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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Grazer response to fire in an African savanna: exploring the role of fires in grazing lawn formation

Pollard, Adrian Drew January 2016 (has links)
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

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