A dissertation submitted in fulfilment of the academic requirements for the degree of
Masters of Environmental Science, School of Animal Plant and Environmental Sciences. University of the Witwatersrand. October 2016. / Fire and grazing are important drivers of grassland composition and function in
savanna ecosystems. Fire alters the forage quality and vegetation structure, so
changing fire regimes also changes grazer utilisation of the landscape. This study
aimed to investigate how different fire regimes, specifically changes in fire size and
season of burn, influence grazer attraction as well as grazing intensity and duration
in the short-term, and further to determine how long-term fire-grazing interactions
may influence the development of grazing lawns. In the short-term experiment, fires
of three different sizes were applied in both the early dry season (EDS) and late dry
season (LDS), and periodic collection of grass height and dung count data was
conducted over a full year. Results showed that grazers were immediately attracted
to the burned areas after the fires, and that fire and grazing together can maintain a
short grazed patch for a full season. The greatest grazer visitation and grazing
pressure (shortest grass) was observed on the intermediately sized burns (5ha).
Furthermore, EDS treatments exhibited less initial grazer visitation but grass was
kept in a short state for longer than on LDS burns. LDS burns had more intense
grazing but over a much shorter time. For the long-term experiment, a long-standing
fire experiment (Experimental Burn Plots, Kruger National Park, South Africa) was
used to investigate change in grass community composition as influenced by firegrazing
interactions over a 60 year period. Historical data were used, and grass
composition data were also collected on three treatments that allowed for
comparison of communities that experienced grazing and fires repeated at different
fire frequencies and different seasons (April biennial and August annual burns), as
well as a natural fire regime (control). By investigating the change in abundance in a
few key grass species, grass ecological status classes, and grass functional guilds,
results found that grasses associated with grazing lawns (stoloniferous, ‘disturbed’)
increased in abundance, while grasses of bunch grass communities decreased, and
that this change was more pronounced on April biennial burns. The results of this
study show that small fires can act as a catalyst for grass community compositional
and structural change by attracting grazers.
Key words: Grazing lawns, fire size, fire season, pyric-herbivory, savanna. / TG2016
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/21699 |
| Date | January 2016 |
| Creators | Pollard, Adrian Drew |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | Online resource (120 leaves), application/pdf |
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