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1
Kraaij, Tineke. "Fire regimes in eastern coastal fynbos: drivers, ecology and management." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1008047.
Full textAbstract:
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.
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Ott, Theresia. "The response of biological communities to spatial and temporal changes in a regenerating coastal dune forest along the north-east coast of South Africa." Thesis, University of Pretoria, 2013. http://hdl.handle.net/2263/26029.
Full textAbstract:
Ecological restoration that aims to reinstate indigenous processes may be constrained by regional and local conditions, especially those that drive dispersal and colonisation. Local conditions can be managed, while regional conditions cannot. The management of costly rehabilitation programmes is considered best practice when scientifically informed. My thesis documents the responses of biological communities to a range of local conditions developing in coastal dune habitats in response to ecological restoration. Here, landscape-level (spatial structure of patches of tree canopies) local conditions were distinguished from site-level (topography, soil nutrient content, woody plant community richness, microclimatic variables) local conditions. The spatial structure of tree canopies varied over time and differed between the mining lease site and the relatively undisturbed benchmark site prior to (1937- 1970), and after (1990-2006) mining. For example, approximately 20% of the mining lease site and 40% of the benchmark site was covered by tree canopies prior to mining. However, after mining and rehabilitation, the structure of tree canopies began to converge towards that of the benchmark. The topographic profile of coastal dunes was less heterogeneous after mining and rehabilitation than before. Aspect, elevation and gradient of dune slopes were also different and had shifted in space. Variability in the structure of tree canopies could not explain variability in species richness, forest-associated species richness and proportion of benchmark species for the millipede, dung beetle and bird communities ashad been expected. However, species composition did change (though idiosyncratically) with age-related changes in soil nutrient availability and tree species diversity. Temperature, relative humidity and light intensity varied with dune topography, but soil nutrient content (C: N ratio and pH) was better accounted for by the age of the regenerating forest than by dune topography. Similarly, analysis of covariance suggested that tree canopy density, woody plant richness and millipede species richness only responded to the aspect, elevation and gradient of restored coastal dunes when age was taken into account as a covariate. However, the response of keeled millipedes to dune topography, regardless of regeneration age, suggested that the microclimatic variability brought about by topographic heterogeneity may provide these specialists with suitable microhabitats. Throughout my thesis, the age of regenerating patches of indigenous canopies was often more important as an explanatory variable than habitat conditions per se. Age itself is not a determinant of biological communities, but merely the axis along which habitat conditions change with succession, and later, patch dynamics. Therefore, as elsewhere, my thesis has highlighted age as a useful proxy for the response of biological communities to local conditions. It seems that managing local variables such as those considered in my assessment is not an avenue through which to enhance restoration. After kick-starting initial conditions, best practice rehabilitation management should therefore focus on minimizing external disturbances rather than interfering with natural processes.Thesis (PhD)--University of Pretoria, 2013.
Zoology and Entomology
unrestricted
3
Tshaduli, Ndivhuwo. "Regeneration ecology of the bamboo climber Flagellaria guineensis in the Transkei Coastal Forests, Eastern Cape, South Africa." Diss., University of Pretoria, 2017. http://hdl.handle.net/2263/63350.
Full textAbstract:
Economic benefits obtained from Flagellaria guineensis, a climbing bamboo, by local people
received attention in previous studies but little is known about its regeneration ecology in three
different forest stand conditions, i.e. forest edges, forest gaps and mature closed-canopy stands.
In the Eastern Cape of South Africa the species grows in the Transkei Coastal Forests. The main
aim of this study was to assess the regeneration ecology of F. guineensis in those forests. The
specific objectives were to describe the phenological state that would influence the flowering,
fruiting and growth of the species, and to compare the culm (stem) development from the
rhizome between the different forest stand conditions. Phenological comparison was done in
forest edge and forest interior conditions two forests. Rating scales were applied to determine the
phenological states of the presence and amount of flower buds, open flowers, fruits, shoots and
seedlings. Development of F. guineensis was assessed by sampling clusters in the three different
forest stand conditions in three forests.
The observation made in two Transkei Coastal Forests indicate that F. guineensis regenerates by
producing seed, new vegetative shoots from rootstocks and also shoots at the growing tips. The
flowering and fruiting period occurred only in the rainy season in Mtambalala forest but both
rainy and dry seasons in Bulolo forest. More flowers and fruits of F. guineensis were found in
Bulolo forest and in the forest edge (where F. guineensis is able to form tangles on the canopy of
its host tree) respectively. This climbing bamboo clings on any plant around it for support and
forms tangles on the canopy of its host in forest edges with no direct damage caused to host
trees. The production of seedlings, shoots from the rhizome and shoots at the growing tips was constant during the study period in both study sites. The growth pattern of F. guineensis was
different when comparing the three Transkei Coastal Forests studied. Manubi forest was found to
have clusters and culms with the highest diameters and length compared to Mtambalala and
Mnenga forests. There was a significant difference in culm diameter and length of F. guineensis
between all three forests, whereas cluster diameter and number of culms per cluster were not
influenced by forest stand conditions. F. guineensis clusters were common in the forest edges or
gaps, and formed tangles in the canopy of their host trees. The described pattern of growth of F.
guineensis contributes to recovery of the forest edges or gaps by restricting easy movement in
and out of the forests. Several recommendations were made for harvesting of culms for basketmaking,
such as: it should be done with care to reduce tangles in the forest and tree canopies; it
must take place during the dry season, when the culms in a cluster are not flowering or fruiting;
and studies are needed on the growth rate of seedlings and their growth into the forest canopy
and how the bamboo can be cultivated outside the forest for better production of culms.Dissertation (MSc)--University of Pretoria, 2017.
SAFCOL
Microbiology and Plant Pathology
MSc
Unrestricted
4
Burns, Michael Edmund Reid. "A synecological study of the East London coast dune forests." Thesis, Rhodes University, 1987. http://hdl.handle.net/10962/d1006134.
Full textAbstract:
Quantitative community descriptions, based on point quarter sample data, are made for a number of dune forest units along the East London coast. These are supported by multivariate classifications and ordinations which illustrate the inter community variation between the sampled seaward, landward and dune valley sites. Climax valley forest is floristically most characteristic and can be clearly distinguished from the seaward and landward thicket communities which tend to show a degree of similarity. Within-forest community differences are shown to be more significant than variation along the coast. This appears to indicate that climoedaphic gradients established laterally to the coast induce a greater floristic response than the rainfall gradient within the study area. The state of developnent within the dune soil profile and the rate and effect of salt spray deposition are considered to be important factors influencing dune forest succession and are discussed in some detail. An overview of certain other climatic variables as well as the geological features within the study area is also given. A phenology study of the dune forest, scrub-thicket and strand plant cornnunities shows some general patterns of flowering and fruiting phenorhythms. Although much variation was observed, there appears to be a bimodal hyperactive phenophase response which is thought to be related to rainfall or periods of favourable soil moisture conditions. A brief discussion of some of the positive and negative human influences on the coastline is given. This includes a description of the management activities carried out in the area as well as the demands placed on ·the coastal resource.
