OpenUCT :: Browsing by Author "Midgley, Jeremy J"

Browsing by Author "Midgley, Jeremy J"

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Open Access
Acacia karoo and its effects on the succession of dune forests in the Eastern Shores, Kwazulu-Natal
(1997) Maddams, C J; Midgley, Jeremy J
Acacia karoo arises following disturbance in the Dune Forests of Northern KwaZulu-Natal. Patches of A. karoo which had arisen as a result of the abandonment of fields by subsistence farmers in a dune forest matrix were studied. Previous authors have considered A. karoo to be part of a successional mechanism which leads towards a climax forest canopy (Mentis and Ellery, 1994; von Maltitz et al, 1996). This succession is questioned as a number of the conclusions of these authors were not verified by my own work. The present paradigm holds that the A. karoo is even aged and will senesce after 25 years, while recruitment does not occur in the patches. I find no evidence of canopy senescence and microhabitats within which recruitment of A. karoo occurred were identified. Further the introduction of other species in the patches is facilitated not through the A. karoo canopy but was shown to be facilitated by the presence of multi-stemmed canopy-trees of other species which had not been removed by the farmers. However, this introduction of other species into the patches was still limited, with certain species not found in even the very oldest patches (37 years old). No discernible chronosequence could be identified when comparing patches of different age, which casts doubt on the belief that these patches will eventually revert to climax dune forest.
Open Access
Additive basal area in Knysna Forest - myth or reality?
(2000) Parker, Ruth; Midgley, Jeremy J
This paper explores the additive basal area phenomenon wherein the basal area of large above-canopy trees in a plot appears additive or extra to the total basal area of the plot. The mean basal area of Podocarpus falcatus and Podocarpus latifolius in 0.04 ha plots were studied in 2032 plots at eleven sites in the Knysna Forest in relation to the basal area of the remaining species and the total basal area. Mean basal area regressions indicated that the basal area of P. falcatus and P. latifolius were 'additive'. The basal area of plots with big trees and those without were compared and significant differences provided further support for this 'additive basal area' theory.
Open Access
Attributes that make Acacia karroo dominant : stable N and C isotope analysis of nine Acacia species from KwaZulu-Natal (South Africa)
(2006) Mgidi, Theresa Nobuhle; Midgley, Jeremy J; Stock, WD
This study focuses on nine Acacia species from Hluhluwe-Imfolozi Park in KwaZulu-Natal, South AFrica. The study was motivated by the need to understand the dominance of legumes in the process of bush encroachment in Southern Africa. A. karroo has been identified as a particularly invasive species in HUP, and determining what makes this Acacia species and any of the other acacias in HUP invasive formed the foundation of this study.
Open Access
The birds, the bees and Erica: vulnerability of plant-pollinator communities in fragmented fynbos landscapes
(2016) Angoh, Siow Yan Jennifer; Midgley, Jeremy J; Brown, Mark
Habitat fragmentation has been identified as a major cause of pollination mutualism collapse that can eventually impinge on plants' reproductive success (e.g. through pollen-limitation). Agriculture, timber plantations, invasion by alien trees and the urbanisation of the southern Cape lowlands have transformed and fragmented large parts of the former distribution range of many Erica species. Recent evidence suggests that in the Fynbos biome, small remnants of natural and disturbed vegetation are likely to display depauperate plant communities. In the present study, it was found that Erica species richness declined significantly as patch size decreased. Limited nectar resources available on those small 'islands' might not be enough to attract essential bird and insect pollinators. Insect-pollinated species were more impacted by reduced patch size than the bird-pollinated ones. Further investigation using Erica discolor showed that for this widespread ornithophilous species, pollination mutualism still occurred in smaller fynbos patches. These findings stressed the importance of conserving small fragments for maintaining remnant plant populations, which can act as reliable food sources for avian pollinators. In addition, to cope with the effects of pollen limitation, highly resilient plant species have evolved and adopted different compensatory mechanisms. From a short-term perspective, adopting compensatory reproductive strategies (e.g. autonomous self-pollination, vegetative growth, and generalised pollination systems) could reduce dependence on specific pollinators and increase the chances of a species being able to persist through a period of low-pollinator abundance. The prevalence of autogamy and geitonogamy as alternatives to xenogamy was assessed in six different obligate seeder Erica species in the eastern coastal part of the Cape Floristic Region. Despite the long history of plantation-based timber production that fragmented the study area, and the subsequent possible pollinator loss, none of the species analysed in this study have adopted autonomous self-fertilisation as a response mechanism. Erica sessiliflora was the only species that showed a high compatibility for self-pollen. The species under investigation in a breeding system conducted here were also incapable of vegetative propagation and were plants targeting specific animal taxa (e.g. birds or insects) for successful pollination. Having limited compensatory mechanisms, further degradation of their habitat and weakening of their ecological interactions could be extremely detrimental to these Erica species' reproductive success.
Open Access
The burning questions about Hluhluwe : causes and consequences of a severe wildfire
(2009) Browne, Catherine; Bond, William J; Midgley, Jeremy J
The biophysical drivers of fire; ignition, fire weather conditions, fuel biomass, and flammability, differ in varying ecosystems. The rates of occurrence of these factors influence fire regimes. This study investigated the causes and consequences of a severe wildfire that swept through the Hluhluwe Game Reserve, KwaZulu-Natal South Africa in September 2008. This fire was an extreme event that seems only to have been possible due to the combination of circumstances that occurred in the days prior to and during the 14th/15th September 2008. The event was considered extreme because it burnt from savanna into thicket and forest patches, which is atypical of fires. The fire caused large structural change in tree demography, however, not much change in densities. The results of this study indicate that coupled weather conditions conducive to fire; namely low relative humidity, high temperatures and high wind speeds, occurred at the time of the fire. The synergistic influences of fire weather conditions and the state of available fuel caused this severe fire. The fire continued to bum for 48 hours before weather conditions relaxed and became less dangerous. These data suggest extreme fires such as the September 2008 event may be exploited by managers to reclaim former grasslands and savannas that have suffered the effects of bush encroachment and/or create open areas allowing grasslands to develop. However, severe fires run the risk of leading to the loss of forests and the biodiversity that they support. This study has identified the conditions likely to promote such severe fires.
Open Access
Can and do Ericas self pollinate?
(2011) Arendse, Brittany; Van der Niet, Timotheus; Midgley, Jeremy J
Within the Cape Floristic Region many lineages are characterised by large floral diversity. The genus Erica is one of these lineages, making up -7% of the CFR. Surprisingly, even though pollinators have been suggested to be a driving force of floral morphology, the role of pollinators in the floral diversification and speciation of this genus is not yet well understood. Therefore the aim of this paper was to establish if Erica species can and do self-pollinate. Two Erica species, E. plukenetii and E. urnaviridis, were obtained from Kirstenbosch nursery, where hand-pollinations were performed on 15-20 flowers of each of three treatments (self-pollination, crosspollination and autogamous self-pollination. Additionally pollen tube analyses were performed on seven Erica species, which were collected from the Constantia Mountain. In E. plukenetii, self-incompatibility seems to be the predominant breeding system. It appears that, like E. urna-viridis, most of the other species analysed, via pollen tube analyses, have the potential to self-pollinate. However, more experiments are required to establish if these species are truly self-compatible. Autogamy, on the other hand, does not appear to set seed in the species studied. Therefore it would be fair to say that some ericas can self-pollinate but none actually do self-pollinate. These results indicate that ericas have a strong dependence on pollinators for seed set and in the past speciation may have occurred due to adaptation to different pollinators, when opllinators were scarce.
