The ecology of plant species at Sandford Rocks Nature Reserve (SRNR) was studied. The study site is an important nature reserve that contains relatively undisturbed natural vegetation. It has a mosaic of exposed granite rocks, scrublands and woodlands. The study involved: a description of the structure and composition of the vegetation; the population characteristics of selected Acacia species; aspects of reproduction in Acacia; germination and seedling characteristics of some Acacia and grass species that dominate the reserve; the effect of seed size on germination and seedling characteristics; and, the relationship of seed size to seed coat thickness in selected Acacia species. Five different areas were studied using the point centered quarter method to sample the woody perennial species. Thirteen Acacia species were examined for reproduction characteristics; and in 2 selected Acacia species, the effects of phyllode and/or inflorescence removal on reproduction was investigated. Germination tests were conducted to identify germination characteristics in 8 Acacia and 7 grass species dominant at SRNR. The possible effects of variation in seed size on germination; seedling characteristics; and, seed coat thickness were investigated in Acacia fauntleroyi and Acacia prainii. A total of 85 species from 20 families of woody perennials were collated. All areas were dominated by the Myrtaceae, Mimosaceae and Proteaceae families. There was considerable variability in the structure and composition of vegetation. Most species were present in particular sites and the composition of communities appears to be related to the heterogeneity of the habitat within the reserve. In areas of shallow or rocky soil, vegetation types present include Allocasuarina huegeliana woodland, Grevillea paradoxa low scrubland and Acacia neurophylla medium shrubland. / In a seasonally wet area, vegetation types present include low open grassland; Eucalyptus capillosa (wandoo) woodland; and, Acacia saligna thicket. In deep, dry sandy soil, vegetation types include Phebalium tuberculosum shrubland, Acacia acuminata and Acacia coolgardiensis thickets. On relatively flat areas that gain water from adjacent large granite hills, the vegetation consists mainly of tall, open woodlands of Eucalyptus species. Vegetation types include: medium tall Eucalyptus salmonophloia woodland with Kunzea pulchella shrubland at the periphery of the Eucalyptus woodland. At rock areas, vegetation types present include dense Leptospermum erubescens thicket, low open Acacia prainii and Dodonaea viscosa shrubland. Of the Acacia populations studied, in A. lasiocalyx no recent seedling establishment was observed. It is hypothesised that recruitment occurs in particular periods. As the plants are associated with rock and soils are generally shallow, it appears that recruitment depends on run-off water from the rocks in winter. Continuous recruitment seems to be the pattern in A. prainii with both seedlings and saplings represented. A. fauntleroyi forms relatively small populations; apparently long drought periods (>l00 d) result in mass death and limit its population size. In A. hemiteles, no seedling stage was found, root competition (for water) from associated Eucalyptus species presumably limits its recruitment. Reproductive success of Acacia is affected by rainfall. A wet winter is required to induce flowering and further rain is required after flowering to promote pod development and good seed set. / All Acacia species suffer from drought in the reproduction season, however they differ in their degree of susceptibility. Leaflessness and tree shape also affect Acacia fecundity. Plants bearing more phyllodes produce more flowers and pods, and branches in the upper part of the crown bear heavier inflorescences. In 1998, all Acacia species at SRNR produced mature seed of low weight, with many immature and diseased seed, which gave poor germination. A late spring frost in 1998 is believed to be responsible for limited seed development. In two selected Acacia species, removal of phyllodes reduced the number of pods produced. Presumably, phyllode removal reduces photosynthate produced, therefore the competition among inflorescences (or pods) for resources is more intense and subsequent abortions are likely to occur. All Acacia species studied showed best germination in the cool winter temperature range. Apparently, seeds are adapted to germinate in winter when seasonal moisture is more likely to be available. The best temperature however, varied slightly between species. The grass species dominant in the reserve, except for Aristida contorta, also had more germination in cooler rather than warmer temperatures. The flora of SRNR is similar to typical vegetation of the Southwest. Generally, Acacia species are present only in particular sites, presumably were habitat moisture allows. Seedlings of Acacia species growing in naturally dry areas have greater root: shoot masses than those growing in seasonally wet areas. Biomass partitioning is an apparent strategy to conserve water. Of the 7 grass