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Turner, Russell Sean School of Biological Earth & Environmental Science UNSW. "An airborne Lidar canopy segmentation approach for estimating above-ground biomass in coastal eucalypt forests." Awarded by:University of New South Wales. School of Biological, Earth and Environmental Science, 2006. http://handle.unsw.edu.au/1959.4/27362.
Full textAbstract:
There is growing interest in airborne lidar for forest carbon accounting and precision forestry purposes. Airborne lidar systems offer a cost-effective, versatile, operationally flexible and robust sampling tool for forest managers. The objective of this study was to develop and test lidar canopy surface enhancement and segmentation processes for estimating dominant above-ground biomass (DAB) in a harvested eucalypt forest on the Central Coast of New South Wales (Australia). The Crown Infill, Trim and Smooth (CITS) process, incorporating a series of filters, algorithms, and selective multi-stage smoothing, was used to enhance lidar canopy surfaces prior to segmentation. Canopy segmentation was achieved using a vertical crown template approach termed the Spatially and Morphologically Isolated Crest (SMIC) process. SMIC delineates dominant tree crowns by detecting elevated crown crests within a 3D lidar canopy surface. Consolidated crown units constitute the basic sampling, analysis and reporting units for wall-to-wall forest inventory. The performance, sensitivity and limitations of these procedures were evaluated using a combination of simulated forest models and actual lidar forest data. Automated crown polygons were used as a sampling template to extract dominant tree height values which were converted to DAB estimates via height-to-biomass relationships derived from field survey and on-site destructive sampling. Results were compared with field based tree height and biomass estimates. Compared against a manually derived crown map from a 2ha field plot, canopy segmentation results revealed a producer???s accuracy of 76% and overall accuracy of 67%. Results indicated a trend toward greater crown splitting (fragmentation) as trees increase in age, height, stem diameter and crown size. Extracted dominant tree height values were highly correlated with ground survey height estimates (r2 0.95 for precision survey and r2 0.69 for standard survey). There was also no significant difference between SMIC and manual crown height estimates. SMIC units overestimated ground-based DAB by 5%; this increased to 36% with the inclusion of segmentation errors. However, SMIC estimation of total plot above-ground biomass (AGB) was within 9% of the ground-based estimate. Results are encouraging considering the mixed-species, multi-aged composition of the forest, and the combined effects of SMIC segmentation and lidar height errors.
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Klinka, Karel. "Plant diversity in old-growth and second-growth stands in the coastal rainforests of British Columbia." Forest Sciences Department, University of British Columbia, 1997. http://hdl.handle.net/2429/652.
Full textAbstract:
One of the human activities impacting biodiversity is the cutting of old-growth forests. In response to the controversy surrounding the cutting of old-growth in the coastal rainforest of BC, the Ministries of the Environment and Forests have produced biodiversity guidelines that are to be applied when manipulating stands in the provincial forest.
This study augments these guidelines by investigating the diversity differences between second-growth and old-growth forests in relation to site quality. We demonstrate how standlevel plant diversity differs between 40-year-old and old-growth stands in the Very Wet Coastal Western Hemlock subzone (CWHvm) on Vancouver Island. This information is intended to provide foresters with an understanding of the effects of age, disturbance and site quality on stand-level plant diversity, thereby allowing for informed professional management decisions.
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Dore, David William Biological Earth & Environmental Sciences (BEES) UNSW. "Application of simple physiological growth models to coastal eucalypt regrowth forests in New South Wales." Awarded by:University of New South Wales. Biological, Earth and Environmental Sciences (BEES), 2006. http://handle.unsw.edu.au/1959.4/26200.
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This thesis explores issues relating to the application of physiological-process models (???process models???) of forest growth to mixed species, mixed age forests, in particular the coastal blackbutt forests of New South Wales. Using a dataset provided by State Forests of New South Wales (Carter 1994 unpubl.) a numeric description of the forest was developed and stand-level parameters of interest were derived, in particular the plot by plot stemwood volume growth from 1975 to 1999. The amounts of harvested volume, volume that died and volume that grew into the measurement population were identified separately, and several different means of accounting for volume change over time were investigated. A method for quantifying the impact of harvesting and other silvicultural practices on the growth of the forest was developed and programs were written to convert the stand-level summary of the harvest impact into a semi-random selection of trees that would be ???harvested??? from the database under the set of silvicultural assumptions (Dore et al. 1999). A number of process models were investigated and reviewed before selecting one particular model, SUSTAIN (Dewar 1997) for adaption to these forests. This model is a relatively simple process model with a small number of input parameters. The model was adapted so that it could be used to compare the SUSTAIN estimate of growth with the growth of an individual stand of trees in the Kendall Forest Management Area, between Wauchope and Taree on the mid-north coast of NSW. To improve the accuracy of the prediction of growth by SUSTAIN, a method of re-setting the state of the stand to the actual condition at the time of remeasurement was developed. In addition, the SUSTAIN model was extended to enable two separate levels of canopy to be described and grown separately. Ultimately the model was only partially successful in mirroring the growth predicted by the empirical data. Its partial success is attributed primarily to the difficulties associated with correctly determining the allocation parameters used by the model to assign net photosynthate to the roots, foliage and stemwood. The nature of the change in allocation parameters when the forest stand is disturbed by harvest or fire needs further investigation.
8
Cazier, Penelope Williams. "Hardwood Forest in the Coastal Plain of Virginia East of the Suffolk Scarp." W&M ScholarWorks, 1992. https://scholarworks.wm.edu/etd/1539625724.
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Klinka, Karel. "Classification of natural forest communities of coastal British Columbia." Forest Sciences Department, University of British Columbia, 2001. http://hdl.handle.net/2429/668.
Full textAbstract:
Vegetation science, like any science, uses classification to organize knowledge about plants and plant communities. Classification is helpful for understanding how different plant communities relate to one another and their environments, for facilitating further studies of vegetation, and for conservation. To familiarize onself with vegetation of a large area, it is very convenient and efficient to begin with a few general units, such as plant orders rather than with many very detailed units, such as plant associations and subassociation. We offer such an approach and think that the information given in this
series will be sufficient to assign any forested coastal community to one the orders or suborders.
In spite of a history of vegetation studies in British Columbia, there has not yet been any attempt to develop a comprehensive hierarchical classification of plant communities for the province. As the culmination of fifty years of detailed surveys carried out by V.J. Krajina and his students, the Ecology Program Staff of the BC Forest Service, and other workers, we used tabular and multivariate analyses of 3,779 sample plots established in natural, old-growth, submontane, montane, and subalpine forest communities in coastal BC to develop a hierarchy of vegetation units according to the methods of biogeoclimatic ecosystem classification.
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Matthesius, Arne. "Testing the Janzen-Connell model for species diversity in a West African montane forest." Thesis, University of Canterbury. Biological Sciences, 2006. http://hdl.handle.net/10092/1347.
