Ecosystems Change with Time

Succession = natural sequence of events where one community replaces the old community over time until a climax community is achieved.

Climax community = stable community that's in equilibrium with the existing environment.

Two types of succession:

Primary = series of community changes of an entirely new habitat which has never been cononised before. Eg. a newly quarried rock face

Secondary = series of community changes in a habitat that has been previously colonised but was disturbed. Eg. an area of trees burnt down by a fire.

The area is initially colonised by a pioneer community which is replaced over time by other organisms.

Orderly sequence of events - at each stage species can be recognised which are changing the environment to make it more suitable for other species.

The biomass that accumalates can increase the number of ecological niches available, and can increase the depth and nutrient content of the soil.

The process continues until a climax community is formed.

Sequence of events:

blue-green bacteria --> lichens, liverworts --decays--> mosses -->

herbs, grasses, small flowering plants --> ferns, bracken, small

shrubs, brambles --> large shrubs, small trees --> larger trees -->

oak, ash

abc = pioneer species abc = early coloniser species abc = late coloniser species  abc = climax community