the 1-3m height class. Woody biomass increased at all sites, contrary to previous fuelwood models of the area. Change detection in the vertical canopy structure revealed that biomass increases were almost solely attributable to the 1-3m and 3-5m height classes. These changes were exacerbated by wood extraction intensity in the communal lands – the communal land with the highest wood extraction pressure experienced the greatest biomass increases, likely a strong regrowth response to high harvesting levels. Within communal lands, areas closest to roads and settlements experienced substantial biomass increases as a result of shrub level gains. This relationship was mediated by the usage gradient – the greater the wood extraction pressure on the communal land, the larger and more spatially coalesced the ‘hotspots’ of shrub-level increases were in relation to ease of access to the communal land. However, biomass increases are not necessarily indicative of woodland recovery, as shrub-level increases were coupled with losses of trees >3m in height. To explore these tall tree dynamics further, we tracked >450 000 individual tree canopies over two years over contrasting landscapes – a private reserve containing elephants, two communal lands under different wood extraction pressures, and a nature reserve fenced off from both elephants and humans. Humans are considerable drivers of treefall (defined here as a ≥75% reduction in the maximum height of each tree canopy) in communal lands. Humanmediated biennial treefall rates were 2-3.5 fold higher than the background treefall rate of 1.5% treefall ha-1 (in the control site – the reserve containing neither elephants nor humans). Elephant-mediated treefall was five fold higher than the background rate. Rate and spatial patterns of treefall were mediated by geology and surface water provision in the elephantutilised site where relative treefall was higher on nutrient-rich geology, and intense treefall hotspots occurred around permanent water points. Human-mediated rates and spatial patterns of treefall were influenced by settlement and crop-land expansion, as well as ease of access to communal lands. Frequent fires facilitated the persistence of trees >3m in height, but was associated with height loss in trees <3m. The combined loss of large trees and gain in shrubs could result in a structurally simple landscape with reduced functional capacity. Shrub-level increases in the communal lands are likely an interactive combination of newly established woody encroachers and strong coppice regrowth in harvested species. The more intensely used the communal land, the greater the bush thickening and the stronger the relationship between biomass gains and structural changes in the lowest height classes. The exacerbation of bush thickening in natural resource-dependent communities has critical implications for ecosystem service provision. There is potential for coppice regrowth to provide fuelwood to communities using ‘tree thinning’ programmes, but there is a lack of data on the quantity and quality of the regrowth, as well as the sustainability of coppice, the impacts of different harvesting methods, and the potential feedbacks with changing climate and CO2 fertilisation. Woody resource spatial distribution in communal lands is centred around settlement-level wood extraction pressure, as well as natural resource accessibility in the woodlands. In highly utilised areas, woodland regenerative capacity has been underestimated. Additionally, natural resource extraction is still highly localised, even at the communal land scale, with major structural changes occurring around the periphery or close to existing infrastructure. However, it is these underrated coupled adaptive responses in social-ecological systems that explain the failure of fuelwood supply-demand models’ predictive abilities. Nevertheless, loss of large trees in the landscape and the persistence of ‘functionally juvenile’ coppice stands will have implications for seedling production and establishment in the landscape with repercussions for the future population structure and ecosystem service provision. I discuss the implications of increased natural resource reliance in an African development context and the positive feedback between rural poverty and environmental impoverishment. Potential constraints to the data are unpacked, together with opportunities for further research in this area. / LG2017

Approximately 11 500 ha of coastal plain and mountain vegetation in the Cape Hangklip area of the South-Western Cape Province of South Africa was studied. The suitability of homogeneity functions and of the association-analysis techniques for the analysis of large areas of the distinctive coastal and fynbos vegetation found in the Mediterranean type of climate in this region were investigated. Data were collected at 150 sampling sites of 10 x 5 metres each, which were randomly located on grid intersections within physiographic-physiognomic units delimited on aerial photographs. Phytosociological techniques were used to arrange the data prior to further analysis using frequency modulated homogeneity functions. A classification of the vegetation into 32 communities is proposed with primary subdivisions into Broad-leaved Scrub and Fynbos. This classification is based on the results of the association-analysis of the data.

