1 |
Standardizing quarter degree grid data for plant species in the Western Central Bushveld for more explicit use in spatial models / Sabine Eva Maria Johanna KurzwegKurzweg, Sabine Eva Maria Johanna January 2011 (has links)
South Africa is a megadiverse country, and its biodiversity is endangered by population pressure and the development needs of a developing country. In order to address the rapid decline in biological diversity, biodiversity planning has become a key focus area that aims at identifying priority areas for species and ecosystem conservation within and outside of formally protected areas. Plant conservation hotspots are identified by the quantification of indicator taxa such as plant taxa richness, rarity and endemism. But the urgent and enormous task of biodiversity assessment for conservation planning requires that we make most of what we know. Therefore, this study seeks to make a contribution by finding new ways of biodiversity pattern estimation from the extrapolation of incomplete sets of plant species distribution data at the Quarter Degree Grid level. Incomplete sampling across the grids of a study area results in false records of species absence and thus a biased biodiversity estimation. As a possible solution, plant distribution data for the western Central Bushveld Bioregion has been standardized using two profiles, namely the ‘Centroid Grid’ and ‘Integrated Grid’ profile. The former involves the strengthening of under-sampled grids by extrapolating species occurrences from three adjacent grids with the most similar vegetation units, whereas the latter integrates phyto-diversity data for the four grids intersecting at each grid reference point. Standardized data has proved to provide a means to counter the bias in plant diversity data linked to Quarter Degree Grids by a) strengthening of under-sampled grids and b) visibly smoothing out the gaps between under- and well-sampled grids, which resulted in improved biodiversity estimation for more representative spatial biodiversity modelling. Interpolation created geo-referenced polygons for more explicit use in the identification of areas of conservation concern at bioregional scale. However, well-sampled grids still dominate the outcomes of the analysis by creating spatial sampling bias. Therefore, this approach to calibrate Quarter Degree Grid resolution of spatial data is an additional attempt to achieve more representative mapping of biodiversity patterns, which is a prerequisite for strategic conservation planning for ‘living landscapes’. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2012
|
2 |
Standardizing quarter degree grid data for plant species in the Western Central Bushveld for more explicit use in spatial models / Sabine Eva Maria Johanna KurzwegKurzweg, Sabine Eva Maria Johanna January 2011 (has links)
South Africa is a megadiverse country, and its biodiversity is endangered by population pressure and the development needs of a developing country. In order to address the rapid decline in biological diversity, biodiversity planning has become a key focus area that aims at identifying priority areas for species and ecosystem conservation within and outside of formally protected areas. Plant conservation hotspots are identified by the quantification of indicator taxa such as plant taxa richness, rarity and endemism. But the urgent and enormous task of biodiversity assessment for conservation planning requires that we make most of what we know. Therefore, this study seeks to make a contribution by finding new ways of biodiversity pattern estimation from the extrapolation of incomplete sets of plant species distribution data at the Quarter Degree Grid level. Incomplete sampling across the grids of a study area results in false records of species absence and thus a biased biodiversity estimation. As a possible solution, plant distribution data for the western Central Bushveld Bioregion has been standardized using two profiles, namely the ‘Centroid Grid’ and ‘Integrated Grid’ profile. The former involves the strengthening of under-sampled grids by extrapolating species occurrences from three adjacent grids with the most similar vegetation units, whereas the latter integrates phyto-diversity data for the four grids intersecting at each grid reference point. Standardized data has proved to provide a means to counter the bias in plant diversity data linked to Quarter Degree Grids by a) strengthening of under-sampled grids and b) visibly smoothing out the gaps between under- and well-sampled grids, which resulted in improved biodiversity estimation for more representative spatial biodiversity modelling. Interpolation created geo-referenced polygons for more explicit use in the identification of areas of conservation concern at bioregional scale. However, well-sampled grids still dominate the outcomes of the analysis by creating spatial sampling bias. Therefore, this approach to calibrate Quarter Degree Grid resolution of spatial data is an additional attempt to achieve more representative mapping of biodiversity patterns, which is a prerequisite for strategic conservation planning for ‘living landscapes’. / Thesis (MSc (Environmental Sciences))--North-West University, Potchefstroom Campus, 2012
|
3 |
Foraging ecology of white sharks Carcharodon carcharias at Dyer Island, South AfricaJewell, Oliver Joseph David 20 June 2013 (has links)
Dyer Island is thought to host one of the most abundant populations of
white sharks on the planet; this is often credited to the large (55 – 60,000) Cape fur
seal colony at Geyser Rock. Yet relatively little work has ever been produced from
the area. This may be attributed to the harshness in its location as a study site, exposed
to wind and swell from west to east which limits research periods. This study
accounts for over 220 hrs of manual tracking at Dyer Island with a further 68 added
from the inshore shallow areas of the bay. Sharks focused their movements and
habitat use to reefs or channels that allowed access to Cape fur seals. Movement-
Based Kernel Estimates (MKDE) were used to compute home range estimates for
shark movements through and around the heterogeneous structures of Dyer Island and
Geyser Rock. Inshore two core areas were revealed, one being the major reef system
at Joubertsdam and the other at a kelp reef where the tracked shark had fed on a Cape
fur seal. At Dyer Island one core area was identified in a narrow channel, ‘Shark
Alley’, here a second tracked shark foraged for entire days within meters of rafting
Cape fur seals.
Rate of Movement (ROM) and Linearity (LI) of tracks were low during daytime and
movements were focused around areas such as Shark Alley or other areas close to the
seal colony before moving into deeper water or distant reefs with higher rates of ROM
and LI at night. If moonlight was strong foraging would take place to the south of
Geyser Rock but with higher ROM and LI than observed during the day. Foraging
patterns in this study contrast studies from other sites in South Africa and home range
and activity areas were comparatively much smaller than observed in Mossel Bay. It has been established that several known white sharks forage at Dyer Island and the
other studied aggregation sites, such differences in foraging would suggest that they
are able to adapt their foraging behaviour to suit the environment they are in; making
them site specific in their foraging ecology.
Both satellite and acoustic telemetry are revealing aggregation hotspots of white
sharks in South Africa. It is important that such information is used to assist the
recovery of the species which has been protected since 1991, yet is rarely considered
in planning of coastal developments. / Dissertation (MSc)--University of Pretoria, 2012. / Zoology and Entomology / MSc / Unrestricted
|
Page generated in 0.1019 seconds