Development and Parameterization of a Rain- and Fire-driven Model for Exploring Elephant Effects in African Savannas |
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Authors: | Peter W J Baxter Wayne M Getz |
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Institution: | (1) Department of Environmental Science, Policy and Management, University of California, 201 Wellman Hall, Berkeley, CA 94720-3112, USA;(2) Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria, 0002, South Africa;(3) Present address: The Ecology Centre, School of Integrative Biology, University of Queensland, St. Lucia, Brisbane, Queensland, 4072, Australia |
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Abstract: | We describe the development and parameterization of a grid-based model of African savanna vegetation processes. The model
was developed with the objective of exploring elephant effects on the diversity of savanna species and structure, and in this
formulation concentrates on the relative cover of grass and woody plants, the vertical structure of the woody plant community,
and the distribution of these over space. Grid cells are linked by seed dispersal and fire, and environmental variability
is included in the form of stochastic rainfall and fire events. The model was parameterized from an extensive review of the
African savanna literature; when available, parameter values varied widely. The most plausible set of parameters produced
long-term coexistence between woody plants and grass, with the tree–grass balance being more sensitive to changes in parameters
influencing demographic processes and drought incidence and response, while less sensitive to fire regime. There was considerable
diversity in the woody structure of savanna systems within the range of uncertainty in tree growth rate parameters. Thus,
given the paucity of height growth data regarding woody plant species in southern African savannas, managers of natural areas
should be cognizant of different tree species growth and damage response attributes when considering whether to act on perceived
elephant threats to vegetation. |
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Keywords: | Elephants Herbivory Loxodonta africana Plant demography Spatial modeling Tree– grass coexistence Woody plants |
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