• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 7
  • 2
  • Tagged with
  • 9
  • 9
  • 9
  • 9
  • 3
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Delineating the current and potential distributions of prosopis glandulosa in the square kilometre array South Africa, Karoo site

Buthelezi, Nomcebo Siphesihle January 2019 (has links)
A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Geographical Information Systems and Remote Sensing, 2019 / Prosopis species (also known as Mesquite), in particular P. glandulosa (Honey Mesquite) have a negative impact on indigenous biodiversity and the livelihood of communities in the semi-arid and arid parts of South Africa. The spread of these species is a threat to the environments in which they have been introduced as they spread at high rates, increase the mortality of indigenous trees and disrupt important ecosystem processes such as hydrological and nutrient cycles. Due to the negative impacts of Prosopis on important ecosystem services and South Africa’s native biodiversity, it is essential for the distribution of these species to be identified, controlled and monitored in order to mitigate their spread and restore damaged ecosystems. The objectives of this study were to use Remote Sensing and Geographic Information Systems (GIS) tools to: (i) delineate the distribution of Prosopis using high resolution satellite imagery, (ii) determine the changes in spatial distribution of these species in the period 2003-2017, and (iii) use moderate spatial resolution satellite imagery and ancillary environmental data to predict areas susceptible to future invasion.. The study area used in this investigation is the Square Kilometre Array (SKA SA) site, situated in Northern Cape Province, South Africa. Satellite images were classified using Multi-layer Perceptron (MLP) Neural Network classification algorithm to improve the land use land cover classification accuracy. A WordView-3 image with 1.24 m spatial resolution was used to delineate the distribution of Prosopis in the study area for the year 2016. Landsat images from the years 2003, 2008, 2013 and 2017 were used to conduct a change detection analysis. The prediction model developed in the study was able to predict Prosopis cover for the years 2017 and 2022 cover using ancillary environmental data and land use land cover maps. The study was also able to quantify the area covered by Prosopis species for the years 2017 and 2022. / XN2020
2

Mapping Prosopis glandulosa (mesquite) invasion in the arid environment of South African using remote sensing techniques

Mureriwa, Nyasha Florence January 2016 (has links)
A dissertation submitted to the School of Geography, Archaeology and Environmental Studies, Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science in Environmental Sciences. Johannesburg, March 2016. / Mapping Prosopis glandulosa (mesquite) invasion in the arid environment of South Africa using remote sensing techniques Mureriwa, Nyasha Abstract Decades after the first introduction of the Prosopis spp. (mesquite) to South Africa in the late 1800s for its benefits, the invasive nature of the species became apparent as its spread in regions of South Africa resulting in devastating effects to biodiversity, ecosystems and the socio-economic wellbeing of affected regions. Various control and management practices that include biological, physical, chemical and integrated methods have been tested with minimal success as compared to the rapid spread of the species. From previous studies, it has been noted that one of the reasons for the low success rates in mesquite control and management is a lack of sufficient information on the species invasion dynamic in relation to its very similar co-existing species. In order to bridge this gap in knowledge, vegetation species mapping techniques that use remote sensing methods need to be tested for the monitoring, detection and mapping of the species spread. Unlike traditional field survey methods, remote sensing techniques are better at monitoring vegetation as they can cover very large areas and are time-effective and cost-effective. Thus, the aim of this research was to examine the possibility of mapping and spectrally discriminating Prosopis glandulosa from its native co-existing species in semi-arid parts of South Africa using remote sensing methods. The specific objectives of the study were to investigate the spectral separability between Prosopis glandulosa and its co-existing species using field spectral data as well as to upscale the results to different satellites resolutions. Two machine learning algorithms (Random Forest (RF) and Support Vector Machines (SVM)) were also tested in the mapping processes. The first chapter of the study evaluated the spectral discrimination of Prosopis glandulosa from three other species (Acacia karoo, Acacia mellifera and Ziziphus mucronata) in the study area using in-situ spectroscopy in conjunction with the newly developed guided regularized random forest (GRRF) algorithm in identifying key wavelengths for multiclass classification. The GRRF algorithm was used as a method of reducing the problem of high dimensionality associated with hyperspectral data. Results showed that there was an increase in the accuracy of discrimination between the four species when the full set of 1825 wavelengths was used in classification (79.19%) as compared to the classification used by the 11 key wavelengths identified by GRRF (88.59%). Results obtained from the second chapter showed that it is possible to spatially discriminate mesquite from its co-existing acacia species and other general land-cover types at a 2 m resolution with overall accuracies of 86.59% for RF classification and 85.98% for SVM classification. The last part of the study tested the use of the more cost effective SPOT-6 imagery and the RF and SVM algorithms in mapping Prosopis glandulosa invasion and its co-existing indigenous species. The 6 m resolution analysis obtained accuracies of 78.46% for RF and 77.62% for SVM. Overall it was concluded that spatial and spectral discrimination of Prosopis glandulosa from its native co-existing species in semi-arid South Africa was possible with high accuracies through the use of (i) two high resolution, new generation sensors namely, WorldView-2 and SPOT-6; (ii) two robust classification algorithms specifically, RF and SVM and (iii) the newly developed GRRF algorithm for variable selection and reducing the high dimensionality problem associated with hyperspectral data. Some recommendations for future studies include the replication of this study on a larger scale in different invaded areas across the country as well as testing the robustness of the RF and SVM classifiers by making use of other machine learning algorithms and classification methods in species discrimination. Keywords: Prosopis glandulosa, field spectroscopy, cost effectiveness, Guided Regularised Random Forest, Support Vector Machines, Worldview-2, Spot-6
3

