The coastal grasslands that occur along the Eastern Shores of Lake St. Lucia are rich in plant species, including endemics. These grasslands in North KwaZulu-Natal, South Africa, are remnants of a severely threatened vegetation type. Large portions of the Eastern Shores have been utilized for commercial pine plantations over the last 50 years; however these have been removed over the last 17 years. It is therefore important that efforts to restore grasslands that have been previously afforested stands of pines are successful. These grassland systems are fire driven and therefore many plants have adapted to these conditions by having massive storage organs below the ground. Using several response variables I was able to assess the effects of plantations on alpha- and beta-diversity and functional traits of forb and other grassland species and attempted to determine whether these disturbed grassland were returning to their original state. A high level of community heterogeneity was found at both scales for natural vegetation, while more homogenous, species low patterns were seen in post-plantation sites. Most notable was the large number of missing resprouting species in pine sites and that, in contrast to forest rehabilitation studies, no evidence for succession was found. The implication of this is massive as grassland rehabilitation may be a lot harder than was previously thought. It is likely that the fire adapted forb species are bad colonizers and have struggled to return to disturbed sites. These grasslands are therefore susceptible to activities that remove or eliminate the considerable amount of below ground biomass from the soil, and these sorts of disturbances should be avoided. Active rehabilitation methods will be required if any progress is going to be made and until such methods are effective considerable effort should be made in conserving the remaining grasslands that we have left and promoting its pharmaceutical, horticultural and societal value.

The purpose of this study was to establish if hydraulic limitation and branch junction constriction explain the trade-off between longevity and increased ramification in species of the Cape Proteaceae. This was done by establishing if branch nodes are regions of greater resistance to xylem sap flow in the study species; attempting to quantify nodal resistance for a plant as a whole; and by determining if there is any evidence for hydraulic limitation or compensation in Leucadendron laureolum (Lam.) Fourc. and Leucospermum oleifolium (Berg.) R. Br. individuals. The extent of branch junction constriction was established by comparing the ratio of the xylem sap flow rates of adjacent branch segments of equal length. The ratio of a proximal intemodal to a distal intemodal segment was compared against the ratio of a proximal intemodal segment to a distal node. Branch nodes were found to create significant resistance to xylem sap flow rates in both species (p < .005 for L. laureolum, and p < .05 for L. oleifolium). Total nodal resistance in L. laureolum was modelled as equivalent extra branch length, and as loss of sap flow rate. Equivalent extra branch length increased exponentially with increased branching order, and increased much faster in more ramified plants. Loss of flow rate increased linearly with increased branching order and was unaffected by differences in ramification. This was because the nodes in more ramified plants had smaller basal sapwood areas, and the resistance imposed by nodes decreased with decreased basal sapwood area. As more ramified plants tend to branch earlier, and/or with greater temporal frequency, they will still accumulate greater nodal hydraulic resistance faster than less ramified plants, and thus may be limited to smaller size and younger maximum age. Branch specific conductivities (kₛ), leaf specific conductivities (LSC) and transpiration rates were investigated in higher (11 nodes) and lower (10 nodes) order branches of L. laureolum. All were found to be significantly lower in higher order branches (11 nodes), which can be related to greater nodal resistance to sap flow limiting the amount of water available to the area of developing xylem, causing the vessels to have narrower diameters. There was no significant difference in leaf to sapwood area ratios (Aₗ/As) between the two branching orders. Previous studies have suggested that changes in Aₗ/Aₛratios occur to compensate for hydraulic limitation. Reductions in Aₗ/Aₛin plants with greater hydraulic restriction allow LSC values, and thus transpiration rates, to stay as high as plants with less hydraulic restriction. As there was no such compensation, LSC values, and thus transpiration rates, were much lower in branches of higher order. Transpiration rate is a good indication of rates of photosynthesis. Lower transpiration rate in higher order branches is thus a good indication of hydraulic limitation on rates of photosynthesis with increased branching order. Hydraulic resistance in nodes thus imposes an important limitation on size and/or age of L. laureolum individuals, and explains the apparent trade-off between longevity and degree of ramification in the Cape Proteaceae.

