Succession is the change in a community over time due to abiotic and biotic factors.
A pioneering species is the first species to collonise a land.
They must be able to live in harsh conditions so they must be able to photosynthesise as food is scarce so they can make their own food. They must be nitrogen fixing as nutrients are limited. They must be able to rapidly germinate as they don't require a period of dormancy.
How does succession happen?
Once the pioneering species are dead, their body provides nutrients for microorganisms to eat and they decay. the decay releases nutrients into the soil allowing other plant species to start to germinate and so a new plant species is created. once these plants die, more nutrients are in the soil and so other plant species can form, the plants provide food for insects and birds so new animal species emerge and so on.
During succession the environment will become less hostile, along with more habitats and complex food webs are created. There is an increase in biomass.
A climax community is a community that has animals and plants living together. In a climax community there is often a dominant species and which species is dominant depends on the climate and other abiotic conditions.
Another type of Succession...
When there are forest fires or farms, this often results in a land clearance. However, it is a rapid succession as there are still seedlings in the soil and there is a migration of animals from other communities allowing the cleared area to regain a climax community. However, this climax community will be different.
How can natural succession occur?
Natural succession can be caused by many things such as glaciers, volcanic eruptions leaving the lava to cool and dry to provide a pioneering species with land to grow. Sand dunes brought in from the sea or wind. Lakes and ponds can cause land to subside.
Burning and grazing of sheep and heather can stop tree saplings growing preventing woodland growing which prevents the series of successional changes. This allows ecosystems to reach a climax community natually.