Open Access
Carbon based secondary metabolites in African savanna woody species in relation to anti-herbivore defense
(2014) Hattas, Dawood; Midgley, Jeremy J; Scogings, Peter; Julkunen-Tiito, Riitta
Chemical defense in African savanna woody species have been inferred from foliar condensed tannin and total phenolic concentrations. However these measures are controversial since condensed tannin chemical heterogeneity compromises its simple quantification and total phenolics, which is a measure of general foliar phenolics, includes many different low molecular weight phenolics. Some of these low molecular weight phenolics have been shown to deter herbivory individually or in combination with others. The growth differentiation balance hypothesis predicts a trade-off between costs of chemical defenses or carbon based secondary metabolites relative to the demand for photosynthate by growth. However, this hypothesis was developed in northern boreal and temperate forests and the extent to which it applies to African savanna woody species remains unclear. In this study we: 1) Compared the use of Quebrachowith Sorghumtannin as standards for condensed tannin quantification, relative to absolute condensed tannin concentration in selected species; 2) Determined low molecular weight phenolic profiles of 6 species with different life history, morphological and functional traits; and 3) Investigated whether the growth differentiation balance hypothesis explains allocation to carbon based secondary metabolites in Combretum apiculatumalong a 6-level N gradient; and following 100% simulated herbivory along the N gradient.Condensed tannins were extracted from 5 tree species and purified. Condensed tannin concentrations were determined using the acid-butanol assay and expressed as Quebracho, Sorghumand absolute tannin concentrations. Chemical composition of different tannin polymers were determined by thiolysis using HPLC and HPLC-MS. Photosynthesis, growth variables andphenotypic phytochemical responses to the different N and N x herbivory treatments were measured in C. apiculatum. Low 7molecular weight phenolics were determined and identified using HPLC and HPLC-MS respectively.Results from this study suggest: that thecontinued use of Quebrachotannin as condensed tannin standard in the acid-butanol assay is unjustified; that generalizations based on life history, morphological and functional traits may be misleading since foliar low molecular weight phenolics are not necessarily related to these traits; and that the growth differentiation balance hypothesis does not explain allocation to carbon based secondary metabolites in C. apiculatum.
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Causes of secondary sexual differences in plants — Evidence from extreme leaf dimorphism in Leucadendron (Proteaceae)
(2010) Midgley, Jeremy J
In extreme cases leaves in male plants of the dioecious genus Leucadendron (Proteaceae) are up to an order of magnitude smaller than female leaves. This secondary sexual dimorphism (SSD) in leaf size has previously been suggested to be due to intra-male sexual selection, leading to an increase in male allocation to reproduction in dimorphic species. After critically evaluating previous data provided to support this hypothesis, I suggest on both theoretical grounds and on re-analysis that this argument is unlikely and unsupported. Leaf size dimorphism could theoretically evolve directly due to disruptive ecological selection between genders, leading to niche dimorphism either within or between habitats. I test this ecological causation hypothesis by providing data on specific leaf area (sla) and water use efficiency (δ 13C) of leaves from males and females of several Leucadendron species. Results confirm the expectation of minimal gender differences. I argue that leaf dimorphism is a consequence of selection on flower size and architecture.
Open Access
Certain syndrome or complex conundrum? : the pollination of Erica lanuginosa
(2010) Mitrani, Leila Mical; Midgley, Jeremy J
The flower of Erica lanuginosa has a tightly closed corolla, held in place by hinged sepals. with a dull reddish-pink colour which makes make it hard to determine a likely pollinator. Rodent trapping and pollen analysis of faecal matter showed it unlikely to be pollinated by a rodent. Flowers excluded from external pollination showed no seed set, hence it is not considered to be self-pollinated. Nectar analysis are inconclusive as an indicator of pollination syndrome. Entomophily by a robust insect with a medium length proboscis is considered unlikely due to phenology and morphology of the flower. Omothiphily is a possibility as stem thickness correlates with previous studies investigating the correlation between stem thickness and pollination syndromes. The pollination syndrome of Erica lanuginosa remains indeterminate by I hypothesize that, due to phenology, thick supportive, stem and large quantities of nectar and close-formed flower, which needs to be manoeuvred open, its pollinator is likely a short-billed generalist-feeding bird restricted by food choice during the winter months.
