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Coping with herbivory at the juvenile stage: responses to defoliation and stem browsing in the African savanna tree Colophospermum mopane

Published online by Cambridge University Press:  13 February 2012

David C. Hartnett*
Affiliation:
Division of Biology, Kansas State University, 104 Ackert Hall, Manhattan, KS 66506USA
Jacqueline P. Ott
Affiliation:
Division of Biology, Kansas State University, 104 Ackert Hall, Manhattan, KS 66506USA
Kathryn Sebes
Affiliation:
Division of Biology, Kansas State University, 104 Ackert Hall, Manhattan, KS 66506USA
Marks K. Ditlhogo
Affiliation:
Department of Biological Sciences, University of Botswana, Private Bag UB0022, Gaborone, Botswana
*
1Corresponding author. Email: dchart@ksu.edu

Abstract:

Responses of plants to herbivory are dependent on the type of damage and the ontogenetic stage of the plant. We compared the effects of stem pruning and defoliation on seedlings of Colophospermum mopane, an ecologically important tree species widely distributed in southern Africa. The growth of 160 greenhouse-grown juveniles were measured for 6-mo after germination and then 6-mo after treatments including 50% defoliation, 100% defoliation, 50% stem pruning and controls. Pruning resulted in 30% reductions in total leaf area, height and biomass. Partial defoliation resulted in 30% reductions in total leaf area and plant biomass. However, complete defoliation resulted in a 30% increase in biomass production, a doubling in leaf and lateral branch number, a 45% reduction in leaf size, and no change in total leaf area. Thus, completely defoliated seedlings showed greater performance than those that were only partially defoliated, indicating that C. mopane has become adapted to the chronic and severe defoliation inflicted by Imbrasia belina caterpillars. Comparison of our results with other studies indicates that C. mopane seedlings are less herbivory-tolerant than adults and that pruning has more negative effects than defoliation. Thus, seedling browsers may constrain recruitment in C. mopane, influencing its population dynamics and abundance.

Type
Research Article
Copyright
Copyright © Cambridge University Press 2012

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