Succession

Succession
The gradual replacement of one type of community by other over a period of time is called succession.
Primary succession: if an area in any of the biotic environment is colonized by a group of organism for the first time; the succession is called primary succession.
Secondary succession: if succession is proceeding in an area from where a community was removed, the procession is called as secondary succession.

General process of succession:
The entire process of primary succession is completed through following steps:
Nudation: it is the development of bare area without any form of life. Exposal of new surface may occur due to several causes like soil erosion and landslides.
invasion: it involves establishment of a species in bare area ,it involves:
Migration: it is the reaching of seed, spore in a bare area through water and air.
Ecesis: it is the adjustment of a species with the preveling condition of that area.
Aggregation: it involves the increase in number of organism through the process of reproduction.
Co-action: due to aggregation of large number of individuals of a species at a limited space, there develops competition on food and nutrients. Individual of a species affect each other life in various ways called as co-action.
Reaction: reaction is the modification of the environment through the influence of living organism .as a result, soil, water changes so; new environment is suitable for other species. Therefore another community comes and replaces the preexisting community.
Stabilization: this is the final state in which a community becomes stable for that environment condition for longer time. The final community is called climax community.


Succession of Plants
Based on the nature of the habitat – whether it is water (or very wet areas)
or it is on very dry areas – succession of plants is called hydrarch or
xerarch, respectively. Hydrarch succession takes place in wetter areas
and the successional series progress from hydric to the mesic conditions.
As against this, xerarch succession takes place in dry areas and the
series progress from xeric to mesic conditions. Hence, both hydrarch and
xerarch successions lead to medium water conditions (mesic) – neither
too dry (xeric) nor too wet (hydric).
The species that invade a bare area are called pioneer species. In
primary succession on rocks these are usually lichens which are able to
secrete acids to dissolve rock, helping in weathering and soil formation.
These later pave way to some very small plants like bryophytes, which
are able to take hold in the small amount of soil. They are, with time,
succeeded by bigger plants, and after several more stages, ultimately a
stable climax forest community is formed. The climax community remains
stable as long as the environment remains unchanged. With time the
Xerophytic habitat gets converted into a mesophytic one.
In primary succession in water, the pioneers are the small
Phytoplanktons, they are replaced with time by free-floating angiosperms,
then by rooted hydrophytes, sedges, grasses and finally the trees. The
climax again would be a forest. With time the water body is converted
into land In secondary succession the species that invade depend on the
condition of the soil, availability of water, the environment as also the
seeds or other propagulates present. Since soil is already there, the rate of
succession is much faster and hence, climax is also reached more quickly.
What is important to understand is that succession, particularly
primary succession, is a very slow process, taking maybe thousands of
years for the climax to be reached. Another important fact is to understand
that all succession whether taking place in water or on land, proceeds to
a similar climax community – the mesic
fig- Succession of Plants