Open Access
Co-occurrence and phenological niche separation in rodent pollinated Proteaceae
(2010) Cowan, Oliver; Midgley, Jeremy J
Despite the numerous studies regarding rodent pollination in the Cape Floristic Region in the last few decades, little or no work has been done on patterns of co-occurrence and flowering phenology. The presence of three potentially rodent-pollinated Protea species at Fernkloof Nature Reserve, two of which were observed to co-occur, facilitated the following questions: i) are P. cordata, P. scabra and P. angustata therophilous? ii) do therophilous species co-exist at a fine scale? iii) do they have the same pollinator? iv) do they exhibit staggered flowering phenology? The floral characteristics of the study species suggest they were rodent pollinated and that the co-occurring species, P. cordata and P. scabra, would have staggered flowering phenologies. All three of the species' pollen was found in the faeces of Acomys subspinosus, the shared pollinator, while the phenological data provided the first empirical evidence of staggered flowering phenologies between fine scale, sympatric therophilous Protea species.
Open Access
Comparative water relations of indigenous and invasive Australian Proteaceae in fynbos
(1998) Bergh, Nicola G; Midgley, Jeremy J
Water-use efficiency (WUE) as reflected in the leaf carbon stable isotope ratio was compared between co-occurring indigenous fynbos proteoids and invasive Australian hakeas H. sericea, H. gibbosa and H. suaveolens. At the driest site, H. suaveolens was slightly more WUE than several co-occurring proteoids; there was no significant difference between hakeas and proteas at the other sites. Transpiration rates of shoots and of whole trees were compared between Hakea sericea and Protea repens growing on Stellenboschberg northeast of Cape Town. Both measurements showed no real difference between the species and it is concluded that differences in water relations are not responsible for the highly competitive growth rates of hakeas in fynbos. It is hypothesised that hakeas may be able to vegetatively outcompete proteoids as a consequence of monopodial architecture and some ability to prevent shade-limitation of photosynthesis. A rough estimate of water loss due to transpiration and interception by H. sericea stands indicates that this species may have a significant effect on catchment water loss relative to open-canopy proteoid fynbos. This effect would be due not to transpiration rates of individual trees but to consistently high densities of mature hakea stands.
Open Access
Contesting the termite hypothesis for the origins of heuweltjies in Clanwilliam, South Africa
(2010) Innes, Sheona; Midgley, Jeremy J; Cramer, Michael D
The age and origins of large earth mounds (locally termed "heuweltjies") is under debate, with ages being proposed for between 4500 and 30 000 years old, and hypotheses including zoogenic and geological origins of the mounds. The widely accepted hypothesis for the origins of the heuweltjies found in the South Western Cape of South Africa is that mounds are ancient termitaria, belonging to the southern harvester termite Microhodotermes viator. Our idea was to use rocks and stone layer profiles to determine approximate ages of the heuweltjies as well as to gather evidence to either support or refute the termite hypothesis. We excavated ten mounds in Clanwilliam, South Africa, to gather stone and rock profiles throughout the mounds, as well as digging a trench through a heuweltjie with bedrock as its matrix in order to determine the extent of the bedrock into the mound. No stone layers as such were found. What we did find was that the mounds are a whole order of magnitude greater in volume than large termite mounds made by the northern harvester termite Macrotermes in tropical regions, and many of the mounds contain large rocks both throughout the mound as well as on the surface. The trench cut through the mound on bedrock revealed the bedrock extending all the way to the centre of the mound, on the same level as the surface of the surrounding matrix. This evidence can be used to refute the termite hypothesis for the heuweltjies of Clanwilliam as it is virtually impossible for termites to move rocks up to 25 kg to the top of a mound, and mining soil from beneath a mound with bedrock at its base is an impossibility.
