Dissertations / Theses on the topic 'Succulence'

The architecture of a plant is intimately tied to its fitness. Knowledge of the processes and patterns of growth form evolution can therefore contribute to a richer understanding of plant evolution. The genus Adenia (Passifloraceae) of ca. 100 species is an Old World lineage in which growth form radiated. I constructed a molecular phylogeny of the group, analyzed the stem and tuber anatomy of over half the species, and investigated patterns of growth form evolution in a phylogenetic context. I also described four new species and a new combination. Predictions based on evolutionary developmental models of growth form evolution were tested in Adenia, and one of them, the homeotic switch hypothesis, was tested throughout the eudicots. The switch hypothesis claims that the storage tissue of tubers and stems results from a common developmental origin. Phylogenetic analyses revealed that growth form transitions were frequent, and anatomical studies revealed traits that are associated with each growth form; moreover, traits are shared between tubers and succulent stems as predicted by the switch hypothesis. As expected, tuberous plants and succulents are also closely related across the eudicots. The switch hypothesis is substantiated in Adenia and the eudicots as a whole.

The task of research: 1.To analyse and systematic body measures data; 2.to analyse and systematic control slaughter’s data; 3.to count correlation coefficients between different features. Methodology. It was found correlation coefficients between body measures, growth speed, carcass output and succulence. Correlation coefficients were count by using computer program – Excel. And correlation coefficient’s reliability was found by Snedekor. Conclusions: 1.Between separate body measures and growth fastness was determinated some connexion. The biggest correlation coefficients were between body measures and growth fastness in different periods of life r = 0,444 – 0,688 (P< 0,01). 2.The biggest correlation coefficients were determinated between hinder body parts measures and succulence r = 0,493 – 0,694 (P<0,01). 3.Because these high correlation coefficients show the firm belonging between determined features, so to fulfill the selection we need to take it to account. 4.It was noticed, that bulls which were dwars, they had bigger weight in different periods of their growth, instead the lofty ones. 5.The biggest growth fastness for Lithuanian Black and White breed bulls was definited from 12 – 15 months. They distinguished the biggest weight in this period. So, the most effective way to feed up these bulls would be till this period – 12 – 15 months.

The salinity tolerance of golden barrel cactus (Echinocactus grusonii), ocotillo (Fouquieria splendens), saguaro cactus (Carnegiea gigantea), and Gentry’s agave (Agave parryi truncata) was tested. Plants were irrigated with a solution of EC 0.6, 5.0, 10.0, and 15.0 dS/m. Duration of treatments were 18 weeks for saguaro and 26 weeks for the other three species. In general, fresh weight, dry weight, and moisture content decreased with increasing salinity levels, with the exception of saguaro dry weight which was not affected by the treatments, and ocotillo moisture content which increased with increasing salinity. Runoff was collected three times during the experiment and indicated that ion uptake was higher for barrel cactus than the other three species. EC of runoff averaged for all dates and species showed an increase of 17%, 54%, 46%, and 64% over the salinity treatment solutions of 0.6, 5.0, 10.0, and 15.0 dS/m, respectively.

This study aims to develop a predictive understanding of the resource use, impacts and interactions of elephant Loxodonta africana and black rhinoceros Diceros bicornis in the succulent thickets of the Eastern Cape, South Africa. While these megaherbivores typically dominate the biomass, elephant are more abundant, such that their impacts off-set that of all other herbivores. Consequently, this thesis has three main foci: first, developing a mechanistic understanding of the influences of elephant; second, developing predictive insights into elephant impacts on plant communities; finally, an understanding of the knockon-effects of the impacts for coexisting rhinoceros. Thus, by documenting the diet and dietary preferences of elephant, I firstly show that only about 18 percent of the species previously thought vulnerable to herbivory, occur in the diet. This refutes the generally held belief that elephant herbivory is the primary driver of decline among plants, and emphasizes the likely contribution of other mechanisms (e.g. trampling, knock-on-effects, etc.). Thus, the accurate prediction of the impacts caused by elephant requires an understanding of previously marginalized mechanisms. From here, I quantify >50 years of impacts on the thicket shrub community and test their spatial and temporal extent near water. I confirm the vulnerability of thicket to transformation (particularly near water) as the accumulated influences of elephant reduce community composition and structure, and predict that these impacts will eventually bring about landscape-level degradation and a significant loss of biodiversity. Importantly, results show an uneven distribution of effects between elements of this community: from community composition and structure, to the structure of individual canopy species and ecological functioning. While these findings confound our interpretation of the extent of the impacts, it demonstrates the importance of explicitly recognizing biodiversity and heterogeneity for the conservation management of elephant. Finally, I test the consequences of the impacts for coexisting rhinoceros. While I show that this causes rhinoceros to change their foraging strategies in the presence of elephant at high densities, I also show that elephant may facilitate access to food for rhinoceros at reduced densities. These findings indicate the importance of elephant in driving the structure and composition of the thicket shrub community and the consequences of this for coexisting large herbivores. Thus, developing a predictive understanding of the spatial and temporal variations of elephant impacts between elements of biodiversity and the mechanisms driving these changes are key to their management. This implies that the effective conservation management of elephant can only be achieved through the careful, scientific design of monitoring programmes.

Effects of media, soil moisture, fertility rate, and plant growth regulators on plant growth were investigated for 13 taxa of succulents. Media: Liners were grown in five common greenhouse substrates: 80% peat, 60% bark + 30% peat moss, 80% pine bark/20% Permatil (v/v), 100% composted pine bark, or whole tree substrate until market ready. Overall, higher percentage bark mixes yielded smaller plants, with lower shoot dry weights, shoot heights and widths. Soil Moisture: Liners were potted into a 60% bark/30% peat soilless potting mix. In group 1 , irrigation to container capacity occurred when volumetric soil moisture content fell below 30%, 20%, or 10%,. Group two (seven species) irrigation thresholds were shifted to 35%, 25%, and 15%. Effects of irrigation rate were significant in three of the 13 species studied, and those effects were species-specific. Fertility Rate: Liners were potted into60% bark/30% peat substrate. Fertility reatments in group were 0, 50, 100, or 200 mg.L-1 nitrogen. Group 2 plants received treatments of 50, 150, 250, or 350 mg.L-1 nitrogen. Four of the 11 species studied were affected by nitrogen rate, with rates up to 200 mg.L-1 generally producing the largest plants. PGRs: Seven species were potted into a 60% bark/30% peat substrate. Group one plants were treated with a foliar application of benzyladenine (Configure) at rates of 0, 400, 800, or 1600 mg.L-1. Group 2 plants were treated either BA at 0, 250, 500, or 1000 mg.L-1, dikegulac sodium (Augeo) at 400, 800, or 1600 mg.L-1, or a tank mix of 500 mg.L-1 Configure and 800 mg.L-1 Augeo. BA caused an increase in branches leaders or offsets in two species.
Master of Science

This thesis focuses on vegetation patterns and plant reproductive processes at the Tierberg Karoo Research Centre (33°1 0'S, 22°17'E) in the semi-arid southern Succulent Karoo, South Africa. It begins with an investigation into the roles of soil properties and competition in explaining variation in species distributions. The aim was to investigate changes in soil properties associated with species turnover (replacement series). Patterns of species abundances have been attributed to cyclic succession driven by disturbance and inter-specific competition. Areas where dominant species replaced each other over apparent edaphic discontinuities were investigated to test the roles of soil properties and competition in explaining variation in species distributions. Only soil pH differed significantly across the gradients studied. However, inter-and intra-specific· competitive interactions were also inferred. It was concluded that species distribution patterns resulted from the combined effects of edaphic factors and competition. The bulk of the thesis focuses on the reproductive biology of key species in the cyclic succession in order to understand the demographic processes underlying these patterns. The vegetation model proposes that heuweltjies (or mima-like mounds) are the source of disturbance which initiates the successional process. A study of reproductive attributes of dominant species occurring on and off heuweltjies indicated that species occurring on heuweltjies had opportunistic life-history traits; seeds did not germinate readily and canopy seed banks were maintained. Species off heuweltjies had higher overall germination and did not maintain seed banks in the plant canopies. The differences in reproductive attributes were related to competition and disturbance.

Includes bibliographical references (leaves 99-106)
This dissertation takes its lead from the need to add to the debate issues of institutional arrangements when evaluating the effectiveness of biodiversity conservation programs. The particular case in point is the Succulent Karoo Ecosystem Program (SKEP), which was initially set up by a NGO, Conservation International (CI), and thereafter transferred to another host institution, a national parastatal called the South African National Biodiversity Institute (SANBI). This dissertation set out to investigate the optimal institutional mechanism for coordinating SKEP. in light of its transition from CI to SANB!. This was done by evaluating the current coordination mechanism. A systems theory approach guided the research. An action research approach ensured that the results would be practical to the coordination unit of the SKEP program. Grounded theory analysis was used to analyze and make sense of the data and provide guidance on the functions and structure of the coordination unit and its supporting structures.

Thesis: S.M. in Science Writing, Massachusetts Institute of Technology, Department of Humanities, Graduate Program in Science Writing, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 41-45).
The Caribbean spiny lobster fishery is one of the most important industries in the economy of the Bahamas, and in turn it is one of the largest lobster industries in the world. The natural geography of the Bahamas makes its waters into a lobster haven that Bahamian fishermen have successfully exploited over the past few decades. In 2009, in order to safeguard the industry's future and earn a higher margin, the government and the lobster processors together sought sustainability certification for their product. However, they came up short. The international assessors deemed the data on the health of the lobster stocks to be too minimal, and the legal structures to protect the lobster from over-harvesting to be too weak. In response, the government, together with the World Wildlife Fund, set up a program called the Fishery Improvement Project to get the country's lobster industry on the right track. Under the auspices of the Fishery Improvement Project, the government, local and international NGOs, the processors, and the fishermen themselves are contributing to improving the availability of information on the lobster and to crafting new laws to control the industry. Despite successes in improved communication and stock assessments, there are many obstacles to be overcome: differences of opinion, the spread-out nature of the country, and the limited resources available to enforce the laws. Through interviews with fishermen, government officials, processors, and scientists, this thesis tells the story of how the Fishery Improvement Project began, what it has accomplished, and where the lobster and the humans who harvest them might go from here, when the program wraps up and the fishery reenters the sustainability certification process.
by Jennifer E. Rood.
S.M. in Science Writing

