Exploring the potential impacts of global change on the woody component of of South African savannas

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dc.contributor.advisorBond, William Jen_ZA
dc.contributor.advisorArchibald, Sallyen_ZA
dc.contributor.advisorErasmus, B F Nen_ZA
dc.contributor.authorStevens, Nicolaen_ZA
dc.date.accessioned2015-05-11T13:33:50Z
dc.date.available2015-05-11T13:33:50Z
dc.date.issued2014en_ZA
dc.descriptionIncludes bibliographical referencesen_ZA
dc.description.abstractLand cover change, elevated CO2 and associated climate change are driving changes in ecosystem structure and function across the world. These changes are best described and understood in northern hemisphere temperate systems. Studies, models and reports from these regions are therefore often used as the basis for understanding, predicting and managing change in other biomes, including African savannas. In savannas elevated CO2 has been implicated in driving an increase in woody cover, however attribution to global drivers is often confounded by land - use management which is also implicated as a driver of tree cover increases. Climate change is predicted to directly drive species range shifts in savannas, however several important gaps exist in the literature which prevent the development of a clear predictive framework to describe these changes. Whilst climate is often assumed to be the primary factor underlying savanna tree distribution this has not been demonstrated for savanna tree species. Additionally the determinants of individual savanna species distributions have seldom been investigated. The few existing studies are correlative species distribution models based on adult plant distribution and underlain by the assumption that climate sets plant distribution. Although a demographic approach is very important in understanding tree: grass coexistence in savannas, this approach is seldom used in understanding species distributions. The aim of this study was therefore to assess how global change might influence South African savannas. We place emphasis on the role of elevated CO2 and climate change. I first report on an analysis of historical changes in woody plant abundance at large spatial scales to assess the magnitude of tree cover change in South African savannas. I attempt to untangle the role of local drivers and global drivers in causing tree cover changes from 1940-2009. I then report on studies aimed at determining what limits the distribution range of two common savanna trees Acacia nigrescens and Colophospermum mopane, at three critical demographic stages. Here I used a series of field studies, transplant experiments, lab experiments and modelling to determine the critical drivers of the distribution of these plants so as to understand how savanna plants might respond to changing climates.en_ZA
dc.identifier.apacitationStevens, N. (2014). <i>Exploring the potential impacts of global change on the woody component of of South African savannas</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Biological Sciences. Retrieved from http://hdl.handle.net/11427/12771en_ZA
dc.identifier.chicagocitationStevens, Nicola. <i>"Exploring the potential impacts of global change on the woody component of of South African savannas."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2014. http://hdl.handle.net/11427/12771en_ZA
dc.identifier.citationStevens, N. 2014. Exploring the potential impacts of global change on the woody component of of South African savannas. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Stevens, Nicola AB - Land cover change, elevated CO2 and associated climate change are driving changes in ecosystem structure and function across the world. These changes are best described and understood in northern hemisphere temperate systems. Studies, models and reports from these regions are therefore often used as the basis for understanding, predicting and managing change in other biomes, including African savannas. In savannas elevated CO2 has been implicated in driving an increase in woody cover, however attribution to global drivers is often confounded by land - use management which is also implicated as a driver of tree cover increases. Climate change is predicted to directly drive species range shifts in savannas, however several important gaps exist in the literature which prevent the development of a clear predictive framework to describe these changes. Whilst climate is often assumed to be the primary factor underlying savanna tree distribution this has not been demonstrated for savanna tree species. Additionally the determinants of individual savanna species distributions have seldom been investigated. The few existing studies are correlative species distribution models based on adult plant distribution and underlain by the assumption that climate sets plant distribution. Although a demographic approach is very important in understanding tree: grass coexistence in savannas, this approach is seldom used in understanding species distributions. The aim of this study was therefore to assess how global change might influence South African savannas. We place emphasis on the role of elevated CO2 and climate change. I first report on an analysis of historical changes in woody plant abundance at large spatial scales to assess the magnitude of tree cover change in South African savannas. I attempt to untangle the role of local drivers and global drivers in causing tree cover changes from 1940-2009. I then report on studies aimed at determining what limits the distribution range of two common savanna trees Acacia nigrescens and Colophospermum mopane, at three critical demographic stages. Here I used a series of field studies, transplant experiments, lab experiments and modelling to determine the critical drivers of the distribution of these plants so as to understand how savanna plants might respond to changing climates. DA - 2014 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2014 T1 - Exploring the potential impacts of global change on the woody component of of South African savannas TI - Exploring the potential impacts of global change on the woody component of of South African savannas UR - http://hdl.handle.net/11427/12771 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/12771
dc.identifier.vancouvercitationStevens N. Exploring the potential impacts of global change on the woody component of of South African savannas. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2014 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/12771en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Biological Sciencesen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherBotanyen_ZA
dc.titleExploring the potential impacts of global change on the woody component of of South African savannasen_ZA
dc.typeDoctoral Thesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnamePhDen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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