The vegetation management of the Botsalano Game Reserve in the North West Province, South Africa.

Bosch, Almero Deon. January 2011 (has links)
Thesis (MTech. degree in Nature Conservation)--Tshwane University of Technology, 2011. / The study was conducted on the Botsalano Game Reserve with the support of the North West Tourism and Parks Agency. No formal management plan is available for the game reserve and therefore the need for an ecological management plan and guidelines for the formulation of a vegetation monitoring plan constituted the basis of the study. The objectives of the study were: 1. To classify and map the plant communities of the Botsalano Game Reserve; 2. To provide quantitative data, collected during a formal vegetation classification, for use by the reserve management in terms of current vegetation condition; 3. To ascertain whether a classification of the vegetation on the BGR could be used for the objective placement of vegetation monitoring sites. Monitoring site placement will be based on representation of plant communities, reflecting community and topographical unit utilization and thus stocking rates based on management decisions.
4

A comparison of selected satellite remote sensing techniques for mapping fire scars in limestone fynbos

Smit, Walter J. (Walter Johan) 12 1900 (has links)
Thesis (MA.)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: There are many reasons to conserve fynbos. Not only does fynbos form part of the Cape floral kingdom, one of the richest floral kingdoms in the world, but the contribution that it makes to the regional economy through utilisation, education, recreation and tourist opportunities is immeasurable. Fire plays an integral role in fynbos ecosystems. According to Van Wilgen, Richardson & Seydack (1994: 322) " ... managing fynbos equates to managing fire". Therefore managers need accurate fire information about a fynbos area to manage it properly. This is where satellite remote sensing can provide the manager with useful information about the fire regime. In other words, satellite remote sensing can help a manager establish where and when an area has burnt. Using readily available satellite data, this study attempts to establish (through comparison) what techniques would be most suitable and affordable to compile a fire information database. Landsat Thematic Mapper data from 1990 - 1996 of the southwestern Cape was used and compared with existing fire records of the area. The results show that techniques such as supervised and unsupervised classification are reliable in identifying burnt areas, but a major drawback of these techniques is that they require a large amount of user input and knowledge. They are thus not regarded as simple or easily repeatable. - The' more simple techniques like image differencing and image ratioing were also found to be reliable in identifying burnt areas. These techniques require less user input and in some instances less data (image bands) to produce similar (or better) results than supervised and unsupervised classification techniques. The results show that differencing temporally different Images, obtained from applying principle components analysis, produces reliable results with very little confusion and little user input. Using such a technique could enable users to procure only two bands of Landsat data and still produce reliable fire information for managing a fynbos ecosystem. / AFRIKAANSE OPSOMMING: Daar is verskeie redes waarom fynbos bewaar moet word. Nie net vorm dit deel van een van die rykste blommeryke in die wereld nie, maar die bydrae wat dit tot die streeksekonomie maak, deur die benutting van veldblomme en die geleenthede wat dit bied vir toerisme en ontspanning, is enorm. Vuur speel 'n belangrike rol in die bestuur van fynbos ekosisteme. Soos beklemtoon deur Van Wilgen, Richardson & Seydack (1994: 322) se stelling: " ... managing fynbos equates to managing fire". Om hierdie rede is dit belangrik dat 'n bestuurder akkurate inligting oor die verspreiding van veldbrande moet he. Satellietafstandwaarneming kan hier 'n belangrike rol speel deur sulke inligting te verskaf Deur gebruik te maak van maklik bekombare satellietdata, poog hierdie studie om te bepaal (d.m.v. vergelyking) watter tegnieke die mees geskikte