Thesis (MSc) -- University of Stellenbosch, 2004.
ENGLISH ABSTRACT: This thesis focuses on the effects of vegetation resting on biodiversity and community dynamics at Rocherpan Nature Reserve (320 36'S, 180 18'E) in the semi-arid coastal strip of the Succulent Karoo known as Strandveld. As a whole, the Succulent Karoo has an extraordinary high level of phyto diversity with high levels of endemism. This is particularly true for succulent shrubs belonging to the groups Mesembryanthemaceae, Crassulaceae and Asteraceae. The thesis begins with an investigation into effects that vegetation resting has on plant diversity. The aim was to determine if resting affected biodiversity levels and if so, which plant groups are affected and why. Through a numerical approach, it was determined that with resting overall species richness remained the same. However, different plant life forms responded to resting differently. With increased resting, abundance of succulent shrubs decreased, while richness of annuals increased. The second aspect under investigation was to determine how resting the vegetation affected community dynamics. The aim was to understand how vegetation structure and interspecific associations changed with resting and to apply these findings to known community models. Through an autocorrelation approach, it was found that horizontal patterning of long-lived woody species, that formed distinctive vegetation clumps, did not change with resting, while differences were found in woody matrix species and succulent species. These changes in structure were investigated further through a study on the demography of specific species. Demography of woody species associated with vegetation clumps did not change with vegetation resting, while significant changes were observed for woody matrix species and succulent species. In longer rested vegetation, woody matrix species showed a greater range in size class distribution (i.e. had both very large and smaller plants) with the tendency towards larger plant sizes. Succulents on the other hand, had a smaller range in size class distribution with a tendency towards larger plants. For all species investigated there were low seedlings counts. It was concluded that succulent shrub populations were 'mature' and continued resting could result in local extinction of some species due to the lack of regeneration. The overall lack of seedlings was attributed to a saturated establishment environment. Implications for conservation management were discussed.
AFRIKAANSE OPSOMMING: Hierdie tesis fokus op die gevolge van plantegroeirus op biodiversiteit en gemeenskapsdinamika by die Roeherpan Natuurreservaat (320 36'S, 180 18"0) in die halfdor kusstrook van die Sukkulente Karoo, bekend as die Sandveld. In die geheel gesien het die Sukkulente Karoo 'n buitengewone hoë vlak plantdiversiteit met hoë vlakke endemie. Dit is veral waar vir sukkulente struike wat tot die groepe Mesembryanthemaceae, Crassulaceae en Asteraceae behoort. Hierdie tesis ondersoek eerstens die gevolge wat plantegroeirus op plantdiversiteit het. Die doel was om te bepaal of rus die biodiversiteitsvlakke beïnvloed het en indien wel, watter plantgroepe en waarom. Deur middel van 'n numeriese benadering is bepaal dat die algehele diversiteit, numeries gesproke, met plantegroeirus dieselfde gebly het. Verskillende plantlewensvorme het egter verskillend gereageer. Met toenemende rus het die diversiteit van sukkulente struike afgeneem, terwyl die diversiteit van jaarplante verhoog het. Die tweede aspek wat ondersoek is, was om te bepaal hoe die plantegroeirus die dinamika van die omgewingsgemeenskap beïnvloed het. Die doel was om te verstaan hoe die struktuur van die plantegroei en die interspesifieke assosiasies verander het met rus en om dan hierdie bevindinge toe te pas op bekende gemeenskapsmodelle. Deur middel van 'n outokorrelasiebenadering is gevind dat die horisontale patrone van meerjarige houtagtige spesies wat in duidelik-uitkenbare plantegroeigroeperings voorkom, nie met rus verander het nie. Veranderinge is egter wel in die houtagtige matriksspesies en die sukkulente spesies waargeneem. Hierdie veranderinge in struktuur is verder ondersoek deur 'n studie te maak van die demografie van spesifieke spesies. Daar is gevind dat die demografie van houtagtige spesies geassosieer met plantegroeigroeperings nie met plantegroeirus verander het nie, maar beduidende veranderinge is waargeneem in die geval van houtagtige matriksspesies en sukkulente spesies. By plantegroei wat langer gerus het, het die houtagtige matriksspesies 'n wyer verspreiding in klasgroottes vertoon (d.i. daar was baie groot plante én kleiner plante) met 'n gemiddelde afname in plantgrootte. Sukkulente, aan die ander kant, het 'n kleiner verspreiding in klasgroottes vertoon met 'n neiging tot groter plante. Vir al die spesies wat ondersoek is, was daar lae saailingtellings. As gevolg van die "volwassenheid" van die populasies van sukkulente struike, sou voortdurende rus, weens die gebrek aan regenerasie, kon lei tot die plaaslike uitwissing van sommige spesies. Die algemene gebrek aan saailinge is toegeskryf aan die versadigde vestigingsomgewing. Die implikasies VIr natuurbewaringsbestuur word bespreek. v

This study looks at the impact of elephant feeding on the Xeric Succulent Thicket component of Eastern Cape Subtropical Thicket (ECST) in Addo Elephant National Park (AENP). Observations of elephant feeding were carried out and vegetation transects were surveyed for impact of elephant feeding. The results indicated that the Nyati elephants spent the majority of their time grazing (nearly 90%), particularly the cow-young herds, and especially when the herd gathered in larger numbers. Browsing events were concentrated on Acacia karroo (81%) and there was no significant difference between the sexes in their preference for this species. Despite being subjected to most of the browsing, the majority of A. karroo trees were undamaged and the effect of elephants was generally light. It appears unlikely that, three years after re-introduction to Nyati, the elephants have had an effect on community structure of the vegetation. Surveys were conducted on stands of the alien invasive weed prickly pear Opuntia ficus-indica, and it was recorded that elephants in Nyati have had a dramatic effect on prickly pear, utilising all adult plants assessed and destroying 70% of them. This level of destruction in such a short period of time suggests that prickly pear is a highly favoured species. The results from the present study suggest that elephants can play a role in the control of prickly pear. Results are discussed in terms of elephants as both megaherbivores and keystone species, and as agents of intermediate disturbance.

Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv & Cons Biol)
Fire as a form of disturbance is unique in the way it impacts upon the environment, acting like a herbivore with a ubiquitous appetite. Consuming both dead and living material, converting complex organic molecules into organic and mineral products, which return to the soil. The role of disturbance has long been considered a driver of diversity within Mediterranean type ecosystems. Recently the interest in soil microbes has been piqued, as the importance thereof has been emphasised, particularly their role in nutrient cycling and the chelation of essential plant nutrients. The occurrence of fire results in several environmental and ecological impacts on soil, as well as the dynamics of the microbial populations present. This study explores the impact of fire as a disturbance on the plant and bulk soil microbial communities of the Succulent Karoo. This was achieved through two sub-studies, in which three different states were studied: unburnt, 7-year and 2-year post-fire. Today microbial profiles are also used as indicators of disturbance, thus many techniques exploring microbial community composition are available.

The purpose of this study was to determine the reproductive biology of Ruellia succulenta and to relate this to the effects of habitat fragmentation. Plants occurring in the intact habitat in Everglades National Park were compared to plants occurring in three different size classes of habitat fragments. The results of the breeding system experiment show R. succulenta to be fully selfcompatible and capable of autofertility via corolla abscission. Results of the inbreeding depression study supported theoretical expectations for selfing species of reduced inbreeding depression and its expression late in the life cycle. The most significant effect of habitat fragmentation, in terms of pollination ecology, was a highly significant difference in the proportion of Hymenopteran and Lepidopteran floral visitors by the size class of habitat. Time since last fire was the most important factor positively affecting reproduction in the different size classes of fragments.

Thesis (MScConsEcol(Conservation Ecology and Entomology)--Stellenbosch University, 2008.
The Succulent Karoo biodiversity hotspot is threatened by pressure caused by increasing human populations and its associated land use types. Land use is primarily focussed on agriculture, with livestock grazing as a dominant land use in the region. Cultivation is also practiced along the major perennial rivers, and in drier areas, where this largely depends on rainfall. Only about seven percent of the biome is formally protected, and this area substantially under-represents the biodiversity of the Succulent Karoo and does not incorporate key ecological processes and biodiversity drivers. Therefore, there is urgent need for outside reserve conservation initiatives, whose success depend on understanding the ecosystem function of the Succulent Karoo. This study aimed to determine the impacts of heavy grazing, light grazing and cultivation (in a 30-year old fallow field) on assemblages of ground-dwelling and flying invertebrates. Seasonal assemblage changes were also determined. Vegetation structure and composition were determined using the line-intercept method to determine if vegetation patterns explain patterns in invertebrate assemblages. Abandoned fields harbour the lowest number of plant species, and these together with the heavily grazed sizes are dominated by a high cover of Galenia africana (Aizoaceae). Lightly grazed sites have the highest structural complexity, with a high cover of succulents and non-succulent perennials. After the winter rains, annual plants occupy most of the bare ground in heavily grazed and previously cultivated sites. Seasonal changes in assemblages of ground-dwelling and flying invertebrates were determined by sampling during the four seasons at the same localities. Results of pitfall traps sampling for ground-dwelling invertebrates and coloured pan traps for flying invertebrates showed that overall species richness and diversity peaked in spring for flying invertebrates while peaks in richness for ground-dwelling invertebrates were in summer, with no difference in overall diversity. Overall abundance for ground-dwelling invertebrates was highest in summer and lowest in winter. Ground-dwelling invertebrate fauna was dominated by Formicidae and Araneae. Grazing and cultivation lead to skewed community composition of ground-dwelling invertebrates which favours disturbance tolerant and generalist species such as Anoplolepis steingroeveri (Forel).

In the semi-arid Succulent Karoo water is one of the most limiting resources, and plants that survive in the area require competitive water-use strategies suited to long periods of drought. Over the years much emphasis has been put on mechanisms that allow for the competitive success of water-use strategies, and root structure features as an important attribute. This study investigated soil drying cycles in the semiarid Succulent Karoo. It measured the rates at which soil water was depleted at two different depths in five different microhabitats, and investigated whether these are related to different rooting systems. Three prevalent plant species in the region were used, namely Leipoldtia schultzei of the Mesembryanthemaceae, Tripteris sinuata of the Asteraceae, and Galenia africana of the Aizoaceae, all of which have their roots in the upper 20cm of soil. However, Leipoldtia's roots are concentrated in the top 5cm of soil, while the other two species root mainly at depths between 10 and 20cm. This vertical separation of roots provided the opportunity to relate soil water depletion at two different depths (0-10cm and 10-20cm) to the different rooting strategies, and explore what this means in te1ms of compatibility between close neighbours and seedling establishment under adult plants. The shallow-rooting Leipoldtia showed the highest rates of soil moisture depletion in both the shallow and deeper soil zones, and is therefore a strong competitor for water and probably an undesirable neighbour. Soils at both depths below Tripteris plants maintained the highest moisture content over the 2-week period of sampling, suggesting it to be favourable site for seedling establishment. Galenia showed intermediate soil-drying effects in the upper 0-10cm, but high rates of moisture depletion at 1 0-20cm below the surface, suggesting that it may be a suitable neighbour for shallow-rooting species but not for other deeper rooting species. Additionally, the two sampling methods - electronic probe readings and gravimetric analysis - were examined. The two methods correlated fairly well to each other (R2 = 0.759 ± 0.002), although the probe readings were consistently higher and showed greater variation (probe SD = 2.8 as opposed to gravimetric SD = 1.2)

Bibliography: leaves 100-114.
Human-induced land management practices are key factors which influence the dynamics of landscapes, land elements and biotic communities in Xeric Succulent Thicket, a notoriously fragile and low resilience ecosystem in the Eastern Cape, South Africa. In its natural state this vegetation type is characterized by a continuous mosaic of clumps of diverse woody shrubs in a matrix of grass, hardy dwarf shrubs and bare ground. When indigenous herbivores are replaced by domestic livestock at unsustainable stocking rates, the ratio of clump to interclump areas decreases. This has impacts on biodiversity at the landscape level, and affects the composition and species richness of plant, arthropod and reptile communities and fungal symbionts. The study has two main objectives: 1) to detennine the local-level effects of different types of land use on biodiversity in Xeric Succulent Thicket; and 2) to better understand the factors which affect biodiversity in different taxonomic groups and at different spatial scales, so that the preservation function of protected areas could be enhanced. The key questions which are addressed in the thesis are what does 'biodiversity' mean, and what are its different dimensions in Xeric Succulent Thicket; what roles do protected areas and other lands play in preserving biodiversity, how are different taxonomic groups affected by different types of land use; and how can biodiversity be monitored and measured? . The regional 'conservation landscape' is seen as the protected area plus the land immediately adjoining it, and is viewed as an integrated mosaic of anthropogenic landscapes (land management units), land elements (patches within landscapes). producer communities (assemblages of interacting plant species), consumer communities (assemblages of interacting herbivores and predators) and soil microorganisms. From a process point of view, the research relates the intensity of disturbance, mainly as a result of herbivory, to landscape complexity, the structure of land elements, and the species richness of producers and consumers within land elements. The patterns which emerge are interpreted in the context of ecosystem functioning, from the point of view of a practicing conservation biologist.

