The feedback effects of canopy architecture : why are African acacias flat-topped?

dc.contributor.advisorMidgley, Jeremy Jen_ZA
dc.contributor.authorMcLean, Philen_ZA
dc.date.accessioned2017-10-11T10:52:32Z
dc.date.available2017-10-11T10:52:32Z
dc.date.issued1999en_ZA
dc.date.updated2017-02-08T08:01:51Z
dc.description.abstractOnly the African acacias have a so-called flat topped crown. This study identifies this architecture using the simple measures of height, diameter and spread. In this way the flat-topped species are identified and differentiated from the other acacia species (A. nilotica & A. tortilis). It has been suggested that this shape is an anti-herbivore mechanism. We demonstrate how these trees spend a lot of energy in defence, which indicates that the canopy shape is a poor anti-herbivore device. Measurements of the height of grass outside the canopies indicate that these species inhabit areas of long grass. At the same time, our data show that at least one of these species (A. nilotica) is extremely fire sensitive (60% mortality). The effect which saves these trees from fire is shorter grass beneath their crowns providing a low-fuel fire buffer for the trunk. However, none of the conventional effects of canopy are able to cause this effect (shade, nutrients). We propose that the shade and nutrient-rich undercanopy grass (as well as the pods of these animal-dispersed trees) encourages large grazing mammals to spend time under these trees. These animals then, are responsible for lowering the height of the grass cover by grazing and trampling, and hence save the trees from fire. We suggest an animal - flat-topped tree mutualism where food and shade are exchanged for seed dispersal and fire protection.en_ZA
dc.identifier.apacitationMcLean, P. (1999). <i>The feedback effects of canopy architecture : why are African acacias flat-topped?</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Biological Sciences. Retrieved from http://hdl.handle.net/11427/25571en_ZA
dc.identifier.chicagocitationMcLean, Phil. <i>"The feedback effects of canopy architecture : why are African acacias flat-topped?."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 1999. http://hdl.handle.net/11427/25571en_ZA
dc.identifier.citationMcLean, P. 1999. The feedback effects of canopy architecture : why are African acacias flat-topped?. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - McLean, Phil AB - Only the African acacias have a so-called flat topped crown. This study identifies this architecture using the simple measures of height, diameter and spread. In this way the flat-topped species are identified and differentiated from the other acacia species (A. nilotica &amp; A. tortilis). It has been suggested that this shape is an anti-herbivore mechanism. We demonstrate how these trees spend a lot of energy in defence, which indicates that the canopy shape is a poor anti-herbivore device. Measurements of the height of grass outside the canopies indicate that these species inhabit areas of long grass. At the same time, our data show that at least one of these species (A. nilotica) is extremely fire sensitive (60% mortality). The effect which saves these trees from fire is shorter grass beneath their crowns providing a low-fuel fire buffer for the trunk. However, none of the conventional effects of canopy are able to cause this effect (shade, nutrients). We propose that the shade and nutrient-rich undercanopy grass (as well as the pods of these animal-dispersed trees) encourages large grazing mammals to spend time under these trees. These animals then, are responsible for lowering the height of the grass cover by grazing and trampling, and hence save the trees from fire. We suggest an animal - flat-topped tree mutualism where food and shade are exchanged for seed dispersal and fire protection. DA - 1999 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1999 T1 - The feedback effects of canopy architecture : why are African acacias flat-topped? TI - The feedback effects of canopy architecture : why are African acacias flat-topped? UR - http://hdl.handle.net/11427/25571 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/25571
dc.identifier.vancouvercitationMcLean P. The feedback effects of canopy architecture : why are African acacias flat-topped?. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 1999 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/25571en_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.titleThe feedback effects of canopy architecture : why are African acacias flat-topped?en_ZA
dc.typeBachelor Thesis
dc.type.qualificationlevelHonours
dc.type.qualificationnameBSc (Hons)en_ZA
uct.type.filetype
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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