Open Access
The demography of Acacia stands on the Hluhluwe-Umfolozi Game Reserve
(2003) Mader, André Derek; Midgley, Jeremy J
Little is known about the demographics of the genus Acacia in Africa, despite its prominence and the economic and environmental importance of this group. The demographics and species composition of stands of four different Acacia species was investigated in the Hluhluwe-Umfolozi Game Reserve in northern Kwazulu-Natal in order to determine whether stands were self-replacing, or whether other Acacia species were invading them. Soil and stand density as well as the density and composition of the grass layer were investigated in order to determine whether any of these affected Acacia demography and species composition. In three out of four cases, the species whose large size class dominated the stand (known as the "stand species") was found to have a strongly bimodal size class distribution, skewed primarily towards the large size class and secondarily towards the small size class. Other Acacia species in the stands, with few or no large individuals present ("nonstand species") tended to have unimodal size class distributions, skewed primarily towards the small size class and secondarily towards the medium size class. Based on the proportion of small to large individuals, non-stand species are more likely to increase in overall numbers in future, suggesting that the species composition of the stands may be in a state of flux. Few relationships were found between stand density, grass density, grass composition and numbers of small and medium acacias. This could be as a result of differentiation between Acacia species, meaning that they cannot be analysed collectively. Furthermore, sample sizes of individual species may have been too small to analyse individually. Alternatively, it could mean that none of these factors have a significant effect on one another and that other explanations need to be found for the demographics of this genus.
Open Access
The demography of Balanites maughamii : an elephant-dispersed tree
(2012) Bijl, Alison; Midgley, Jeremy J; Kruger, Laurence M
Balanites maughamii is an ecologically and culturally valuable tree species, heavily impacted by elephants, which strip bark selectively off the largest trees, increasing their susceptibility to fire damage. Elephants also break intermediate sized trees extensively, keeping them trapped in non-reproductive stages. The trees can however survive breaking, stripping and · toppling by elephants, as well as top kill by fires, because they resprout vigorously in response to damage. They also produce root suckers. independently of disturbance. Vegetative reproduction buffers the populations from the infrequent recruitment of seedlings, and facilitates the maintenance of populations over the short term. Balanites maughamii trees are reliant on African elephants (Loxodonta africana) for seed dispersal and to provide a germination cue through mastication. In the absence of elephants, the population experiences a recruitment bottleneck, but root suckers functionally replace seedlings and fill the "recruitment gap", so over the short term, the population is resilient. In all populations, whether elephants are present or not, another hurdle affects recruitment, and it is seed limitation due to seed predation pre- and post- dispersal. Cafeteria experiments revealed that bushveld gerbils (Tatera leucogaster) were removing many seeds but do not scatter- or larder-hoard. They are simply seed predators.
Open Access
Determinants of blackwaters in the South Western Cape
(2006) Power, Simon C; Cramer, Michael D; Midgley, Jeremy J
Blackwater rivers and lakelets are a common feature of the landscape in the South Western Cape. Contrastingly, white rivers can also be found in the region. Key to the colour of blackwaters is the increased presence of dissolved organic carbon. The vegetation of the regions is known to posses' large amounts of polyphenols and potentially low microbial decomposition. Therefore, are the plant-soil dynamics a possible answer to variation in river colour? To answer this, the chemical correlates of rivers in the region, along with the in vitro leaching of the fynbos vegetation compared to other types and the effects of nutrient fertilisation on microbial activity in soil were determined. The results revealed that organic carbon, Fe and pH are significantly correlated with blackwaters. The Fe in the water appears to be bound to humic compounds. Fynbos vegetation is able to produce greater concentrations of polyphenol leachates (315 mg/l humic acid) compared to savanna species (246 mg/ humic acid) over a four-day period. P fertilisations increased the concentrations of humic acids from 30 mg/1 to 200 mg/l in some soils through their affinity to bind with humic compounds. The N fertilisations moderately increased the humic acid concentrations and in some cases lowered the concentration by 10 mg/l, indicating that it provided a nutrient source to the microbes for carbon breakdown. The interactions between humic compounds, nutrients and Fe are key to the formation of blackwaters in the region. Attached to this is the limited decomposition that takes place due to nutrient limitations. Therefore, the interactions between the carbon leached from the vegetation and below ground activities are determinants of water colour in the South Western Cape.
