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  • 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

Fire regimes in eastern coastal fynbos: drivers, ecology and management

Kraaij, Tineke January 2012 (has links)
Conventional knowledge of fynbos fire ecology is based on the summer-autumn fire regimes of the western Cape Floral Kingdom (CFK) where the climate is Mediterranean. However, the climate in the eastern coastal-CFK is milder and rainfall occurs year-round, with presumed effects on fire regimes. The Garden Route National Park (GRNP) has recently been established in the region, in a landscape where indigenous forests, fire-prone fynbos shrublands and fire-sensitive plantations of invasive alien trees are interspersed. The park faces considerable challenges related to the management of fire, including significant pressure from the adjacent plantation industry to reduce wildfire hazard by burning fynbos at short intervals, and high levels of invasion by alien trees (largely Pinus species originating from plantations). This study sought to improve understanding of fire regimes in eastern coastal fynbos shrublands, and to provide guidelines for ecologically sound management of fire in the area. My approach entailed (i) an assessment of the context within which fire management was practiced during the past century; (ii) characterisation of the recent fire history and fire regime (1900–2010); (iii) characterisation of the seasonality of fire weather and lightning; (iv) estimation of minimum fire return intervals (FRIs) from juvenile periods and post-fire recruitment success of overstorey proteoids (non-sprouting, slow-maturing, serotinous Proteaceae); and (v) determination of the ecologically appropriate fire season from post-fire recruitment seasonality of proteoids. I established that historically, plantation protection enjoyed priority over fynbos conservation in the area that is now the GRNP. Fynbos close to plantations has most likely been compromised by frequent and low-intensity burning in the past, as well as by invasion by alien trees. In terms of area burnt (1900–2010), natural (lightning-ignited) fires dominated the fire regime, particularly in the east, whereas prescribed burning was relatively unimportant. Typical fire return intervals (FRIs; 8–26 years; 1980–2010) were comparable to those in other fynbos protected areas and appeared to be shorter in the eastern Tsitsikamma than in the western Outeniqua halves of the study area. Proteaceae juvenile periods (4–9 years) and post-fire recruitment success (following fires in ≥7 year-old vegetation) suggested that for biodiversity conservation purposes, FRIs should be no less than nine years in moist, productive fynbos. Increases in the total area burnt annually (since 1980) were correlated with long-term increases in average fire danger weather, suggesting that fire regime changes may be related to global change. Collectively, findings on the seasonality of actual fires and the seasonality of fire danger weather, lightning, and post-fire proteoid recruitment suggested that fires in eastern coastal fynbos are not limited to any particular season, and for this reason managers do not need to be concerned if fires occur in any season. The ecological requirements for higher fire intensity may nonetheless be constrained by a need for safety. I articulated these findings into ecological thresholds pertaining to the different elements of the fire regime in eastern coastal fynbos, to guide adaptive management of fire in the Garden Route National Park. I also recommended a fire management strategy for the park to address the aforementioned operational considerations within the constraints posed by ecological thresholds. Finally, I highlighted further research and monitoring needs.
2

Spatial modelling of fire dynamics in Savanna ecosystems.

Berjak, Stephen Gary. January 1999 (has links)
Fire is used in the management of ecosystems worldwide because it is a relatively inexpensive means of manipulating thousands of hectares of vegetation. Deciding how, where and when to apply fire depends primarily on the management objectives of the area concerned. The decision to ignite vegetation is generally subjective and depends on the experience of the fire manager. To facilitate this process, ancillary tools, forming a decision support system, need to be constructed. In this study a spatial model has been developed that is capable of simulating fire dynamics in savanna ecosystems. The fire growth model integrates spatial fuel and topographic data with temporal weather, wind settings and fuel moistures to produce a time-evolving fire front. Spatial information required to operate the model was obtained through remote sensing techniques, using Landsat Thematic Mapper (TM) satellite imagery, and existing Geographic Information Systems (GIS) coverage's. Implementation of the simulation model to hypothetical landscapes under various scenarios of fuel, weather and topography produced fire fronts that were found to be in good agreement with experience of observed fires. The model was applied actual fire events using information for prescribed burning operations conducted in Mkuze Game Reserve during 1997. Predicted fire fronts were found to accurately resemble the observed fire boundaries in all simulations. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1999.
3

The conservation of southern African terrestrial ecosystems, with special reference to the role of fire and the control of invasive alien plants

Van Wilgen B. W. (Brian William) 12 1900 (has links)
Thesis (DSc)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: No abstract available / AFRIKAANSE OPSOMMING: Geen opsomming beskikbaar
4

Response of ground dwelling spider assemblages (Arachnida, araneae) to Montane grassland management practices.