Little is known about the vegetation dynamics of the Karoo region of South Africa. The aim of this study was to focus on the role of the "availability of suitable space" in the regeneration of Succulent Karoo vegetation. By undertaking a series of manipulative experimental transplants and pattern analyses, it was shown not only that shrubs in the Karoo facilitate other species by provision of 'sui table space' beneath their canopies, but also that certain shrub species are more effective "nurses" I than others . The plants dependent on nurse plants are referred to as "patient" plants. Not only did the 'main patient species Tylecodon wallichi require nurse plants generally for successful establishment, but this species was also most successful (in terms of reaching maturity) beneath a specific nurse Pteronia pallens. Thus the patient was "nurse specific". In time however, the initial commensal relationship between the nurse and the patient (whereby the patient benefits and the nurse is unaffected) changes to a competitive one, since nurse vigour declines as the patient grows larger. Despite this area being arid, a manipulative experimental investigation revealed that competition between the nurse and the patient was not for water. An examination of the rooting patterns of the two species showed that their root systems were separated in vertical and horizontal space. Though the mechanism of competition between Pteronia and Tylecodon was not resolved in this study, the patient Tylecodon did appear to reduce nurse vigour and ultimately replace the nurse Pteronia pallens. Since specific species associations do exist (i.e. some patient species are nurse specific), the replacement of one species by another (the nurse by its patient) is predictable and so 'succession' at the scale of the individual plant can be said to occur in the Karoo.

Thesis (MTech (Horticulture))--Cape Peninsula University of Technology, 2018.
Drosanthemum micans and Drosanthemum hallii are endangered succulent shrubs of horticultural and medicinal value. They are restricted to the Succulent Karroo, which is one of the world’s biodiversity hotspots. The species risk extinction from illegal over-harvesting for water-wise gardens, erosion by occasional flush floods from ephemeral rivers, competition from alien invasive species, overgrazing and clearing of land for agriculture and human settlement. Although seeds and cuttings may be used in propagating these species, they often require seasonal collection and planting and cuttings struggle to establish, hence the need for in-vitro propagation as an alternative solution. Thus, the main objective of the study was to develop a method for rapid in-vitro shoot and root multiplication and acclimatization of D. micans and D. hallii. To initiate shoot formation, disinfected leaf and stem nodal explants were cultured in Murashige and Skoog (1962) media supplemented with different rates (0, 10, 20 or 30μM) of 2-isopentyladenine, 6-Benzyladenine and kinetin for D. hallii or 2-isopentyladenine, 6-Benzyladenine and Thiadiazuron for D. micans. Shoots from explants were rooted in varying rates (0, 10, 20 or 30μM) of IAA for root initiation. Three media, which were used in previous studies, were tested for acclimatization of rooted explants in i) vermiculite, ii) sand (50%): vermiculite (50%) or iii) sand (75%): perlite (25%). For quantitative evaluation of plant stress, chlorophyll fluorescence index (Fv/Fm) was measured as a proxy for plant stressf stress. It emerged that stem nodal explants of D. hallii tend to produce multiple shoots whilst leaf explants tended to produce callus when cultured in full-strength Murashige and Skoog (1962). Shoot multiplication was optimal in both D. hallii and D. micans at 10 μM of kinetin. Root formation in both D. hallii and D. micans only occurred when shoots were transferred to a full-strength Murashige and Skoog (1962) media without any phytohormones added. The intensity of tissue browning increased at higher levels of cytokinins, suggesting an interaction of plant growth regulators with exudates from explants. Different acclimatization media tested showed no significant differences in the level of stress (Fv/Fm). It is recommended that Murashige and Skoog (1962) media with10 μM kinetin be used for shoot development and multiplication, followed by transfer of the shoots to fresh full-strength Murashige and Skoog (1962) media without hormones for root development. Acclimatization of the rooted explants was possible in one of the following media: i) vermiculite, ii) sand (50%): vermiculite (50%) or iii) sand (75%): perlite (25%) and in a misted greenhouse (ca. 60% RH), with gradual weekly reductions in humidity by 10% over 2 weeks.

Systematic conservation planning is about making spatially explicit decisions regarding the use of land, based on the observed or expected biodiversity present at a site and the potential for that same site to support alternative /and-uses that are not compatible with the persistence of biodiversity. This thesis examines three questions relating to the application of systematic conservation planning: Which biodiversity surrogates should be used in Namaqualand to do systematic conservation plans? How should targets be set for these surrogates? How can this information be integrated and used within a systematic conservation planning framework? Comparing how well different biodiversity surrogates achieved a set of targets illustrated that continuous biodiversity data (i.e. vegetation types and land-classes) perform better as surrogates than point-based species distribution data. Quarter degree square-based species distribution data cannot be used for on-the-ground conservation planning. It was demonstrated that it is possible to set biologically meaningful conservation targets to represent biodiversity pattern in land classes by applying the Species Area Relationship and using plot-based survey data. The method developed here has the potential to revolutionise conservation planning as it provides for the first time a defensible means for setting representation targets for land classes that are grounded on ecological theory and that use real data. The thesis also explores the potential for metapopulation and fragmentation studies to provide useful insights into developing targets for ecological processes by relating the amount of remaining habitat to key thresholds in probability of population persistence. Two examples, at different spatial scales (1:10 000 and 1:100 000), are used to illustrate how different biodiversity information can be integrated and used within a systematic conservation planning framework. At the finer scale biodiversity and land-use data are 3 used to set priorities for the development of a statutory reserve in the Knersvlakte region of the Succulent Karoo using cadastres as planning units. At the larger scale the data are used in the same region to design a biosphere reserve that promotes the persistence of ecological processes in the landscape using gridded planning units. Both studies use the C-Plan software to assist in the planning and design process. A lesson from both these studies is that there needs to be a paradigm shift in conservation from an on/off reserve mindset to a more integrative whole landscape mindset.

Transformation in the arid succulent thicket of the Eastern Cape of South Africa in response to unsustainable livestock production has been widespread, with less than 10 percent remaining intact. Transformation in succulent thicket has resulted in large areas of dense thicket (comprising a two-phase mosaic of perennial-vegetated patches separated by animal paths and bare patches) being replaced with a ‘pseudo-savanna’ of remnant canopy trees with a structurally simple field layer of ephemeral and short- lived perennial grasses and forbs. There is an extensive literature describing the transformation of succulent thicket, with many speculative statements about the underlying mechanisms of transformation. The central focus of this study was to improve our mechanistic understanding of transformation in succulent thicket using field experiments. Hopefully these results will set another foundation upon which future management of succulent thicket can be improved and large-scale restoration initiated. This study comprises four themes that are linked to the concept of landscape function. The central premise of landscape function is that functional landscapes have mechanisms that capture and retain scarce resources. Conversely, as landscapes become increasingly dysfunctional, so these mechanisms become disrupted. In succulent thicket, dysfunctio n appears to be linked to the reduced ability to harvest water, cycle carbon and a loss of organic carbon. In this thesis I examined some of the key processes that influence water and organic carbon fluxes: perennial vegetation cover, soil fertility, litter fall and decomposition, and runoff and soil erosion. The experimental design that was used for all this work was a factorial ANOVA based on replicated fenceline contrasts that reflect differences in long-term management history. The main objectives of this thesis were to: quantify the patterns of transformation in an arid form of succulent thicket, including changes in the biomass, cover and structure of the dominant vegetation guilds; test the stability of the transformed succulent thicket ecosystem to show whether it is a new stable state or an intermediate stage in a trajectory towards a highly desertified state where only the ephemeral grasses and forbs persist; describe and compare soil fertility across transformation contrasts, concentrating on changes in the spatial patterns of soil resources and the ability of the soil to harvest precipitation; to compare litter fall and decomposition of leaf material from the dominant plants in intact and transformed succulent thicket; to quantify and compare run-off and erosion from run-off plots in intact and transformed succulent thicket. Transformation and stability I quantified the changes in plant diversity, physiognomy and biomass that occur across transformation contrasts. Thicket transformation results in a significant loss of plant diversity and functional types. There is also a significant reduction in the biomass (c. 80 t.ha-1) and structural complexity of the vegetation, both vertically and horizontally. These results were interpreted in terms of their implications for ecosystem functioning and stability. To test the stability of the transformed succulent thicket I used aerial photographs and ground-truthing to track the survivorship of canopy trees over 60 years in pseudo-savanna landscapes. I also measured seedling establishment in different habitats. I show that the pseudo-savanna is not a stable state owing to ongoing adult mortality and no recruitment of canopy trees. Soil fertility and water status I hypothesised that the above-ground changes in ve getation would be accompanied by similar trends in the pattern and levels of soil nutrient resources and the ability of the landscape to harvest precipitation. I compared soil fertility (organic carbon, available nitrogen and phosphorus), texture, matric potential, and surface micro-topography in the two main micro- habitats on either side of the replicated fenceline contrasts. The results show that intact spekboom thicket has a distinct spatial pattern of soil fertility where nutrients and organic carbon are concentrated under the patches of perennial shrubs, compared to under canopy trees and open spaces. Transformation results in a significant homogenisation out of this pattern and an overall reduction in the fertility of the landscape. The proportion of the landscape surface that would promote infiltration of water decreases from 60 – 0.6 percent. Soil moisture retention (matric potential) also decreases with transformation. I interpreted these patterns in terms of the ability of the landscape to harvest and release water after rainfall events. Litter fall and decomposition Surface litter and soil organic matter are critical components to wooded ecosystems; contributing to several ecosystem functions. The rates of litter fall and decomposition are ratelimiting steps in nutrient cycling and incorporation of organic matter into the soil. The ecological mechanisms behind the collapse of succulent thicket in the face of domestic herbivory are not fully understood, but are believed to include the breakdown of several ecosystem processes, including litter fall and decomposition. I quantified the changes in litter fall and litter decomposition of four of the dominant perennial woody plants (Euclea undulata, Pappea capensis, Portulacaria afra and Rhus longispina) across the replicated fenceline. Litter fall was measured over 14 months using mesh traps. Decomposition was measured over 15 months using a combination of litterbags and unprotected leaf packs. I also quantified soil microclimate during the experimental period; hypothesising that transformation would lead to soil conditions less amenable for biotic activity. Litter fall in succulent thicket was very high for a semi-arid system, comparing more to temperate forests. The leaf-succulent P. afra contributed the largest single component of the total litter production at a landscape scale. The effect of transformation on litter fall was species specific. Deep-rooted or drought-adapted species showed no change in litter yield with transformation; shallow-rooted species showed a significant decrease. There were few significant differences in decomposition rates across the transformation gradient and between litter types. Portulacaria afra litter had the steepest rate of mass loss, and was most affected by transformation. The more recalcitrant (high C:N ratio) leaves of P. capensis remained largely unaffected by transformation. These results indicate the critical role of the perennial vegetation in incorporating organic carbon into the soil. Transformation of succulent thicket leads to a disruption of the flow of carbon into the soil, reinforcing the cycle of transformation through reduced fertility. Rehabilitation of this ecosystem will require the active establishment of species, such as P. afra, that will restart the flow of carbon into the soil. Run-off & Erosion The landscape function model predicts that functional semi-arid shrublands efficiently conserve limiting resources such as water and water-bourn sediments (soil and organic matter). As these rangelands become transformed through unsustainable livestock production, so their ability to conserve resources decreases. The primary determinant of landscape function and conservation of resources appears to be the proportional cover of perennial vegetation. I hypothesised that the switch from a two-phase mosaic dominated by perennial succulent and woody shrubs to a single phase system dominated by an ephemeral field layer would be accompanied by disruption of the mechanisms that conserve resources. Specifically, I tested the hypothesis that transformation of succulent thicket increases runoff volume, sediment concentration of runoff, soil erosion and loss of organic matter at a patch scale (c. 100 m2). Runoff and water-borne sediment were measured from runoff plots established across replicated fenceline contrasts. Data were collected from eight extreme weather events over two years. There were no significant differences between runoff and erosion across the transformation contrast, as each extreme weather event was unique in terms of its runoff response. The transformed runoff plots alone also gave inconsistent results, largely due to differences in the cover of ephemeral forbs and weakly perennial grasses. Runoff and erosion were not predictable from the data across the transformation gradient due to complex interactions between the nature of the above-ground vegetation, soil micro-topography and land use history. The results highlighted the need for longer-term catchment experiments to generate a predictive understanding of the effect of transformation on runoff and erosion in succulent thicket.

