AGE STRUCTURE OF PLANT POPULATIONS

 Herbivores can influence the age structure of populations of their plant food species. For example, some herbivores feed on young specimens of a particular plant. If the herbivore is abundant, then the plant population may be dominated by older individuals that have escaped being eaten, perhaps only by chance, and so have grown to a size too large for the herbivore to kill. I have seen a good example of this in the Zambezi Valley, Zimbabwe, where there are large stands of apple-ring acacia (Acacia albida). In weeks of walking about in the Acacia woodland I only saw a handful of young Acacia saplings; the population is dominated by large, old trees. However, Acacia seedlings were seen inside an electrified herbivore exclosure set up by Kevin Dunham, ecologist at Mana Pools National Park. This shows that the dominance of the Acacia woodland by older trees was probably due to herbivory on the younger plants.

The dominance of Acacia woodland in the Zambezi Valley of Zimbabwe by older trees is probably due to herbivory on the younger plants.