Open Access
The dispersal paradox : can lowland granivorous mice also disperse the seeds they devour?
(2003) Gwynne-Evans, David; Midgley, Jeremy J
The relationship between two rodent species and the Cape Reed (Willdenowia incurvata) were examined. Many studies have focussed on the role of rodents as predators of plant seeds. However, it seems that certain rodents may actually perform a crucial role in the dispersal of plants. Experiments to uncover the dispersal mechanism were carried out. Also examined is the role of the appendages present on the Restio seeds, possibly as energy-rich rewards for dispersal for the rodents. It was found that the Restio may be dependent on seed-dispersing rodents, although this mutualism is not so important in fragmented habitats.
Open Access
Dung beetles eat plants : insights into the nutritional world of Euoniticellus intermedius (Reiche) (Coleoptera: Scarabaeinae)
(2007) Yates, Megan; Midgley, Jeremy J; Byrne, Marcus
Dung beetle eggs develop within the finite nutritional environment of the brood ball, which is made using maternally processed animal faeces. It is thought that microbial and gut-derived excretions constitute the major source of N and C for adult dung beetles, while developing larvae, which have retained the mouthparts of their saprophagous ancestors, digest larger particles in the brood ball and rely on symbionts present in the brood ball to provide breakdown products for their nutrition. Stable isotope analysis was used to trace the source of developing larval N and C. Nitrogen and carbon contents, as well as C: N ratios, were used to assess the nutritional quality of this finite food source and to track the changes in these values during the course of development. The main source of both larval and adult N and C was plant-derived and preferential assimilation of gut-derived excretions present in the dung did not occur. Symbionts, including fungi, did not appear to play a significant role in larval nutrition. Extensive amino acid recycling occurs during metamorphosis, indicated by the 0.53 %0 enrichment in 815N in emergent beetles. Maternal processing of bulk dung creates an enhanced nutritional environment for offspring and the maternal faecal deposit, on which the egg is positioned, provides the larvae with an initial, nutrient-rich source of food.
Open Access
Ecological differentiation and the evolution and maintenance of fynbos diversity
(2011) Slingsby, Jasper; Verboom, George Anthony; Cramer, Michael D; Midgley, Jeremy J
Preserving the structure and functioning of ecosystems and the benefits they provide to society depends on our understanding of how biodiversity influences ecosystem function and which processes determine the composition and diversity of biological assemblages. Ecological, evolutionary and biogeographical processes interact to determine the genesis, maintenance and spatio-temporal arrangement of biodiversity. Here I investigate these processes in the Cape fynbos of South Africa by examining the diversification, biogeography and community assembly of a clade of reticulate-sheathed Tetraria species (Cyperaceae:Schoeneae).