Savanna and forest/thicket can exist as alternate stable states, among others, determined by fire ecology feedbacks. Bush encroachment has become an ever-increasing trend converting grassland and savanna biomes to forest/thicket. A severe firestorm occurred in the Hluhluwe-Umfolozi Game Reserve in north-eastern South Africa in September 2008. The fire penetrated closed thicket areas and opened up the landscape. The main aim of this study was to investigate whether repeated fire, following such an extreme fire event, could trigger a biome or regime shift; in this case from forest/thicket to savanna. Fire spread is determined by grassy fuel loads, primarily grass biomass in these ecosystems, and the fire weather at the time of the fire. Grass biomass was found to have significantly accumulated (p=0.0002) in the thicket areas in just three growing seasons since 2008, which allowed fires to burn the area again in 2012. In the 2012 fires, fire intensity, measured by char height on woody stems increased in relation to the increase in grass biomass up to a point after which increasing grass biomass had no effect. The 2012 fires were able to penetrate areas opened up by the 2003 firestorm despite high canopy cover created by tree resprouting. Tree mortality was cumulative with repeated burning (21% mortality post 2008 increasing to 47% mortality in 2012). This was linked to the vigour of post 2008 resprouting with much higher mortality of trees in 2012 that had few (<4) resprouting stems. Thus, this study indicates that, a fire regime of sufficient frequency and intensities could potentially cause a vegetation state shift from forest/thicket to savanna. Therefore, this may provide management options for wildlife parks and protected areas.

A fairly extensive introduction to the theory behind the use of remote sensing products for vegetation survey work is given. This includes the particular benefits of colour air photographs, the relationship between scale of survey and scale of mapping and remote sensing products, and more information about the 'semi-detailed' level of survey operation. The latter is the category of survey which the vegetation survey of the Langebaan area, South Africa, falls into. The importance of the timing of photography in the usefulness of air photographs in vegetation survey work is also emphasised. The particular example of the semi-detailed survey of the vegetation of the Langebaan Area using colour serial photographs of Job 195 was then used in describing the Phases of operation involved. Phase I is essentially the planning stage, Phase II the operational stage, divided into 5 separate sections of operation, and Phase III involves the final mapping and report compilation. Reference to the results is given, as is a short discussion on the merits of air photographic techniques.

This study set out to explore the patterns and determinants of contemporary species distribution in a fynbos landscape based on information on 1) physical habitat characteristics, 2) past disturbance regime, 3) intrinsic properties of individual species and 4) temporal change in communities. The body of the thesis is divided into four parts covering each of these aspects individually. Each chapter has been written up as an individual paper and thus includes some repetition as well as cross-referencing. Each chapter includes a detailed rationale for the study in the introduction, as well as methods, results and a discussion of the findings. Chapter 2 describes the patterns of vegetation units in the Cape of Good Hope Nature Reserve and provides a quantitative assessment of the importance of physical site features as determinants of these units. These results are compared with the vegetation classifications of the area derived in earlier studies by Taylor (1984b) and Cowling et al. (1996a). Chapter 3 is the first study in fynbos to partition the variance in vegetation pattern into that explained by physical site factors and that explained by the recent disturbance regime. The study explores the role of 30 years of fire and alien plant infestations in influencing species distribution at the community and landscape scale. While a number of studies have explored spatial determinants of diversity and pattern in fynbos, temporal change within communities has been neglected. High levels of species turnover through time, as a result of colonisation and extinction, could be an important component of diversity at the landscape scale. Hence Chapters 4 and 5 both explore aspects of temporal dynamics in fynbos. The objectives of Chapter 4 are to determine the stability of populations at the landscape scale over a 30-year period and to establish the determinants of local extinction of species. Information on the stability of species over time and the attributes which enable species to persist or go extinct are important for understanding potential impacts of management practices as well as the importance of temporal dynamics in influencing spatial patterns. This is especially appropriate in the context of the results of Chapter 3, which suggest that a high proportion of the variance in species composition is unexplained despite the inclusion of physical factors, and past disturbance regime. The fifth chapter provides a descriptive account of the change in vegetation composition over a 30-year period. It is recommended that those readers not familiar with the fynbos system read it as it provides an overview of a variety of aspects of fynbos dynamics. Its objective is to show how the various components of the disturbance regime, as well as fluctuations in abundance of overstorey Proteaceae and their resultant competitive effects can influence community composition. The final chapter is a general discussion that summarises the major findings of the study.

