Plant/Ecological Succession

Plant / Ecological Succession

Plant succession (or ecological succession) is the gradual, directional, and sequential process by which one plant community in a given area is progressively replaced by another over time, ultimately leading to a relatively stable, self-perpetuating community known as the climax community. Succession is not random: it proceeds through a recognisable series of stages, called seral stages, each of which alters the local environment — chiefly by building up soil, organic matter, and shelter — in ways that make it possible for the next, usually more complex, community to establish itself.

Succession is broadly divided into two types depending on the starting condition of the site.

Primary succession begins on a bare, essentially lifeless substratum that has never previously supported vegetation and that has no soil to begin with — for example, bare exposed rock, or a newly formed pond. Because there is no soil, no seed bank, and no organic matter already present, primary succession must start completely from scratch: soil itself has to be built up, grain by grain, before more demanding plants can even take root. This makes primary succession a slow process, often taking a very long time to reach a climax community.

Secondary succession, by contrast, occurs on a site that already carried a plant community and already has soil in place, but where the existing vegetation has been removed or disturbed by some event — such as fire, deforestation, or the abandonment of farmland. Since soil, at least some organic matter, and often a bank of dormant seeds or root fragments are already present at the outset, secondary succession does not need to repeat the slow, soil-building early stages that primary succession requires. This is precisely why the climax stage is reached much more quickly in secondary succession than in primary succession — secondary succession is, in effect, rebuilding a community on a foundation that primary succession would otherwise have had to create from nothing. …