Thesis (M.A. (Botany)) --University of Limpopo, 2012
Several South African Euphorbia species are threatened with extinction, yet only a few have been studied in sufficient detail to develop a conservation management plan based on sound scientific principles. The focus of this study was on one of the highly threatened dwarf Euphorbias, namely Euphorbia groenewaldii. Apart from a report on the species distribution and estimated population numbers by Raal (1986), virtually nothing is known about this attractive succulent species. Conservation and management of threatened species requires a thorough understanding of their biology, ecological requirements and spatial distribution which should form the basis of a monitoring programme that must be conducted at regular intervals. Euphorbia groenewaldii is endemic to six rocky schist and quartzite ridges in the vicinity of Polokwane, the capital of South Africa’s Limpopo Province. The species’ small global range, small number of populations and small population sizes in some instances, render the species susceptible to anthropogenic and environmental stochasticity. Biotic and abiotic features were investigated to determine their influences, as well as, the threats (trampling, anthills, herbivory and number of senescent plants) facing Euphorbia groenewaldii. Canopy area was used to determine the stage (age) and size structure of each population. Biotic features and natural environmental components considered were percentage cover of grass, forbs, dead vegetation, stones, fixed rock and bare ground. The percentage cover, of all the biotic features (grass, forbs and dead material) and environmental components (stones, fixed rock and bare ground), most preferred by E. groenewaldii is close to 25% in the direct vicinity of the individual plant. Euphorbia groenewaldii select areas with fixed rock more than in any other biotic feature or environmental component. This could be for protection from, or a result of, trampling by large herbivores, or that it’s most preferred mineral substance is found within this geology. Abiotic features considered in this study were; fire, aspect, slope degree, slope position and soil. The E. groenewaldii population as a whole prefers to grow on the northern aspects. Furthermore, with threats affecting all the populations, it is forced to grow in the middle of steeper slopes. Currently the only fire ‘regime’ is a natural or accidental occurring fire. The area where E. groenewaldii grows belongs to the local government and is open to public traffic. If a regular (once a year) cold-fire regime for E. groenewaldii can be put in place and, if possible, coincide with rainfall events it could help the release of more seeds and help with a more constant rate of seedling recruitment for this species. Such a fire event was witnessed during the study period and subsequent new growth and seedling appearances were recorded. Threats that were noted and considered were mostly of a biotic nature (absence of fire being the exception) and included trampling, herbivory and termite mounds. Other threats not included are urban expansion and mining/quarrying activities. These types of threats are real and more extensive, and if not monitored could completely destroy a population in a very short time period. Trampling is a significant threat facing this species, particularly at the Melkboomfontein population, where 31% of the population shows physical signs of trampling by livestock; mainly cattle. Herbivory is also a threat to E. groenewaldii and causes significant damage (15% over the total population according to the statistical analysis). There is also a significant difference in the effect anthills have on E. groenewaldii as opposed to the other threats, which have almost no effect on its population size. In addition to the above, surveys were conducted to determine the species’ present extent of occurrence and area of occupancy to obtain population size estimates and densities. The results were compared with data of a study by Raal in 1986. The results of this study showed a dramatic decline in population numbers. Possible reasons for the reduction include habitat loss, better survey techniques (that provided better predictions of population density) and a more comprehensive survey and data analysis in this study, and a failure to implement the conservation management plan proposed by Raal (1986). It is estimated that the total number of individuals in all the populations comprise approximately 26 500 individual plants, with all occurring in an area of less than 4 km2 (excluding the Dalmada populations). The small extent of occurrence suggests that E. groenewaldii populations require urgent protection. An investigation of morphological differences between E. groenewaldii and E. tortirama was conducted. This investigation attempted to find external morphological differences by looking at the flower peduncles, colour of bracts and spine shields. Analysis of these data showed differences in the length of the peduncles (longer in E. groenewaldii than in E. tortirama); colour of bracts (colourless in E. groenewaldii as opposed to the reddish-pink bracts of E. tortirama) and the continuation (E. groenewaldii) and non-continuation (E. tortirama) of spine shields. In 1986, Euphorbia groenewaldii’s conservation status was considered endangered; it is still the case today. However, the IUCN status of E. groenewaldii was reevaluated on the current data gathered, which has placed E. groenewaldii in the Critically Endangered category. This is mainly due to the small extent of occurrence (approximately 4 km2) of the species (less than the 100 km2 which according to the IUCN Redlist Categories and Criteria, 2006, criteria B, classifies species as critically endangered).

Thesis (MScConsEcol (Conservation Ecology and Entomology))--Stellenbosch University, 2008.
The widespread ecological impacts of overgrazing by livestock within the Succulent Karoo have received considerable attention. Literature shows communal and commercial rangelands have been thoroughly studied, and vegetation responses have been investigated in an attempt to understand the effects of overgrazing. Regarding animal species, literature is in short supply. In a one-year study of small mammal assemblages, the effect of the rangelands, and subsequently vegetation, on small mammal assemblages was examined, as well as the effects on number of occupied, unoccupied and collapsed burrows. This study shows that vegetation composition differs between rangelands, with a greater perennial shrub cover on the communal rangelands and a greater perennial succulent cover on commercial rangelands, consequently creating different habitats for animal assemblages. This study supports the notion of small mammal composition relating to vegetation structure, with certain species being impacted by heavy grazing. Four small mammal species were found in greater abundances on commercial rangelands, with one being exclusive, while communal rangelands were exclusively occupied by three nocturnal species. Diet and habitat requirements are the most important factors regarding species occurrence. With small mammal species composition differing between rangelands, and species richness not being affected by rangeland type, this study illustrates that the disappearance of certain species may arise without these different rangelands. This could result in reduced species richness, and thus diversity being lost. Regarding species present on both rangelands, no differences were observed in body mass, body size or body condition. Despite no differences found in body condition, calculating a body condition index is a good method for investigating how a species is coping within an environment. The proportion and number of occupied and collapsed burrows can be seen as a measure of trampling effect. It was expected for grazing intensity, as well as vegetation changes, to affect the occurrence of such burrows. This study showed differences between the communal and commercial rangelands as negligible. As expected, numbers of burrowing small mammal species were negatively correlated with numbers of collapsed burrows. However, a lack of consistency deemed this result unimportant. Results show that the effects of overgrazing on small mammal populations are complex and require more attention if to be fully explained. This study provides insights into the effects of land use on small mammals and burrow numbers, which have implications for the conservation of these species within arid regions.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior
RESUMO â Com o aumento significativo da procura e consumo por produtos ornamentais faz-se necessÃrio um aumento da produtividade dessas, o que torna necessÃrios o desenvolvimento de estudos para que esse incremento nÃo diminua a qualidade nem modifique as caracterÃsticas desejÃveis ao mercado consumidor, no que diz respeito a tÃcnicas de produÃÃo e cultivo. O mercado brasileiro de plantas ornamentais à Ãvido por novidades. Alternativa que os produtores veem procurando e com bastante frequÃncia à a inclusÃo de plantas - jà conhecidas e utilizadas em outras Ãreas - no setor da floricultura como plantas ornamentais, sendo esse o caso do mandacaru como ocorre no Projeto Tejucactos no municÃpio de TejuÃuoca. Baseado no exposto, esse trabalho foi conduzido com o objetivo de fornecer dados referentes a tÃcnicas para o cultivo das plantas ornamentais: Caladium x hortolanum cv Freida Hemple e Cereus jamacaru DC. Para o Caladium Freida Hemple utilizou-se o delineamento inteiramente casualizado seguindo um esquema fatorial 2x6 constituÃdo por prÃtica da desponta ou nÃo e de seis concentraÃÃes de AG3 (0, 250, 500, 750, 1000 e 1250 ppm) aplicadas antes do plantio dos tubÃrculos. Maiores comprimentos de raiz foram encontrados em plantas de tubÃrculos despontados e sem aplicaÃÃo de AG3; Maiores alturas de hastes foram encontradas em plantas de tubÃrculos despontados e tubÃrculos intactos tratados com AG3; Maiores nÃmeros de hastes foram encontrados em plantas de tubÃrculos intactos; Maiores comprimento e largura de folha foram encontradas em plantas de tubÃrculos intactos tratados com AG3 e tubÃrculos despontados sem AG3. Para o Cereus jamacaru DC, os tratamentos dispostos em delineamento inteiramente casualizado, constituÃram-se dos substratos 100% fibra de coco (FC) (T1), 100% casca de arroz carbonizada (CAC) (T2), 75%FC+25%CAC (T3), 50%FC+50%CAC (T4), e 25%FC+75%CAC (T5). PlÃntulas de mandacaru com idade de 118 dias foram transplantadas para os substratos e aos 125 dias apÃs o transplantio foram analisados: comprimento, nÃmero, massa fresca e seca de raiz e crescimento, massa fresca e seca da parte aÃrea. O substrato composto somente por fibra de coco apresentou melhores resultados em todas as variÃveis analisadas.
With the significant increase in demand and consumption of ornamental products is necessary to increase the productivity of these items. With the significant increase in demand and consumption of ornamental products is necessary to increase the productivity of these items. Studies are important for the "productivity increase" does not influence the quality, or modify the characteristics desirable to the consumer market, with respect to production techniques and cultivation. The Brazilian market for ornamental plants is hungry for novelties. So producers often seek to include new plants in cultivation, sometimes already known and used them, that being the case of âmandacaruâ, widely used in the Project with neme of âTejucactusâ in TejuÃuoca city in CE. Within this context, this work was carried out to provide information about techniques for the cultivation of three ornamental plants: Caladium, Sansevieria cylindrica and Cereus jamacaru. For Caladium were used a completely randomized design in a factorial 2x6 (or not practice is emerging and six concentrations of GA3 (0, 250, 500, 750, 1000 and 1250 ppm) applied before planting the tubers. Greater root lengths were found in plants, of tubers kept intact and without the application of GA3; Greater heights stems were found in plants of tubers kept intact, treated with GA3; Higher numbers of stems were found in plants of tubers kept intact; Greater length and leaf width was found plants of tubers kept intact and tubers treated with GA3 or Caladium tubers must be kept intact and treated with GA3 or apical dominance (De-eyed) should be performed without the use plant regulator. For Cereus jamacaru treatments in DIC, consisted in coconut fiber (FC) and carbonized rice chaff (CAC) substrates: 100% FC (T1), 100% CAC (T2), 75% FC +25% CAC (T3), 50% FC +50% CAC (T4), and 25% FC +75% CAC (T5). The substrate composed only of coconut fiber showed better results in all variables.