is in terme van bekostigbaarheid en gebruikersvriendelikheid. Landsat Thematic Mapper data van 1990 tot 1996 van die suidwes-Kaap is gebruik en vergelyk met bestaande branddata van die studiegebied. Daar is gevind dat tegnieke soos gerigte en nie-gerigte klassifikasie in staat is om gebrande dele betroubaar uit te ken. Hierdie tegnieke verg egter baie insette en kennis van die gebruiker en is ook nie maklik om jaar na jaar te herhaal nie. Daarom word hierdie tegnieke nie aanbeveel nie. Daar is gevind dat die eenvoudiger tegnieke soos veranderingsanalise ook gebrande dele betroubaar kon uitken. Hierdie tegnieke het die voordeel dat die gebruiker nie baie' kennis van die gebied hoef te he nie en ook nie so baie insette hoef te lewer nie. Hierdie tegnieke word bo gerigte en nie-gerigte klassifikasie aanbeveel. - Die resultate dui daarop dat betroubare resultate verkry kan word deur tempo reel verskillende beeIde, verkry deur hoofkomponentanalise, van mekaar af te trek. Hierdie tegniek vereis relatief min gebruikersinsette en daar kan selfs met slegs twee Landsat bande gewerk word. So 'n tegniek kan beslis 'n bekostigbare en effektiewe manier wees om nodige inligting vir die bestuur van 'n fynbos ekosisteem te bekom.
5

A vegetation survey and mapping of the woodbush granite grassland in the Limpopo Province, South Africa

Matjie, Mapula Rose January 2019 (has links)
Thesis (M. Sc. (Botany)) -- University of Limpopo, 2019 / The Woodbush Granite Grassland (WGG) is the most threatened vegetation type in Limpopo Province of South Africa. However, it has a high conservation value, because few examples of this vegetation type remain in southern Africa. Unfortunately, a large part of it is not formally conserved, making this the vegetation type most urgently in need of conservation. The study aimed at mapping transformation of the WGG, identifying species of conservation importance, and providing a management plan required for maintenance of the WGG. The objectives of the study included compiling a transformation map for the WGG, which also involved describing the remaining patches of the WGG that are in a natural or near-natural state. It also provides information on species of conservation importance, medicinal plants and threats to the WGG. On the four main study sites (Iron Crown Grassland, Haenertsburg Grassland, Ebenezer Dam Nature Reserve Grassland, and Ebenezer Dam Perimeter Grassland), quadratic plots were randomly set with a size of 25 x 25 m, and subplots of 1 x 1 m. Vegetation mapping was done during summer and winter. At each plot data was collected on all plant species occurring within the quadrat. A cover score was assigned to each plant species. A modified Braun-Blanquet data collection sheet was employed to obtain baseline data. For transformation mapping GeoTerra Image (GTI), land cover data were extracted for the WGG, using the modelled boundary as a mask, with 5 categories of transformation defined. Of the surveyed sites, the Ebenezer Dam Nature Reserve Grassland has the highest number of species, while the Haenertsburg Grassland contained the most endemic species of conservation importance. Rare species such as the Aloe zebrina, which does not occur in any formally protected area, and medicinal plants such as Athrixia phylicoides, occur on the WGG. All sites have importance with regard to WGG conservation. Identified threats include the spread of alien invasive plants, uncontrolled collection of medicinal plants, urban development, and poorly timed anthropogenic fire. vi The WGG underwent transformation to other land classes. Grassland clearing for plantations and cultivation were the main causal factors behind the observed WGG losses, with a total of 55.25% transformed. Transformation by afforestation is considered irreversible. It is concluded that the WGG is of conservation importance, and that some of it has been transformed to exotic timber plantations. The grassland is under various threats; therefore it is recommended that: (1) The proposed management plan provided in this study be adopted, (2) further research on the WGG be done on medicinal plants, (3) phytosociological and floristic studies be conducted and, (4) the effects of fire and alien invasive plant species on the grassland be investigated.
6