Open Access
The ecology of rodent pollination in Liparia parva (Fabaceae)
(2005) Letten, Andrew; Midgley, Jeremy J
The evolution of non-flying mammal pollination has given rise to a broad suite of adaptive plant traits including dull coloured and geoflorous flowers, copious sucrose rich nectar, nocturnal anthesis and nectar production and a musky odour. The Fynbos endemic, Liparia parva (Fabaceae) has been recognised to exhibit several of these traits. Based on this observation, field studies were carried out on the Cape Peninsula, South Africa, to investigate the prediction that L. parva is rodent pollinated. Several lines of evidence indicate that flowers of L. parva are visited by rodents. These include; the presence of Liparia pollen in the faeces of live trapped rodents; observations of captive rodents selectively foraging at flowers of L. parva; floral debris underneath L. parva plants; and video footage captured of a rodent visiting L. parva flowers in the field. However, a strong plant-pollinator relationship was apparent only in the Cape spiny mouse, Acomys subspinosis. Captive Acomys foraged non-destructively at flowers of L. parva, becoming visibly dusted with pollen. The exclusion of rodents from flowers resulted in a significant reduction in seedpod set, indicating rodents do contribute to pollination success in L. parva. Additional evidence that L. parva is adapted to pollination by rodents includes nocturnal floral anthesis and large amounts of total nectar in inflorescences. The findings of this study provide substantial evidence for rodent pollination in L. parva and thus represent the first report of rodent pollination in a legume.
Open Access
The ecology of sprouting in South African forests, savannas and fynbos
(2005) Kruger, Laurence; Midgley, Jeremy J
Sprouting has only recently received attention as a key life history strategy, especially in less disturbance prone environments. The aims of this thesis were to explore the ecological role of sprouting in selected South African biomes. In particular, to explore the biogeographic, community and individual level consequences of adopting sprouting as a life history strategy. The thesis is broadly divided into 4 sections. The first three dealing with the ecology of sprouting in forests, fynbos and savannas respectively; and the fourth undertakes to determine whether sprouting is considered in plant ecological strategy schemes. Chapter 1 and 2 deals with the role of sprouting in forests in relation to reseeding as key regeneration strategies in southern Cape forests. Sprouting has been largely been ignored as a regeneration strategy in favour of reseeding in southern African forests. I found that tall forests are dominated by reseeding species, while sprouting species dominate shorter canopied forests. The relative dominance of sprouters has an effect on forest canopy species richness: as sprouter abundance increases, with decreasing canopy height, canopy species richness decreases. Sprouters are able to retain their in situ position in the forests for longer periods of time than do reseeders, which reduces individual and species turnover, and hence canopy species richness. In Chapter 3 and 4, I explore Proteaceae Life History strategies in relation to fire. Sprouting ability and bark thickness are used as key traits in defining Proteaceae life history strategies. Five functional groups are described and are broadly divided into two categories resisters and non-resisters. Resisters include thick barked fire resisting and epicormic sprouting species and non-resisters basal sprouting and thin barked non-resistant species. Sprouting strategy and bark thickness were also found to influence plant architecture and hence individual and stand flammability. Non-resisting species tend to display a more ramified architecture, resulting in a more flammable state. Conversely, thick barked species tend to display a less ramified and therefore more fire resistance architecture. In Chapter 5 I explore how changes in disturbance regime affect Acacia life history strategies in Hluhluwe-Umfolozi Park, KwaZulu Natal, South Africa. Four functional groups are defined based on sprouting ability, bark thickness, seed mass, plant height and wood density. The functional groups are seen to reflect local disturbance regimes: Acacia species found in mesic, frequently burnt portions of the park sprout strongly as adults and/or are fire resistant, but are poorly defended against herbivory. Conversely, species found in more xeric portions, where fire frequency is lower, and herbivore densities higher, are fire-sensitive, well defended against herbivory and sprout weakly as adults. Chapter 6 addresses whether plant ecological strategy schemes take sprouting into account as a key life history strategy. Westoby's LHS scheme, which comprises specific leaf area (SLA), plant height and seed mass, is of the more practicable existing plant ecological strategy schemes. I show that the LHS scheme does not consistently identify sprouting across genera or families. In general, basal sprouters tended to be shorter than congeneric reseeders, but there were no consistent patterns for SLA or seed mass. The results suggest that sprouting ability is mostly orthogonal to other life history traits and should be therefore considered as a separate attribute. A published paper, which is ancillary to the main themes of the thesis, has been included as an appendix.