Full textAbstract:
A major question in ecology is 'why are tropical forests so species diverse?' One hypothesis to explain tropical species diversity is the Janzen-Connell hypothesis. This model assumes high levels of host-specific seed and seedling predation and / or pathogen attack when seedlings occur at high density near to the parent tree; seedlings are more likey to survive and reach maturity the further they are away from parents / conspecific adults. Theoretically this should lead to a random distribution of each species in the forest, which in turn will lead to high species diversity. Here I test the Janzen-Connell hypothesis for the first time in a submontane dry forest in Nigeria, West Africa. Specifically I tested whether or not a) leaf herbivory decreases and b) seedling survival increases with distance from parent / conspecific adult trees. These two components were tested separately on naturally occurring seedlings and on experimentally planted seedlings. I also tested whether or not conspecific adult trees showed clumped distributions by testing if conspecific nearest neighbours were observed more often than would be expected by chance alone. Naturally occurring seedlings of three species, Pouteria altissima, Newtonia buchananii and Isolona pleurocarpa showed significantly greater survival at distances away from parent / conspecific adult trees. Two out of a total of three species (Entandrophragma angolense, Deinbollia pinnata and Sterculia pinnata) of experimentally planted seedlings showed increased survival at distances away from conspecific adult trees, but this trend was non-significant. Leaf herbivory decreased with distance from parent / conspecific adult trees for four out of a total of six study species, but all relationships of leaf herbivory with distance for these six species were non-significant. Of two individual species, Anthonotha noldeae and Carapa procera, and two species groups tested for clumping, all had a greater number of conspecific nearest neighbours than would be expected to occur by chance alone, and this was significant for the two species groups. The decreased survival of seedlings under parent / conspecific adult trees is likely to maintain tree species diversity in West African submontane forests as predicted by the Janzen-Connell model. The role of host specific seedling herbivores in reducing recruitment under parent / conspecific adult trees requires further investigation. Although conspecific adults showed some degree of clumping no conclusion was reached as to whether this was evidence for or against the Janzen-Connell model.
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Derham, Kelly. "Wire Netting Reduces African Elephant (LOXODONTA AFRICANA) Impact to Selected Large Trees in South Africa." TopSCHOLAR®, 2014. http://digitalcommons.wku.edu/theses/1358.
Full textAbstract:
African elephants (Loxodonta africana) are ecosystem engineers in that they substantially alter the environment through their unique foraging and feeding habits. At high densities, elephants potentially have negative impacts on the environment, specifically to large trees. Because of this, recent increases of elephants in the Associated Private Nature Reserves (APNR) on the Western Boundary of Kruger National Park, South Africa have caused concern regarding the health of several species of tree. My objective was to assess the effectiveness of wrapping protective wire netting around the trunk of the tree in preventing and reducing bark stripping by elephants. 2,668 trees, 1352 marula (Sclerocarya birrea), 857 knobthorn (Acacia Nigrescens), and 459 false marula (Lannea schweinfurti), were assessed for elephant impact in the APNR, 1387 (52%) of which had previously been wrapped in protective wire netting (789, 548, and 50 respectively). For knobthorn and marula, wire netting significantly decreased the number of the trees that were bark stripped. For all trees, wire netting decreased the level of bark stripping especially for the highest impact levels. No trees wrapped with wire were ringbarked, compared to 23 unwired trees. In addition, wire netting had an effect on the distribution of damage for the highest impact class incurred regardless of type. A higher relative frequency of wired trees were found in lower impact categories compared to unwired trees. Wire netting is a low maintenance and ecologically valuable technique that alleviates bark stripping for some species. The judicial use of wire netting on trees could serve to maintain elephant and trees populations in areas of heavy confinement with locally high densities of elephants.
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Mcdonald, Shannon Lee. "Understory Diversity and Succession on Coarse Woody Debris in a Coastal, Old-growth Forest, Oregon." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/1045.
Full textAbstract:
This research examines the relationship between understory plant diversity and logs in a Pacific Northwest (PNW) Sitka spruce (Picea sitchensis)-western hemlock (Tsuga heterophylla) old-growth, coastal forest. These forests are renowned for their high forest productivity, frequent wind storms, and slow log decomposition rates that produce unmatched accumulations of coarse woody debris (CWD) yet few studies have examined the relationship between CWD and understory vegetation ecology. My research addressed this topic by comparing understory plant census data between paired fallen log and forest floor sites (n=20 pairs). My objectives were to: 1) determine the influence of substrate type on community composition and diversity, and 2) examine successional pathways and species assemblage patterns on CWD in various stages of decomposition. To meet these objectives I employed non-metric multidimensional scaling (NMDS) ordinations and unsupervised cluster analyses to identify and compare community assemblages on both substrates. These methods revealed similar species diversity and evenness between log and forest floor sites with compositional differences within and between substrates corresponding to habitat availability for colonization and light and moisture gradients. My results also suggest understory successional pathways related to decay class and characterized by an initial abundance of bryophytes, forbs, and seedlings followed by woody shrubs. Understory communities developing on logs also experienced increasing diversity, evenness, and divergence from forest floor communities consistent with log decomposition. These results differ from findings for boreal forests that reveal increasing similarity between substrate communities with increasing decay class. Recommendations for future research include the employment of a more robust sample size and direct measurements of environmental variables. Additional comparator studies are also needed to confirm the effects of forest type and decomposition on the relationship between CWD and forest understory communities. This study demonstrates how fine-scale wind disturbance fosters biodiversity through the creation of CWD substrate. My results and future research are essential for the development of silvicultural models designed to promote biodiversity in PNW coastal forests.
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Rolek, Brian William Hill Geoffrey E. "Microhabitat associations of wintering birds in a southeastern bottomland forest within the easter Gulf coastal plain of Florida." Auburn, Ala., 2009. http://hdl.handle.net/10415/1795.
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Thompson, Hazell Shokellu. "The breeding biology and ecology of the White-necked Picathartes Picathartes gymnocephalus temminck 1825, in Sierra Leone." Thesis, Open University, 1997. http://oro.open.ac.uk/57719/.
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This thesis investigates the ecology, taxonomic affinities and conservation management in Sierra Leone of a threatened West African forest bird, the White-necked Picathartes Picathartes gymnocephalus, which has not been previously studied in detail. The incubation and nestling periods (20 and 25 days) respectively were longer than is usual for most tropical passerines. In most cases, one clutch of two eggs was laid between June and December, immediately followed by moult between January and May (the dry season). Peaks in egg laying occurred 1-2 months after the maximum monthly rainfall. Both parents cared for the young and fed nestlings disproportionately more earthworms, frogs, millipedes and earwigs in relation to their abundance in the environment. Nestlings fledged when still as much as 30% below adult size. Food abundance peaked in both forest and farmbush (forest regrowth) habitat at the start of the wet season and in the early part of the dry season; coinciding with the period immediately prior to egg-laying and with dispersing fledglings respectively. Potential Picathartes prey were more abundant in farmbush than forest habitat. The proportion of eggs laid that resulted in fledged young was 22.9% and productivity was 0.22 chicks per adult. Nest predation was the main cause of nest failure but infanticidal behaviour played a significant role. A substantial number of non-breeding birds were apparently present in populations and infanticidal behaviour may have been a consequence of competition for limited nest sites. Population density was estimated as 0.37 individuals km-' and the total population in Sierra Leone as about 1100. Local populations in forest reserves are close to the theoretical minimum for long-term viability in all cases but populations are apparently stable or declining only very slowly. Abandonment of colonies was associated with habitat degradation but there was also evidence that Picathartes may be fairly tolerant to disturbance in some areas. Phylogenetic analysis using mitochondrial DNA of the cytochrome b gene suggests that Picathartes is more closely related to the thrush-babbler assemblage than the crows.