Vegetation change detection using remote sensing and GIS in Makhado Town, Limpopo Province, South Africa

Zongho, Kom 29 January 2016 (has links)
MEVNSC / Department of Geography and Geo-Information Sciences / Vegetation is one of the most important renewable natural resources to play a role in the preservation of the environment and biodiversity. Various land use activities such as urbanization, population growth and other anthropogenic activities, as well as climate change have been some of the major drivers which alter vegetation cover and contribute to biodiversity loss. This research study uses remote sensing and Geographical Information System to quantify vegetation and land cover change in Makhado over a five-year period (2007 - 2012). This study used multi-temporal satellite image data to identify the dynamic pattern of vegetation change and the negative impacts it has on the environment. The research uses remote sensing techniques and GIS software to analyse data. In addition, satellite imageries were used to study the spatial and temporal distribution of vegetation. The results of the study show that settlement areas have been on a stable positive and mostly uncontrolled expansion from 17.73% of the study area in 2007 to 30.52% in 2012. Vegetation on the other hand, has been on a steady decline, from 10.65% in 2007 to 5.92% in 2012, as well as the ecosystems quality on which biodiversity depends for their existence and to a greater extent the climate conditions, with an increase in temperature, methane, nitrous oxide and carbon dioxide. The monitoring of vegetation change can play a vital role in knowledge generation, best practices and as well as Environmental Monitoring and Evaluation which can be abated in the near future. This study recommends that the South Africa Government and public agencies concerned develop policies and strategies to bring about balanced, coordinated and sustainable development in the municipality and its district.
7

