A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2015. / Mountains are one of the most important and yet environmentally sensitive
habitats in the world, they act as reservoirs of species, and have frequently served as
refugia for organisms during periods of climate change and provided subsequent sources
for speciation. As temperatures increase due to global climate change, species are shifting
to higher altitudes to escape the effects of warming at lower altitudes. The spatial
distribution and diversity of alpine vegetation is strongly influenced by environmental
factors such as snow cover, solar radiation, soil moisture, humidity, and air/ground
temperature. Snow cover is one of the most important factors controlling ground level
microclimate and alpine plant growth. My study was undertaken near Kotisephola Pass at
ca. 3300 m.a.s.l. in eastern Lesotho. Three zones were identified namely, upper, middle
and lower zones at the site, as a result of vegetation differences that were observed along
a 30 m transect from the rock scarp to the tussock grasses. The environmental variables
of temperature, soil moisture, solar radiation, snow depth and humidity were measured
over a period of 17 months using i-Buttons, Hobo and Tinytag data loggers, probes, solar
radiation and temperature data loggers. Vegetation sampling was undertaken to determine
aerial cover, and species composition, richness and diversity during the summer growing
season of January and February 2013. The study site portrays strong fine-scale botanical
micro-zonation owing to ground level microclimatic differentiation as a consequence of
topographic (i.e rock scarp) shading and snow capture. Temperatures were >5 °C warmer
in the upper zone from July – September 2012 due to the deep (1 m) snow cover which
lasted for two months longer than in the middle zone, and only lasted for 36 hours in the
lower zone. Accordingly, the upper zone had the lowest solar radiation throughout the
data collection period due to the continuous snow cover and shading from the rock scarp.
Three botanical zones were identified as characterised by different Helichrysum species.
The upper zone (21 species) was more species rich than the the middle (19) and lower
(18) zones. The vegetation is dominated by grasses which cover >35% of the study site,
whilst herbs and shrubs cover only ca. 6% with an average of 12.3% bare ground. The
strong zonation in plant species composition is a response to the fine spatial-scale
changes in the environment, resulting from snow cover acting in ameliorating the harsh
iii
alpine conditions in winter. More detailed research on a larger scale is still required to
fully comprehend phenology and morphology of the plants at the study region.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/19332 |
| Date | January 2016 |
| Creators | Cingo, Pumeza |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
Page generated in 0.0019 seconds