The gradual, sequential and predictable changes in the species composition of an given area are called ecological succession. During the succession some species adopts and colonise an area and their population becomes more numerous whereas the population of other species declines and gradually disappears from that area.
The entire sequence of communities that successfully and successively changes in a given area is called sere. The species that invades a bare area and starts the ecological succession are called pioneer species. The ecological changes leads finally to a community that is in equilibrium with the existing environment and this is called climax community. It is the most stable stage. All the existing present day communities in the world have to be because of succession that has accurred over millions of years since life started on the plant Earth. Types of ecological succession:
- Hydrarch succession
- Xerarch succession.
Types of Ecological succession:
Primary succession begins in an area where no previous living organisms are presents. It is a very slow process as it includes soil formation which takes thousands of years for climax to be reached. For example cooled lava, bare rock, newly formed pond etc.
Secondary succession begins in an area where natural biotic communities have been destroyed because of any reason man-made or natural for example abandoned form land, burned or cut forests, it is faster process as soil is already available for succession.
Hydrarch Succession: It occurs in wet area or water, leading to successional series that progress from hydric to the mesic conditions.
In hydrarch succession pioneers are phytoplankton. These phytoplanktons with time are replaced by free floating angiosperms followed by rooted hydrophytes, sedges, grasses and finally the trees, leading to mesic conditions.
Xerarch Succession: It occurs in dry areas and the series progresses from xeric to mesic condition. The climax community remains stable as long as environment remains unchanged. With time, the xerophytes habitat gets converted into mesophytic conditions.
Stages of xerarch succession are:
