No description available.

Four grids, each 3,42 ha (4 morgen) in size, were live trapped from April 1967 through May 1969 in two soil and vegetation types (black turf~ Acacia nigrescens community, and brown reddish soil: Acacia tortilis community) at Pongola, northern Zululand, to determine the effect of dieldrin coverspraying, at a dosage of 87,4 g/hectare (2,64 oz/morgen), on rodents. Low population numbers before and especially at the time of spraying made clear-cut conclusions impossible to reach. Rodent populations (mainly Praomys (Mastomys) natalensis, Saccostomus campestris, and Lemniscomys griselda) were apparently not adversely effected, although L. griselda numbers showed a decline which was not in correspondence with that on the control area. This might be ascribed to dieldrin spraying. Relatively higher numbers of s. campestris and L. griselda were observed during periods of lower P.( M.) ~talensis numbers. Decreases in P.( Me) natalensis populations coincided with times of food scarcity. Praomys (Mastomys) natalensis are thus found in association with other rodents when abundant food is available, but seems to give way when competition due to food scarcity occurs. Reproductive data obtained from the study were too meagre to allow any conclusions concerning the effect of spraying thereon. The method involving the calculation of maximum distance between captures was used to express movement patterns of the species studied. Populat~on structure is express~d in terms of sex ratios, and frequency per mass class for each season. The size of animals was investigated by measuring total length, tail length, and head and body length. Behavioural features of the species captured were also noted. / Dissertation (MSc)--University of Pretoria, 1972. / gm2014 / Zoology and Entomology / Unrestricted

Philosophiae Doctor - PhD / In the Succulent Karoo biome of South Africa vegetation degradation by overgrazing is a recognized threat to biodiversity. In the eastern Little Karoo region of the Western Cape Province, ostrich farming has degraded large areas of natural vegetation, particularly in the Gannaveld habitat of the Oudtshoorn basin. Little quantified vegetation data exists on the impacts of degradation and the composition of the Gannaveld vegetation types. This study quantifies the composition of Oudtshoorn Gannaveld and the impacts of degradation on this critically endangered vegetation type. The diversity of this vegetation type is added to by the occurrence of mima-like circular soil mounds, termitaria, which support distinctive plant assemblages. Perennial plant data and soil data were collected from the largest remaining remnant of Oudtshoorn Gannaveld perceived to contain different levels of degradation from near pristine to severely degraded. The results show 72 species in 49 genera and 17 families were recorded with the Aizoaceae, Asteraceae and Amaranthaceae families being dominant. The off termitaria plant community is dominated by the Asteraceae, Aizoaceae and Crassulaceae families while the on termitaria community is dominated by the Asteraceae, Amaranthaceae and Zygophyllaceae families. Four levels of degradation were identified in each of the broader on and off termitaria communities. It was found that grazing and trampling induced degradation on termitaria results in the loss of perennial plant cover and plant litter and an increase in bare ground while degradation off termitaria results in a loss of species. There are changes in soil chemistry both on and off termitaria as a result of vegetation degradation. Degradation results in palatable species being replaced by unpalatable and disturbance indicating species. Perennial plant cover off termitaria is resilient to grazing and trampling, however species richness, plant functional type composition and the abundance of individual species are not. Species richness on termitaria is resilient to grazing and trampling but cover, plant functional type composition and the abundance of individual species are not. Degradation results in shifts from succulent and woody shrub dominated communities to dwarf succulent and dwarf succulent shrub dominated communities. These changes hold implications for agriculture,biodiversity conservation and the provision of ecosystem services.

