Botswana Ash (Pty) Ltd which is situated in Sua Pan, north east Bostwana, is one of Africa's largest suppliers of salt and soda ash. For a number of years, the company has been experiencing problems which have resulted in the final soda ash product being contaminated and discoloured. The problems experienced at Sua Pan have been reported also to occur in other salt works all over the world. It has been suggested that contamination in many salt works could be possibly be due to the microbial activity by halophilic algae and bacteria that grow in the solar ponds. This study was undertaken to investigate the nature of the contaminating organic compounds present in the brine, to identify the compounds, and to establish how these components vary during the various stages of the soda ash processing. For this study, two sets of brine samples were used; the first set was collected before the summer rains and the second set was collected after the summer rains. Solid bicarbonate and soda ash samples were also used. Extractions, desalting, UV and HPLC analysis and oxidative biotransformations using four enzymes, were used for developing profiles and characterizing the brine components. From these studies, we were able to confirm that the components of the brine are organic in nature. A thorough study of one of the compounds isolated,from solid bicarbonate and soda ash was conducted using UV, HPLC, IR, NMR, HPLC-MS, GC-MS and TLC. The results of these analyses, show that the. isolated compound was benzyl butyl phthalate which is generally regarded to be humic in nature. This compound was found to be present in all the brine samples collected after the summer rains including the well brine, suggesting this compound occurs naturally and is not formed during the processing.

The fig–fig wasp interaction is a classic example of obligate mutualism and coevolution. It is also a nursery pollination mutualism and supports a diversity of exploiter/parasite/non-pollinating fig wasp species. Mutualists and exploiters comprise the fig wasp community. All the wasp community members are obligately dependent on the fig syconium (a globular closed structure comprising of hundreds to thousands of uniovulate florets) for completing their life cycle. The fig florets can be sessile (without a stalk) or pedicellate (stalked) and can support a community comprising 3–30 wasp species. Fig wasps can access the floral resources for oviposition directly by entering into the syconium (internal oviposition) or by penetration of the syconium surface (external oviposition). Most studies on the fig–fig wasp interaction have investigated the stability of the interaction, pollination biology, pollen dispersal, co-evolution or the effect of exploiters on this mutualism. However, studies dealing with community ecology and species coexistence mechanisms in these communities are rare. Factors contributing to coexistence of mutualists and exploiters in a fig wasp community were studied using a reasonably speciose fig wasp community associated with Ficus racemosa in south India. The wasp community of Ficus racemosa comprises a single species of pollinator and six species of exploiters; together they represent three genera of fig wasp species. The community members show differences in their feeding habit; they could be 1) gallers (feed on floral tissue after pollination and/or after inducing abnormal tissue development of the floret that is also called the gall), 2) inquilines (feed on gall tissue but cannot induce galling; survive by feeding on gall tissue and starving the host larva to death), or 3) parasitoids (lay eggs in or on developing offspring of a galler or inquiline species; develop by feeding on host tissue). Resource partitioning across temporal and spatial axes on this fig wasp community have been quantified. Ovipositor traits of each community member were also investigated since variation in ovipositor traits might facilitate resource partitioning. Finally, the role of life-history traits in species coexistence in this community was also explored. Temporal resource partitioning among members of the fig wasp community was studied (1) across the resource phenology, i.e. over the development phases of the fig syconium, and (2) on a diel scale. The seven members of the wasp community were found to partition their oviposition periods across fig syconium development phenology; some species used very young syconia (soft and smaller in size) for oviposition whereas others used mature (hard and bigger in size) syconia for oviposition. The first species to colonise the syconia were gallers and these were followed by parasitoids in a definite oviposition sequence. Pollinators arrived concurrently with an exploiter galler species and had the shortest oviposition window in terms of days. Although fig wasps are known to be largely diurnal, night oviposition in several fig wasp species was documented for the first time. Wasp species showed a peak in their activity period across the diel cycle and phenology. This is probably the first study to simultaneously investigate temporal partitioning across the syconium phenology as well as the diel scale in a fig wasp community. Partitioning of syconium space was investigated by quantifying the quality (type of floret—sessile or pedicellate) of floral resources. The number of individuals of each species developing in a syconium was quantified along with host accessibility during oviposition by each wasp species. The association between community members developing within a syconium was also tested. The differential occupancy of florets by each species based on their distance from the base of the syconium was evaluated. For the first time the relative distribution of males and females of the entire fig wasp community was quantified. The wasp community members used similar types of florets for oviposition. Seeds were found mostly in sessile florets and wasps were present in large numbers in pedicellate florets. Except for one wasp