Succession

Succession

• Ecological succession is the orderly and predictable change in the species composition of a community over time.

• It involves two main types: Primary succession and Secondary succession.

Primary Succession

• Primary succession begins in lifeless environments, where there’s no soil, like bare rock or a newly cooled lava field.

• The first species to colonise such areas are known as pioneer species. These pioneer species are typically hardy organisms, such as lichens or mosses, that can live in harsh conditions.

• As these pioneer species grow, die, and decompose, they break down the rock and contribute to soil formation, making the environment more hospitable for other species.

• Over time, more complex species like shrubs and trees may take over. These species are more competitive and replace the pioneer species.

• This process continues until a stable community of species, called a climax community, is established. This community remains until a disturbance, such as a fire or hurricane, restarts the succession process.

Secondary Succession

• Secondary succession is the sequence of community changes, similar to primary succession, but it occurs in areas that have been disturbed, but not completely devoid of life (like after a forest fire or the retreat of a glacier).

• Here, some soil and a few species (remnants of the original community) still remain. So, the area may be re-colonised more quickly than in primary succession.

• Eventually, secondary succession also leads to a stable climax community, unless there is another disturbance.

Succession and Biodiversity

• In both types of succession, biodiversity initially increases as new species colonise the habitat.

• However, as dominant species begin to take over, these may out-compete other species leading to a decline in biodiversity until the climax community is established.

• The climax community is the most stable and biodiverse the ecosystem can support.

Influence on Succession

• Succession is influenced by a range of factors, including the type of pioneer species, the rate at which soil is generated, the climate, and human intervention.

• Facilitation, inhibition, and tolerance are three models used to explain how different species interact during succession.

• Facilitation model: early species modify the environment in ways that benefit later species.

• Inhibition model: early species inhibit the establishment of other species.

• Tolerance model: species essentially ignore each other and modify the environment independently.

The specific model that applies depends on the types of species present and the specific conditions of the environment.