Land cover change and its effect on landscape function in the Koue Bokkeveld

Vos, Elizmay 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Natural vegetation and wetlands in regions of the Western Cape are being replaced by agricultural development. Previous studies on one such region - the Koue Bokkeveld, a high mountainous region at the source of three major drainage basins, demarcated for study purposes to cover nearly 2500 km2, have failed to provide a comprehensive overview of such change and its landscape outcomes. This research aimed to detect, capture, record and classify the spatial nature, extent and change dynamics of various landscape elements and functions due to change in the land cover of this region. It assembled a comprehensive spatial database by digitising existing maps, aerial photograph mosaics and satellite imagery. Land cover maps were created for three historical and land cover change analyses were performed for the interim periods. Morphological landscape images were derived from a DEM and used to explain and interpret the location of land cover types and trends in change patterns. The effects on three landscape functions were determined, namely modelled run-off production, biodiversity deduced from landscape pattern structure and SANBI ratings, and carbon storage potential based on published figures. The research found that the regional landscape has undergone substantive land cover change , since the reference state. Increased intensity and productivity of agriculture and its related infrastructure increased its coverage to nearly 45 000 ha or 20 % of the total area. Perennial agriculture (nearly 10 000 ha of orchards and plantations) and annual (intensive vegetable growing and diminishing cereal crops) agriculture, accompanied by improved enabling infrastructure, such as irrigation technology (large storage dams, pipelines, micro delivery modes), transportation, roads, product cooling and packing plants, have extensively replaced natural vegetation. Located in valley bottoms and along toe-slope locations, where they compete for space directly with expanding and constantly intensifying agricultural activities, wetlands, shale fynbos and renosterveld face complete replacement. Land use and land cover changes have profoundly affected landscape functioning. Modelled rainfall run-off has increased (2% overall) in most subregions, opening possibilities for sedimentation and erosion. A high degree of fragmentation of the vulnerable and affected vegetation types threatens biodiversity. Increased carbon storage in perennial agriculture offers a benefit of change, as opposed to the negative outcomes on biodiversity of change in the Koue Bokkeveld. The research recommends improved institutional provision of the data required for system and regional modelling of processes like run-off in developing communities and for meeting the requirements of more sophisticated and accurate landscape models. Improved availability and appropriateness of GIT software solutions to conduct regional research and the use of more economical open software for GIS applications are to be encouraged. Ongoing and improved management and control are advocated for the expanding and intensified agriculture in a sensitive fynbos setting and for the maintenance of healthy landscape functioning. Concerning the discipline of geography, the exploitation of landscape functioning as a transdisciplinary focus inherent to a new regional geography is encouraged to arrest disciplinary drift. Specifically, future research should intensify the examination of the linkages between land use, land cover, change and ecological landscape functioning. / AFRIKAANSE OPSOMMING: Natuurlike plantegroei en vleilande in