ECOLOGY

Adaptations | Water Stress | Dispersal | Recruitment | Fire | Communities

Fire response

The responses of Acacia plants to fire depends not only on the species but, of course, on the fire intensisty and frequency, and age of the plant and the season. Generally, however, species response vary from those which are killed outright (such as Acacia dealbata, A. falcata and A. suaveolens) and rely on re-establishment from soil seed bank, the obligate seeders, to the resprouters or vegetative regenerators - those which have their aerial parts killed (such as A. doratoxylon and A. implexa) and then re-establish by shooting from the roots. In either case, plants may regenerate quickly, often producing a dense fire-induced even-aged stand. Many acacias will also shoot from mechanically damaged surface roots.

Fire can also be a factor which leads to speciation. Firstly, local extinctions following a fire can fragment a population and prevent interbreeding and gene flow between the newly formed disjunct populations. Without the sharing of genetic material small environmental and biological differences acting on the genetic makeup of a disjunct population may provide, over time, sufficient selective pressure to allow new adaptive traits to develop. Speciation occurs when sufficietnt divergence eventually eliminates the natural ability of the members of the disjunct populations to interbreed.

Obligate seeders can be eliminated from a site if fires are too frequent or if there is a very long interval between fires (eg. see Auld (1987) - study on A. suaveolens).

Adaptations | Water Stress | Dispersal | Recruitment | Fire | Communities |