Bibliography: p. 123-124. / The genus Holothrix in South Africa is desc.ribe.d and its taxonomic history discussed. The results of using a computer to draw up a key and a dendrogram of the species are briefly discussed, as are some of the problems experienced. Various morphological characters are evaluated for their usefulness or otherwise in distinguishing species, and a key is provided. Where applicable, problems commonly encountered when attempting to identify the species are mentioned, and those characters pointed out which will distinguish the species. Details of biological interest are mentioned. Each species is illustrated by a drawing of sepal, petal and lip. Those species available in liquid preservative have the whole flower drawn as well, while those where a live plant could be obtained are illustrated in full, with a drawing of the whole plant, leaves, column and pollinia. In those cases where a range in shape, as opposed to size, is experienced, drawings are presented to illustrate this range. A detailed map of each species is presented, using the 1° gridsquare system, and also a table of the ranges of rainfall and altitude within the range of each species.

MSc., Faculty of Science, University of the Witwatersrand, 2011 / Both indigenous “Tamarix usneoides” and alien T. ramosissima co-occur in South Africa. Tamarix usneoides is potentially a metal and salt phytoremediation species. However, hybridisation is occurring between the two species and hybrids growth characteristics are deemed to be invasive. This study was undertaken at two sites on one Highveld gold mine, characterised by different soil types, where plant growth, reproductive potential and insect abundance and diversity were measured. This aims to establish the growth of T. usneoides in two site-species trials, and to identify differences between Tamarix taxa that are consistent across different environmental conditions and can be used for identification. This study also set out to establish if higher reproductive effort and enemy release are promoting the invasiveness of T. ramosissima. Trees in one site (a water logged, clayey “Glenrosa” soil) displayed significantly greater percentage survival, growth and reproductive effort than trees in the other site (a well drained, sandy “Hutton” soil). Extensive hybridisation between T. usneoides and T. ramosissima was observed with two hybrid states, morphologically similar to each parent species. The reproductive effort is consistently greater in T. ramosissima and T. ramosissima hybrid than T. usneoides and T. usneoides hybrid. After sampling 217 trees in this study, the three characteristics of (1) insertion of filaments into the nectar disc, (2) petal shape and (3) presence of salt glands on leaves most accurately distinguished between T. usneoides and T. ramosissima taxa. Three insect species have been identified from this study as potentially damaging agents on Tamarix spp. Insects can discern between the Tamarix tree taxa and T. ramosissima is being released from insect herbivore pressure, as very few insects and a lower diversity were recorded on T. ramosissima and its hybrids (T. ramosissima hybrids > T. ramosissima). To achieve phytoremediation objectives, careful tree identification and selection of genetically pure individuals for cloning is recommended. Additionally the removal of existing alien and hybrid plants, and further research to find a suitable host specific insect biological agent to control alien Tamarix is necessary.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in partial fulfilment of the requirements of the degree of Master of Science, Johannesburg, 2018 / Grevillea robusta is classified as a Category 3 invader by the National Environmental Management: Biodiversity Act (NEMBA) in South Africa. The species has recently been observed invading riparian areas from old cultivated trees in Limpopo, Mpumalanga and Gauteng provinces. Since the early 1980’s Grevillea robusta A.Cunn populations have increased from 15 observations in 1980─1985 to 39 in 1996─2000 and 47 between 2016 and 2017 in South Africa. The species is currently distributed in a total of 188 localities in 7 South African provinces. The aim of this study was to assess the invasiveness of G. robusta in South Africa and determine its appropriate Category status by assessing its invasive capacity by conducting a population census and assessing its transformative capacity at Moederlief farm, South Africa. Grevillea robusta is widespread in South Africa, however, there are no recorded observations in the Free State and Northern Cape provinces. The results from iSpot, CLIMEX, Southern African