species, Amphipogon strictus appears to have fastest growth. / Eriachne ovata has greater root than shoot mass, while in all other species, shoot mass is greater than root mass; a characteristic of species that grow well in moist habitats. The longest shoots and roots are in Austrostipa elegantissima, an understorey species of eucalypt woodland. In A. fauntleroyi, the degree of hard-seededness varies between seed sizes. There is a higher proportion of soft seed in smaller seed. Seed of different sizes show some responses to different pre-treatments and incubation temperatures for germination. Larger seeds generally germinate in greater numbers after higher treatment temperatures. The best treatment for small seeds is pre-treatment at 75°C and incubated at 15°C. For medium and large seed, best pre-treatment is at 75°C with incubation at 30°C or soaking in boiling water and incubation at either 15 or 3°C. In A. prainii, seed size; pre-treatment; incubation; and, their interaction all affected germination; larger seeds are more viable. The best treatment to promote germination of A. prainii is soaking in boiling water and incubation at 25°C. In both A. fauntleroyi and A. prainii, larger seeds produce larger seedlings. Seedlings from large seeds have the potential for more rapid pre-photosynthetic growth. Larger, heavier seed has a thicker seed coat. The seed coat of A. prainii is thicker than in A. fauntleroyi; the difference in seed coat thickness is reflected by more soft seed in A. fauntleroyi (35%) than in A. prainii (6%).

Acacia species producing gum Arabic are of great (socio)-economic, and ecological importance in Sudan. Insect attacks are one of the main causal agents in the decline in the gum Arabic yielding trees. Infested trees are almost totally damaged if the infestation is left untreated. The beetle family Cerambycidae is one of the largest groups of insects. Commonly referred to as long-horned beetles, these pests destroy host trees, having a great affect during times of drought. Many studies have been completed about the effect of long-horned beetles in various global settings. However, in Sudan, there is limited information about the insects’ ecological, biological, and even basic, profile. Thus, in this dissertation I study the spectrum, relative abundance, and phenology of the long-horned beetle species that are infesting Acacia species in Kordofan region (Sudan). Seven species were recorded using interception traps. These included Anthracocentrus arabicus (Thomson, 1877), Crossotus strigifrons (Fairmaire, 1886), Crossotus subocellatus subocellatus (Fairmaire, 1886), Doesus telephoroides Pascoe, 1862, Gasponia gaurani Fairmaire, 1892, Titoceres jaspideus (Serville, 1835) and Tithoes sp.. Two species were recorded using ground - photoeclectors: Crossotus albicollis (Guérin, 1844) and Coelodon servum White, 1853. Most of the species are known from other Arabian and African countries. However Coelodon servum White, 1853, Doesus telephoroides Pascoe, 1862, and Gasponia gaurani Fairmaire, 1892 were recorded in this study for the first time in Sudan. Results from flight interception traps indicated peak activity density of long-horned beetles during the rainy season (June – September), with maximum occurrence in June and peak occurrence in August. All study sites showed infestations of long-horned beetles, but the level of infestation varied between sites and Acacia species. The El Demokeya reserve forest indicated the highest percentage of infestation out of all the sites surveyed in this study. The infestation ranged between 57.1% and 100.0% for Acacia senegal, between 5.9% and 26.7% for Acacia mellifera, and 0% to 23.1% for Acacia seyal study sites. Acacia species differed also with respect to the spatial infestation pattern. Results indicated the maximum (95.5%) presence of holes of infestation in the branches of A. senegal when compared to the trunk. Holes of infestation were recorded in all directions, with a minimal occurrence on the south side (18.2%). Opposite results were obtained for A. mellifera with the maximum number of holes in the trunks (46.2%), while branches were less affected. In addition results obtained showed no presence of holes in the branches of A. seyal. Moreover, this study focuses on the assessment of tree characteristics that may trigger the infestation. Logistic regression indicated that tree age was the only predictor for the infestation with long-horned beetles – at least for Acacia senegal. A significance difference was obtained for the stand height curve between non-infested and infested trees of Acacia species, except A. senegal stands at El Demokeya. The study was supplemented by qualitative data, produced from a survey of gum landowners. This questionnaire indicated the level of awareness that gum landowners had with regard to long-horned beetles and their infestations. The results of this survey denoted that 95.0% of gum farmers were aware of the long-horned beetles, while 49.2% indicated an awareness about infestations, mentioning the emergence holes as damage characteristics.

>Magister Scientiae - MSc / The Cape Floristic Region, situated at the southern tip of Africa, is one of the world’s most botanically diverse regions. The biodiversity of this region faces various types of threats, which can be divided into three main categories, namely increasing urbanisation, agriculture expansion, and the spread of invasive alien vegetation. It has been shown that botanically diverse areas are more prone to invasion by invasive alien plant (IAP) species. The Hawequa conservation area, in the south-western Cape, is particularly botanically diverse, such that it is very prone to aggressive invasion by IAP species. Therefore, conservation management of the Hawequa conservation area urgently need to map, prioritise and clear IAP species. Due to the topographical complexity of this mountainous area, it is not possible to map the distribution of IAP species throughout the protected area by conventional field methods. Remote sensing may be able to provide a suitable alternative for mapping. The aim of this research was to assess various image classification methods,using two types of high-resolution imagery (colour aerial photography and WorldView-2 satellite imagery), in order to map the distribution of IAP species, including small stands and individuals. Specifically, the study will focus on mapping Pinus and Acacia spp. in a study site of approximately 9 225ha in the Hawequa conservation rea. Supervised classification was performed using two different protocols, namely per-pixel and per-field. For the per-pixel classification Iterative Self-Organising Data Analyses Technique (ISODATA) was used, a method supported by ERDAS Imagine. The per-field (object-based) classification was done using fractal net evolution approach (FNEA), a method supported by eCognition. The per-pixel classification mapped the extent of Pinus and Acacia spp. in the study area as 1 205.8 ha (13%) and 80.1 ha (0.9%) respectively, and the perfield classification as 1 120.9 ha (12.1%) and 96.8 ha (1.1%) respectively. Accuracy assessments performed on the resulting thematic maps generated from these two classification methods had a kappa coefficient of 0.700 for the per-pixel classification and 0.408 for the per-field classification. Even though the overall extent of IAP species for each of these methods is similar, the reliability of the actual thematic maps is vastly different. These findings suggest that mapping IAP species (especially Pinus spp.) stands and individuals in highly diverse natural veld, the traditional per-pixel classification still proves to be the best method when using high-resolution images. In the case of Acacia spp., which often occurs along rivers, it is more difficult to distinguish them from the natural riverine vegetation. Using WorldView-2 satellite images for large areas can be very expensive (approximately R120 per km2 in 2011), but in comparison with the cost of mapping and the subsequent clearing, especially in inaccessible areas, it might be a worthwhile investment. Alternative image sources such as the high resolution digital colour infrared aerial photography must be considered as a good source for mapping IAP species in high altitude areas.