Differing plant canopy structures between the sexes of the dioecious Cannomois congesta (Restionaceae) were found to be the result of the destructive pre-dispersal seed predation methods used by the four-striped grass mouse (Rhabdomys). Mature, reproductive culms on female plants were felled down (mid way along the culm) in large numbers by Rhabdomys in order for it to access the seeds held terminally on culms. Male plants were largely unaffected due to their lack of seeds. Seeds acquired through culm-felling by Rhabdomys were all eaten shortly after their discovery, leading to significant seed mortality each year and reducing the rate of seed dispersal by ants (myrmecochory). I studied the physiological effects of culm-felling by Rhabdomys in C. congesta. Firstly I investigated nutrient resorption from senescing culms and considered the effects of reproductive effort (higher in females) and sex-specific nutrient losses. I found that nutrient resorption from mature culms was highly efficient in both sexes. Culm-felling by Rhabdomys lead to the loss of pre-senescent culm tissue in females and therefore lead to the loss of a significant proportion of potentially resorbed nutrients. Nutrient resorption was found not to be flexible as a strategy to compensate for higher reproductive costs/nutrient-losses in females. This was possibly due to nutrient resorption occurring near is physiological maximum. Plant photosynthetic performance was also investigated using stable isotopes and gas exchange and was found to be similar in both C. congesta sexes throughout the year. The influence of culm-felling by Rhabdomys on female micro-climate also did not appear to have a significant influence on photosynthetic performance between sexes. There was a general lack of evidence to suggest compensatory physiological changes or reductions in fitness (photosynthetic capacity/growth/reproduction) in females due to higher reproductive costs/nutrient-losses. The lack of physiological differences and the fact that females supported a greater number of culms relative to males suggested that other compensatory mechanisms could exist. Phenological differences were discovered and could be important in allowing flexibility between sexes to best use available resources for their specific sexual requirements. Another possibility is that compensatory growth occurred in females at the cost of rhizome-stored nutrients. This has been shown to occur in graminoids after high levels of herbivory (Bryant et al 1983).

The Greater Cape Floristic Region (GCFR) is divided into two subregions, the Core Cape Subregion (CCR) and Extra Cape Subregion (ECR), which are mainly characterized by Fynbos and Succulent Karoo biomes, and are recognized among global biodiversity hotspots. The soils in the ECR are mostly shale derived and richer in nutrients compared to the CCR which is characterized by nutrient-poor sandstone soils mainly from the Cape System. The Fabaceae (Leguminosae) is the second largest family in the CCR with a total of about 764 species (belonging to 43 genera, of which 83% of the species are endemic to the CCR), and sixth largest in the ECR with about 140 species currently recognised with 39.3% of these species endemic to the ECR. Wiborgia Thunb. is a legume genus made up of 9 perennial shrub species of height 0.5-3.0 metres, with distinct ascending to erect habit, which share morphological similarities with some Lebeckia, especially sect. Viborgoides currently referred to as Wiborgiella. The aim of this dissertation was to understand the evolution and biogeography of the genus Wiborgia in the GCFR. This involved (i) inferring phylogenetic relationships within the genus using multiple molecular markers and testing the monophyly and the support of Dahlgren's (1975) morphological subgeneric classification; (ii) determining nutritional characteristics of soils occupied by different Wiborgia species and compare them with sites where Wiborgia species have not been recorded to occur and testing whether Wiborgia species occupy habitats with similar nutrient concentrations; (iii) evaluating the potential of Wiborgia species to grow and nodulate in soils from within and outside distribution range and characterizing of rhizobia nodulating Wiborgia species in field and glasshouse conditions. Phylogenetic relationships in Wiborgia were inferred using multiple molecular markers (ITS, rpl32-trnL, rps16, trnS-trnG, and trnT-trnL) and the data were analysed using model based approaches (Maximum Likelihood, Bayesian inference). Wiborgia was well supported as monophyletic and sister to both Wiborgiella and Aspalathus, with Wiborgiella humilis well supported as being part of the Wiborgiella clade. Within the Wiborgia clade, two strongly supported subclades were observed. In subclade 1, W. tetraptera was strongly supported as sister to W. fusca, whilst W. monoptera was strongly supported as sister to W. incurvata. In subclade 2, a novel well-supported sister relationship between W. mucronata and W. tenuifolia was observed. Wiborgia obcordata, the only species in Dahlgren's subgenus Wiborgia, was found to be embedded within subgenus Pterocarpia and thus the subgenera classification of Dahlgren was not supported. It was also identified that sister species pairs (W. incurvata and W. monoptera; W. fusca and W. tetraptera; W. tenuifolia and W. mucronata) all showed the tendency to co-occur or have overlapping distribution ranges, and showed subtle differences in floral morphology and habitats.