The grasslands of South Africa, and especially the higher altitudinal grasslands, are under increasing human pressure. In this study a floristic-ecological account of the vegetation of the southernmost Drakensberg and its foothills is given. This is the first comprehensive botanical study undertaken in this floristically poorly known region. The study area is situated in the magisterial districts of Barkly-East, Elliot and Maclear between 30°40' and 31°35' S, and 27°25' and 28°35' E. In the study area afforestation is the greatest threat at lower altitudes, whereas at the higher altitudes overgrazing, trampling and invasion by exotic plant species impact negatively on the native vegetation. A brief review of the history and previous botanical exploration of the area, as well as the physical environment are given. Four main plant communities - the Maytenus undata- Rhus dentata woodland and forests communities, Harpechloafalx- Pycreus cooperi hygrophilous communities, Themeda triandra - Alloteropsis semialata high altitude communities and Alloteropsis semialata- Rendlia altera Afromontane grassland communities, with various sub-communities and variants are identified and described. An annotated check-list of the plant species collected in the study area and distribution maps of all the Drakensberg Alpine Region and local endemic species found in the study area are given. Twenty two local endemic species and 74 rare and threatened taxa were identified. During the study 1 991 species and infraspecific taxa of vascular plants were collected or listed. Most of the endemic species in the study area are located above 1 500m altitude. Due to the relatively low number of local endemic species (22) the study area can at best be considered as a weak centre of endemism. However, it is clearly linked with two other major centres of plant endemism, namely the Drakensberg Alpine Region (DAR) and Maputaland-Pondoland Region (MPR). Within the study area 194 DAR and 86 MPR endemic species were recorded. No local endemic species occur in the forest and wetland communities. Most of the rare and threatened species are found in open grassland which are the areas most suitable for afforestation. This causes a major conflict between the forestry industry and conservation agencies in the area. All grasslands situated at an altitude of above 1 600 m are floristically very diverse and adequate representative areas should be protected, especially the areas of Tentkop and Elands Heights. Soils here are highly erodible and forestry and trampling in these areas should therefore be avoided at all costs. The higher lying grasslands and, to a lesser extent, the lower lying grasslands are ecologically sensitive areas. This is particularly so where the underlying mother rock is basalt, which weathers into highly erodible soils. It is suggested that all areas above 1 600 m be declared "no-go" areas for afforestation. This is based on not only the number of endemic and rare species found in these areas, but also because of the floristic diversity and aesthetic value they hold for eco-tourism. All habitats are sensitive to some degree, but the most threatened areas are the higher lying and open grasslands. Areas that are generally unsuitable for afforestation include rocky outcrops, vleis, drainage lines and forests. Most of these areas are protected by law, albeit for reasons not to do with biodiversity or endangered species. AFRIKAANS : Die grasvelde van Suid-Afrika, en veral die hoërliggende grasvelde, is onder toenemende menslike druk. In hierdie ondersoek word 'n floristies-ekologiese weergawe gegee van die plantegroei van die mees suidelike Drakensberg-eskarp en voetheuwels. Hierdie is die eerste uitgebreide plantkundige ondersoek in dié gebied. Die studiegebied is geleë in die Barkly-Oos, Elliot en Maclear landdrosdistrikte tussen 30º40' en 31º35' S, en 27º25' en 28º35' 0. In die studiegebied is bosbou die grootste bedreiging in laerliggende gebiede, terwyl oorbeweiding, vertrapping en indringing van uitheemse plantspesies die grootste negatiewe impak op die inheemse plantegroei van die hoërliggende gebiede bet. 'n Kort historiese oorsig, die vernaamste vorige versamelaars in die gebied en 'n beskrywing van die fisiese omgewing word verskaf. Vier hoof plantgemeenskappe word onderskei - die Maytenus undata - Rhus dentata boomveld en woud gemeenskappe, Harpechloa falx - Pycreus cooperi vlei gemeenskappe, Themeda triandra - Allotercpsis semialata hoogliggende grasveld gemeenskappe en die Alloteropsis semialata - Rendlia altera Afromontaan grasveld gemeenskappe met verskeie sub-gemeenskappe en variante. 'n Spesielys van aile spesies wat tot nog toe in die studiegebied aangeteken is, asook verspreidingskaarte van alle Drakensberg Alpynse en lokale endemiese spesies wat in die studiegebied versamel is, word verskaf. Twee-en-twintig lokale endemiese spesies en 74 skaars en bedreigde spesies is vir dié gebied geïdentifiseer. Gedurende die ondersoek is 1 991 spesies en infraspesifieke vaatplanttaksa versamel of gelys. Die meeste van die endemiese spesies in die studiegebied word hoër as 1 500 m bo seevlak aangetref. As gevolg van die relatief lae getal endemiese spesies (22) in die studiegebied, kan hierdie streek slegs as 'n swak sentrum van endemisme beskou word. Die gebied vorm egter deel van beide die Drakensberg Alpynse Sentrum en die Maputaland-Pondoland Sentrum van endemisme. Vir die studiegebied is 194 Drakensberg Alpynse en 86 Maputaland-Pondoland endemiese spesies aangeteken. Geen lokale endemiese spesies word in die woud en vlei gemeenskappe aangetref nie. Die meeste van die skaars en bedreigde spesies is met oop grasvelde geassosieer. Laasgenoemde is ook die mees geskikte habitat vir bosbou. Dié feit is verantwoordelik vir die meeste konflik tussen die bosboubedryf en bewaringsgroepe. Grasvelde bokant 1 600 m het 'n hoë floristiese diversiteit en daadwerklike pogings behoort aangewend te word om dit te bewaar, veral in die Tentkop en Elands Heights gebiede. Gronde in hierdie gebiede is besonder maklik erodeerbaar. Bosbou en vertrapping deur vee behoort ten alle koste vermy te word. Die hoogliggende, en tot 'n mindere mate die laagliggende grasvelde is ekologies baie sensitief. Dit is veral die geval waar die onderliggende moedermateriaal basalt is, omdat laasgenoemde gesteente tot gronde met 'n hoë erosie-potensiaal verweer. Daar word voorstel dat geen bosbou in gebiede bo 'n hoogte van 1 600 m beoefen word nie. Hierdie voorstel word nie net gemaak op grond van die aantal endemiese, skaars en bedreigde spesies nie, maar ook met die oog op die voordele wat die estetiese landskap vir ekotoerisme mag inhou. Enige habitat is tot 'n sekere mate sensitief, maar in die studiegebied is die mees sensitiewe dele uit 'n plantkundige oogpunt is die hoërliggende oop grasvelde. Laerliggende gebiede wat nie vir bosbou geskik is nie sluit vlei gebiede, klip koppies en randjies, woude en dreinerings lyne in. Die meeste van hierdie gebiede word deur die wet beskerm, alhoewel nie noodwendig as gevolg van biodiversiteit of bedreigde spesies nie. / Dissertation (MSc)--University of Pretoria, 2013. / Plant Science / unrestricted