Acacia species producing gum Arabic are of great (socio)-economic, and ecological importance in Sudan. Insect attacks are one of the main causal agents in the decline in the gum Arabic yielding trees. Infested trees are almost totally damaged if the infestation is left untreated. The beetle family Cerambycidae is one of the largest groups of insects. Commonly referred to as long-horned beetles, these pests destroy host trees, having a great affect during times of drought. Many studies have been completed about the effect of long-horned beetles in various global settings. However, in Sudan, there is limited information about the insects’ ecological, biological, and even basic, profile. Thus, in this dissertation I study the spectrum, relative abundance, and phenology of the long-horned beetle species that are infesting Acacia species in Kordofan region (Sudan). Seven species were recorded using interception traps. These included Anthracocentrus arabicus (Thomson, 1877), Crossotus strigifrons (Fairmaire, 1886), Crossotus subocellatus subocellatus (Fairmaire, 1886), Doesus telephoroides Pascoe, 1862, Gasponia gaurani Fairmaire, 1892, Titoceres jaspideus (Serville, 1835) and Tithoes sp.. Two species were recorded using ground - photoeclectors: Crossotus albicollis (Guérin, 1844) and Coelodon servum White, 1853. Most of the species are known from other Arabian and African countries. However Coelodon servum White, 1853, Doesus telephoroides Pascoe, 1862, and Gasponia gaurani Fairmaire, 1892 were recorded in this study for the first time in Sudan. Results from flight interception traps indicated peak activity density of long-horned beetles during the rainy season (June – September), with maximum occurrence in June and peak occurrence in August. All study sites showed infestations of long-horned beetles, but the level of infestation varied between sites and Acacia species. The El Demokeya reserve forest indicated the highest percentage of infestation out of all the sites surveyed in this study. The infestation ranged between 57.1% and 100.0% for Acacia senegal, between 5.9% and 26.7% for Acacia mellifera, and 0% to 23.1% for Acacia seyal study sites. Acacia species differed also with respect to the spatial infestation pattern. Results indicated the maximum (95.5%) presence of holes of infestation in the branches of A. senegal when compared to the trunk. Holes of infestation were recorded in all directions, with a minimal occurrence on the south side (18.2%). Opposite results were obtained for A. mellifera with the maximum number of holes in the trunks (46.2%), while branches were less affected. In addition results obtained showed no presence of holes in the branches of A. seyal. Moreover, this study focuses on the assessment of tree characteristics that may trigger the infestation. Logistic regression indicated that tree age was the only predictor for the infestation with long-horned beetles – at least for Acacia senegal. A significance difference was obtained for the stand height curve between non-infested and infested trees of Acacia species, except A. senegal stands at El Demokeya. The study was supplemented by qualitative data, produced from a survey of gum landowners. This questionnaire indicated the level of awareness that gum landowners had with regard to long-horned beetles and their infestations. The results of this survey denoted that 95.0% of gum farmers were aware of the long-horned beetles, while 49.2% indicated an awareness about infestations, mentioning the emergence holes as damage characteristics.

For scientific or socio-economic reasons it is often necessary or desirable that biological material be identified. Given that there are an estimated 10 million living organisms on Earth, the identification of biological material can be problematic. Consequently the services of taxonomist specialists are often required. However, if such expertise is not readily available it is necessary to attempt an identification using an alternative method. Some of these alternative methods are unsatisfactory or can lead to a wrong identification. One of the most common problems encountered when identifying specimens is that important diagnostic features are often not easily observed, or may even be completely absent. A number of techniques can be used to try to overcome this problem, one of which, the Self Organizing Map (or SOM), is a particularly appealing technique because of its ability to handle missing data. This thesis explores the use of SOMs as a technique for the identification of indigenous trees of the Acacia species in KwaZulu-Natal, South Africa. The ability of the SOM technique to perform exploratory data analysis through data clustering is utilized and assessed, as is its usefulness for visualizing the results of the analysis of numerical, multivariate botanical data sets. The SOM’s ability to investigate, discover and interpret relationships within these data sets is examined, and the technique’s ability to identify tree species successfully is tested. These data sets are also tested using the C5 and CN2 classification techniques. Results from both these techniques are compared with the results obtained by using a SOM commercial package. These results indicate that the application of the SOM to the problem of biological identification could provide the start of the long-awaited breakthrough in computerized identification that biologists have eagerly been seeking. / Dissertation (MSc)--University of Pretoria, 2011. / Computer Science / unrestricted