Succession is a change in the structure and species composition of a community. It occurs due to changes caused by the presence of established organisms or by external influences.
The changes that result when the starting point is bare, uncolonised land are called primary succession. This occurs in:
- sand dunes
- lava and ash from volcanoes
- land and lakes left by retreating glaciers
The first colonisers on bare rock are lichens and mosses. Their presence allows some soil to build up, allowing ferns and flowering plants to appear. When the bare ground is particulate, colonisation is faster because vascular plants can take root without lichen and moss stage. Eventually the soil becomes deep enough to support shrubs and then trees. In Europe, woodland is the endpoint of succession on land…