Ecological Succession
Ecological Succession is a unidirectional, gradual change in vegetation, soil or animal community with ecological time. Succession may be initiated either by formation of new, unoccupied habitat (e.g., a lava flow or a severe landslide) or by some form of disturbance of an existing community (e.g. fire, severe wind throws, logging).
Types of Ecological Succession
Primary Succession
Primary Succession begins on an area that has not been occupied by a community. It occurs on bare, lifeless substrate, such as rocks, or in open water, where organism gradually move in and change it nature. Pioneer or opportunistic organisms are the first organisms to occupy newly exposed area such as rock or an area which has been disturbed by a disruption. Typical pioneers in a succession include lichens on rocks or grasses in a ploughed field. Pioneer organisms modify the environment and create conditions which are favorable for more advanced organisms to colonize.
On bare (mineral-poor soil) lichens grow first forming small pockets of soil. Acidic secretion from the lichens breaks down the substrate. Mosses then colonize these soil particles and build up enough nutrients for shrubs to take hold.
Secondary Succession
Secondary Succession begins on an area where a community has previously existed but has been destroyed by natural disaster such as fire, floods or destruction by human. Secondary succession has a higher level of production of biological material at a faster rate than primary succession. When natural disaster occurs, the damaged ecosystem is likely to recover in a series of successional stages that eventually result in a stable system similar to the original one that occupied the area.
Succession ends in a stabilized community and ecosystem called the ecological climax.
The tendency for an ecosystem to reach a stage where it stays in equilibrium (stable) is an example of Homeostasis. The climax community last for hundreds or thousands of years unless again disrupted.