Plant Invaders Atlas (SAPIA) and field observations in figures 13, 14, 15 and 16 shows 52 observations in Limpopo and 37 between KwaZulu-Natal and Mpumalanga provinces. A climatic match index by CLIMEX was employed, and results indicate that G. robusta has the potential to grow well in Limpopo, Mpumalanga and Gauteng provinces and along the coastal regions. Furthermore, healthy populations of G. robusta were observed at Moederlief farm, where the biggest recorded tree in the field was estimated to be 45 to 52 years old. Grevillea robusta produces viable seed which may be dispersed 364 m away from parent trees. Looking at the population structure, age of reproduction, seed viability and ease of dispersal, the populations of G. robusta at Moederlief farm will continue to grow and invade even in other areas that are yet to be considered risk areas. Grevillea robusta is an invader that needs further evaluation of all the localities in South Africa. The species should be placed in Category 1b of invasive species and immediate control is required in all riparian zones. / XL2019

Ph.D. (Botany) / Please refer to full text to view abstract

Thesis (MSc)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Many authors express the value of riparian vegetation in terms of the function and number of species per unit area. Although riparian vegetation is confined to narrow bands of plants along watercourses, kloofs and gullies, it is a specialised habitat for many species. To determine the contribution of riparian vegetation to the species richness of the Jonkershoek Valley, Western Cape Province, South Africa, a checklist was compiled, by referring to past research and to the PRECIS national database for the South African flora for a list of species recorded from the area. A total of 1 743 taxa and 108 families were included in this list for the Valley. Specific characteristics were attributed to each of the 1 743 species on the basis of characters determined from the literature. Analysis of these data indicates that woody perennial shrubs with sclerophyll leaves are the representative plant type for the study area as a whole. The specialist structural description of a riparian species in the Jonkershoek Valley is: an unbranched woody perennial phanerophyte of a height between 2.0-8.0 m with microphyllous sclerophyilleaves. This group contributes 63% towards the riparian flora. Riparian habitats occupy only 2.5% of the total study area but contribute 26% of the vascular plants. The riparian communities of the Santa Monica Mountains (USA) cover 0.7% of that mountain study area and provide a habitat for 20.5% of the total vascular plants of the area. Both areas, therefore, show a similar level of diversity. This remarkable species richness of riparian zones is consistent with that found in other riparian communities i.e. Sweden and France. The study area was sampled by means of relevés arranged along 53 transects through the main stem and it's tributaries. A total number of 139 relevés were recorded which were used to identify, characterise and describe the riparian communities. Eight vegetation units, consisting of two groups, three communities, two subcommunities and one form, were described. The one group described the riparian communities while the other described a seepage community. The bigger groups exhibit environmental properties over a broader spectrum, while smaller groups exhibit characteristic environmental properties. The vegetation is found to represent a continuum rather than discreet entities. Many indicator species are encountered in the communities. Because of the characteristic canopy-understorey physiognomy of riparian vegetation, many communities are interspersed, making it difficult to delineate discreet community boundaries. The vegetation of the riparian zone of the Eerste River in the Jonkershoek Valley, is relatively pristine. Thirty-six species not native to the Valley were included in the checklist of which only four were recorded during the phytosociological study. / AFRIKAANSE OPSOMMING: Verskeie skrywers beklemtoon die kosbaarheid van rivieroewerplantegroei in terme van hul funksie en aantal spesies per oppervlakeenheid. Alhoewel rivieroewerplantegroei beperk is tot 'n noue band van plante langs waterweë, klowe en skeure, is dit 'n gespesialiseerde habitat vir baie spesies. Om die bydrae wat rivieroewerplantegroei tot die spesie-rykheid van die Jonkershoekvallei, Wes-Kaapprovinsie, Suid-Afrika te bereken, is 'n spesieslys saamgestel uit vorige studies en 'n PRECIS nasionale databasis vir die Suid-Afrikaanse flora waaruit 'n lys saamgestel is van spesies wat aangeteken is vir die area. 