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Fetherston, Kevin L. "Pattern and process in mountain river valley forests /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/5563.
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Skov, Martin Wiggers. "Reproduction and feeding ecology of East African mangrove crabs, and their influence on forest energy flow." Thesis, University of Liverpool, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250459.
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Fishlock, Victoria L. "Bai use in forest elephants (Loxodonta africana cyclotis) : ecology, sociality & risk." Thesis, University of Stirling, 2010. http://hdl.handle.net/1893/2758.
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Forest elephant (Loxodonta africana cyclotis) sociality is relatively little-studied due to the difficulties of making direct observations in rainforests. In Central Africa elephants aggregate at large natural forest clearings known as bais, which have been postulated to offer social benefits in addition to nutritional resources. This thesis explores the role of these clearings as social arenas by examining bai use within three main themes; ecology, sociality and risk factors. Seasonal changes in elephant use of the Maya Nord bai (Republic of Congo) are described, along with the demography of the visiting population. Elephant visit rate was highly variable; the number of elephants using Maya Nord in an observation day ranged from 0 to 117 animals. This variability was unrelated to local resource availability and productivity suggesting that bai use occurs year round. Elephants in Odzala-Kokoua do not show high fidelity to a single clearing; 454 elephants were individually identified and re-sighted an average of 1.76 times (range 1-10) during the twelve month study period. Previous bai studies have yet to quantify how elephants associate with one another within the bai area. This study examines socio-spatial organisation and associate choice using two measures of association within the 0.23 km2 bai area; aggregations (all elephants present in the clearing) and parties (elephants spatially co-ordinated in activity and movement) and distinguishes these from parties that range together (i.e. arrive and leave together). Social network analyses (SocProg) were used to describe inter- and intra-sexual multi-level organisation in the bai environment, and to illustrate the non-random nature of elephant aggregations and parties. Bais were shown to function as social arenas; female elephants showed active choice of certain associates and active avoidance of others when creating parties, whereas males were less discriminatory. Parties formed in the clearing (mean size= 3.93, SE= 0.186) were larger than ranging parties (mean size= 2.71, SE= 0.084) and elephants stayed for 50% longer in the clearing when they associated with individuals from outside their ranging party. Inter- and intra-sexual relationships were maintained within the clearing, and these are suggested to offer elephants essential opportunities for social learning. The patterning and nature of the relationships observed at the Maya Nord clearing indicates that forest elephants use a fission-fusion social structure similar to that of savannah elephants (Loxodonta africana africana); relationships are significantly structured by age- and sex- and underpinned by individual identity. Old experienced females hold key roles for forest elephants, and male relationships are superimposed on the network of female associations. Odzala-Kokoua elephants use bais to maintain their social relationships despite being highly sensitive to the anthropogenic risks involved in using these open areas. The results of this study suggest that forest and savannah elephants lie on the same social continuum, balancing social “pulls” to aggregate against the ecological “pushes” that force groups to fission. Previous models of savannah elephant sociality construct levels of association and social complexity upwards from the basic mother-calf unit (e.g. Wittemyer & Getz 2007). My results suggest that it may be more appropriate to consider elephant sociality and associations as in dynamic equilibrium between social and ecological influences acting at all levels of grouping, and to explicitly test how these underlie the opportunity costs that elephants are willing to pay in order to maintain social groupings.
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Ogurcak, Danielle E. "The Effect of Disturbance and Freshwater Availability on Lower Florida Keys’ Coastal Forest Dynamics." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2288.
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Coastal forest retreat in the Florida Keys during the 20th century has been attributed to a combination of sea level rise and hurricane storm surge impacts, but the interactions between these two disturbances leading to forest decline are not well understood. The goal of my research was to assess their effects over a period spanning more than two decades, and to examine the relationships between these press and pulse disturbances and freshwater availability in pine rockland, hardwood hammock, and supratidal scrub communities. Impacts and recovery from two storm surges, Hurricanes Georges (1998) and Wilma (2005), were assessed with satellite-derived vegetation indices and multiple change detection techniques. Impacts were greater at lower elevations, and in hardwood hammock, spectral signatures indicative of plant stress and productivity returned to pre-disturbance levels within a few years. In pine rockland, impacts were predominately related to Hurricane Wilma, however, a similar return to pre-disturbance conditions was absent, suggesting that trajectories of disturbance recovery differed between the two communities. Long-term monitoring of forest composition, structure, and groundwater salinity showed that compositional shifts in the low shrub stratum were associated with salinization of the freshwater resource attributable to sea level rise. Throughout the course of twelve months of climate and groundwater monitoring (2011-2012), groundwater salinity generally decreased in response to large precipitation events. Modeling of geophysical data indicated that groundwater salinity was an important predictor of community type. Isotopic analysis of d18O in plant stem water and foliar d13C was used to determine temporal and spatial patterns in water use and plant stress in two community dominants, slash pine, Pinus elliottii var. densa, and buttonwood, Conocarpus erectus. Both species relied heavily on groundwater, and plant stress was related to increasing groundwater salinity. The results of this work suggest that the interaction of press and pulse disturbances drive changes in community composition by causing mortality of salt-sensitive species and altering the freshwater resource.
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Jalba, Adriana. "Risk assessment for linear alkylbenzene sulfonates in Mediterranean coastal forest exposed to marine aerosols: a physiological perspective." Doctoral thesis, Universite Libre de Bruxelles, 2011. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209974.
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The aim of this study was to understand the contribution of Linear Alkylbenzene Sulfonates (LAS) to the decline of Mediterranean coastal forest exposed to marine aerosols. LAS are a group of synthetic anionic surfactants widely used in the composition of household or industrial detergents and agrochemicals. This study was part of a large project (RISICO) aiming the assessment of the environmental impact of the LAS at multiple levels: biodegradation in the coastal waters, sorption – desorption processes in the sediments, toxicity to the aquatic life and toxicity to the coastal forest (by aerosolisation of the sea water). Previous studies pointed out this group of surfactants as the main cause of the coastal forest decline. However, the quantification of this surfactant in the environmental samples (mainly sea water and foliar deposition) was done using non-specific analytical methods as methylene blue active substances (MBAS), leading to overestimation of the environmental concentrations of LAS.
The work hypothesis was that at actual environmental concentrations, the LAS does not play a key role in the foliar uptake of the sea salt deposited on the coastal vegetation by the marine aerosols, therefore the LAS may not be the main cause of the coastal forest decline.
