Ecological Succession

Dr. Richa Singh
M.Sc. Ph.D.
Director
Vishveshwarya College of Agriculture

Ecological Succession stands for change of plants and animal communities over a period of time. Biotic Communities are dynamic in nature and change over a period of time. The process by which communities of plant and animal species in an area are replaced or changed into another over a period of time is known as ecological succession. Both biotic as well as a biotic components are involved in this change. This change is brought about both by the activities of the communities as well as by the physical environment in that particular area. The physical environment often influences the nature, direction, rate and optimal limit of changes. During Succession both plant and animal communities undergo change. There are two type of succession: 1. Primary Succession 2. Secondary Succession.1. Primary Succession Primary Succession takes place over a bare or unoccupied areas such as rocks out-crop, newly formed delta and sand dunes, emerging volcanic islands and lava flows as well as glacial moraines (muddy area exposed by a retreating glacier where no community had existed previously. The plants that invade first bare land, where soil is initially absent are called pioneer species. The assemblage of pioneer plants is collectively called pioneer community. A pioneer species generally shows high growth rate but short life span. Primary succession is much more difficult to observe than secondary succession because there are relatively very few places on earth that do not already have communities of organisms. Further more, primary succession takes a very long time as compared to secondary succession as the soil is to be formed during primary succession while secondary succession starts in an area where soil is already present. The Community that initially inhabits a bare area is called pioneer community. The pioneer community after some time gets replaced by another community with different species combination. this second community gets replaced by a third community. This processes continues sequence wise in which a community replaced previous by another community. Each transitional (temporary) community that is formed and replaced during succession is called a stage in succession or a seral community. the terminal (final) stage of succession forms the community which is called a climax community A climax community is stable, mature, more complex, and long lasting. The entire sequence of communities in a given area, succeeding each other during the course of succession is termed sere. The animals of such community also exhibit, succession which to a great extent is determined by plant succession. However animals of such successional stages are also influenced by the types of aimals that are able to migrate from neighbouring communities. A climax community as long as it is undisturbed remains relatively stable in dynamic equilibrium with the prevailing climatic and habitat factors.Pioneer Communities-Pioneer Plant-Pioneer Species (High growth rate but short life span Succession that occurs on land where the moisture content is low e.g. on bare rock is known as Serach. Succession that takes place in a water body like pond or lake is called haydrarch.(2) Secondary Succession Secondary succession is the development of a community which forms after the existing natural vegetation that constitutes a community is removed, disturbed and destroyed by a natural event like hurricane or forest fire or by human related events like tillingor harvesting land. Secondary succession is relatively fast as the soil has the necessary nutrients as well as a large pool of seeds and other dominant stages of organisms.