substreke van die Wes-Kaap word voortdurend vervang deur landbou-ontwikkeling. Vorige studies oor een so 'n streek - die Koue Bokkeveld, 'n hoogliggende bergagtige streek op die oorsprong van drie groot dreineerbekkens, wat afgebaken vir studie-doeleindes byna 2500 km2 dek  bied geen omvattende oorsig van sodanige verandering en die landskapsuitkomste daarvan nie. Hierdie navorsing was daarop gemik om die ruimtelike aard, omvang en veranderingsdinamika van verskillende landskapselemente en -funksies as gevolg van die verandering van grondbedekking van hierdie streek na te spoor, op te teken en te klassifiseer. 'n Omvattende ruimtelike databasis is saamgestel uit versyferde bestaande kaarte, lugfoto-mosaïeke en satellietbeelde. Grondbedekkingskaarte vir drie historiese tydsnitte is geskep en verandering oor die tussentydse periode is ontleed. Morfologiese landskapselemente is uit 'n DEM onttrek en gebruik om die patroon van grondbedekking en tendense in veranderingspatrone te verklaar en te verduidelik. Die nagevolge op drie landskapsfunksies, naamlik reënval-afloop produksie, biodiversiteit soos afgelei van die landskap se patroonstruktuur en SANBI graderings, en koolstof-opgaringspotensiaal gebaseer op gepubliseerde syfers, is bepaal. Die navorsing het bevind dat die streekslandskap sedert die vroegste verwysingstaat wesenlike grondbedekkingsverandering ondergaan het. Verhoogde intensiteit en produktiwiteit van die landbou en sy verwante infrastruktuur het die dekking daarvan vergroot tot byna 45 000 ha of 20% van die totale oppervlakte. Permanente (nagenoeg 10 000 ha boorde en plantasies) en jaarlikse (intensiewe groente en dalende graangewas verbouing) landbou, saam met verbeterde infrastruktuur, soos besproeiingstegnologie (groot opgaardamme, pypleidings, mikroleweringstoerusting), vervoer, paaie, produkverkoeling en -verpakkingsgeriewe, het natuurlike plantegroei grootskaals vervang. Geleë in valleivloere en aanliggende heuwelhange, waar hulle direk om ruimte meeding met die uitbreidende en voortdurend intensiferende landbou-aktiwiteite, is vleilande, skalie-fynbos en renosterveld onderhewig aan volledige vervanging. Grondgebruik- en bedekkingsverandering raak landskapsfunksionering wesenlik. Gemodelleerde reënvalafloop het toegeneem (2% in totaal) in die meeste substreke en vergroot so die moontlikhede vir sedimentasie en erosie. ‘n Hoë vlak van landskapsfragmentasie in die kwesbare en geaffekteerde plantegroeitipes bedreig biodiversiteit. Verhoogde koolstofopgaring in meerjarige landbougewasse impliseer wel 'n positiewe opbrengs van grondbedekkingsverandering, in teenstelling tot die negatiewe biodiversiteitsuitkomste van verandering in die Koue Bokkeveld. Die navorsing beveel aan dat institusionele voorsiening van data wat benodig word vir stelsel- en prosesmodellering (bv. reënvalafloop) in ontwikkelende gemeenskappe, en die vereistes van meer gesofistikeerde en akkurate landskapsmodelle, verbeter word. Die beskikbaarheid en geskiktheid van GIT sagteware-oplossings vir streeksnavorsing, en die gebruik van meer ekonomiese oop-programmatuur vir GIS-toepassings, word aangemoedig. Vir praktiese doeleindes word deurlopend-verbeterde bestuur en beheer oor die uitbreiding en intensifering van van landbou in 'n sensitiewe fynbosomgewing en die instandhouding van gesonde landskapsfunksionering bepleit. Met betrekking tot die dissipline van geografie, moedig die navorsing die ontginning van die landskap se funksionering as 'n transdissiplinêre fokus inherent aan 'n nuwe tipe streeksgeografie aan, om dissiplinêre uiteenloping te stuit. Toekomstige navorsing kan spesifiek die ondersoek van die skakels tussen grondgebruik, grondbedekking, verandering en ekologiese landskapsfunksionering verskerp.
8

