Browsing by Author "Desmet, Philip George"

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    The application of systematic conservation planning in the succulent Karoo biome of South Africa
    (2004) Desmet, Philip George; Cowling, Richard
    Systematic conservation planning is about making spatially explicit decisions regarding the use of land, based on the observed or expected biodiversity present at a site and the potential for that same site to support alternative /and-uses that are not compatible with the persistence of biodiversity. This thesis examines three questions relating to the application of systematic conservation planning: Which biodiversity surrogates should be used in Namaqualand to do systematic conservation plans? How should targets be set for these surrogates? How can this information be integrated and used within a systematic conservation planning framework? Comparing how well different biodiversity surrogates achieved a set of targets illustrated that continuous biodiversity data (i.e. vegetation types and land-classes) perform better as surrogates than point-based species distribution data. Quarter degree square-based species distribution data cannot be used for on-the-ground conservation planning. It was demonstrated that it is possible to set biologically meaningful conservation targets to represent biodiversity pattern in land classes by applying the Species Area Relationship and using plot-based survey data. The method developed here has the potential to revolutionise conservation planning as it provides for the first time a defensible means for setting representation targets for land classes that are grounded on ecological theory and that use real data. The thesis also explores the potential for metapopulation and fragmentation studies to provide useful insights into developing targets for ecological processes by relating the amount of remaining habitat to key thresholds in probability of population persistence. Two examples, at different spatial scales (1:10 000 and 1:100 000), are used to illustrate how different biodiversity information can be integrated and used within a systematic conservation planning framework. At the finer scale biodiversity and land-use data are 3 used to set priorities for the development of a statutory reserve in the Knersvlakte region of the Succulent Karoo using cadastres as planning units. At the larger scale the data are used in the same region to design a biosphere reserve that promotes the persistence of ecological processes in the landscape using gridded planning units. Both studies use the C-Plan software to assist in the planning and design process. A lesson from both these studies is that there needs to be a paradigm shift in conservation from an on/off reserve mindset to a more integrative whole landscape mindset.
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    The Vegetation and Restoration Potential of the Arid Coastal Belt Between Port Nolloth and Alexander Bay, Namaqualand, South Africa.
    (1996) Desmet, Philip George; Richard Cowling and Dave Richardson, Kristal Maze
    This thesis introduces the environment and the vegetation of the Namaqualand coastal belt between Port Nolloth and Alexander Bay. Aspects of the abiotic environment are discussed and related to patterns and processes observed in the vegetation of the study area. The restoration of the natural vegetation impacted by diamond mining activities is discussed. 1-4 The study area, located within the winter rainfall area of the Namib Desert, is one of four global fog deserts. The area is characterised by a near ubiquitous covering of Recent to Tertiary amorphous dunes of marine origin. The dunes can be divided into two broad categories: Recent, mobile white dunes, and Tertiary to Late Quaternary, semi-mobile red dunes. The red dune soils are considered arenosols, underlain by dorbank and calcrete hardpans, whereas the white dunes generally lack this structure, unless they are superimposed on an older dune series. The dune landscape is interrupted by outcrops of bedrock, such as river canyons (Holgat River); inselbergs (Buchu Twins); and koppies. Gravel plains and rocky outcrops cover much of the area on the south bank of the Orange River, as far south as Cape Voltas. The low rainfall.
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    The vegetation and restoration potential of the arid coastal belt between Port Nolloth and Alexander Bay, Namaqualand, South Africa
    (1996) Desmet, Philip George; Cowling, Richard M; Richardson, Dave
    This thesis introduces the environment and the vegetation of the Namaqualand coastal belt between Port Nolloth and Alexander Bay. Aspects of the abiotic environment are discussed and related to patterns and processes observed in the vegetation of the study area. The restoration of the natural vegetation impacted by diamond mining activities is discussed. 1-4 The study area, located within the winter rainfall area of the Namib Desert, is one of four global fog deserts. The area is characterised by a near ubiquitous covering of Recent to Tertiary amorphous dunes of marine origin. The dunes can be divided into two broad categories: Recent, mobile white dunes, and Tertiary to Late Quaternary, semi-mobile red dunes. The red dune soils are considered arenosols, underlain by dorbank and calcrete hardpans, whereas the white dunes generally lack this structure, unless they are superimposed on an older dune series. The dune landscape is interrupted by outcrops of bedrock, such as river canyons (Holgat River); inselbergs (Buchu Twins); and koppies. Gravel plains and rocky outcrops cover much of the area on the south bank of the Orange River, as far south as Cape Voltas. The low rainfall ( <70 mm) is offset by frequent fog and dew. Summers are dominated by high energy, southerly winds and winters by gentle land-sea breezes interrupted by occasional, warm-easterly "berg" winds. A complete bio-inventory of higher plants of the study area was undertaken. Patterns of diversity and endemism were analysed in relation to plant growth form and habitat. 300 plant species were collected in the study area representing 40 families, with 28 being endemic to the coastal region. The flora is dominated by the Asteraceae (53 species), Mesembryanthemaceae (47), Crassulaceae (28), Poaceae (17) and Aizoaceae (15). Endemic species are over-represented in the Mesembryanthemaceae (60 endemic) and Crassulaceae (44), and under represented in the Asteraceae (8), Poaceae (0) and Aizoaceae (0). Rocky outcrops have the highest species:area ratio (3.77). They are characterised by their own distinct flora as well as representing a significant proportion ( 46) of the species from the surrounding dune landscape. Endemic species are concentrated on these, as well as on the gravel plain habitats. Dune habitats are the most widespread. However, they are characterised by a widespread, generalist flora with low species:area ratio (0.81), few endemics, and share an expected number of species with other habitat types (21 ). An endemic species in the southern Namib can be characterised as being a dwarf leaf succulent in the Mesembryanthemaceae which is most likely to be encountered on a rocky outcrop.