The main aim of this study was to investigate the effects of water availability and SO2 pollution, imposed separately or simultaneously, on the photosynthetic metabolism of Augea capensis Thunb., a succulent of the Namib Desert in the region of Skorpion Zinc mine, Namibia. The main driver for this investigation was the need to distinguish between the effects of water availability on plants native to a desert environment, where water availability dominates plant response, but where the possibility of anthropogenic SO2 pollution poses a new threat to the unique succulent vegetation. Fifteen measuring sites were selected in the vicinity of the mine to determine how rainfall influenced the physiological status of the vegetation. Chlorophyll a fluorescence measurements, and analysis of recorded OJlP fluorescence transients with the JIP-test, were used for this purpose. A series of laboratory experiments were also conducted on A. capensis to determine the precise physiological response that water deprivation and SO2 pollution had under controlled growth conditions. Potted plants were exposed to water deprivation or SO2 fumigation in the light or dark. Besides chlorophyll a fluorescence, photosynthetic gas exchange and Rubisco activity were also measured. Changes in fast fluorescence rise kinetics observed under field conditions suggest considerable modulation of photosystem II function by rainfall with concomitant involvement of a heat stress component as well. In both the field and laboratory experiments, one of the JIP-test parameters, the so-called performance index (PIABS), was identified as a very sensitive indicator of the physiological status of the test plants. Moreover, under laboratory conditions, a good correlation existed between the water deprivation-induced decline in CO2 assimilation rates and the decline in PIABS values. The JIP-test in general, and the PIABS in particular, shows considerable potential for application in the investigation of water availability influences on desert ecosystems. In the laboratory experiments, water deprivation caused stomatal closure but also a slight elevation in intercellular C02 concentration and inhibition of Rubisco activity, suggesting that mesophyll limitation was the dominant factor contributing to the decrease in C02 assimilation rates. Following re-watering, A. capensis showed remarkable recovery capacity. Fumigation of A. capensis with 1.2 ppm SO2 in the dark or light revealed relatively small effects on C02 assimilation. The inhibitory effects on photosynthesis were also fully reversible, indicating no permanent metabolic/structural damage. The effects on photosynthesis were more pronounced when fumigation occurred in the dark. This phenomenon might be related to diurnal differences in cellular capacity for SO2 detoxification. When long-term moderate water deprivation was combined with simultaneous SO2 fumigation, there was no additional inhibitory effect on photosynthesis. These findings suggest that water deprivation do not increase sensitivity towards SO2 pollution in A. capensis. Fumigation with SO2, singly or in combination with water deprivation also had no major effect on chloroplast ultrastructure. It appears that A. capensis is remarkably resistant to SO2 pollution even in the presence of low water availability, which is a common phenomenon in desert ecosystems. Since A, capensis seems to be highly tolerant to S02, its suitability as an indicator species for the detection of SO2 pollution effects at Skorpion Zinc mine is questionable. Because water availability dominates the physiological/biochemical response in this species, subtle SO2 pollution effects might be difficult to detect against this dominant background. The high water content of A. capensis and similar succulents might act as a substantial sink for SO2 and could convey considerable tolerance against this form of air pollution.
Thesis (M.Sc. (Botany))--North-West University, Potchefstroom Campus, 2006.

Thesis (MSc (Conservation Ecology)--University of Stellenbosch, 2004.
89 leaves single sided printed, preliminary pages i-xiv and numbered pages 1-89. Includes bibliography. List of tables, figures used.
Scanned with a Hp Scanjet 8250 Scanner to pdf format (OCR).
ENGLISH ABSTRACT: The main aim of an old field rehabilitation trial initiated in 2000 was to find a solution to the rehabilitation process for approximately 90 000 ha of unutilised land in the Little Karoo, South Africa. Depending only on a natural succession process to restore unutilised old fields would mean that the period of recovery would be longer than the life span of an average farmer. The trial, initiated by Witbooi in 2000 aimed to see how human intervention can facilitate the process of rehabilitation of old-fields. Three years later, the trial was again monitored to evaluate the success of reseeded indigenous species and method of cultivation in the rehabilitation process. A second objective was based on a result of Witbooi (2002) who showed that there was a tendency of 0. pes-caprae to invade disturbed areas, and aimed to evaluate the effect of this species on the rehabilitation process. Seven indigenous species were reseeded in 2000, of which only four species germinated and survived to the present. These surviving species are Pteronia incana Burm Dc., Tripteris sinuata DC., Ehrharta calycina SM and Chaetobromus dregeanus Nees. The highest level of recruitment in 2001 was recorded for T sinuata followed by P. incana, E. calycina and C. dregeanus. In September 2003, three years after the trial was initiated, the highest number of surviving seedlings were of T sinuata followed by E. calycina, C. dregeanus and P. incana. Five different cultivation methods were used to enhance the germination rate and survival of seedlings. The number of seedlings that survived differs according to the cultivation methods and soil type. Tripteris sinuata had the highest number of surviving seedlings in all cultivation methods off-heuweltjies. Tripteris sinuata was therefore selected to analyse the effect of various cultivation methods. The second objective was to study the impact of Oxalis pes-caprae on species diversity in restored old fields by assessing its ability to disperse in old fields under different cultivation methods. The multivariate ANOVA results showed that there was a significant difference in the density of O. pes-caprae between on and off heuweltjies (sites) and treatments (cultivation methods). There was a significant difference in the density of O. pes-caprae between cultivation methods. A Post Hoc LSD test showed a significant difference in the density of aboveground O. pes-caprae plants between control sites (no disturbance) compared to those sites that underwent some sort of soil disturbance. There was, however, no significant difference in the abundance of O. pes-caprae on plots that underwent some sort of disturbance (i.e Cleared vs Tilled vs Disked vs Ploughed sites) on heuweltjies. There was a significant difference in the number of O. pes-caprae bulbs collected between blocks (on and off-heuweltjie) and significant differences between cultivation methods. There was also a significant difference in bulb diameter between cultivation methods when compared between on and off-heuweltjie sites. The bulbs were classified into four measurement classes. The highest number of small (2-5 mm diameter) and medium (5-8 mm diameter) sized bulbs were found in the Tilled cultivation method. In contrast the Control treatment (uncultivated) had the highest number of large sized bulbs (14-17 mm diameter) and medium bulbs size categories. In conclusion, T. sinuafa has the potential to be used for rehabilitation of old fields in combination with Tilled cultivation method. Attention should be paid to the effect of O. pes-caprae especially on heuweltjies where this species showed a complete dominance in the rehabilitation trial.
AFRIKAANSE OPSOMMING: Die hoof doel van 'n ou veld rehabilitasie eksperiment wat in 2000 geinisieer is was om 'n oplossing te vind vir die rehabilitasie proses vir ongeveer 90 000 ha onbenutte land in die Klein Karoo, Suid-Afrika. Indien daar slegs op natuurlike suksessie prosesse staatgemaak word om die onbenutte ou lande te restoreer, sou dit beteken dat die periode van herstel langer sou wees as die lewensverwagting van die gemiddelde boer. Hierdie eksperiment, wat in 2000 deur Witbooi geinisieer is, het gepoog om te bepaal hoe menslike inmenging die proses van rehabilitasie van ou velde kan fasiliteer. Drie jaar later is die eksperiment weer gemonitor om die sukses van die teruggesaaide inheemse spesies en bewerkings-metodes in die rehabilitasie proses te evalueer. 'n Tweede doelwit is gebaseer op 'n resultaat van Witbooi (2002) wat aangetoon het dat daar 'n neiging was vir O. pes-caprae om versteurde areas binne te dring, en het dus gemik om die effek van hierdie spesie op die rehabilitasie proses te evalueer. Sewe inheemse spesies is in 2000 teruggesaai, waarvan slegs 4 spesies ontkiem en oorleef het tot die hede. Hierdie oorlewende spesies is Pteronia incana Burm Dc., Tripteris sinuata DC., Ehrharta calycina SM en Chaetobromus dregeanus Nees. Die hoogste vlak van werwing in 2001 is vir T sinuata aangeteken, gevolg deur P. incana, E. calycina en C. dregeanus. In September 2003, drie jaar na die aanvang van die eksperiment, was die hoogste getal oorlewende saailinge die van T sinuata, gevolg deur E. calycina, C. dregeanus en P. incana. Vyf verskillende bewerkings-metodes is gebruik om ontkiemingstempo en saailing oorlewing aan te help. Die aantal saailinge wat oorleef het varieer volgens die bewerkings-metode wat gevolge is en die grondtipe. Tripteris sinuata het die grootste aantal oorlewende saailinge gehad in al die bewerkings-metodes af van heuweltjies. Tripteris sinuata is daarom geselekteer om te analiseer vir die effek van verskillende bewerkings-metodes. Die tweede doelwit was om die inpak van Oxalis pes-caprae op spesie-diversiteit in die gerestoreerde ou land te bepaal deur die vermoë van hierdie spesie om in ou velde te versprei onder verskillende bewerkings-metodes te evalueer. Die multi-veranderlike ANOVA resultate het aangetoon dat daar 'n beduidende verskil in O. pes-caprae digtheid tussen heuweltjie en nie-heuweltjie (persele) en verskillende bewerkings-metodes was. Daar was 'n beduidende verskil in die digtheid van o. pes-caprae tussen verskillende bewerkingsmetodes. 'n Post Hoc LSD toets het 'n beduidende verkil in die digtheid van bogrondse O. pes-caprae plante tussen kontrole terreine (geen versteuring) vergeleke met persele wat een of ander vorm van grondversteuring ondergaan het aangedui. Daar was egter geen beduidende verskil in die volopheid van 0. pes-caprae op persele wat een of ander vorm van versteuring ondergaan het (i.e Skoongemaakte vs Getilde vs Geskottelde vs Geploegde persele) op heuweltjies nie. Daar was 'n beduidende verskil in die aantal O. pes-caprae bolle wat versamel is tussen blokke (op en af van heuweltjies) en beduidende verskille tussen die bewerkings-metodes. Daar was ook 'n beduidende verskil in bol-deursnitte tussen bewerkings-metodes wanneer dit tussen heuweltjie en nie-heuweltjie persele vergelyk is. Die bolle is in vier metingsklasse verdeel. Die grootste aantal klein (2-5 mm deursnit) en medium (5-8 mm deursnit) bolle is in die Getilde bewerkings-metode gevind. In kontras het die Kontrole behandeling (onbewerk) die grootste aantal groot (14-17 mm deursnit) en medium bolle gehad. Samevattend het T. sinuata die potensiaal om gebruik te word in die rehabilitasie van ou lande in kombinasie met die tilting bewerkings-metode. Aandag moet geskenk word aan die effek van 0. pes-caprae, veral op heuwetjies waar hierdie spesies 'n totale dominansie in die rehabilitasie eksperiment getoon het.

Includes bibliographical references.
Species turnover is a measure of a diversity that attempts to quantify the change in species composition along a spatial, temporal or environmental gradient. One such environmental gradient that has been shown to affect species turnover is local edaphic variation. This is seen in the Western Cape Province of South Africa, where the unique edaphic character of large earth mounds, known as heuweltjies, support distinct plant communities. The aim of this study is to assess whether these mounds, and the termite Microhodotermes viator commonly associated with them, also support distinct invertebrate communities, thereby contributing to invertebrate species turnover in the region. Pitfall and emergence traps were set on heuweltjies and in the surrounding matrix in the Karoo Desert National Botanical Gardens, Worcester, Western Cape Province. On- and off-mound community contrasts were assessed by means of a cluster analysis, and species turnover was measured using the Jaccard distance. Invertebrates were more abundant on the heuweltjies, which also had distinct communities when compared to the matrix. Spiders (Aranaea) were more abundant on the heuweltjies, as were in the invertebrates emerging from the frass, suggesting a trophic cascade. Invertebrates commonly associated with M. viator were found more commonly on the heuweltjies. The Jaccard distances indicated that environmental homogenisation of the heuweltjies resulted in homogenisation of the on-mound invertebrate communities. Heuweltjie soil enrichment was most similar to that of termite frass when compared to the matrix, supporting a termite origin for the heuweltjies.