Macrophyte distribution and responses to drought in the St Lucia Estuary

Nondoda, Sibulele Phefumlela January 2012 (has links)
This study investigated the response of the macrophytes in St Lucia Estuary, northern KwaZulu-Natal to drought. The present distribution of vegetation (2010 / 2011) was mapped and changes over time recorded from past aerial photographs. The changes in macrophyte cover in response to environmental factors (sediment and groundwater characteristics) was measured along four transects in 2010 and compared with results from previous years, in 2005 and 2006. In the current study, 1960 images were digitized to illustrate macrophyte distribution and cover of the Narrows, Makakatana and the Eastern Shores during a low rainfall period which started in 1958. The 2001 images were digitized to illustrate vegetation distribution and cover of the same area prior to the current drought which started in June/ July 2002. The 2008 images were digitized to illustrate vegetation distribution and cover of estuarine vegetation within the floodplain during the drought (after 6 years). The sites were visited in June 2011 for verification of the distribution and boundaries of each macrophyte habitat. The area covered by the water column varied over time. In 1960 during a low rainfall period the water was 32705 ha, 33320 ha in 2001 and reduced to 30443 ha in 2008. The area cover of inundated and dry reeds fluctuated with the water level. Under high water levels, low-lying areas such as Fanies Island and Selley‟s Lake were flooded and under low water levels, intertidal sand and mudflats were exposed and colonised by succulent salt marsh (Sarcocornia spp. and Salicornia meyeriana). Similar conditions were observed at Makakatana. Mangroves were observed from the mouth to the Forks. Avicennia marina was the dominant mangrove species and primary colonizer of dredge spoil. The area cover of mangroves in the vicinity of the mouth fluctuated as a result of fluctuating water levels, dredging operations, excavation of the Back Channel and Cyclone Gamede which killed intertidal vegetation. Between 2001 and 2008, mangrove expansion was faster in the Mfolozi Swamps area (± 1.4 ha yr -1) compared to the Narrows (± 0.4 ha yr -1). Long term monitoring transects were set up in 2005, at Makakatana, Charters Creek, Catalina Bay and at Listers Point to document changes in sediment conditions and vegetation cover. These were sampled in July 2005, October 2005, February 2006 and May 2010. Silt was the dominant particle size at Catalina Bay, Charters Creek and Makakatana. At Makakatana, average ground water salinity was 17.2 ± 6.6 ppt, 4.1± 4.9 ppt at Catalina Bay and 32.9 ± 19.3 ppt at Charters Creek. Drought resulted in the accumulation of salt on the surface sediment layer at Listers Point and Charters Creek due to low rainfall. Listers Point, the site with the lowest freshwater input and habitat diversity had the lowest macrophyte species richness with only three species. The dominant species at this site were Sporobolus virginicus and Chenopodium album L. which are highly salt tolerant species. Catalina Bay had the highest species richness (18 to 27); as a result of freshwater input via groundwater seepage from the sand dune aquifers on the Eastern Shores. Along the Eastern Shores, vegetation was dominated by species of Cyperaceae, Juncaceae and Juncaginaceae. Fluctuations in groundwater depth were observed at all sites, Listers Point groundwater depth in February 2006 was 80 cm and the ground water level was not reached during the May 2010 field trip. During the May 2010 field trip, the water column salinity of the St Lucia system was highly variable, Makakatana had the lowest water column salinity of 7.1 ppt, 42.1 ppt at Catalina Bay, 44 ppt at Charters Creek and Listers Point had the highest water column salinity of 95 ppt. An assessment of the changes in macrophyte cover along the transects showed that cover fluctuated in response to rainfall, water level and drought. At Listers Point, there was a continuous decline in the abundance of Sporobolus virginicus over time which was sparsely distributed in the first 40 m of the transect. Sarcocornia natalensis, a succulent and obligate halophyte, was recorded, in areas with high sediment conductivity. In May 2010, bare ground increased to an average percentage cover of 96.5% and was covered with dead organic matter and a salt crust at Listers Point. At Makakatana, there was a significant decrease in bare ground from July 2005 to May 2010 (H = 24.58, N = 197, p<0.001) as bare areas were colonized by salt marsh. Multivariate analysis showed that the abundance of Sporobolus virginicus was positively influenced by sediment moisture content and Paspalum vaginatum abundance was strongly influenced by the water column salinity. At Catalina Bay, low sediment conductivity at the groundwater seepage area resulted in terrestrial vegetation encroaching on estuarine vegetation. Sarcocornia natalensis became more abundant towards the water column. During the period of study, species richness at St Lucia ranged from 2 (Listers Point, May 2010) to 27 (Catalina Bay, February 2006). Salinity and water level fluctuation have a significant impact on the distribution of macrophytes at St Lucia during the drought. In saline areas salt marsh plants have colonized exposed shorelines and along the Eastern Shores groundwater seepage has increased macrophyte species richness. Low water levels have resulted in the exposure and desiccation of submerged macrophytes, which are replaced by macroalgae.
9

Vegetation ecology of Drakensberg foothill moist grassland on Hlogoma Mountain, Underberg, KwaZulu-Natal

Berruti, Sharron Marion 11 1900 (has links)
Hlogoma Mountain is a small inselberg surrounded by farms and commercial forestry in the Underberg district (KwaZulu-Natal) within the Gs10 Drakensberg Foothill Moist Grassland. As little is known about the vegetation on Hlogoma, a survey was undertaken to classify, map and describe the plant communities occurring on the inselberg. A total of 100 (16 m2) randomly stratified sample plots were placed in homogeneous vegetation units within the 117 ha study area. A TWINSPAN classification, refined by Braun-Blanquet procedures, resulted in the identification of two major communities, five communities, 12 sub-communities and four variants. All communities were described and a vegetation map constructed. Ordinations identified key environmental variables that have an impact on the vegetation at the study site. A plant species checklist was created and analysed for floristic composition; rarity and threatened species; medicinal plants; endemism; phenology; flower colour and elevation range; species richness and plant community biodiversity. A total of 467 species were identified, represented by 271 genera and 87 families. Four Red Data species and a new Aspidoglossum species were discovered. Two near-endemic genera, two endemic species and 88 near-endemic species belonging to the Drakensberg Alpine Centre were found on Hlogoma. This study showed that Hlogoma Mountain is an inselberg with high plant species richness and endemism, and is a refuge of conservation importance for biodiversity. / Environmental Sciences / M. Sc.(Environmental Science)

Page generated in 0.1677 seconds