Ecological succession is a fundamental concept in ecology and it refers to orderly, predictable changes in the community. This succession can be initiated by the formation of new habitat which was unoccupied or from disturbance of an existing community.
"Let us try to understand the reason for the occurrence of ecological successions".
Each species in the ecosystem has set of environmental conditions under which these species grow and reproduce. As long as these conditions remain constant, the species that are adapted to these conditions flourish in the environment. Succession is caused by a change in the ecosystem and its impact on the species and their own environment. The first environment may be optimal for the first species and it the altered conditions can be optimal for other species of organism. Under the altered conditions the first species may fail to flourish and the second species may flourish.
Ecological succession may also happen when the conditions of the changes drastically and suddenly. Conditions of environment like the forest fires, wind storms and anthropogenic activities can alter the environmental conditions drastically. This may result in destruction of species and also alteration of the dynamics of the ecological community and may also trigger a struggle for dominance among the present species in the altered environment.
Ecological succession is defined as the process by which there is a structural change in the biological community of a species over time. Ecological community initiates with a few plants and animals and the development of these species increases until it becomes stable. The "engine" of succession causes a change in the ecosystem and the change impact the established species on their own environment.
There are two different types of succession
- Primary succession and
- Secondary succession.
Primary ecological succession occurs in the lifeless areas like in the regions which are incapable of sustaining life as result of lava flows, sand dunes newly formed; left over rocks from the retreating glacier. It is the beginning of a new habitat in a uninfluenced area without any pre-existing communities.
Secondary ecological succession occurs in areas where a community has been removed from a previously existing area. This succession may be triggered by smaller-scale disturbances and they do not eliminate all the life and nutrients from the pre-existing environment. Secondary succession occurs after the disruption of a pre-existing community.
There are three fundamental stages involved in the order of ecological succession. They are as follows:
- Primary Succession
- Secondary Succession and
- Climax Community.
The order of ecological succession can be altered depending upon the location of the region and its climatic conditions. Although there are stages in which succession occurs.
The order is as follows:
- Pioneer species,
- Eventually a climax community stage is reached where the succession process is stabilized until the land is forced to turn into a barren land once again.
Primary succession happens simultaneously with the growth of the pioneer species. During the primary succession, a barren land is transformed from a lifeless environment into a environment which supports life.
Secondary succession is the process where one community is changed into another. It occurs in the place where life is already present.
Climax community is where succession leads to a single stage which is stead and terminal known as the climax stage.
Climax concept is a classical theory concerned with ecology; it states that succession stops at a stage where the biotic and the physical environment have arrived at an equilibrium stage or a steady state. This succession will persist indefinitely, facing the major disturbance and this end point of succession is known as climax.
Some of the features or the characteristics of the climax community are:
- The vegetation of this region is tolerant to the environmental conditions.
- The species diversity is large and the food chains of these species are complex and with spatial structure.
- It is a balanced ecosystem.
- In the climax ecosystem there is a balance between the primary production, total respiration and also the energy being used from sunlight and also the energy being released by the process of decomposition.
- There is also a equilibrium between the nutrients taken in from the soil and the return of the nutrients to the soil by litter fall.
- The individual organisms in the climax ecosystem are replaced by other organisms of the same kind. Thus maintaining species equilibrium.
- The life and growth here indicates the climatic types of an area.
Some of the observable examples of ecological succession include:
Example 1 - Harwood tress like oak grow within the red pine plantations. The consequences for the growth of this hardwood is the increase in shading and the mortality of the sun loving red pine trees and by the hardwood seedlings which are tolerant to shade. The forest floor is shaded by the pines and thus prohibiting the growth of the sun-loving pine seedling and promoting the growth of the shade loving hardwood trees. The hardwood trees are grown on the consequence on the decline and senescence of the pine forest.
Example 2 - Another simple of ecological succession would be formation of islands from the activity from a valcano in the ocean. The first organisms to appear on the island would be pioneer species like bacteria, fungi and moss and it followed by grasses, shrubs and trees.
Three main causes of ecological succession are identified for the process of succession.
- Initiating causes - The initiating causes include biotic and climatic factors which destroy the existing populations of the area. The climatic factors include wind, fire, natural disasters, erosion, etc. The activities of other organisms constitute the biotic factors.
- Continuing causes - The continuing causes of the succession is also known as ecesis. These processes are continuous like aggregation, competition and migration etc. These continuous causes result in a series of changes in the soil structure of the area. The common changes here include changes in soil nutrients, accumulation of organic matter and changes in soil pH etc.
- Stabilizing causes - The stabilizing causes include climatic factors that result in the stabilization of a community.