species, all others occurred uniformly within the syconium with respect to the distance from the base of the syconium. Species distribution models revealed higher prediction ability for the location of mutualists (seed and pollinator) within the syconium compared to exploiters. Within a syconium, all species pairs exhibited positive associations indicating either an absence of or low competitive exclusion. Some florets were modified by their gall occupants such that they were longer in length indicating the possibility of creation of an enemy-free zone by the gall occupant. Yet, most florets were accessible to ovipositing wasps based on ovipositor lengths and flexibility. The probability of finding a male decreased with increase in floret length when all wasp species were grouped together; however, this trend did not hold true when males and females of species were tested individually. Based on these results, the fig wasps of F. racemosa could be grouped into—(1) Early-arriving galler species which used immature florets, inducing large galls that protruded into the cavity, and with fewer individuals per syconium, (2) Galler species arriving concurrently with the pollinator, inducing galls that were morphologically indistinguishable from those of the pollinator, and with many individuals developing per fig syconium, and (3) Parasitoids and/or inquilines of the galler species, with variable abundance per syconium. Thus, these results show that the wasp species do not clearly partition floral resources between syconia and within syconium but they can modify their oviposition sites and also differ in the proportion of florets within a syconium used for oviposition. Oviposition sites of the fig wasps can be reached only by using their ovipositor. The resources for oviposition are hidden and hence might require tools for resource location and utilisation. The frequency and diversity of sensilla on the ovipositor, as well as ovipositor structure (morphology and sclerotisation of the tip) was documented for the entire wasp community. The internally-ovipositing pollinator had the simplest ovipositor, negligible sclerotisation and only one type of sensillum on its ovipositor; the externally ovipositing exploiter species had teeth on their ovipositors, sclerotisation and various types of ovipositor sensilla. Ovipositor sclerotisation and lateness of arrival for oviposition in syconium development were positively correlated. Ovipositor teeth height increased from gallers to parasitoids. Presence of different types of sensilla was noted which included mechano- and chemosensilla, as well as combined mechano-chemosensilla. Chemosensilla were most concentrated at ovipositor tips while mechanoreceptors were more widely distributed. Ovipositor traits of one putative parasitoid/inquiline species differed from those of its syntopic galler congeners and clustered with those of parasitoids within a different wasp subfamily. Thus ovipositor tools show lability based on adaptive necessity, and are not constrained by phylogeny. Life-history traits such as fecundity, pre-adult and adult lifespan were studied for each wasp member of the community. Trade-offs in life-history traits were also investigated. Interspecific variation in life-history traits was observed. Gallers were pro-ovigenic (all eggs were mature upon adult emergence) whereas parasitoids were synovigenic (eggs matured progressively during adult lifespan). Initial egg load was correlated with body size for some species, and there was a trade-off between egg number and egg size across all species. Although all species completed their development and left the syconium concurrently, they differed in their adult and preadult lifespans. Providing sucrose solutions increased parasitoid lifespan but had no effect on the longevity of some galler species. While feeding regimes and body size affected longevity in most species, an interaction effect between these variables was detected for only one species. Life-history traits of wasp species exhibited a continuum in relation to their arrival sequence at syconia for oviposition during syconium development, and therefore reflected their ecology. The largest number of eggs, smallest egg sizes, and shortest longevities were characteristic of the earliest-arriving galling wasps at the smallest, immature syconia; the converse characterised the later-arriving parasitoids at the larger, already exploited syconia. Thus life-history is an important correlate of community resource partitioning and can be used to understand community structure. The comparative approach revealed constraints and flexibility in trait evolution. This is probably the first comprehensive study of life-history traits in a fig wasp community.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg. in fulfilment of the requirements tor the degree of Master of Science / This thesis develops the theoretical basis of the qualitative frame based modelling technique, a paradigm recently proposed by Starfield for the modelling of ecosystems with a multiplicity of stable states. This technique is a refinement of the State-and- Transition conceptual model of Westoby et al which involves the division of the ecosystem dynamics into a catelog of stable 'states' and a suite of transitions between these states. The frame models of Starfield associate with each stable configuration of the ecosystem a qualitative rule based model for the key processes in that stable configuration. The aims of this thesis are the following, 1. A rigorous definition of frame modelling of dynamic ecosystems is proposed, and this theoretical foundation is used to demonstrate that qualitative frame models may be used to mode! dynamic ecosystems to an arbitrary accuracy. 2. The development of implementation software. A qualitative rule based frame modelling environment is presented. and a specification for an improved environment is proposed based on the theoretical work. / Andrew Chakane 2019

No description available.