Makaka, Lukhanyo January 2012 (has links)
M. Tech. Environmental Management. / Aims to investigate the impacts of Montane grassland management practices, particularly through grazing intensity and burning frequency, on ground living spider assemblage structure.More specific aims include:to note any relationship between particular spider species to specific forms of habitat management ; to note the loss of particular species at detected thresholds in management practices ; and to model spider assemblage structure based on grassland management.
5

Post-fire effects of invasive exotic plants on seed banks, regeneration, soil chemistry and selected soil microbial populations in the Silvermine Nature Reserve, Cape Peninsula, South Africa

Cilliers, Charl Daniel 04 1900 (has links)
Thesis (MSc) -- University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The fires, which occurred during January 2000 on the Southern Cape Peninsula, Cape Province, South Africa, focused attention on the importance of sound, informed management of exotic plant invaders in fynbos, especially at the urban interface. The fires also highlighted the relative lack of knowledge about the combined impacts of fire, exotic plants and the exotic-clearing programme on soil seed banks and regeneration. This study examines soil borne seed banks, regeneration, soil chemistry and micro biota in different postfire environments, focusing on three components of exotic plant management: The post-fire effects of standing invasive exotic plants; stacks of slashed exotic plant material which were deliberately burnt and stacks reduced to heat scars by a wildfire. The primary hypothesis addressed is that post-fire vegetation regeneration patterns, seed bank diversity and seed bank abundance are linked to pre-fire vegetation characteristics and, in particular, to the treatment of exotic plant species. It is also hypothesised that soil microbe population sizes are linked to pre-fire vegetation and soil chemical composition. Differences in soil seed banks, soil micro biota and vegetation regeneration patterns occur in different post-fire environments. High volumes of (live or dead) woody exotic biomass negatively impact upon postfire indigenous species diversity and abundance, both above and below-ground. Soil seed banks and above-ground regeneration decline with increasing fire intensity, wildfire burnt stack treatments showing the largest declines followed by wildfire burnt standing exotics, control burnt stacks, wildfire burnt cleared areas and wildfire burnt Mountain Fynbos treatments. Persistent indigenous seed banks are found under some exotic dominated stands. Heat damage, associated with high woody exotic biomass, affects seeds of all species into deep soil layers. Depth of burial is a more important determinant of seed survival during fires than seed size. Soil microbial populations are variably affected by exotic plants, their management and increases in fire intensity. The most drastic microbial population changes are in post-fire treatments of high exotic plant biomass. Soil chemistry affects microbial population sizes as does seasonal climatic changes. In this thesis vegetation, seed bank and microbial responses to various exotic plant management practices are shown and management recommendations are made. Keywords: exotic plants, fire, Fynbos Siome, microbes, post-fire succession, soil seed banks. / AFRIKAANSE OPSOMMING: Die Januarie 2000 vure op die Suid Kaapse Skiereiland het fokus gerig op die belangrikheid van goeie, ingeligte bestuur van uitheemse indringerplante in fynbos, veral naby stedelike gebiede. Die vure het ook 'n relatiewe .gebrek aan kennis aangaande die gekombineerde impakte van vuur, uitheemse plantegroei en indringer plant beheer programme op grond saadbanke en die hergroei van plante na 'n vuur aan die lig gebring. Hierdie projek bestudeer die invloed van vuur op grond saadbanke, hergroei van plante, grond chemie en mikro-organismes. Die klem lê op drie komponente van uitheemse plant bestuur: waar staande uitheemse plante voorkom; waar skoongekapte uitheemse plante in hope gestapel is en gekontraleerd gebrand is en waar soortgelyke hope in 'n onbeplande weghol vuur gebrand is. Die primêre hipotese is dat plant herstelpatrone, saadbank diversiteit en grootte gekoppel is aan veldtoestande voordat daar gebrand is, en veral aan die bestuur van uitheemse plantspesies. Nog 'n sentrale hipotese is dat die grootte van grond mikrobiale populasies gekoppel is aan veld toestande voor die brand en aan grond chemiese samestelling. Hierdie studie dui verskille aan in grond saadbanke, mikro-organismes en plant hergroeipatrone onder verskeie toestande na vuur. Die brand van hoë volumes (lewende of dooie) houtagtige uitheemse plant biomassa benadeel inheemse plant spesie diversiteit en getalle (bo en onder die grond oppervlak). Grond saadbanke neem af met vehogings in vuur intensiteit. Die grootste afnames is in wegholvuur gebrande gestapelde uitheemse plantmateriaal gevolg deur wegholvuur gebrande staande uitheemse plante, opsetlik gebrande hope uitheemse plante, gebrande skoongekapte areas en wegholvuur gebrande Berg Fynbos. Ou inheemse saadbanke is gevind onder sommige areas wat voor die vuur oorheers was deur uitheemse plantegroei. Hitteskade, geassosieer met hoë volumes houtagtige uitheemse biomassa, affekteer sade van alle spesies tot diep in die grond. Saad oorlewing tydens brande is meer geaffekteer deur diepte van begrawing in die grond as deur saad grootte. Grond mikro-organisme populasies is geaffekteer deur uitheemse indringer plante, die bestuur van uitheemse plante en vuur intensiteit. Die grootste veranderinge is waar die biomassa van uitheemse plantegroei baie hoog is. Grond chemiese samestelling en seisoenale veranderinge in weerspatrone affekteer die grootte van mikrobiale bevolkings. In hierdie tesis word verskille in plantegroei, saad store en grond mikrobes, soos geaffekteer deur uitheemse plant beheer programme uitgewys en voorstelle vir toekomstige bestuur gemaak. Sleutelwoorde: Fynbos Bioom, grond saad stoor, mikrobes, plant hergroei, uitheemse plante, vuur.
6

