A model-framed evaluation of elephant effects on tree and fire dynamics in African savannas

Baxter, P. W. J. and Getz, W. M. (2005) A model-framed evaluation of elephant effects on tree and fire dynamics in African savannas. Ecological Applications, 15 4: 1331-1341. doi:10.1890/02-5382

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Author Baxter, P. W. J.
Getz, W. M.
Title A model-framed evaluation of elephant effects on tree and fire dynamics in African savannas
Journal name Ecological Applications   Check publisher's open access policy
ISSN 1051-0761
Publication date 2005
Sub-type Article (original research)
DOI 10.1890/02-5382
Open Access Status File (Publisher version)
Volume 15
Issue 4
Start page 1331
End page 1341
Total pages 11
Place of publication Washington, DC, United States
Publisher Ecological Society of America
Language eng
Abstract There is a concern that high densities of elephants in southern Africa could lead to the overall reduction of other forms of biodiversity. We present a grid-based model of elephant-savanna dynamics, which differs from previous elephant-vegetation models by accounting for woody plant demographics, tree-grass interactions, stochastic environmental variables (fire and rainfall), and spatial contagion of fire and tree recruitment. The model projects changes in height structure and spatial pattern of trees over periods of centuries. The vegetation component of the model produces long-term tree-grass coexistence, and the emergent fire frequencies match those reported for southern African savannas. Including elephants in the savanna model had the expected effect of reducing woody plant cover, mainly via increased adult tree mortality, although at an elephant density of 1.0 elephant/km(2), woody plants still persisted for over a century. We tested three different scenarios in addition to our default assumptions. (1) Reducing mortality of adult trees after elephant use, mimicking a more browsing-tolerant tree species, mitigated the detrimental effect of elephants on the woody population. (2) Coupling germination success (increased seedling recruitment) to elephant browsing further increased tree persistence, and (3) a faster growing woody component allowed some woody plant persistence for at least a century at a density of 3 elephants/km(2). Quantitative models of the kind presented here provide a valuable tool for exploring the consequences of management decisions involving the manipulation of elephant population densities.
Keyword Ecology
African savanna
Loxodonta africana
plant demography
spatial model
tree-grass coexistence
woody plants
Wildlife Research Area
Northern Botswana
Luangwa Valley
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
Spatial Ecology Lab Publications
School of Biological Sciences Publications
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Created: Fri, 25 Jan 2008, 16:37:08 EST