The aims of this study are to increase objectivity in stratification, sampling and classification of vegetation, thereby, improving repeatability, predictability and relevancy of vegetation classifications. The aims are achieved by: relating stratification, sampling and classification to scale; improved small-scale vegetation mapping using, satellite imagery; improved plant cover estimations; and vegetation classification by minimum entropy. A comprehensive computer program package was developed to facilitate the aims of this study and reduce time spent on vegetation analyses. It is recommended that the vegetation resource be given the highest national priority because correct vegetation management can also ensure conservation of soil and soil water. / Thesis (PHD)--University of Pretoria, 2009. / Plant Science / unrestricted

Climate change will affect Arctic plant communities directly, by altering growth and recruitment, and indirectly, by increasing the frequency of natural disturbance. Since the structure of northern vegetation influences global climate, understanding both temperature and disturbance effects on vegetation is critical. Here, I investigate the influence of temperature and disturbance on Low Arctic vegetation at several spatio-temporal scales in the Mackenzie Delta Region, N.W.T. To disentangle the relative impact of temperature and disturbance on forest-tundra and tundra ecosystems, I sampled microenvironmental variability, plant community composition, and green alder abundance, growth, and reproduction on disturbed (burns and thaw slumps) and undisturbed sites across a regional temperature gradient. Disturbed areas showed increases in alder productivity, catkin production, and seed viability, as well as differences in plant community composition and microenvironment. The magnitude of plot-level responses to disturbance compared to variation across the temperature gradient suggests that in the short-term, increasing the frequency of disturbance may exert a stronger influence on tundra ecosystems than changes in temperature. At the plot level, increases in alder seed viability and recruitment at warmer sites point to the fine-scale mechanisms by which shrub abundance will change. To examine the relative influence of temperature and biophysical variables on landscape-level patterns of shrub dominance, I mapped Low Arctic vegetation using aerial photos. At this broader scale, correlations between temperature and the areal extent of shrub tundra suggest that warming will increase the dominance of shrub tundra. To assess the magnitude of changes in temperature and thaw slump activity, I analyzed climate records and mapped retrogressive thaw slumps using aerial photographs. An increase in thaw slump activity in recent decades, coincident with higher temperatures, suggests that continued warming will change the area affected by thermokarst disturbances like slumps. Taken together, my research indicates that the effects climate change will be magnified by shifts in the frequency of disturbance, initiating changes to Arctic vegetation with significant implications for global climate. My work also shows that to fully understand the influence of patch-landscape feedbacks on Arctic vegetation dynamics, the effects of disturbance must be examined across longer temporal and broader spatial scales. / Forestry, Faculty of / Graduate