Ecological characterisation and effects of fire and grazing on Cyrtanthus nutans (R.A.Dyer) in North-Western Kwazulu-Natal, South Africa

Ruddle, Lynne Michelle 05 1900 (has links)
Cyrtanthus nutans (RA Dyer) is a KwaZulu-Natal Province near-endemic species, classified as vulnerable in South Africa (IUCN Red Data categories). Literature references suggest that no recent ecological research has been conducted on Cyrtanthus nutans. Last assessed in 2007, the current study determined the demographics and the abiotic and biotic factors that influenced the distribution and range of Cyrtanthus nutans. Key determinants influencing the autecology, distribution and population dynamics of Cyrtanthus nutans were investigated. Anthropological factors influencing the decline of populations were addressed. Two investigations were undertaken for the current study on Cyrtanthus nutans in Dundee in North-western KwaZulu-Natal, South Africa namely a survey to determine the population dynamics and autecology of the species and the effect key determinants have on the recruitment and survival. Sites of occurrence and the ecological and anthropological factors that influence the existence of plants were documented. Experimental plots were conducted to determine the influence of climatological factors, fire and defoliation on the emergence and survival of Cyrtanthus nutans plants. A preference was found for soils with high nitrogen and organic carbon, low phosphorus and acidity levels situated on slopes of < 10% on mid to lower terrain slopes within an altitude range of between 1 100 and 1 300 m (a.m.s.l.) in the Sour Sandveld and Moist Tall Grassveld Bioresource Groups. The influence that climatological factors, fire and defoliation had on the emergence and seed recruitment of Cyrtanthus nutans were determined through a small plot experiment in the Dundee area. Mean relative humidity (%) and mean rainfall two weeks before emergence in conjunction with treatments were highly significant (P<0.001). Burning treatments B (fire inclusion and defoliation inclusion) and BC (fire inclusion and defoliation exclusion) were more highly significant on the emergence of Cyrtanthus nutans plants than any other treatments. ii | P a g e Increasing fragmentation of thriving populations of Cyrtanthus nutans populations is occurring through landuse change, mismanagement of veld and non-compliance of legislation. Continued monitoring and awareness is essential in the survival of this species. / Environmental Sciences / M. Sc. (Environmental Sciences)
7

Ant assemblages in a Southern African savanna : local processes and conservation implications