Thesis (MSc (Conservation Ecology and Entomology)--University of Stellenbosch, 2006.
A pilot study was conducted at the Namakwa Sands Mineral Separation Plant, to investigate the effects of acidic gaseous emissions from the Mineral Separation Plant on the adjacent Succulent Karoo vegetation. Sulphuric acid fumes, a major gaseous emission of the mineral processing, was the subject of investigation of the present study, due to the potential high negative impact of elevated concentrations thereof on vegetation in the ecosystem. Permanent sample plots along three transects radiating from the Mineral Separation Plant were laid out in the eastern, south-eastern and southern directions following the prevailing wind directions and practical consideration of land accessibility. The ecological components assessed as indicators of possible pollution levels in the environment included percentage plant mortality, foliar sulphur content of selected plant species, chemical composition of solubles in mist and dust samples, and soil pH. In addition, the vegetation was screened for plant species suitable to be used as potential bioindicators. Potential bioindicator plant species were selected on the basis of their relatively wide distribution in the study area and apparent sensitivity to the ambient air pollutants. The percentage of dead plants of each species that occurred on the sample plots was used as a criterion of the possible sensitivity of the plant species towards air pollution. The bioindicator plant species selected for potential monitoring purposes were: Galenia fruticosa, Lampranthus suavissimus, Lycium ferocissimum and a Ruschia sp. (SP 9). Plant mortality was greater nearer the emission source, with 28 + 5 % dead plants at 400 m, 19 + 6 % at 800 m and only 10 + 4 % at 1,200 m from the Mineral Separation Plant. Data summed for all species recorded and pooled for all three transects per sampling distance. With the methods used in this study, in the case of all sample plots on the three transects, no significant difference was found between the mean pH values of soil samples collected from open spaces without plant cover (8.01 + 0.46) and those collected underneath shrubs (8.91 + 0.96). Subsequently only the pH values of soil samples collected on open spaces were used to investigate the variation in soil acidity with distance and direction from the emission source. The means represent total number of samples from open space versus those collected from underneath shrubs. The pH of soil samples increased with distance from the emission source along the transects to the south and south-east of the emission source. Eastward of the emission source, soil pH values remained relatively low at all sample distances. This pilot study could not determine whether the continuous acidity of the soil along the eastern transect in the direction of the prevailing wind, was caused by increased deposition of gaseous emissions on the higher lying hilly terrain in this area, or by the underlying geology. Ion chromatographic analysis of mist and dust samples collected on each sample plot indicated the presence of several chemicals that had probably originated from the gaseous emissions from the Mineral Separation Plant as well as wind blown constituents from the adjacent surroundings of the sample plots. Of these chemicals, only the sulphate concentrations of the mist and dust samples were further evaluated, since that could be related to the emission of sulphuric acid fumes by the Mineral Separation Plant. Results indicated that the mean sulphate concentration of mist and dust samples collected from sample plots relatively close to the Mineral Separation Plant, 118.8 + 31.6 mg/litre (400 m), were higher than further afield, decreasing to 57 + 30.1 mg/litre at 800 m and 43.1 + 19.6 mg/litre at 1,200 m. These values, representing the mean sulphate concentrations of mist and dust samples at each sampling distance (data of the three transects pooled), differ significantly at the 85 % confidence level. Statistical evaluation of the data of the mist and dust pH measurements, pooled for the three transects on the basis of distance, indicated a gradual increase of the mean values from 400 m (7.3 + 0.26), through 800 m (7.7 + 0.34), to 1,200 m (8.2 + 0.83), although these values were not significantly different. A decreasing trend in accordance with that in the case of the sulphate concentrations of mist and dust samples with distance from the mineral processing plant, was also observed in the sulphur content of the leaves of selected plant species, with mean sulphur content higher at 400 m sampling distance (0.29 + 0.091 %) than at 800 m (0.264 + 0.086 %) and a further decline at 1,200 m (0.232 + 0.079 %), data of the three transects pooled. However, these values were also not significantly different. Although not significantly so, the decreasing trend in the results of the sulphate concentration of mist and dust samples, the sulphur content of plant leaf samples as well as plant mortality observed, and increasing soil pH values with distance from the Mineral Separation Plant, suggest that the gaseous emissions from the Mineral Separation Plant could probably have had a detrimental effect on the adjacent Succulent Karoo vegetation. A more detailed study is necessary to confirm this trend. In addition it is recommended that in order to clarify the soil pH measurements outcome along the eastern transect that were contradicted by the results of the mist and dust pH measurements, a more intensive survey over a greater distance (at least further than 1.2 km from the Mineral Separation Plant), be conducted to quantify vegetation damage and acid deposition to the east of the emission source.

This study has shown that using active rehabilitation in combination with improved management strategies (e.g. rest from grazing) may induce recovery of certain ecosystem services within practically relevant time scales. However, these benefits might not be tangible for landowners or society as of yet, due to the small-scale nature of the rehabilitation application along with the relatively high, short-term associated costs. To alleviate financial constraints on farmers and in order to socially and financially enhance local communities, the focus for now should be on sourcing funds from government and private sectors for rehabilitation implementation.

The historically poorly conserved subtropical transitional thicket (STT) of the Eastern Cape is overutilised by domestic stock and game in the more xeric areas, and has shown no signs of recovery from this grazing pressure. It has been postulated that no regeneration through seeding occurs. This project was undertaken to determine: 1) how much STT has disappeared between 1950 and present, and what the current conservation status is; and 2) whether regeneration of the xeric succulent thicket is taking place through seeding, and if so, where. The study was conducted at the Andries Vosloo Kudu Reserve near Grahamstown. Approximately one-third less STT was mapped in this study, based on 1981 Landsat images, than was mapped in 1950. Approximately 10 % of all remaining STT is conserved. The order Kaffrarian thicket is poorly conserved. Newly germinated seedlings of a wide range of shrub species occurred under the canopies of a wide range of shrubs which served as nurse plants, throughout a gradient of veld condition. Seedlings of Portulacaria afra, the dominant shrub in xeric succulent thicket, were most common. Similarly all saplings recorded in a survey of saplings were associated with bushclumps. One-third of all saplings have the potential to contribute to the spread of bushclumps. Regeneration of xeric succulent thicket through seeding probably does occur, contrary to current ideas. Ptareoxylon obliquum was the most common sapling, despite mature trees now being scarce following earlier heavier utilisation . P. obliquum was also the nurse plant which supported the highest density of newly germinated seedlings. The possible role of P. obliquum in the functioning of xeric succulent thicket is discussed. The confinement of seedlings and saplings to areas under the canopies of trees and shrubs implies that the xeric succulent thicket will not recover rapidly if allowed to rest. Active management techniques will be necessary if rapid recovery is required. Bare areas between bushclumps may no longer be suitable germination habitats because of high Al concentrations. There was no evidence to support the idea that germination and establishment of shrubs in clear areas is linked to episodic climatic events. Dung middens of recently reintroduced black rhinoceros may however aid in germination of seeds and establishment of seedlings under certain climatic conditions. Recommendations for further studies, based on the findings of this project, are made. Possible management techniques aimed at the rapid recovery of this veld are suggested, and management proposals for the Sam Knott Nature Reserve/Andries Vosloo Kudu Reserve complex are made.

The similarities in the structure of the sclerophyllus evergreen shrublands of the five disjunct mediterranean-type ecosystems is thought to be the result of convergent evolution. In the Mediterranean, California, and Chile the length of the summer drought and the cold winter temperatures are hypothesized to be the primary selective pressures. In Australia and South Africa low soil nutrients are thought to be important, as they are in defining the structurally similar heathlands found with a range of climatic types. The fynbos vegetation in an area with a mediterranean-type climate was sampled for a period with low xylem pressure potentials and restricted leif conductances to water loss during the summer drought, and the patterns of plant response to desiccation. The presence of patterns of plant water relations in the fynbos similar to those found in other mediterranean-type ecosystems could demonstrate the importance of water as a selective pressure in the fynbos.

Livestock grazing is a key form of land-use around the world. Sustained, heavy grazing pressure, however, changes the vegetation structure of arid and semi-arid regions, often resulting in the local extinction of perennial, palatable species. It also causes changes in species composition through its impact on the recruitment of palatable and unpalatable rangeland species. Fence-line contrast studies are often used as natural experiments, since they contrast the long-term impact of herbivory between two different land tenure regimes and grazing intensities. This study used a fence-line contrast approach to investigate the long-term impact of high grazing pressure at a site in Namaqualand, South Africa. Forty pairs of permanently marked plots, separated by a fence (with communal grazing land on one side and commercial rangelands on the other) were established in 1996 to study the long term impacts of livestock grazing. Vegetation structure and composition of the plots were analysed in 1996 and 2006. The plots were resurveyed in 2016 as part of an on-going monitoring programme in the area. The main objective of this study was to investigate changes in the vegetation structure between the overgrazed communal rangelands and the relatively lightly grazed commercial rangelands over the 20 year period. All species in the paired plots were identified and assigned to 10 growth forms based on their height and life histories (e.g. annuals, perennials, geophytes). Differences in the average % cover as well as the number of species in each of the growth forms were compared across treatments. Differences in shrub volume, mean number of adults and the number of seedlings for each of five key indicator perennial shrub species between treatments and over time were also assessed. The five-indicator species covered a range of palatabilities from unpalatable and semi-toxic (Galenia africana), moderately palatable (Ruschia robusta, Eriocephalus microcephalus) and highly palatable (Tripteris sinuatum, Pentzia incana). Monthly rainfall totals and livestock grazing pressure for locations on the communal side of the fence, recorded by an on-site assistant, were also related to the changes recorded in rangeland composition over the study period. Results indicated that there was a decline in total vegetation cover in both commercial and communal rangelands in 2016 relative to the two earlier sampling periods. The patterns observed appeared to have been influenced strongly by the reduction in annual plant cover which was especially noticeable on communal rangelands. This in turn was probably as a result of the low rainfall experienced in the seven months prior to the 2016 sampling period. The number of species in the remaining growth forms did not differ between treatments and over time. Galenia africana had the largest volume of the perennial shrub species although considerable variation exists between treatment and years. The average number of individuals of mature G. africana shrubs was significantly greater in the communal plots at all time steps. The relative patterns of abundance of the different growth forms between land use treatments were maintained across sampling periods. Continuous heavy grazing over long periods in spatially constrained grazing systems changes the vegetation from being perennial to annual-dominated. This is analogous to switching from a predictable equilibrium system with forage reserve being transferred from one year to the next to one driven more directly by seasonal rainfall. Such rangelands are more characteristic of disequilibrium systems which are more unpredictable in terms of forage supply and livestock production potential. Vulnerable people who are not buffered from economic shocks will be more severely affected by the variability in forage supply for their livestock. The impact of sustained heavy grazing over long periods of time, therefore, has important consequences for people's livelihoods.

Includes bibliographical references (leaves 132-151).
The Succulent Karoo is a biodiversity hot spot situated along the west coast of southern Africa. While it is predominantly recognized as a west coast vegetation type its borders stretch as far east as Steytlerville in the Little Karoo. The area contains the largest number of endemic succulent species in the world and harbors nearly 10 percent of the of the total number of succulent species worldwide. Furthermore, spring mass-flowering events draw thousands of tourists to the region, providing welcome input to the local economies. The floral diversity is however, under threat from various environmental forces. These forces include inappropriate land use practices resulting in Land Degradation and the ever-present threat of Climate Change.

Includes bibliographical references (p. 110-122).
This thesis presents ecological investigations of vegetation at an ecotone between the Namaqualand shrublands and Bushmanland arid grassland at the climatic transition between the predominantly winter rainfall Succulent Karoo and the predominantly summer rainfall Nama-Karoo biomess. The work focused on the determinants of grass and succulent shrub vegetation characterising the ecotone, and on determining the current and past distribution of this vegetation. A combination of detailed community the current and past distribution of this vegetation. A combination of detailed community level investigations (both observational and experimental), and a variety of remotely sensed data and techniques were applied to capture processes and patterns at different scales. In the first set of investigations, I have investigated the role of soil and competition on vegetation patterns. Secondly, field data were combined with remote sensing technology to establish the current distribution of grasses and shrubs along the ecotone, and to determine how this vegetation has changed over the past 20 years.

