The process of community development is called succession. Different stages are involved in the development of succession in a bare area. These stages are migration ecesis. aggregation, competition reaction and stabilization
All bare areas are without seed or other propagules. Seeds, spores and runners of the pioneer species migrate to this area. Following factors affect the migrations:
(a) Mobility: The ability of a species to move out of the present area is called mobility. It depends upon the nature of dispersal mechanism, number of seeds produced and the position of seeds or spores. Thus plant may be spore distributed, ‘seed distributed. Fruit distributed. offshoot distributed and plant distributed.
(b) Dispersing agents: Migration also depends upon the dispersing agents. The important dispersing agents are water. wind, explosive mechanism, animals and man.
The phenomena of growth of propagules and their adjustments in the new surrounding area is called ecesis. It consists of three essential processes: germination, growth and reproduction.
(a) Germination: It is the first critical process of ecesis. The dormant embryo become active and begins to grow. Some seeds do not grow. They are called dormant seeds. They remain dormant for few weeks, months or even years. Dormancy may be due to both external and internal causes. Proper depth is also an important condition for successful seed germinationt.
(b)Growth: The seed grow and develop seedling. It is a very critical stage for the survival of plants. There is excessive competition among themselves and with other species. Competition may be for space. nutrition water and light.
(c) Reproduction: The plant grows and become mature. Then it develops different reproductive structures. Some plants reproduce asexually. Some undergo sexual reproduction.
The growth of plants in the form of colonies is called aggregation. The aggregation may be simple or mixed. The grouping and growing of offspring around the parent plant is called simple aggregation.The gradual spreading and mixing of the neighbouring plants is called mixed aggregation. It is caused due to process of migration.
The struggle for existence between the plants is called competition. The simple and mixed aggregation causes competition. Sometimes, two plants demands light nutrients or water in excess of the supply. It causes competition between these two plants. It is universal characteristics of all plant communities. It increases with increase in population density. There are two types of competition:
(a) IntraspecifIc Competition: The competition within the individual of the same species is called intraspecific competition. These individuals have same demands. So it is r are severe.
lnterspecific competition: The competition between different species it is called interspecific competition. Different species have different requirements for water, nutrients and space. So it less severe form of competition.
In climax communities every strata and every kind of plants adjust themselves to the habitat. So they become interdependent upon each other. All the plants living in a climax community do not face any competition for food, water, space and air. A dominant plant does not compete with secondary dominant one. under shrubs herbs or ground flora. Each layer and’ each species have different requirements for water, light. space and nutrients
The effect of plants on the habitat is known .as reaction. Some reactions are direct result of the plant activities. These include decrease of water by absorption and increase in humidity due to transpiration .There is a death and plants or plant organs. It adds organic matter into the soil. Therefore,the physical and chemical properties of the soil are changed. Thus soil fertility is increased and water holding capacity of the soil is improved.
Many reactions have taken place in the community and habitat. Now a time has come that no reactions are possible. Therefore, now the habitat can not be modified further. At this stage, a stable and complex community is formed. It becomes more or less permanent and stabilized. Now this community is fully developed, stable, self perpetuating. It is in equilibrium with the climate. This type of community is known as Climax Community. The climax is thus a product climatic factor.