Parr, Catherine Lucy 19 May 2005 (has links)
The structuring of ant assemblages in a Southern African savanna was investigated using data from the only long-term, large-scale savanna fire experiment in Africa. A comprehensive survey of three habitats in the Kruger National Park (KNP) revealed a total of 169 ant species from 41 genera. The sampling efficiency and consistency of pitfall traps and Winkler samples for inventory, bioindicator and ecological studies in savanna habitats was compared using ants. Pitfall traps were more efficient and productive than Winkler sampling for epigaiec ants, with a greater total species richness and higher abundance of ants recorded. Suggestions were made to improve Winkler sampling output, and to allow quantitative data to be collected. With the structuring of local assemblages, competition was the most significant local factor tested. The relationship between ant dominance and ant species richness was consistent across three continents. A model developed to test mechanisms that could be responsible for the form of this relationship supported the hypothesis that competitive exclusion by dominant ants at least partially reduces species richness. Stress was only partially responsible for low dominance and low species richness, while scatter in the data points is related to patchiness of ants at baits. These findings contrast strongly with previous claims regarding the relationship between richness and dominance. Habitat complexity was not found to play an important role in determining ant assemblage body size in this savanna system. The size-grain hypothesis (Kaspari&Weiser 1999) which predicts that environmental rugosity results in positive allometric scaling of leg length on body length because of changes in locomotion costs, was tested by comparing the body sizes of ants from areas of contrasting habitat complexity. No support for the hypothesis was found. Phylogenetic independent contrast methods did however support the allometric relationship found by Kaspari and Weiser (1999). Ant assemblages in KNP exhibited a remarkable degree of resistance, and in some cases resilience, to burning. Species richness or abundance did not vary with different burning treatments, although ant assemblage composition was sensitive to burning treatment. This difference, however, was only pronounced between burnt and unburnt plots, not between burning treatments. The degree of response of ant assemblages is likely to be related to two main contributory factors: mean annual rainfall and changes in vegetation structure with burning, and the assemblage's history of association with fire. An overview of published research on the effects of fire on fauna in Southern Africa was undertaken. Few studies have examined the effects of fire on amphibians or reptiles and few experimental studies have been undertaken using an experimental fire regime applied over appropriately long time intervals. Most studies provided no information on the scale of the study. Replication was often not reported, and was generally inadequate. Information on the effects of fire on fauna in Southern Africa is fragmentary, and consequently informed management decisions regarding the consequences of burning policies on the conservation of biodiversity both within and outside protected areas are problematic. Recommendations and suggestions for improving fire research are given. / Thesis (DPhil (Zoology))--University of Pretoria, 2005. / Zoology and Entomology / unrestricted
8

Monitoring the re-growth rate of alien vegetation after fire on Agulhas Plain, South Africa

Fatoki, Oluwakemi Busayo 03 1900 (has links)
Thesis (MSc (Geography and Environmental Studies))--University of Stellenbosch, 2007. / The Agulhas Plain, an area rich in fynbos, was monitored within six months after the February 2006 fire. The potential of using medium resolution imagery, specifically from the Moderate Resolution Imaging Spectroradiometer (MODIS) in determining the re-growth rates of indigenous and alien vegetation types after fire was explored. Pixels representing dense areas of each vegetation type were selected. There was a significant difference in the pixels selected for each vegetation type. A time series of Normalized Difference Vegetation Index (NDVI) data was derived and fitted to functions, such as Double Logistics and Asymmetric Gaussian as implemented in the TIMESAT software. The results show that alien vegetation grows faster after a fire occurrence than in its absence. Within the specified months of monitoring, it was observed that fynbos grew faster than the alien vegetation. Also, the re-growth rates of vegetation on the coastal soils were higher than those of vegetation on the inland soils. The determination of the re-growth rate was necessary to assist resource managers determine the appropriate time for follow-up of clearing invaded sites after fire.
9

Assessment and analysis of wildfires with the aid of Remote Sensing and GIS

Vorster, Willem Adriaan 12 1900 (has links)
Wildfires destroy large tracts of veld and forest land every year in South Africa. These fires can be devastating, resulting in loss of human lives, the destruction of property and the loss of income, for example the forest fire in the Sabie district in Mpumalanga in 2007 which destroyed about 7% of South Africa’s forested areas. There are frequently legal disputes with respect to the origin of wildfires, the extent of the fire and the land cover destroyed by the fires. The forensic capabilities of remote sensing in detecting and analysing post-wildfire characteristics have become an important contribution towards solving such legal disputes and in understanding wildfire characteristics. These post fire products can be used as evidence in court cases. Most of the time those court cases came up a few years after the fire event. By then, little or no evidence can be found on the terrain where the fire was. Remote sensing archives provide a reliable source of data that can be used to analyse these events after these long intervals. The objective of this project is to highlight the methods used to generate these post-wildfire analysis products. / Environmental Sciences / M. Sc. (Environmental Science)
10

Assessment and analysis of wildfires with the aid of Remote Sensing and GIS

Vorster, Willem Adriaan 12 1900 (has links)
Wildfires destroy large tracts of veld and forest land every year in South Africa. These fires can be devastating, resulting in loss of human lives, the destruction of property and the loss of income, for example the forest fire in the Sabie district in Mpumalanga in 2007 which destroyed about 7% of South Africa’s forested areas. There are frequently legal disputes with respect to the origin of wildfires, the extent of the fire and the land cover destroyed by the fires. The forensic capabilities of remote sensing in detecting and analysing post-wildfire characteristics have become an important contribution towards solving such legal disputes and in understanding wildfire characteristics. These post fire products can be used as evidence in court cases. Most of the time those court cases came up a few years after the fire event. By then, little or no evidence can be found on the terrain where the fire was. Remote sensing archives provide a reliable source of data that can be used to analyse these events after these long intervals. The objective of this project is to highlight the methods used to generate these post-wildfire analysis products. / Environmental Sciences / M. Sc. (Environmental Science)

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