The research involved both greenhouse experiments and field measurements. The experimental work was conducted on young Mediterranean trees (Laurus nobilis L. Quercus ilex L. and Pinus halepensis P. Mill.) and investigated the synergistic toxic effects of exposure to simulated marine aerosol contaminated with surfactants. An array of endpoints was used including photosynthetic activity, relative water content, foliar deposition and uptake of salt and LAS, and pigments analysis. The results of those experiments revealed that LAS itself did not have phytotoxic effects. Nevertheless, the surfactant was shown to enhance the foliar uptake of the salt in the tested species, especially in Pinus halepensis, confirming the conclusions of previous studies regarding the sensitivity of this species to polluted marine aerosols.
The field work was conducted in San Rossore National Park (Italy) and Porquerolles Island (France) and was focused on evaluating the health status of the Mediterranean forest (Quercus ilex L. Pinus halepensis Mill. and Pinus pinaster Aiton.) and also on quantification of LAS in coastal aerosols using highly specific analytical methods, like the mass spectrometry (MS). The frequencies and extent of injuries in the coastal trees were found to be correlated to the salt but not with the LAS content of the leaves. The concentrations of LAS in the Pinus and Quercus leaves were comparable in the two studied sites but the concentrations of salt were extremely high in San Rossore, suggesting that other factors may determine the excessive salt foliar uptake. The parallel MS and MBAS carried out in the same set of aerosol samples revealed that MBAS measurements were not relevant for LAS concentrations in the marine aerosols. Projecting the experimental results to the real LAS and salt exposure of the coastal forest, we concluded that LAS may play a marginal role in coastal vegetation decline.
Doctorat en Sciences
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Cole, Lydia Eve Spencer. "Disturbance, recovery and resilience in tropical forests : a focus on the coastal peat swamp forests of Malaysian Borneo." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:a135aff3-ea84-4766-8046-b3bb4ce31275.
Full textAbstract:
Tropical forests have existed for up to one hundred million years, and today provide many ecosystem services vital for human well-being. They also harbour great biodiversity, which, in addition to its intrinsic value, plays a key role in the functioning of these ecosystems. Despite their local to global significance, there are still many knowledge gaps concerning the dynamic processes that govern the functioning of tropical forests. Rapid rates of deforestation and landscape conversion, predominantly for logging and industrial agriculture, are limiting the time and opportunity available to collect the information needed to fill these gaps. This research aims to shed light on the long-term ecological functioning of tropical forests, specifically investigating the history of disturbance in these ecosystems and the response of forest vegetation to past perturbations. The carbon-rich tropical peat swamp forests found along the coast of Sarawak, Malaysian Borneo, are a central focus of this study. For these forests in particular, a large deficit of knowledge surrounding their history and unique ecological functioning is coupled with some of the highest conversion rates of all tropical forest ecosystems across the world. In this thesis, palaeoecological data has been used to reconstruct temporal variability in forest vegetation coincident with external perturbations in order to identify changes in the resilience of these ecosystems through time, via indicators such as slowing rates of recovery and reduced regeneration of forest vegetation. Results suggest that tropical forest ecosystems have, for the most part, shown resilience to natural disturbances in the past, ranging from instantaneous localised tree-fall to longer-term regional climatic change; but that recent anthropogenic disturbances, of novel forms and greater intensities, are jeopardizing the potential for forest recovery and thus compromising ecosystem resilience. These findings enhance our understanding of the ecology of tropical peat swamp forests, and tropical forests more broadly. They also provide a context for contemporary tropical forest management, allowing for predictions on future responses to disturbance and enabling more ecologically sustainable landscape planning.
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Gaugris, Jerome Yves. "The impacts of herbivores and humans on the utilisation of woody resources in conserved versus non-conserved land in Maputoland, northern KwaZulu-Natal, South Africa." Connect to this title online, 2008. http://upetd.up.ac.za/thesis/available/etd-06052008-162658.
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McAlister, Gareth. "You don't love your mother just because she feeds you : amaXhosa and woodlands in the Peddie district, Eastern Cape." Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1006044.
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This thesis will discuss how the application of place theory might provide insight into how a selection of Xhosa-speaking people in a rural village (Ntloko), in the former Ciskei of the Eastern Cape, interact with and establish relationships with the local indigenous thicket forest (ihlathi). I am concerned with how these influence residents' perceptions and attitudes (relational epistemologies) towards this resource, and how these may (or may not) translate into conservation practices. I am also interested in how socio-political and economic changes have altered these people/place relations (including gender) and their corresponding cultural perceptions. It is argued that the local thicket forest's significance and importance moves beyond the economic and utilitarian value of its natural resources. The thicket plays an important part in local identity construction, due to both its socio-cultural significance and its role in local livelihoods. People form meaningful attachments and relationships (relational epistemologies ) with the thicket as a place, through their interactions with it. While this may or may not result in actions and attitudes in-line with the conservation agenda, it is shown that this relationship is necessary for a local concern and stake in the natural environment. Those who have no or minimal interaction, such as many of the young women of Ntloko, have no opportunity to forge a relationship with it. Ihlathi may be known through narrative, but not personal experience, and as such no significant attachments can be formed, and thus concern for its conservation status is irrelevant. It is clear that if you remove people from an environment, you remove the stake they hold in the environment in question, thereby disrupting the relationship, and alienating people from nature. While a relational epistemology may not equate to conservation practices, it does imply a stake or concern in the environment, and as such, may provide an opportunity for conservationists to work with local communities. Resistance to conservation and development projects that aim to exclude local interaction, and therefore relationships, with the environment, will always be strong when local identities are intricately tied to the places and experiences that form them. Threatening that relationship threatens local identities and the attachments that orient them.
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Bechara, Fernando Campanhã. "Unidades demonstrativas de restauração ecológica através de técnicas nucleadoras: Floresta Estacional Semidecidual, Cerrado e Restinga." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/11/11150/tde-22082006-145733/.
