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Defences and responses

woody species and large herbivores in african savannas

Rooke, Tuulikki (2003). Defences and responses. Diss. (sammanfattning/summary) Umeå : Sveriges lantbruksuniv., Acta Universitatis agriculturae Sueciae. Silvestria, 1401-6230 ; 276
ISBN 91-576-6510-9
[Doctoral thesis]

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Abstract

Plant-herbivore interactions influence both plant characteristics and feeding patterns of herbivores. In this thesis, I focus on patterns of defence in a wide range of woody species in semi-arid savannas in Botswana, and on responses in woody species to different types of browsing. Methods included both surveys of plant traits relevant to herbivory, and controlled experiments using simulated browsing. On a regional scale gradient, the proportion of spinescent and evergreen species decreased, while fast-growing species increased, with increasing resource availability. On smaller landscape scale gradients, the proportion of spinescent and evergreen species increased, fast-growing species either increased or decreased, while C-based defences generally decreased and nutrients increased, with increasing resource availability. In some species, levels of defence (phenolics) were higher in young trees, compared to mature trees. However, contrary to our predictions, shoots within, compared to above, browsing height on mature trees were less defended (phenolics and tannins). Simulated twig-biting during the dry season (on five species) induced compensatory growth responses in annual shoots during the growth season, and cutting at ground level induced sprouting. Leaf removal late in the growth season (on one species) induced foliage re-growth, although total leaf production during the season did not increase. The application of saliva had a small, but significant, effect on shoot growth following clipping. No evidence was found for a connection between patterns in allocation to defensive traits in shoots of different exposure to browsers, or strength of responses to clipping, and other species characteristics, e.g. leaf fall patterns, growth rate, presence of spines or natural browsing pressure. I suggest further studies focusing on both chemical and structural defences, on different spatial scales and resource gradients. I also conclude that additional studies are needed on potential effects of different traits on different types of herbivores, and stress the advantage of studying a wider range of plant species to obtain more general results.

Authors/Creators:Rooke, Tuulikki
Title:Defences and responses
Subtitle:woody species and large herbivores in african savannas
Year of publishing :May 2003
Volume:276
Number of Pages:34
Papers/manuscripts:
NumberReferences
ALLI. Skarpe, C., Rooke, T., Bergström, R., Danell, K., Marokane, W. and Ramotadima, M. Herbivore-related traits of woody plants along resource gradients in southern Africa. (Manuscript). II. Rooke, T., Danell, K., Bergström, R., Skarpe, C. and Hjältén, J. Defensive traits of savanna trees: the role of shoot exposure to browsers. (Submitted manuscript). III. Rooke, T., Bergström, R., Skarpe, C. and Danell, K. Morphological responses of woody species to simulated twig-browsing in Botswana. (Accepted for publication in Journal of Tropical Ecology). IV. Rooke, T. and Bergström, R. Growth, chemical responses and herbivory after simulated leaf browsing in Combretum apiculatum. (Manuscript). V. Rooke, T. Growth responses of a woody species to clipping and goat saliva. (Accepted for publication in African Journal of Ecology).
Place of Publication:Umeå
ISBN for printed version:91-576-6510-9
ISSN:1401-6230
Language:English
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:L Animal production > L20 Animal ecology
F Plant production > F40 Plant ecology
Subjects:Not in use, please see Agris categories
Agrovoc terms:herbivores, savannas, browsing, feed resources, growth, defence mechanisms, woody plants, phenolic compounds, tannins, thorns, ungulates, botswana
Keywords:Botswana, growth responses, herbivory, nitrogen, phenolics, resource availability, spines, tannins, ungulates, woody species
URN:NBN:urn:nbn:se:slu:epsilon-40
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-40
ID Code:268
Department:(S) > Institutionen för skoglig zooekologi
Deposited By: Tuulikki Rooke
Deposited On:05 May 2003 00:00
Metadata Last Modified:02 Dec 2014 10:03

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