Includes bibliographical references / Erica makes up 7% of all species in the Cape flora. It is the most species-rich genus in the Cape Floristic Region (CFR), which has an area 0f 90 000km². Erica species have great inter- and intra-specific variation in floral form as well as in post-fire regeneration strategies. Previous studies of other plant groups (Barrett et al. 1996; Button et al. 2012) have illustrated changes in floral traits with a shift from outcrossing to selfing. The aim of this thesis was to determine whether similar changes occur in Erica. I thus analysed breeding systems in Erica in relation to floral traits, pollinators, and fire survivals strategies. Seed and fruit set data obtained from hand-pollination treatments suggested that self- fertilization occurs rarely. Autonomous selfing did not generally yield significant seed set. When comparing changes in floral traits with increased selfing ability and pollination syndromes weak relationships were observed. Average plant height showed a positive relationship with selfing ability but this correlation was not significant. Comparing traits within small and large flowered species separately yielded significant relationships between corolla size and selfing ability of small-flowered species.. Furthermore, general trends indicate that small-flowered species have increased ability to self-fertilise when corolla sizes are larger, corolla apertures larger and herkogamy reduced. Large-flowered species employ the same strategy but average corolla aperture is reduced. A trade-off between the size and the number of flowers was seen within the Erica genus. Small-flowered species had significantly more flowers compared to larger- flowered species that had markedly fewer flowers per unit height. This finding has implications for the selfing potential of small-flowered species as increased self- incompatibility may have evolved in order to reduce the effects of increased geitonogamy due to increased floral number. The prediction that self-fertilisation would be increased in seeders compared to resprouters, on the basis that seeders are more reliant on seeds for persistence than resprouters, was not realised when comparing the selfing ability of different fire- survival strategies. Erica mammosa, a species with morphs possessing both fire-survival strategies, shows no significant differences in selfing ability, this includes differences in pollen-ovule (P/O) ratios. However, indices suggest the resprouting form of E. mammosa to have an increased ability to self-fertilize while the seeder form has an increased ability for autonomous selfing. The 29 species analysed were divided into outcrossers and facultative outcrossers based on selfing indices but these did not fit neatly within Cruden’s proposed P/O ranges (facultative autogamy: P/Os= 32-397; facultative outcrossers: P/Os= 160.7 - 2258.6; outcrossers: P/Os= 1062 - 19525). This may be due to his classification of species into breeding systems being based on relatively few distantly related species per category with extremely variable P/O ratios per category. For example, outcrossers ranged an order of magnitude (from 1000+ to 20 000). It is also true that this ratio can be influenced by a variety of different factors, these include: habitat, evolutionary history and pollination syndrome. Consequently, P/O ratios in Erica do not seem to reflect pollination syndromes very well. Presumably, sex allocation theory may explain the relationship of breeding system with P/O ratios better. Histological studies of pollen tube growth for self- and cross-pollinated flowers of eight species suggested that Erica has late acting self-incompatibility (LSI). LSI is a barrier to selfing that occurs in the ovary. However, I could not determine if the rejection process occurs pre- or post-fertilization. Although, a large amount of knowledge is still lacking, this preliminary study provided insight into the reproductive biology of Erica.

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