Includes bibliographical references.
In the arid and semi-arid western parts of southern Africa, Aloe dichotoma Masson, a long-lived succulent tree species, is thought to be responding to anthropogenic climate change. However, differences in response across its distribution are likely to be related to rainfall seasonality. This study investigated change in ten Aloe dichotoma populations within winter and summer rainfall zones in South Africa and southern Namibia. Using repeat photography over a timespan of approximately 30 years, demographic patterns, population dynamics (including mortality, recruitment and overall population change) and growth were assessed and modelled with climatic variables. Long-term patterns of recruitment and longevity were also investigated by using individual plant growth data to reconstruct recruitment histories for each population. Finally, the influences of climatic conditions on recruitment were evaluated by superimposing historical rainfall and temperature data. Differences in response between rainfall zones are clearly evident throughout. Generalised linear models revealed lower mortality, higher recruitment and positive population change at winter rainfall sites, while summer rainfall sites showed negative population change. Growth data revealed more rapid growth in height of juveniles than adults, and slower growth in height in the winter rainfall zone, most likely related to differences in tree architecture. It is evident that biotic and anthropogenic factors such as herbivory, nurse plants and theft are likely to moderate observable patterns as opposed to driving them. Recruitment modelling suggested that A. dichotoma attains a maximum age of 300 to 350 years, and revealed recent recruitment peaks in the winter rainfall zone and peaks around the turn of the 19th century in the summer rainfall zone. Changes in temperature and rainfall are likely to be the main drivers. Rising temperatures within the last century may have driven increased recruitment and low mortality in the cold-limited winter rainfall zone, while decreasing rainfall within the summer rainfall zone, combined with increasing temperatures, may explain this region's low recruitment and high mortality. The advancement of knowledge of broad spatial and temporal patterns in A. dichotoma and the likely causes, coupled with fine-scale future studies, will enable more detailed prediction of the species' response to future global change.

Philosophiae Doctor - PhD
Gethyllis multifolia L. Bolus and G. villosa Thunb. are winter-growing, summerblooming,deciduous and bulbous geophytes that grow naturally in the semi-arid succulent Karoo biome of South Africa. Both species grow under full sun conditions and have four distinctive growth phases: a winter (cold and wet) growing phase, leaf senescence phase towards spring, flowering phase during the hot and dry summer months, and fruit and leaf formation phase in autumn. The medicinal uses of this genus (including G. multifolia “Kukumakranka” and G.villosa “hairy kukumakranka”) range from cures for colic, digestive disturbances,teething problems, fatigue, boils, bruises and insect bites, to being used as an aphrodisiac. Gethyllis multifolia is threatened in its natural habitat and is listed in the ‘Vulnerable’ category of the ‘Red Data List of Southern African Plants’ and the ‘IUCN-World Conservation Union List of Plants’. The literature indicate that the habitats of both species are being exposed to drier conditions and is further threatened by the encroachment of invasive indigenous plant species. It is not known to which extent these factors may pose a threat to the existence of both species. The first objective of this investigation was to determine the costs of vegetative and reproductive growth during the seasonal life cycle of the plant, using carbon(C) and nitrogen (N) as a physiological currency. The second objective was to elucidate a functional basis to explain the difference in the conservation status of both species in their natural habitat. Both species were subjected to drought and shading as environmental stresses and the plant physiological performance was investigated via photosynthetic gas exchange. The third objective of the study was to evaluate the antioxidant content (total polyphenol, flavonol/flavone and flavanone content) and antioxidant capacity [ferric reducing antioxidant power (FRAP), oxygen radical absorbance capacity (ORAC) and 2,2'-azino-di-3-ethylbenzthiazoline sulphonate (ABTS) radical cation scavenging ability] of natural populations and plant samples that were exposed to photo-and-drought environmental stresses. This study was done to elucidate the antioxidant profile of plant parts of natural populations as well as providing farmers, traditional healers and pharmaceutical companies with cultivation environmental conditions to enhance the antioxidant properties of the species. This investigation also attempted to isolate and characterize, by means of thin-layer chromatography (TLC) and column chromatography (CC), natural compounds from both species to lend support to the purported antioxidant benefit of both species and to further lend support to claims made by traditional healers of the medicinal potential of the genus. This study, however, did not engage in any in vivo studies or human trials to support published literature of the medicinal benefits of the genus.

What are the roles of alternative modes of speciation in the generation of biological diversity? This question is fundamental to the debate surrounding the origins of extraordinarily diverse regions and clades. Diversification in the Cape flora of South Africa has been intensively studied owing to its remarkable diversity, for which significant roles for both ecological and non-ecological speciation have been invoked as drivers. However, much of this research has focused on the mesic fynbos vegetation, with far less attention paid to its neighboring biodiversity hotspot, the arid Succulent Karoo (SK), which has hosted the spectacular radiation of the ecologically dominant ruschioid Aizoaceae, a succulent group which exhibits extreme morphological diversity and convergence. This thesis focused on ruschioid Aizoaceae in the Knersvlakte, a small region of the SK which holds a diverse and endemic-rich flora specially adapted to the ecologically unusual quartz fields - whose patchy distribution in the landscape suggests that diversification may have been facilitated by divergence of populations isolated on these 'environmental islands' in a similar fashion to serpentine systems such as those in California - and continues from previous work on the Knersvlakte-endemic ruschioid genus Argyroderma which supported an adaptive radiation in allopatry hypothesis. A population genomic approach was used to investigate the scale of seed dispersal (which is thought to be very limited due to the group's highly specialized ballistic dispersal mechanism) as well as correlates of population divergence in two ruschioid quartz-field specialists with very different growth forms (the shrubby Ruschia burtoniae versus the dwarf Conophytum calculus) and which co-occurred at four sites distributed throughout the Knersvlakte. This, in combination with ecological and experimental transplant data to test the adaptive underpinning of edaphically-driven community structure, ecological isolation and niche divergence in these and other quartz field species, made it possible to tease apart the roles of local adaptation and limited dispersal in driving gene flow and speciation in the system. Quartz fields were found to be a highly insular habitat with strong internal edaphic community structure, suggesting that they represent an environmental island system. In addition, intrinsic dispersal ability was very poor in the specialist shrub, which showed complete genetic isolation between the four populations separated by just 17-42 km. This species showed strong local adaptation between the populations as well as some evidence that this inhibited gene flow, though it is more likely that dispersal limitation allowed for fundamental niche divergence. In contrast, the dwarf showed surprisingly good dispersal ability and consequent weak genetic structure, which accounted for the lack of edaphic local adaptation between the populations. The study showed that, contrary to expectation, not all ruschioid Aizoaceae are poor dispersers, and also suggested that the likelihood of ecological speciation in response to edaphic heterogeneity is contingent on dispersal ability. Strongly limited dispersal may thus have contributed to the group's diversification either through non-adaptive radiation or edaphically driven adaptive radiation, but other factors are more likely to have driven diversification in sections of ruschioid Aizoaceae that possess mechanisms of long-distance dispersal. Future work might focus on inferring the scale of dispersal (e.g. based on morphological traits) and whether it predicts diversification rates. Finally, the lack of morphological variation in R. burtoniae belies its strong ecological and genetic divergence; in light of this, systematists are encouraged to investigate cryptic speciation in the group.

Das Ziel der Arbeit war die Entwicklung einer Begrünungsmethode für Gleisbette mit schneller Vegetationsentwicklung. Zur Begrünung wurden Sedumpflanzen verwendet, die durch den Einsatz von Bacillus subtilis, Lactobacillus und Nährsubstrat (allein und kombiniert) in verschiedenen Vegetationssystemen auf dem nährstoffarmen Standort Gleisbett etabliert werden sollten. Die Aktivität der inokulierten Mikroorganismen wurde indirekt über den Einfluss auf die Vegetationsleistung ermittelt. Der Einsatz von B. subtilis und Lactobacillus bewirkte eine signifikante Wachstumsförderung der oberirdischen Pflanzenteile. Die Anwendung von Nährsubstrat als Bodenhilfsmittel war ebenfalls für das Pflanzenwachstum besonders wirksam, sowohl allein appliziert als auch in Kombination mit den Bakterien. Darüber hinaus führte die Applikation der Bakterien und des Nährsubstrates zu einem reduzierten Trockenstress auf Geotextilmatten. Die Wahl des Substrates war entscheidend für die Wirksamkeit der Bakterieninokulation. Jedoch hatten höhere Versuchstemperaturen und pH-Werte ebenfalls eine positive Wirkung auf das Pflanzenwachstum. Diese Einflüsse waren in Kombination mit Ziegelbruchsubstrat wesentlich stärker als mit den anderen getesteten Substrattypen. Das Ziegelbruchsubstrat kombiniert mit einer Bakterien- und Nährsubstratbehandlung bewährte sich als günstiges, umweltschonendes Begrünungsverfahren von Gleisbettanlagen.
The aim of the present study was to develop and improve existing methods for the remediation of rail tracks using soil borne bacteria. Through the use of Bacillus subtilis and Lactobacillus ssp. alone and in combination with a nutrient solution three different growth substrates were tested. The substrates were brick chips, textile mats, and mineral wool mats. Brick chips were tested along railway tracks in Munich but all three substrates were tested along an artificial rail track on the experimental station at the Humboldt University-Berlin. Plants selected for remediation belong to the genus Sedum, which is relatively tolerant to dry conditions. The use of Bacillus subtilis and Lactobacillus in combination with a nutrient solution improved plant growth significantly. Plants inoculated with bacteria showed increased growth during the first three months but after four months there was no longer any significant difference between treatments. The addition of nutrient solution alone improved plant growth. Plant growth was significantly different on all three substrates, whereas brick chips were the best substrate. The results of this study indicate that the quality of the substrate is the most important factor for remediation and greening of rail tracks. Both bacteria tested had only a limited effect. High temperature and pH resulted in larger Sedum plants in the open field. Brick chips are a cheap substrate which can be used for rail track greening. The rapid growth of plants can be influenced by the application of an additional nutrient solution as well as inoculation with Lactobacillus and/or B. subtilis.

Crassulacean acid metabolism (CAM) provides desert plants with distinct advantages over the C3 and C4 photosynthetic pathways in harsh climates where water is scarce. CAM is, however more metabolically costly than C3 or C4 photosynthesis, and some plants, such as Mesembryanthemum crystallinum, facultatively utilize CAM when water is abundant, and water conservation unnecessary. In such situations, these plants behave akin to a C3 plant when photosynthesizing. CAM is divided into four phases, with each phase displaying unique metabolic processes. Certain changes, including changes in the timing of CO2 fixation, stable carbon isotope ratios, and tissue malic acid content accumulation patterns can indicate that a plant has shifted from CAM to C3 photosynthesis. Such shifts have been observed to be regulated primarily by water availability and ontogenic development. While facultative CAM is well documented in species like Mesembryanthemum crystallinum, and it has not been studied extensively in Agave with the exception of Agave deserti, and Agave angustifolia. A better understanding of this phenomenon would apply to the agricultural growth of this genus. This study aimed to trigger C3 to CAM shifts in Agave sensu lato species, in order to expand upon the findings of previous studies, and better understand the prevalence of facultative CAM expression in the genus. Gas exchange and stable carbon isotope measurements were taken from 2-month-old, 10-month-old, and mature agaves grown in controlled ocnditions. Tissue acid content measurements were taken from mature plants. Despite the Agave sensu lato species in this study being subjected to moisture applications ranging from dry to saturated, we were unable to observe any distinct shifts from CAM to C3 photosynthesis in any of the species tested for both seedlings and mature plants. Diel net CO2 fixation rates also increased with age, and water applications for seedlings, and decreased with heavy irrigation in mature plants. Stable carbon isotope ratios revealed that some carbon in the plant tissues was fixed by rubisco, and that some species (Polianthes tuberosa, Prochnyanthes mexicana) had carbon isotope ratios of a C3 plant, but these ratios did not change with different irrigation treatments. Malic acid accumulation remained typical of CAM plants for the species tested as well, with one exception in Polianthes tuberosa. As such, we conclude that the Agave sensu stricto species tested in this study are obligate CAM plants, and that they perform poorly mature individuals are over-watered. Additionally, the Agave sensu lato species P. mexicana, and P. tuberosa appear to be C3 plants given the results of this study.

