Biotic Succession
Abiotic factor such as water, solar energy and minerals determine which populations, especially plant populations, can survive in an area. In general, climate and soil are the main factors that control where plants can survive on land. It is noticeable that plants serve as food for animals and other consumers. The results is that plant distribution will determine which animal populations will be present. On the other hand, it is true that the nonliving environment influences populations, and it is also true that populations influence the nonliving environment.
Abiotic factor and biotic factors interact to produce changes in the ecosystem. As conditions change with time, some populations gradually become less capable of surviving while others become more capable. The ecologists have studied that there is a successive replacement of one community by another. This sequence of replacement of one community of organisms with another is called ecological or biotic succession. Succession is a process with certain types of microorganisms always present in a particular stage of development in a given area.
The points that invade the base land initially, are called pioneer species. The accumulation of pioneer species becomes the pioneer community. Generally, the pioneer species show high rate of growth but of short life span.
In time, a pioneer community is replaced by another community with combination of different species. This second community is replaced by third community, and process goes on. Different communities, are represented by combinations of lichens, mosses, herbs, shrubs and trees replacing one another during succession, they are called seral stages or seral communities.
The plant species which are established later are called late successional species.
For any particular kind of climate and soil, succession leads to a certain community structure of an ecosystem is called the climax community. A specific sequence of development of a community is related to a particular set of physical and chemical conditions. This is known as a sere and is composed of a number of biotic successions replacing each other in course of time.
The biotic succession may be of two types
1) Primary succession and
2) Secondary succession.
When the succession proceeds from a bare and sterile area or from an area which has not been changed physically by organism, is known as primary succession. For example, succession on bare rock(Xerarch), succession in a pond(hydrarch) succession in newly exposed sea floor, lava sediments or sand dunes.
The succession occuring in terrestrial areas with low moisture, such as bare rock, is known as Xerarch. The succession, that occurs in water bodies, such as ponds and lakes is called hydrarch succession.