Ecological Succession - Botany

  Environment plays an important role in the development of communities because the change in environment is a continuous process so due to these changes it is difficult for a community to maintain itself. The process of changes in biotic communities on bare area from birth to maturity is called ecological succession.

       Term "Succession" first of all used by Hult in 1985. There are two main types of succession.

1. Primary Succession.
2. Secondary Succession.

Primary Succession: Succession beginning in primary areas that developed due to landslides, erosion, and newly form sand dunes is called primary succession. The initially establishing plants in such area are called as pioneers or primary community.

Secondary Succession: The type succession occurs on those which were previously occupied by living things but were destroyed by fire or any other climatic or biotic changes. The rate change is more rapid and the time required for completion of sere is much shorter than in primary succession. On the basis of habitat primary and secondary succession are further divided into three types, i.e. Hydro sere, Mesosere and Xerosere.

     (a) Hydro sere: Primary succession in pond, lake, marsh or a stream are together known as Hydro sere. Succession actually occur in both plants and animals. The water is deep in the middle and become progressively shallow towards the bank.

1. Phytoplankton Stage: The phytoplankton's are the pioneer species and so they pioneer community, they include unicellular and colonial forms of blue green algae, green algae, diatoms and bacteria. There is no plant life in bottom mud. The animals, which feed on the dead phytoplankton, are above fall down to the bottom after death.
2. Submerged Stage: The dead and decay of phytoplankton's and zooplanktons make the soil suitable and softer for the growth of rooted hydrophytes like hyrilla, Valliisneria, potomageton, elodea etc, the animal life is mainly represented by blue fish, sunfish etc. The hydrophytes die and decompose so nutrients release and depth of water reduced.
3. Floating Stage:  The death & decay of submerged hydrophytes results in making the water so shallow (decrease water level up to few feet). Therefore pond become suitable for development of another type of plants which are rooted in soil, but their leaves float on the surface of water, like nymph ea, eichornia, trap and nelumbium. Most of these plants transpire due to which water level is very much reduced. Hydra, snails, frog, diving beetles ect mainly represent the animal life.
4. Reed Swamp Stage: This stage is also called as amphibious stage. After floating stage when the water is only 2 feet in depth the plants like typha, phragmites, rum ex etc. develop they cut off light from floating plants. These plants make the water still shallower by the setting down of sedimentary material and the deposition of plant humus. The animals like Lynea, phys ea, and insects like water scorpion and giant bug are present in this stage.
5. Sedge meadow stage: The continuous decrease in water table and favourable changes in substratum makes the pond suitable for plants, they have much branched rhizome system. The dense growth of plants increases the rate of trarispiration, which ultimately exposes the marshy soil. The representative plant species of this stage are juneus, cyperus & Carex. The animals of this stage are snails like anodonta and psidium.
6. Woodland Stage: The moist soil, formed as a result of sedge meadow stage, so marshy vegetation disappears and area becomes favors for the growth and development of Terrestrial like Salix (shrub) and Populs (tree). The animals at this stage are of terrestrial habiat like Zebras, Deer etc.
7. Climax Stage: Now the soil and humus become richer and this soil favors the growth of Mesophytic trees. Thus the area under deep water becomes finally transformed into a forest by the process of Hydrosere plant succession. If there is moderate rainfall as in temperature regions then the mixed forest is developed.