The rate of extinction of plant and animal species has accelerated at an alarming rate throughout the 20th century. This depletion has resulted in greater legislative control over wildlife within the United States, and the eventual passage, in 1973, of the Endangered Species Act (ESA). The ESA establishes regulations designed to protect species which are threatened with extinction. The ESA has evolved out of past legal statutes and jurisprudence concerning the management and protection of wildlife, but the ESA has created controversy since inception. The latest criticisms concern its lack of success in meeting stated policy goals of preserving species richness and recovering listed species. As a result, a new movement has developed which seeks to change the traditional species-by-species approach of the ESA to an approach which concentrates on entire ecosystems. Ecosystem approach proponents sight various advantages, one of which is cost-effectiveness. This thesis analyzes the development of wildlife protection within the United States, and the Endangered Species Act in particular. The purpose of this analysis is to examine both the legislative powers granted for wildlife protection, and the feasibility of the ESA to encompass ecosystem protection. Modifications to the ESA are proposed. The Clinch River Valley, in Southwest Virginia and Northeast Tennessee, is used as a case study for a cost-effectiveness analysis of an ecosystem approach and species-by-species approach. Costs generated through Fish and Wildlife Service recovery plans are used in conjunction with generated ecosystem plan recovery costs. The results of the cost-effectiveness analysis show that an ecosystem approach is more cost-effective in meeting the recovery goals within the 0inch River Valley. The ESA can be modified to incorporate an ecosystem approach. Such modification can protect species richness and allow for a priority ranking system for protection. / M.S.

To improve the study and management of Havens Wildlife Management Area (HWMA) in Roanoke County, Virginia, the ecological history of the Ridge and Valley Province of Virginia was investigated. Palynological, paleontological, archaeological, and historical data were synthesized into a comprehensive history of the region's vegetation, fauna, and humans from 25,000 B.P. to Euroamerican settlement. A linear programming model was developed to examine the relationship between the energy demand of a human band and the food resources of HWMA 2,500 years ago. The model was based on the assumption that prehistoric human foraging was impelled by the need to satisfy energy requirements and that prehistoric human foragers strove for maximum energetic efficiency. The model was driven by an objective function, that minimized the cost (expressed in hours of labor) of the human foragers' diet. Constraints on the achievement of this goal were the available metabolizable energy in selected mountain food resources and the energy demand of a 25-person band. The product of the model was a regimen of food resources that met the band's annual energy requirement at the lowest cost. The model predicted that fall was the dominant foraging season on HWMA. Chestnut was the major food resource, satisfying 54% of the bandâ s annual energy demand. Additional primary resources were opossum and raccoon, elk, woodchuck, white-tailed deer, and black bear. Secondary and tertiary resources were passenger pigeon, bitter acorns, hickory nuts, and false Solomon's seal rhizomes. Marginal food resources were wild turkey, Jack-in-the-pulpit corms, eastern cottontail, gray squirrel, sweet acorns, and box turtle. An annual foraging strategy with a fall-winter focus in mountain ecosystems and a spring-summer focus in lowland ecosystems was suggested by the model. A comparison of the model results with an archaeological data indicated that hickory nuts were over represented and chestnuts underrepresented at archaeological sites, and that clothing, not food, limited human population density in upland western Virginia ecosystems. / Master of Science