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Refazer ecossistemas de forma artificial representa um desafio de iniciar um processo de sucessão o mais semelhante possível aos processos naturais. A recuperação ambiental tem se baseado no modelo da silvicultura tradicional, plantandose árvores sob espaçamento 3 x 2 m, em área total, com altos insumos de implantação/manutenção, e gerando-se bosques desenvolvidos em altura, porém com baixa diversidade de formas de vida e regeneração. Técnicas nucleadoras de restauração formam microhabitats em núcleos propícios para a chegada de uma série de espécies de todas as formas de vida, que num processo de aceleração sucessional, irradiam diversidade por toda a área. As técnicas foram implantadas em áreas piloto de um hectare, denominadas Unidades Demonstrativas (UDs). As UDs foram montadas em Floresta Estacional Semidecidual (Capão Bonito-SP), Cerrado (Santa Rita do Passa Quatro-SP) e Restinga (Florianópolis-SC). Na primeira UD, com um ano de idade, as técnicas nucleadoras introduziram 1.603 mudas de 148 espécies nativas, dentre 84 espécies arbóreas (883 mudas), 12 arbustivas (124 mudas), 30 herbáceas (242 mudas), 20 trepadeiras (260 mudas) e 2 bromeliáceas (3 mudas), além de 94 mudas de hábito indeterminado. Entre as espécies, ocorreram 69 zoocóricas, 32 autocóricas e 29 anemocóricas, além de 21 plantas indeterminadas. Desconsiderando-se as 47 espécies arbóreas implantadas por mudas, houve introdução de: 25% de arbóreas, 8% de arbustos, 20% de ervas, 14% de lianas e 1% de bromeliáceas. Na UD de Cerrado, apesar de impactada por gado, aos dois anos de idade, foram introduzidos 354 indivíduos de 31 espécies nativas. Destas, 39% foram espécies arbóreas, 13% arbustivas, 16% herbáceas, 16% lianas e 16% indeterminadas. Foram registradas 35% de espécies zoocóricas, 29% de anemocóricas, 19% de autocóricas e 16% de plantas com síndrome indeterminada. Na UD de Restinga, foram detectadas, aos dois anos e meio de idade, 180 espécies de 108 gêneros e 55 famílias. As técnicas nucleadoras resultaram num custo experimental estimado em torno de 34% mais barato em relação ao modelo tradicional que varia em torno de R$ 5.500,00 reais/ha. O uso da nucleação aumentou nitidamente a eficiência da restauração ecológica. Foi restituída a diversidade, não só em seu aspecto estrutural, mas considerando-se também os diferentes nichos, formas e funções, formando um mosaico de ambientes e permitindo uma maior dinâmica das comunidades. No atual estágio de conhecimento, é importante a definição de qual paradigma almejamos para a restauração de nossas florestas: cultivar plantações de árvores nativas ou permitir e acelerar a sucessão natural? O novo paradigma das técnicas nucleadoras, ao contrário dos modelos tradicionais de recuperação que apenas satisfazem exigências legais, promovem a restituição de produtores, consumidores e decompositores, gerando a conservação efetiva dos ecossistemas, e assumindo, desta forma, um compromisso ético com as futuras gerações.To remake ecosystems of artificial form represents a challenge to initiate a process of the possible most similar succession to the natural processes. The environmental recuperation has based on the model of traditional forestry, standing trees under 3 x 2 m spacing, in total area, with high implantation/ maintenance inputs, and generating forests developed in height, however with low diversity of forms of life and regeneration. Restoration nucleation techniques form microhabitats in nuclei propitious for the arrival of a series of species of all the life forms that in a process of sucessional acceleration, radiate diversity for all the area. The techniques had been implanted in pilot areas of one hectare, called "Demonstrative Units" (UDs). The UDs had been mounted in seasonal semidecidual forest (Capão Bonito-SP), Brazilian savanna (Santa Rita do Passa Quatro-SP) and coastal plain vegetation (Florianópolis-SC). In the first UD, with one year of age, the nucleation techniques had introduced 1,603 seedlings of 148 native species, amongst 84 arboreal species (883 seedlings), 12 shrubs (124 seedlings), 30 herbaceous ones (242 seedlings), 20 lianas (260 seedlings) and 2 bromelias (3 seedlings), in addition to 94 seedlings of indeterminate habit. Among the species, 69 zoochore, 32 autochore and 29 anemochore had occurred, plus 21 indetermined plants. Disrespecting the 47 arboreal species implanted by traditional seedlings, there was introduction of: 25% of arboreal, 8% of shrubs, 20% of herbaceous, 14% of lianas and 1% of bromelias. In Brazilian savanna UD, although affected by cattle when two years of age, 354 individuals of 31 native species had been introduced. Of these, 39% had been arboreal species, 13% shrubs, 16% herbaceous, 16% lianas and 16% indetermined. There had been registered 35% of zoochore species, 29% of anemochore, 19% of autochore and 16% of plants with indetermined syndrome. In coastal plain vegetation UD, in two years and half of age, 180 species of 108 genus and 55 families had been detected. The nucleating techniques had resulted cheaper in an esteemed experimental cost around 34% in relation to the traditional model that varies around R$ 5,500.00 reais/ha. The use of the nucleation clearly increased the efficiency of the ecological restoration. The diversity not only restituted its structural aspect, but also the different niches, forms and functions, forming an environment mosaic and allowing a dynamic growth of the communities. In the current period of knowledge, is important the definition of which paradigm we wish for the restoration of our forests: to cultivate plantations of native trees or to allow and to speed up the natural succession? The new paradigm of the nucleation techniques, in contrast to the traditional models of recovery that only satisfy legal requirements, replenishes the producers, consumers and decompositors, promoting the conservation of the ecosystems, and adopting an ethical commitment with the future generations.
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Boyemba, Bosela Faustin. "Ecologie de Pericopsis elata (Harms) Van Meeuwen (Fabaceae), arbre de forêt tropicale africaine à répartition agrégée." Doctoral thesis, Universite Libre de Bruxelles, 2011. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209883.
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Pericopsis elata is an African forestry species commercialized under the vernacular names afrormosia or assamela. It is one of the principal species commonly exploited for timber in the Democratic Republic of Congo (DRC) and in a lesser extent in Cameroon and Congo. In view of its sustainable resource exploitation, the species is in centre of numerous polemics notably in the European Union. It is one of the rare commercialized species that produce wood, since 1992, as listed in the CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) annex II specifying that “the exploitation of afrormosia necessitate the deliverance and a prior presentation of exploitation permit”. The most important reserves of afrormosia are found in DRC. This doctoral thesis presents the ecology of this particular tree and its behaviour regarding forestry exploitation. It allows to inform the international organisms such as CITES as well as the national policy-makers on the vulnerability of afrormosia and to propose appropriate measures that can avoid future unsustainable/unregulated exploitation activities/Pericopsis elata est une espèce forestière africaine commercialisée sous les noms d’afrormosia ou d’assamela. Elle est une des principales espèces exploitées pour le bois d’œuvre en République Démocratique du Congo (RDC) et dans une moindre mesure au Cameroun et au Congo. Elle est au centre de nombreuses polémiques, notamment dans l’Union européenne, en ce qui concerne la durabilité de son exploitation. C’est une des rares espèces commerciales productrice de bois d’œuvre listée, depuis 1992, dans l’Annexe II de la CITES (Convention sur le commerce international des espèces en danger d’extinction) qui spécifie que « L'exportation d'un spécimen d'une espèce inscrite à l'Annexe II nécessite la délivrance et la présentation préalables d'un permis d'exportation ». Les plus grandes réserves d’afrormosia se trouvent en RDC. Cette thèse de doctorat porte sur l’écologie de cet arbre et sur son comportement vis-à-vis de l’exploitation forestière. Elle permet d’informer les organismes internationaux comme la CITES et les décideurs nationaux sur la vulnérabilité de l’afrormosia et de proposer des mesures à prendre pour que l’espèce ne soit pas menacée par une exploitation mal conduite et non réguléeDoctorat en Sciences
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Wassenaar, Theodorus Dallein. "Coastal dune forest regeneration : the response of biological communities to rehabilitation." Thesis, 2004. http://hdl.handle.net/2263/24545.
