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Heavy impact on seedlings by the impala suggests a central role in woodland dynamics

Published online by Cambridge University Press:  12 April 2012

Christopher A. J. O'Kane ,
Kevin J. Duffy ,
Bruce R. Page  and
David W. Macdonald
Christopher A. J. O'Kane*
Affiliation:
Wildlife Conservation Research Unit, Department of Zoology, University of Oxford, The Recanati-Kaplan Centre, Tubney House, Abingdon Road, Tubney, Oxon OX13 5QL, UK Institute of Systems Science, Durban University of Technology, P.O. Box 1334, Durban 4000, South Africa School of Biological and Conservation Sciences, Westville Campus, University of KwaZulu Natal, Private Bag X 54001, Durban 4000, South Africa
Kevin J. Duffy
Affiliation:
Institute of Systems Science, Durban University of Technology, P.O. Box 1334, Durban 4000, South Africa
Bruce R. Page
Affiliation:
School of Biological and Conservation Sciences, Westville Campus, University of KwaZulu Natal, Private Bag X 54001, Durban 4000, South Africa
David W. Macdonald
Affiliation:
Wildlife Conservation Research Unit, Department of Zoology, University of Oxford, The Recanati-Kaplan Centre, Tubney House, Abingdon Road, Tubney, Oxon OX13 5QL, UK
*
1Corresponding author. Email: [email protected]
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Abstract:

Research has increasingly established that mesoherbivores influence the regeneration of woody plants. However the relationship between mesoherbivore density and degree of impact, and the spatial component of this impact, has not been well established. Using a novel sampling design, we assessed in iMfolozi Park, South Africa, the impact of impala (Aepyceros melampus) across the full complement of woody species within the home range, evaluating its spatial component and relationship to impala density. We used four GPS collars, in separate breeding herds, and a GIS to detect zones of different density of impala in the landscape, thus defining a fine-grain browsing gradient. We assessed impact on woody recruits (≤ 0.5 m height) across this gradient by means of 1600 random 1 × 1-m quadrats. Densities of woody seedlings, and mean percentage of remaining canopy, were significantly less in areas of high impala density versus low-density areas. There was a significant correlation between increasing impala density and decreasing density of favoured woody recruits. We propose a hypothesis of impala-induced patch dynamics. It seems likely that the ubiquitous impala may create and sustain a shifting mosaic of patches, and thus function as a key determinant of landscape heterogeneity.

Keywords

Aepyceros melampusbrowserelephantguildskeystonepatch dynamicssavannaseedlingsSouth Africa
Type
Research Article
Information
Journal of Tropical Ecology , Volume 28 , Issue 3 , May 2012 , pp. 291 - 297
Copyright
Copyright © Cambridge University Press 2012

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