A computerized system for estimating rainfall values was developed for western Virginia using data from 15 weather stations in that area. This system, called VARAINS for VirginiA RAINfall System, is designed to run on a microcomputer. System programs were created using Borland Pascal, version 7. The system models were developed using study station coordinates, elevation, aspect, distance from West Virginia, distance to the Virginia coast, as well as transformations, as independent variables. Additionally, a distance-weighting variable was developed using the inverse distance to each of the 5 closest study stations. The system provides estimates for annual, seasonal, and monthly rainfall at single or multiple ungaged sites. Rainfall models were validated using comparable periods of record from 3 stations within the study zone not previously used to develop study models. VARAINS was demonstrated using 4 sites occurring on the Havens Wildlife Management Area of the Virginia Department of Game and Inland Fisheries. Potential system applications for wildlife management include incorporating system output files into a geographic information system, using Outputs as independent variables in regression analyses of habitat phenomena, and in ecosystem models of interest in endangered species research. Ideas for supplemental research on the model are explored and include testing VARAINS in other areas, evaluating the impact of using fewer years of data in model development, and combining these models with those developed in a recently completed temperature study. / Master of Science

Little Lake Worth (LLW) (800 m x 200 m x 8« m) is an artificially deep, monomictic marine basin. Pigments and other water quality parameters (O2, pH, T, S, NO3 -. etc.) were utilized to characterize phototrophic communities and water quality. The water column is dominated by diatoms except in the hypolimnon during stratification events (late Summer) when strong anoxia and H2S favors abundant Chlorobium sulfur bacteria. Results indicate nitrate-enriched freshwater baseflow indicative of septic tank seepage during the wet season. This also appears to lead to the accumulation of concentrated organic matter in the sediment. LLW is a potential threat to the health of the ecosystem and the humans using it recreationally. More research is required to verify the effectiveness of restoration options. The spatial and temporal distribution of Chlorobium (phaeovibiroides tent.) and their Bacteriochlorophyll-e homologues is described and compared to similar studies. / by Keren Prize Bolter. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg 1992. / The aim of the study was to develop understanding of the relationships between vegetation types of the grassland biome of South Africa and the environment, with an emphasis on structural and functional characteristics. The grassland biome in South Africa has traditionally been divided into 'pure' grasslands, assumed to be climatically determined, and 'false' grasslands of recent anthropogenic origin. A review of literature from several disciplines including palaeobotany, archaeology, ecology and biogeography indicates that this is not a valid distinction. It is clear that the distribution of the grassland biome as a whole is poorly understood, but the general correlation between the distribution of biomes and climate elsewhere in the world suggests that this warrants more detailed investigation. A water balance approach was used to develop climatic incices that both predict the distribution of grasslands, and are easy to interpret biologically. The indices are the mean. number of days per annum when moisture is available for plant growth, tbe mean temperature on days when moisture is available for plant growth (wet season temperature),. and the mean temperature when moisture is not available for plant growth (dry season temperature). Based on these three.indices the grassland biome in South Africa call be distinguished from neighbouring biomes. The fynbos and succulent karoo biomes have rainfall in winter. The grassland, nama-karoo and savanna biomes have' rainfall in summer. The forest biome experiences rainfall throughout the year. Of the summer rainfall biomes, the quantity of water available in the grassland biome b greater than in the nama-woo, similar to savanna, but less than forest. Grasslands experience cooler dry season temperatures than savannas. The localised distribution of woody plants within the. grassland biome suggests that it is the effect of climate on the fire regime that may be of overriding importance h'l determining the distribution of the biome as a whole. Woody elements are restricted to sites that are either protected from fire, or experience fires of lower intensity than sites that support- grassland, The unifying feature of the grassland biome is its proneness to fire. The presence of a warm, moist season promotes plant production and leads to a high standing crop close to the ground. The prolonged dry season causes vegetation to dry out annually, rendering it flammable. More arid biomes have plants more widely spaced, making it difficult for fire to spread. In more mesic biomes where rainfall is less sea.sonal than in the grasslands or savannas, fuels do not dry out sufficiently to ignite, A number of additional climatic features may promote burning in the grassland biome, It has the highest lightning density of all South Africa's biomes. 