Concommittant with an increasing trend towards the ecological classification of forest land in British Columbia is the need for more detailed vegetation inventories and larger mapping scales. Although existing classification schemes (biogeoclimatic, provincial biophysical and habitat type classification) usually present a useful initial stratification of broad zonal vegetation patterns, they seldom provide, or were intended to provide a classification suitable for detailed vegetation inventory and mapping in a particular study area. In most instances, primary vegetation data must be collected and classified at a level of detail compatible with the scale of mapping and the variability of the vegetation landscape. Limited access and steep mountainous terrain are additional problems contributing to the acquisition, classification, interpretation and mapping of vegetation at large scales. Dissimilarity Analysis is a numerical classification analysis programmed and studied by the provincial government as a means to stratify large volumes of vegetation data in a relatively objective and efficient manner. As a divisive-polythetic classification strategy it demonstrates several advantages over other numerical analyses. Although it is now used as a routine analysis by the provincial biophysical survey, it has not yet been thoroughly evaluated or formally presented with regard to its suitability for vegetation classification and mapping on an operational basis. This study investigated four related questions: a. What methods can be employed for detailed vegetation mapping (scale 1:15,840) in mountainous terrain with limited access? b. What is the value of Dissimilarity Analysis for the classification of vegetation in primary survey? c. What is the predictive capability of the pretyping (prestratification) approach developed for vegetation mapping? d. What is the reliability of the vegetation maps. The study was divided into two separate but related investigations: the operational classification and mapping of vegetation in two small mountainous watersheds and a detailed systematic sampling study of two representative areas within one of the watersheds to assess the vegetation mapping procedure and map reliability. A detailed vegetation mapping procedure was developed which utilized permanent physiographic landscape features directly observable or inferred from black and white stereo aerial photographs (scale 1:15,840), macro and meso physiognomic vegetation features, a simple concept relating the above features to the available moisture for vegetation, and information about existing vegetation (e.g. forest cover maps; concepts and maps of vegetation zonation). Dissimilarity Analysis was found to be an objective and efficient method of vegetation stratification by reducing personal bias and ensuring an optimum and consistent utilization of the available information in the data set. It was felt to be an appropriate technique for stratifying primary vegetation data since it maximizes differences between groups, defines limits to classes and facilitates the formation of a hierarchical identification procedure. It was concluded that the vegetation pretyping approach developed for operational mapping provided a methodical, preliminary stratification of the landscape upon which improved mapping criteria could be added to better predict present vegetation condition. A quantitative assessment of map reliability in two representative areas of one of the watersheds resulted in a value of 79% relative to an independent chance of agreement of 6.2% and an optimum chance of agreement of 29%. It was felt that these values were representative of the map reliability in the remainder of the watershed. / Forestry, Faculty of / Graduate

Strandveld vegetation around the Groen river mouth was sampled using complementary ordination and classification techniques (DCA and TWINSP AN). Four communities can be recognised, although samples are primarily divided into inland and coastal plots. Two inland communities are: Stoebaria utilis-Salvia lanceolata community, characterised by tall vegetation(> 1m), on deep, loose soils; Hermannia spp-Leserlia diffusa community of short (<0.6m) vegetation on shallow soils with a hardpan dorbank layer. Two coastal Strandveld communities are: Vanzylia amulata-Limonium peregrinum community which has short vegetation ( <0.5m) on characteristic shallow soils with a calcrete layer at 50 cm deep; Ruschia hutchensonia-Sasola nolothensis community characterised by deep alkaline soils. Of the environmental variables sampled, soil resistance and the presence of calcium carbonate in the soil best explain the distribution of plots and species in ordination space. Communities classified in this study differ subtly from the Tall, Medium and Short Strandveld communities and Strand communities proposed by le Roux and Boucher, 1989 and 1993.

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.

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