Ecological Succession
Uploaded by ihatesuchin on Jul 05, 2004
Succession is "A sequence of ecological changes in an area whereby one group of plant or animal species successively gives way to another, culminating in a climax community." This succession occurs in a number of sereal stages. A sere is a stage in a sequence of events by which succession occurs. The complete chain of seres is called a prisere. It begins with a pioneer community and ends with a climax community. This climax community occurs when the ultimate vegetation has become in equilibrium with the local environment.
There are four main areas where succession occurs rocky environment called a lithosere, sandy environment called a psammosere, a fresh water environment called a hydrosere and a salt-water environment called a halosere.
Two examples of a litosere are Sutsey a newly, formed volcanic island and Krakatoa an island striped of all its vegetation by a series of volcanic eruptions. Sutsey is located to the south east of Iceland and is slowly becoming colonised. The first colonisers of the bare rock on a lithosere environment are blue-green bacteria and single cell photosynthesisers, both of which have no need of a root system. Blue-green bacteria are autotrophs producing their own food through photosynthesis. The presence of blue-green bacteria along with weathering processes help to break up soil creating a very thin soil layer. More advanced plant life can then be supported in this thin soil. Once this plant life dies it rots down to create a humus layer to the soil. This humus layer is then capable of supporting grass seeds. As time progresses the grass species will give way to more dominant species such as small shrubs which in turn will replaced by relatively fast growing trees such as rowan. Eventually these trees will face competition from slow growing trees such as ash and oak. Sutsey however is unlikely to ever reach this climax community due to its frequent salty spray, storms and low temperatures for much of the year. Krakatoa however has reached its climax community with eight hundred different species being recorded in 1983 one hundred years after the clearance of the island.
Psammoseres occur in a sandy environment. An example of this is Camber Sands, which has developed over time from a small beach to a complete dune system. The pioneer community in a psammosere is usually lyme grass, sea twitch and marram grass that begin to initiate dune development. These plants hold...