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A synthesis of the demography of African acacias

Published online by Cambridge University Press:  27 November 2001

J. J. MIDGLEY
Affiliation:
Botany Department, University of Cape Town, P Bag Rondebosch, 7700 South Africa
W. J. BOND
Affiliation:
Botany Department, University of Cape Town, P Bag Rondebosch, 7700 South Africa

Abstract

Although acacias are ecologically and economically important, their demography is poorly known. In part this is because few field experiments have been undertaken. Also, a bewildering diversity of factors have been suggested to determine their demography. These factors include disease, fire, large and small browsers and grazers, climatic variation, competition with grass, seed predation and anthropogenic impacts. This synthesis concentrates on the life-history period from seed to adult plant and indicates that important hurdles have been demonstrated for some species in some habitats. Seed and seedling limitation have not been clearly demonstrated, nor has the value of dispersal been quantified. In contrast, the impacts of herbivores and fire in affecting the escape or release of resprouts has been repeatedly demonstrated. Whether fire and herbivory merely slow down the rate of promotion through size-classes or actually prevent it, needs further work. We note that very little comparative work amongst Acacia species has taken place. Most studies have concentrated on single aspects of their life history (especially seed predation), and have not been analysed in relation to population growth. Few field experiments, especially concerning seedling biology, have been performed. We conclude with some suggestions of a framework for interpreting acacia demography.

Type
Research Article
Copyright
2001 Cambridge University Press

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