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Human appropriation of natural resources, and the consequent loss of habitats, means that ecological restoration may in the future become a vital conservation tool. For this to happen, we have to understand the processes and factors that govern community assembly, and their management. Here I analyze data on community structure (richness, evenness, diversity, composition) of assemblages (millipedes, spiders, dung beetles, plants, birds, rodents), and on soil chemical and physical properties, to describe and evaluate post-disturbance dune forest regeneration patterns. Data were collected from program of a dune mining company), from post-mining rehabilitating dune forests, and from self-regenerating dune forests in northern KwaZulu-Natal. Both succession theory and community assembly theory predict that a species' niche will determine when it will colonize new sites, and by extension, what the eventual species composition will be. This type of control should result in deterministic regeneration patterns for a community. In support of this view, I found that the majority of habitat-age related changes in community structure and ecosystem function were either towards benchmark values (and will reach these values in less than 65 years post-disturbance), or were already equal to the benchmark. Age-related trajectories were repeatable between surveys and post-mining sites were changing as fast or faster than spontaneously regenerating sites. Moreover, detailed analysis of changes in community composition of millipedes, dung beetles, herbs, trees, birds and rodents showed that all of the taxa were also regaining the benchmark's species composition. However, community change was dependent on how it was measured - dung beetles recovered only species presence, but others relative abundances as well. Changes were almost never exponential, suggesting that colonization and extinction are not the orderly events foreseen by equilibrium biodiversity theory. Furthermore, the average abundances of birds, trees and millipedes in undisturbed dune forest patches were correlated with colonization success, suggesting that post-disturbance recovery through colonization may be controlled from outside the local community, rather than by species interactions. The recovery of the spider community appeared to be towards the benchmark forest community, but spider species composition was critically linked to microhabitat structure. Because microhabitat is not necessarily restored concurrently with forest community structure, the spider assemblage (and possibly other invertebrates) may not recover the desired pre-disturbance structure or composition. Dune forests thus seem to be resilient to mining disturbances, since most taxa were recovering structure and composition. However, classic successional and community assembly theories are unlikely to fully explain these community recovery mechanisms. More likely, post-disturbance recovery occurs because a new habitat passively "samples" the rain of dispersing propagules and individuals, leading to a high probability of capturing the average species composition of the region. A conceptual model of dispersal in the landscape suggested that species composition of new habitats might equilibrate to the composition of the closest habitat undergoing the least amount of species compositional change, although this may not apply to all taxa. This model may serve as the basis for directing future research and restoration management.Thesis (DPhil (Zoology))--University of Pretoria, 2006.
Zoology and Entomology
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"The influence of the monocarpic herb, Isoglossa woodii, on subtropical forest tree dynamics and diversity." Thesis, 2009. http://hdl.handle.net/10413/2718.
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Dominant understorey species, such as herbs, ferns, palms and shrubs may influence forest tree species diversity and dynamics. Their influence may be through shading the forest floor, thereby affecting regeneration of shade-intolerant species and reducing species diversity, or it may be through competition with seedlings for space and belowground resources, thus modifying or changing the structure of the forest. These effects may be compounded if the life cycle of the understorey species consists of synchronized reproductive and mortality events. This study examines the influence of a dominant understorey species, Isoglossa woodii (Acanthaceae), on regeneration of trees in Indian Ocean subtropical coastal dune forest in southern Africa. The species is a semiwoody herb and has population-wide synchronous reproduction at 4-7 year cycles after which it dies and regenerates from seed. In this thesis I examine three aspects of the ecology of this suppressive herb: (i) the ecological and environmental correlates of the distribution of I. woodii; (ii) the evolutionary advantages of synchronous monocarpy; and (iii) the ecological effects of the extensive cover and putative recruitment window caused by I. woodii on forest tree seedling dynamics and diversity. Isoglossa woodii covered 65–95 % of the understorey, while gaps in this understorey cover occupied the remaining 5–35 % of the area. The spatial distribution of I. woodii was strongly related to tree canopy structure, with the species excluded from sites with dense canopy cover. Woody seedling establishment was inhibited by low light availability (Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.
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Boyes, Lauren J. "Regeneration failure and the Acacia karroo successional pathway in coastal dune forests in KwaZulu-Natal, South Africa." Thesis, 2007. http://hdl.handle.net/10413/4707.
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Monospecific stands of Acacia karroo establish naturally on disturbed coastal dunes in KwaZulu-Natal, South Africa. While the A. karroo successional pathway is successful in rehabilitating mined dunes at the Richards Bay Minerals mining company (RBM), the same pathway has become arrested in the coastal dune forest at Cape Vidal in the Greater St. Lucia Wetland Park. This study examines the efficacy of the A. karroo successional pathway for restoring disturbed coastal dune forests. Dispersal of seeds and successful recruitment of seedlings are essential for habitat restoration. Seed and seedling banks were compared between previously disturbed A. karroo stands and adjacent forest at Cape Vidal. Different seed bank composition and higher seed bank richness in the forest suggest that seed dispersal into A. karroo stands is limited. Protected seed banks in A. karroo stands had increased seedling richness, indicating that dispersal limitation does not fully explain the lack of seedling establishment. At RBM, the seed bank richness of A. karroo stands increased with age since mining. While cumulative species richness of the seed bank of the oldest A. karroo stand at RBM was marginally lower than that at Cape Vidal, successful rehabilitation at RBM is associated with low seedling mortality. Consequently, forest tree species richness is high at RBM in the A. karroo stands and is converging on natural forest richness and composition. Although seed dispersal is reduced, it does not totally limit establishment of forest tree species in A. karroo stands at Cape Vidal, which implicates a post-establishment factor. Soil fertility potentially reduces seed germination and seedling growth. Soil nutrients in A. karroo stands at Cape Vidal were similar to those in the adjacent forest, and total nitrogen levels in A. karroo stands at Cape Vidal were higher than at RBM. Thus, soil conditions were unlikely to be limiting tree regeneration in A. karroo stands. Total nitrogen accumulated in the oldest stand at RBM at a rate of 10.0 g.m2.y(1 and a similarly rapid rate occurred at Cape Vidal. Therefore the A. karroo stands were not nitrogen limited. Nitrogen supplementation experiments at Cape Vidal demonstrated that a range of forest tree species establish in A. karroo stands regardless of nitrogen level, but there is low survival of seedlings. Thus, nitrogen availability is not arresting succession at Cape Vidal. Herbivory can also inhibit seedling recruitment. Selective feeding may enhance the persistence of species with defences against herbivory, such as A. karroo, ultimately altering the tree community composition. Browsing and trampling by large mammalian herbivores in A. karroo stands at Cape Vidal decreased survival and growth of forest tree seedlings. Large herbivores such as kudu, waterbuck, bushbuck and red duiker preferentially used the A. karroo stands as they offer abundant food and their topography allowed easy movement. This topdown pressure reduced recruitment, growth, and survival of seedlings of undefended species. Few wild herbivores occur at RBM, which allowed succession to proceed unhindered, ultimately restoring coastal dune forest at this site. Despite successful rehabilitation of coastal dune forest on mined dunes at RBM, limited seed dispersal and high levels of herb ivory have arrested succession at Cape Vidal. Thus, the A. karroo successional pathway must be implemented only after careful consideration of site-specific factors such as distance to a source of propagules and the intensity of herbivory in the system. In areas where herbivore densities are high, management interventions focusing on reducing herb ivory and encouraging visitation by seed dispersers are necessary for the successful use of this successional pathway.Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2007.