There are many factors that have been proposed to contribute to plant invasiveness in nonnative ecosystems. Traits of invading species are one of them. It has been proposed that successful species at a certain invasion stage share particular traits, which could be used to predict the behaviour of potentially invasive plants at the respective stage. Three main stages of invasion are distinguished: introduction, naturalization, and invasion. I conducted a stageand trait-based analysis of available data for the invasion of New Zealand by the flora of southern Africa. Using 3076 southern African native vascular plant species introduced into New Zealand, generalised linear mixed model analysis was conducted to assess association of several species traits with the three invasion stages. The results showed that plant traits were significantly associated with introduction but fewer traits were associated with naturalization or invasion, suggesting that introduction can be predicted better using plant traits. It has been also hypothesized that species may become invasive in non-native ecosystems because they are removed from the regulatory effects of coevolved natural enemies (Enemy Release hypothesis). A detailed field study of the succulent plant Cotyledon orbiculata var. orbiculata L. (Crassulaceae) was conducted in the non-native New Zealand and native Namibian habitats to compare the extent of damage by herbivores and pathogens. C. orbiculata is a southern African species that is currently thriving in New Zealand in areas seemingly beyond the climatic conditions in its native range (occurring in higher rainfall areas in New Zealand than are represented in its native range). As hypothesised, C. orbiculata was less damaged by herbivores in New Zealand but, contrary to expectation, more infected by pathogens. Consequently, the plant was overall not any less damaged by natural enemies in the non-native habitat than in its native habitat, although the fitness impacts of the enemy damage in the native and invaded ranges were not assessed. The results suggest that climatic conditions may counteract enemy release, especially in situations where pathogens are more prevalent in areas of higher rainfall and humidity. To forecast plant invasions, it is concluded that species traits offer some potential, particularly at the early stage of invasion. Predicting which introduced plants will become weeds is more difficult. Enemy release may explain some invasions, but climatic factors may offset the predictability of release from natural enemies.

Soil salinity is predicted to become more severe and widespread adding more challenges for sustainable crops production worldwide. Salinity stress tolerance is a complex trait, both physiologically and genetically, and halophytes represent a rich resource for understanding different strategies used by plants to cope with saline condition. While many previous studies explored various physiological and genetic aspects of salinity tolerance in halophytes, most of them were focused on annual species. However, this knowledge is hardly applicable to perennial crops that need to maintain capability of growth and development for many successive seasons and, therefore, cannot rely on the strategy associated with salt exclusion from uptake. Succulence is one of that important strategies by which perennial halophytes conserve water and dilute immense salt concentration in their susceptible tissues. Succulent halophytes can be used as convenient models for understanding the mechanistic basis of plant adaptation to salt stress. This understanding is important for improving water use efficiency (WUE) in crop plants that undergo a salt-induced physiological drought under saline condition. How a perennial succulent halophyte then will manage this issue, morphologically, anatomically, and physiologically? The major aim of this study was understanding the mechanistic basis of long-term salt tolerance strategy employed by the succulent perennial halophyte, Sarcocornia quinqueflora. The following specific objectives were addressed: • To quantify the relative contribution of organic and inorganic osmolytes towards osmotic adjustment and turgor-induced growth in succulent shoots. • To link osmotic adjustment and stomatal characteristics with salinity stress tolerance and water use efficiency (WUE) of succulent stems. • To dissect specific morphological and anatomical features of succulent shoots and investigate their potential contribution toward their salt tolerance strategy. • To investigate the causal relationship between salinity and oxidative stress tolerance in succulent stems of this perennial halophyte. • To understand the role of ROS signalling in regulating activity of membrane transporters mediating ion homeostasis in this plant. The whole-plant responses of S. quinqueflora to soil salinity was investigated using a broad range of salinity (0 – 1000 mM NaCl). S. quinqueflora showed the typical growth response of a succulent halophyte, with maximum growth obtained at 200 mM NaCl, while growth was reduced at concentrations exceeding 600 mM NaCl. Elevated salinity levels up to 400 mM NaCl largely promoted dry matter yield, succulence, shoot surface area and stomatal characteristics. The osmolality of shoot sap increased as salinity increased from 0 to 1000 mM NaCl. Osmotic adjustment in succulent shoot was achieved, even at the highest salinity levels, by a massive accumulation of inorganic ions, with Na\(^+\) and Cl\(_-\) contributing ~85 % of its osmolality, while organic compatible solutes and K\(^+\) were responsible for only ~15%. These facts suggest that cell expansion growth in this species is relying heavily upon the coordination between the cell vacuolar sequestration capacity (VSC) of Na\(^+\) and Cl\(_-\) and the extent of the cell wall extensibility (CWE). The maximum VSC of Na\(^+\) and Cl\(_-\) is required to keep the cytosol toxic-free and to lower the cell osmotic potential which in turn elevates turgor pressure (hence, succulence). Carbohydrates were not reduced at high salinity compared to plants at optimal conditions, implying that growth retardation at severe salt dosages was attributed to limitations in VSC rather than inadequate photosynthesis and substrate limitation. The control of stomatal operation seems to be critical for S. quinqueflora performance under saline conditions. The fact that transpiration rate was maintained unchanged over the very broad (200 to 1000 mM NaCl) range of salinities, despite the large difference in stomatal density and aperture size, suggest superior plant’s ability to optimize WUE and balance water loss with CO\(^2\) assimilation. Importantly, shoot K\(^+\) was unchanged across the entire range of salinity treatments (200 – 1000 mM NaCl) and positively correlated with transpiration rate (R=0.98), indicative of the likely role of K\(^+\) in controlling stomatal transpiration. Therefore, the superior salt tolerance of succulent shoots is achieved by effective reliance on Na\(^+\) and Cl\(_-\) accumulation for osmoregulation and turgor-induced growth and maintaining K\(^+\) threshold levels for efficient stomatal operation. The leafy stems of S. quinqueflora shoot are composed of assimilating oblong internodes (beads), representing the main photosynthetic organ. Anatomically, the plant develops two distinct layers: an endodermis-like layer (ED), and an additional internal photosynthetic layer (IP). We followed the morpho-anatomical changes in S. quinqueflora leafy stem under varied salt levels in beads of different ages to assess this biological barrier (ED) from non-senescent to senescent stages. Our findings revealed that S. quinqueflora utilizes senescence process to discard excess salt being accumulated in outer tissues of their leafy stems (salt shedding). The development of ED and IP appears to be important to enable this process and determines the whole salt-coping strategy for the plant. Elevated salinity leads to an accelerated development of the ED. In addition, its development strongly affected ion distribution between outer (senescent) and inner (non-senescent) tissues. A positive correlation between the ratio of ED to a bead diameter and the outer to inner concentration of Na\(^+\) was observed. These ratios were highest in older (basipetally-located) beads and progressively decreased towards the tip. The Na\(^+\)/K\(^+\) ratio was substantially higher in outer region compared to the inner one. In addition, different leafy stem regions had showed that a ratio for any given NaCl concentration was the lowest for the top stem region with maximum impact being observed in the bottom stem region. High K\(^+\) content in the tip of the leafy stem also drives the expansion growth of the plant. Accordingly, the top leafy stem region kept Na\(^+\)/K\(^+\) ratio at the constant level regardless of external salt concentration. This correlates with the plant’s ability to grow/survival even at the highest (1000 mM) NaCl concentration tested. Furthermore, the Na\(^+\)/K\(^+\) ratio in inner tissues of bottom beads at highest salinity treatments (800 and 1000 mM NaCl) that showed clear senescence symptoms was ~1.0, indicative of complete separation of the outer and inner tissues at late developmental stage due to the presence of the fully suberized endodermis multilayer (ED). Accordingly, a model was suggested for bead tolerance strategy at early, middle, and late stages under saline conditions involving a suggested role for the internal photosynthetic layer (IP). Two main features are envisaged. The first one is an accelerated development of a biological barrier (ED) which, in its earlier developmental stage, control water and solute movements to the water storage tissue (WS) and determine Na\(^+\)/K\(^+\) ratio in both senescing and non-senescing tissues. At a later stage, this tissue becomes multilayered and highly suberized, thus protecting the internal tissues for many successive seasons. The second feature is a difference in the energy supply (source) for the outer and the inner tissues. The outer layer (palisade tissue) will fuel the water storage cells to mediate Na\(^+\) and Cl\(_-\) sequestration in their vacuoles while the internal photosynthetic layer operates as an energy provider for young beads and roots. The ability of S. quinqueflora to extend growth for many successive seasons under saline condition also implies an efficient and well-regulated ROS-scavenging and signalling systems at both organ and tissue levels. The causal relationship between activity of key membrane transporters involved in maintaining plant ionic homeostasis and oxidative stress tolerance in succulent stems was investigated. S. quinqueflora possess a well-developed antioxidant system, including betalains, ascorbic acid, α-tocopherol, polyphenols, and flavonoids. The optimal growth level (200 mM NaCl) had the lowest antioxidants concentrations, indicating its capability to maintain favorable ROS levels at moderate salinity. Moreover, both sugars and ROS were positively correlated suggesting that growth/biomass reduction at these conditions probably mediated by re-allocation of the energy pool towards sugar production to operate as non-enzymatic antioxidant scavengers. Also, a negative correlation was recorded between plant biomass and antioxidant activity, implying that the latter should be treated as a damage control mechanism rather than a trait that confers salinity tolerance. In addition, ROS-induced net K\(^+\) and Ca\(^{2+}\) fluxes were measured from various bead tissues being located either in outer (palisade tissue, Pa; and water storage tissue, WS), or inner leafy stem part (internal photosynthetic layer, IP; and stele (vascular cylinder) parenchyma, SP) in addition to the in-between barrier (ED). Two types of ROS were used to induce ion fluxes, hydroxyl radical (OH\(^•\)) and hydrogen peroxide (H\(_2\)O\(_2\)). The flux responses to oxidative stresses were governed largely by (1) the type of ROS applied (OH\(^•\) or H\(_2\)O\(_2\)); (2) the tissue-specific origin and function (parenchymatic or chlorenchymatic); and (3) the tissue location in either outer (senescent) or inner (non-senescent) bead part. ROS-induced K\(^+\) effluxes that were highly tissue-specific, with inner tissues of the plant beads being more sensitive to ROS applied, as compared to the plant outer parts. The magnitude of ion flux response to OH\(^•\) was higher compared to response to H\(_2\)O\(_2\). The ability to retain cellular K\(^+\) under OH\(^•\) stress varied between different bead tissues and was ranked in the following descending order: WS > Pa > IP > SP. Hydroxyl radicals (OH\(^•\)) always led to Ca\(^{2+}\) influx with all bead tissues, while treatment with H\(_2\)O\(_2\) induced opposite Ca\(^{2+}\) flux responses: the Ca\(^{2+}\) influx was recorded only from the photosynthetically active tissues (Pa and IP), while the parenchyma tissues (WS and SP) had transient Ca\(^{2+}\) efflux. These results indicate high tissue-specific ability of S. quinqueflora to maintain their ion homeostasis upon exposure to ROS; a feature that is mainly determined by the developed suberized barrier (ED). In conclusion, the salt tolerance strategy of perennial S. quinqueflora halophyte relies on a set of morphological, anatomical, and physiological traits, enabling the ability to extend growth for many successive seasons. This work emphasized the importance and a requirement to engage specific anatomical features in studying salinity tolerance mechanisms of halophytes, in addition to the traditional whole-plant phenotyping. To the best of our knowledge, none of the previous works provided a causal link between salinity-stress tolerance and ROS activation of ion transporters mediating ionic homeostasis in S. quinqueflora succulent tissues. This gap in our knowledge was filled by the current study. The future work should be focused on comparing tissue-specificity of long-term salinity tolerance mechanisms in other perennial succulent and non-succulent halophytes.