Succession is a scientific term describing the long-term progression of biological communities that occurs in a given area. Ecological succession breaks down into three fundamental phases: primary and secondary succession, and a climax state. The study of ecological succession generally focuses on the plants present on a particular site. But animal populations also shift over time in response to the changing habitat.
Ecological succession is the term used to describe what happens to an ecological community over time. It refers to more or less predictable and orderly set of changes that happen in the composition or structure of ecological community. When you are born, your learn to crawl, then walk and then run. When you grow old, your body goes through certain predictable changes over a period of time as in your body grows taller, your hair grows longer, your mind and body develops. Similarly, when you plant a tree, it grows slowly and then grows bigger and bigger and bigger. Basically, its a predictable set of changes that are visible over a period of time. The time scale can be decades or even millions of years.
It is different from Ecological Evolution because the changes that occur aren’t evolutionary in nature, but they may be adaptive. It is based on the principle and knowledge that nothing in life ever remains the same, but that all habitats are in a process of constant change as a result of the inter-dependencies and reactions within the ecological system itself.
Primary succession occurs when organisms colonize an area devoid of life, usually after a catastrophic natural event that leaves the land barren. Often the first organisms to take hold are algae, fungi and simple plants such as lichens and mosses.
Over time a thin layer of soil builds up so that more advanced plants, such as grasses and ferns, can take root. Along with the successful colonization of plants come animals such as insects, birds and small invertebrates. One example of primary succession is the pioneer communities that begin to inhabit a newly created lava bed, where life cannot exist until the rock surface cools to a moderate temperature.
Most ecological change occurs as secondary succession. In fact, most biological communities are in a continual state of secondary succession. This term describes the process in which an established community is replaced by a different set of plants and animals.
Secondary succession is gradual, always moving toward the climax community. Most ecosystems, however, experience disturbances — either natural events such as wildfires or flooding, or man-caused events such as logging — that set back the progress of succession.
An ecosystem undergoes many intermediate stages of succession. These changes form a continuum between the two endpoints, with the actual stages being merely a fixed glance at the never-ending progression of plants and animals.
The emergence of the climax state of succession may occur more quickly in some ecosystems, and likely never occur in other biomes that experience routine disturbances. Examples of quickly forming climax communities are the short-grass and long-grass prairies of the Great Plains of the United States.
Climax communities are relatively stable and can vary widely in a given region, especially when the landscape consists of high mountains and low valleys. In such cases, the final biological matrix of plants and animals can cover vast tracts of land or be limited to a very small pocket within the landscape. Overall, a climax community is very dependent on rainfall, soil, altitude and temperature. California, for instance, includes many different and distinct ecosystems. One of the most unique places is the redwood forest, which can be found only in the fog banks along the coastal waterways of the northern part of the state.
The path and endpoint of succession
The early ecologists who first studied succession thought of it as a predictable process in which a community always went through the same series of stages. They also thought that the end result of succession was a stable, unchanging final state called a climax community, largely determined by an area’s climate.
For instance, in the example above, the mature oak and hickory forest would be the climax community.Today, the idea of a set path for succession and a stable climax community have been called into question. Rather than taking a predetermined path, it appears that succession can follow different routes depending on the specifics of the situation. Also, although stable climax communities can form in some cases, this may be uncommon in many environments.
Ecosystems may experience frequent disturbances that prevent a community from reaching an equilibrium state or knock it quickly out of this state if it manages to get there.
Importance of Ecological Succession
Ecological succession is of great importance as:
- It provides information, which help to have control on the growth rate of one or more species in a given geographical area.
- It helps in reforestation and forest management programmes.