Urbanisation is an ever-growing global phenomenon which creates altered environments characterised
by increased human habitation, exotic species, impermeable surfaces, artificial structures, landscape
fragmentation, habitat loss, and modified energy– and resource pathways. The vulnerable Rand
Highveld Grassland vegetation unit in the Tlokwe Municipal area, South Africa, has been extensively
degraded and transformed by urbanisation and agriculture. Only 1% of this endangered ecosystem is
currently being actively conserved. Grassland fragments in urban areas are considered to be less
species rich and less functional than their more “natural” counterparts, and are therefore not a priority
for conservation.
In this study the effects of landscape matrix quality on intra patch variables, namely plant species
diversity and functional diversity, and fine-scale biogeochemical landscape function (as determined
by Landscape Function Analysis or LFA) of 30 fragments of the Rand Highveld Grassland vegetation
unit were explored. Four urbanisation measures (percentage urban land cover, percentage grass land
cover, edge density, and density of people), acting as indicators for patterns and processes associated
with urban areas, were calculated for matrix areas with a 500m radius surrounding each selected
grassland fragment to quantify the position of each grassland remnant along an urban-to-rural
gradient. Using the specific urbanisation measures, the grassland fragments were objectively
classified into two classes of urbanisation, namely “rural/peri-urban” and “urban”, to allow for
statistical comparisons between intra-patch variables for grassland remnants exposed to similar
urbanisation pressures. Plant species composition and diversity were determined in the selected
grassland fragments and nine functional traits were described for each species. Plant functional
diversity was determined by five functional diversity indices, namely functional richness, evenness,
divergence, dispersion, and specialisation. Fine-scale biogeochemical landscape function was
determined by executing the LFA method. LFA assesses fine-scale landscape patchiness and 11 soil
surface indicators to produce three main LFA parameters (stability, infiltration, and nutrient cycling),
which indicates how well a system is functioning in terms of resource conservation and soil processes.
Possible relationships between fine-scale biogeochemical landscape function and plant species- and
functional diversity were also investigated. NMDS ordinations and basic statistics were used to
determine trends and effects within the data.
The results indicated that urban grassland remnants had lower mean plant species richness, Shannon
species diversity (significantly), and Pielou species evenness than rural/peri-urban grassland
fragments. Urban grassland fragments also contained significantly higher percentage of exotic
species. Correlations were found between the four urbanisation measures and percentage species of
the total species richness possessing certain functional attributes. This indicated that increased urbanisation may influence the species composition and the occurrence of certain plant traits in the
selected grassland fragments.
Urbanisation seems to have no effect on fine-scale landscape heterogeneity of the selected grassland
fragments. Rural/peri-urban grassland fragments had higher infiltration capacity, nutrient cycling
potential, and total SSA functionality (although not significantly), which may be ascribed to
differences in management practices, such as mowing in urban areas and grazing in rural areas.
Rand Highveld Grassland fragments in the urban landscape matrix of Potchefstroom city are just as
conservable in terms of plant species diversity and functional diversity, as well as on a biophysical
function level involving soil processes than rural/peri-urban grassland fragments. High plant species
diversity and the presence of certain plant traits did not contribute to high soil surface stability,
infiltration capacity, nutrient cycling potential and total soil surface functioning. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2013
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/9732 |
| Date | January 2013 |
| Creators | Van der Walt, Luanita |
| Publisher | North-West University |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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