'tVarm, dry 'berg' winds desiccate fuels and 1 omote burning in the more mesic grasslands, The 'curing' of the grass sward due to dry season frost and temperature drop is important in establishing early dry season flammability. Savanna trees are fire tolerant, but they appear sensitive to the cold temperatures prevaient in the grassland biome in. the dry season, The relationship between the distribution of functional characters of grassland plants and environmental conditions was investigated. The distincrion between sweetveld, mixed veld and sourveld was recognised as one of the most Important functional features of South Africa's grasslands, The distribution of these vegetation types was examined in detail. Sweetveld occurs In warm, dry areas; sourveld in cool, moist areas. There Is overlap between these tyP.Js that Is dependant on soil nutrient status. Sweetveld that occurs in climatic conditions that would be expected to support mixed veld and sourveld, is on soils derived from basic parent material, including basalt, dolerite, gabbro and norite. Similarly, sourveld that occurs in areas that climatically would be expected to support sweetveld, is on soils derived from acid parent material such as sandstone and quartzite .. Soil nutrients that are most highly correlated to the occurrence of these three veld types are phosphoms availability and an index of nitrogen mineralization potential. 'l'here is an increase in bot; available phosphorus and the index of readily mineralizable nitrogen from sourveld to mixed veld to sweetveld. These features am inc01).10111tedinto a conceptual model that relates the distribution of these grassland types to carbon and nitrogen metabolism, with the role of phosphorus either similar to nitrogen, or else it may act indirectly by affecting the. rate of nitrogen mineralization, Nitrogen mineralization OCcursat lower water availability than carbon assimilation, and its temperature optimum is higher than that of carbon assimilation. Where nitrogen mineralization is favoured ielative to carbon assimilation, sweetveld is likely to (}C(.1\Xr. Where carbon assimilation is. favoured relative to; nitrogen mineralization, sourveld is likely to occur ....Soil texture affects the balance between these two processes in the degree to wm.r;h it protects soil organic matter, and thereforv the size of the nitrogen and ph_QSPllO_rOll.S pools. Changes in the rlj,stribution of South Africa's b~\omesfor a scenario of climate change are predicted using the biome model developed in this study. This illustrates the value of developing predictive models. / MT2017

The primary aim of this study was to investigate the role of food supply and ground cover on the community structure, population dynamics and demography of terrestrial small mammals in a subtropical grassland. This aim was achieved through a series of food supplementation and cover manipulation experiments conducted at eKundizeni Farm near Matsapha, Swaziland, over a 28 month period. The effects of five different diets on the rodent Mastomys natalensis were investigated in the laboratory, and the results showed that rolled oats and rabbit pellets were suitable for growth and reproduction in this species. The effects of supplementary food were investigated on two supplemented grids and one control over a twelve month period. Small mammal biomass increased significantly on the supplemented grids in relation to the control. This increase in biomass was the result of a twofold increase in the numbers of M natalensis. Food supplementation further affected M. natalensis by: extending the breeding season of females; increasing body weight; increasing survival; and decreasing home range area. Food supplementation had a weak positive effect on the density of another rodent Lemniscomys rosalia, but did not affect any other demographic feature of this species. Food supplementation did not have a demographic effect on any other species of small mammal captured. The effects of vegetative cover were investigated, over a twelve month period, on two control grids and four manipulated grids on which the vegetative cover was mechanically reduced. Supplementary food was added to two of the latter four manipulated grids. The biomass of small mammals, including M. natalensis, was lower on grids with reduced vegetative cover than on the controls. However, food supplementation resulted in a significant increase in the biomass of M. natalensis on one of the manipulated grids. Hence, M. natalensis was induced to shift to a habitat with reduced cover by the provision of supplementary food. Additional information on the population dynamics, age structure, reproduction and diet of M natalensis, L. rosalia, Mus minutoides and Steatomys pratensis is also presented. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1997.