'n Totaal van 1 746 taxa uit 108 families is ingesluit in die plantelys. Vir elk van die 1 743 spesies, is spesifieke karakters uit die literatuur bepaal. 'n Analise hiervan dui aan dat die verteenwoordigende plant van die Jonkershoekvallei as gehele studie area 'n houtagtige, meerjarige struik met sklerofil blare is. Die spesialis strukturele beskrywing van 'n plant vir die Jonkershoekvallei is as volg: 'n onvertakte houtagtige meerjarige fanerofiet met 'n hoogte van 2.0-8.0 m met mikrofilliese sklerofil blare. Hierdie groep dra tot 63% by tot hierdie flora. Rivieroewer habitatte beslaan slegs 2.5% van die totale studie area, maar het tot 26% tot die vaatplante bygedra. Die Santa Monica Berge (VSA) se rivieroewerplantegroei bedek 0.7% van die bergagtige studie area en voorsien 'n habitat vir 20.5% van die vaatpplante. Beide gebiede toon dieselfde mate van diversiteit. Hierdie uitstaande spesiesrykheid is in lyn met wat gevind is in ander rivieroewergemeenskappe bv. in Swede en Frankryk. Die studie area is gemonster deur relevés wat uitgemerk is langs 53 transekte deur die hoofstroom en die sytakke. 'n Totaal van 139 releves is gemonster wat gebruik is om die gemeenskappe te identifiseer, karaktifiseer, en te beskryf. Agt plantegroei-eenhede, bestaande uit twee groepe, drie gemeenskappe, twee subgemeenskappe en een vorm, is beskryf. Die een groep beskryf rivieroewergemeenskappe terwyl die ander groep "n gemeenskap in die syfersone beskryf. Die groter groepe het wyer omgewingseienskappe getoon, terwyl die kleiner groepe spesifieke eienskappe toon. Dit is vasgestel dat die plantegroei eerder "n kontinuum voorstel as diskrete eenhede. Dit het tot gevolg dat dit moeilik is om die grense van gemeenskappe uit te wys. Vele indikatorspesies is aangetref. Die plantegroei van die rivieroewer van die Eersterivier in die Jonkershoeksvallei, kan beskryf word as relatief onversteurd. Ses-en-dertig spesies wat nie eie aan die Vallei is nie, is ingesluit in die spesieslys waarvan vier tydens die fito-sosiologiese studie aangeteken is.

A Thesis submitted to the Faculty of Science, University of the Witwatersrand, in fulfilment of the requirement for the degree of Doctor of Philosophy. Johannesburg March 2016 / This study aims to provide a comprehensive description of the Flora, biogeography and diversity of the serpentine outcrops of Barberton Greenstone Belt in Mpumalanga, South Africa in order to set conservation priorities for these areas. About 30 large and many smaller serpentine outcrops form part of the Barberton Greenstone Belt and consist of various combinations of serpentinized minerals. Seven outcrops were selected to be studied in detail. A floristic analysis recorded 744 species and subspecies, 319 genera and 94 families. The flora includes 33 taxa endemic to serpentine soils and six taxa, which are hyperaccumulators of nickel. The endemic taxa make up 41 % of the endemics of the Barberton Centre of Endemism. The serpentine flora was found to be different to the surrounding non-serpentine vegetation in terms of numbers of species per family, the ratios of dicotyledons to monocotyledons and familial composition. The Asteraceae and the Anacardiaceae support a higher number of endemics than expected, which suggests genetic pre-adaptation within these families and specifically within the genera Berkheya, Helichrysum and Ozoroa. Most of the endemic taxa exhibit long-range dispersal suggesting gene flow between populations on different outcrops. The endemics represent a mix of neo-endemics and paleoendemics. Non-parametric species richness estimators used to predict the species richness of each site, indicated that five serpentine outcrops have higher species richness than the surrounding non-serpentine areas. Indices of diversity calculated showed similar patterns to those of the species richness estimates. The Barberton Greenstone Belt serpentine outcrops show relatively high plant diversity when compared to some other serpentine outcrops around the world. Beta diversity calculated for each site was not correlated with altitude and weakly correlated with the size of outcrops. Species turnover between outcrops is high and is positively correlated with the geographical distance between outcrops. Diversity at higher taxonomic levels were calculated, and results suggest that genera have some potential for facilitating the ranking of outcrops in terms of biological richness to select sites for conservation planning. Less than 30% of serpentine outcrops are adequately conserved. Species and genus richness and endemism were used to select five outcrops that have high conservation priority / MT2016