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Nzunda, Emmanuel F. "Resprouting and multi-stemming and the role of the persistence niche in the structure and dynamics of subtropical coastal dune forest in KwaZulu-Natal province, South Africa." Thesis, 2008. http://hdl.handle.net/10413/76.
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Resprouting is an important means of plant regeneration especially under conditions that do not favour regeneration through seeding such as frequent disturbances, low productivity, unfavourable soil conditions, extreme cold and limited understorey light availability. Sprouts may be advantageous over seedlings because they have higher survival and growth rates than seedlings, since they use resources from parent plants unlike seedlings that have to acquire their own resources. Resprouting is well documented for ecosystems that experience severe disturbances that damage aboveground biomass. For example, resprouting is important for plant persistence against fire in fire-prone savannas and Mediterranean shrub-lands, and hurricanes and cyclones in tropical forests. In these ecosystems, resprouting often results in multi-stemming, because this dilutes the risk of damage among many stems, improving the chances of individual survival. This study was conducted at coastal dune forest at Cape Vidal in north-eastern South Africa, where there is a high incidence of multi-stemmed trees due to resprouting in response to chronic disturbances of low severity. This study examines (1) the importance of resprouting to tree survival and dynamics in an environment where disturbance severity is low but pervasive, and (2) how this resprouting strategy differs from the more familiar sprouting response to severe disturbances such as fire and hurricanes. Analysis of the relationship between multi-stemming and a number of disturbances potentially causing multi-stemming revealed that stem leaning and substrate erosion were the most important disturbances associated with multi-stemming. There were fewer multistemmed trees on dune slacks that had a stable substrate and were protected from sea winds than on dune crests and slopes that had unstable substrate and were exposed to sea winds. Trees resprouted and became multi-stemmed from an early stage to increase their chances of survival against leaning caused by strong sea winds and erosion, and occasional slumping of the unstable dune sand substrate. These low severity disturbances are persistent and are referred to as chronic disturbances in this thesis. As a result of these chronic disturbances, both single and multi-stemmed trees had short stature because taller individuals that emerged above the tree canopy would be exposed to wind damage. Under chronic disturbances plants may manifest a phylogenetically determined sprouting response. However, in this study resprouting and multi-stemming were the results of the tree-disturbance interaction and not a property of a plant or species and were not phylogenetically constrained. Because the disturbances are predominantly of low severity, leaning trees were able to regain the vertical orientation of the growing section by turning upward (a process referred to as ‘turning up’ in this study) and hence survive without resprouting. Species that were prone to turning upward had a low incidence and degree of leaning of their individuals, low frequency of loss of primary stems and high abundance of individuals. Although turning up is less costly to the individual than resprouting, it could only be used by leaning trees that had small angles of inclination and were not eroded. High intensities of the latter require that individuals resprout to survive. The form and function of resprouting varied between seedlings and juvenile and mature trees. Resprouting in seedlings resulted in a single replacement shoot, unlike sprouting in juvenile and mature trees that resulted in multi-stemmed trees. Like sprouting in juvenile and mature trees, sprouting in seedlings was not phylogenetically constrained. Resprouting in seedlings increased seedling persistence; hence species with more sprout seedlings had larger individual seedlings and seedling banks. Resprouting in seedlings increased the chances of seedling recruitment, whereas resprouting in juvenile and mature trees increased the chances of an established plant maintaining its position in the habitat. After disturbances of high severity, which destroy the photosynthesizing parts, plants resprout using carbohydrates stored below- or above ground. In this study, good resprouters stored more carbohydrates both below- and above ground than poor resprouters. The carbohydrates were mobilized for resprouting after disturbance. More carbohydrates were stored in stems than in roots because the prevailing disturbances were mostly of low severity and hence above ground resources were readily available. Similar to storage by plants in severely disturbed habitats, carbohydrates were stored by reserve formation, which competes for carbohydrates with growth and maintenance and forms permanent storage, rather than accumulation, which temporarily stores carbohydrates in excess of demands for growth and maintenance. Stored carbohydrates are not necessary for resprouting of plants after disturbances of low severity because they can resprout using resources remobilized directly from the disturbed photosynthesizing parts. However, in this study, stored carbohydrates served as a bet-hedge against occasional severe disturbances that occurred in addition to chronic disturbances. Allocation of carbohydrates to permanent storage diverts them from growth and reproduction and hence good resprouters had lower growth rates, seed output, seed size and seedling recruitment than poor resprouters. However, the costs of these traits that resulted in low recruitment from seed by good resprouters, were compensated for by high persistence of established individuals of good resprouters through recruitment of sprout stems. This study demonstrates that resprouting is not only advantageous in severely disturbed environments, but also in environments where disturbances are of low severity but nevertheless confer an advantage on individuals that persist. Thus in forest environments where aboveground biomass is seldom destroyed and individuals are relatively long-lived, resprouting can confer significant fitness and selective advantage on individuals.Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.
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Theron, Leon-Jacques. "Distribution and abundance of rodents, millipedes and trees in coastal dune forests in northern KwaZulu-Natal." Diss., 2001. http://hdl.handle.net/2263/23556.
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A widely observed pattern in nature is a positive relationship between local abundance and spatial distribution. This study investigates this relationship amongst three taxa namely rodents, millipedes and trees on regenerating and unmined coastal dune forests at Richards Bay, KwaZulu-Natal. No sensible analyses were possible on the rodent data. Both millipedes and trees had a positive relationship between local abundance and distribution (measured as species incidence). Millipedes showed no changes in the relationship with changes in habitat regeneration time. For trees, the regression slope decreased with time due to changes in abundance and incidence of Acacia karroo. Lack of bimodality in incidence frequency distributions ruled the core-satellite metapopulation hypothesis out as a mechanism producing the positive abundance-incidence relationship. The resource availability hypothesis was a most likely mechanism. This study confirmed that rare species tend to be restricted in both abundance and incidence.Dissertation (MSc (Zoology))--University of Pretoria, 2007.
Zoology and Entomology
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Sutherland, Elizabeth F. "Fire, resource limitation and small mammal populations in coastal eucalypt forest." 1998. http://ses.library.usyd.edu.au/handle/2123/5344.
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Cleminson, Tania. "Quantification of the resource base and impact of harvesting of coastal hardwood species by a rural community." Thesis, 1993. http://hdl.handle.net/10539/22826.
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Research report submitted in partial fulfillment of requirements for the degree of Master of Science in
Quantitative Conservation Biology at the University of the Witwatersrand, Johannesburg.The study aimed: (1) to provide baseline data on aspects of wood utilisation in a resource area and a communal area In KwaZulu, (2) to investigate the effects of this wood utilisation on the resource base, and (3) to discuss the sustainability of current wood. utilisation. Wood utilisation in this study refers to the harvesting of dead and livewood for fuelwood, building poles and fencing posts. (Abbreviation abstract)
AC2017
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Degger, Natalie. "The application of passive artificial devices for monitoring of metallic and organic pollutants along the South African coastline." Thesis, 2012. http://hdl.handle.net/10210/4745.
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