Ecological Succession

                                                                                  SMRITI singh
                                                                   UNIVERSITY DEPT. OF ZOOLOGY

                                  S.K.M.UNIVERSITY

                                DUMKA-814110

                                (JHARKHAND)

INTRODUCTION  

Ecology is the study of interdependent relationships between biotic and abiotic factors.

An ecosystem means interaction of biological community with its physical environment.

·        Abiotic factor and biotic factors interact to produce changes in the ecosystems, 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 community. This sequence of one replacement of one community of organisms with another community is called ecological succession or biotic succession.

·        The community that invade the barren 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 (the length between birth to their natural death).

·        Gradually 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.

·        The stable community structure of an ecosystem is called the climax community which can not be replaced naturally.

TYPES OF ECOLOGICAL SUCCESSION

There are two types of ecological succession based on their progress or success-

(1) Primary Succession

(2)  Secondary Succession

(1)  Primary Succession-

·        The process of creating life in an area where no life previously existed. No soil is present.

·        The development of an ecosystem in an area that has never had a community living within it occurs by a process called primary succession.

·        An example of an area in which a community has never lived before would be a new igneous rock from a volcano that makes a new island or a glacier receding.

Primary Succession 

(2)  Secondary Succession-

·        The process take place after a disturbance such as forests fire, floods, tree falls occurs in an established ecosystem.

·        It takes place in faster scale because soil is pre-existed.

·        Examples include areas which have been cleared of existing vegetation such as after tree felling in a woodland and destructive event such as fires.

Secondary Succession 

3. Autotrophic Succession- It happens in rich inorganic nutrients area. Gradually, the organic matter also increases due to energy flow. When autotrophic component such as green plants start dominating over the community then it’s called autotrophic succession.

4. Heterotrophic Succession- It starts in organic rich areas and gradually energy content decline. Here, heterotrophs dominate the area.

5. Allogenic Succession- Sometimes, the existing communities replaced by external conditions and then this process is called allogenic succession.

6. Autogenic Succession- Sometimes, the existing communities modifies itself in its own environment and it shows replacement of community by another community. This is called autogenic succession.    

 

The ecological succession classified into two, where this process occurs-

·        The succession occurring in terrestrial areas or on land with low moisture, such as bare rock, is known a Xerarch succession or Xerosere.  

·        The succession occurs in water bodies, such as ponds and lakes is called Hydrarch succession or Hydrosere.

Characteristics of community that appear during ecological succession

·        The characteristics of community that appear during ecological succession vary with their habitats and its conditions.

·        The seral community differ from climax community on the basis of their structure and function. The average size of individual plants or animals increases and the organization of community becomes more complex in comparison to seral community.  

·        The food webs become more complex during various successional stages. At the same time, the efficiency of energy use and nutrient conservation increase as the community increases towards the climax stage.

·        The composition species at the climax stage is determined by the climate of particular region, as well as local environmental factors or soil conditions.

·        Topography of the region and water availability are also responsible for species composition, where heavy rains are available the forests appear.

·        The climax stage shows the highest level of vegetation and the associated fauna (plants) that can be supported under the surroundings of environment.

   

Significance of Ecological Succession

·        The achievement of a measure of stability or homeostasis, rather than a mere increase in productivity, in a fluctuating physical environment may well be the primary purpose of ecological succession when viewed from the evolutionary viewpoint.

·        A mature community with its greater diversity larger organic structure, and balanced energy flows is often able to buffer the physical environment to a greater extent than the young community.

·        The principles of Ecological succession are of the greatest importance to mankind. Man must have early successional stages as a source of flood, since he must have a large net primary production to harvest.

·        In the climax community, because production is mostly consumed by animal and plant respiration.

·        It is important that both types of ecosystems be considered together in proper relation.

·        According to ‘Elton’, succession of communities plays an important part in the slow dispersal of animals.

·        It allows new areas to be colonized and damaged ecosystems to be recolonized, so organisms can adapt to the changes in the environment and continue to survive.   

  

Quiz time

1.     Define Ecology.

2.     What do you mean by life span?

3.     Define the term climax community.

4.     Define xerarch succession.

5.     Define hydrarch succession.

Multiple Choice Questions

1.     A community that starts the process of ecological succession in a habitat is called-

(a)  Abiotic community 

(b)  Biotic community

(c)   Pioneer community

(d)  None of these

2.     Which of the following are pioneer community organizes in primary succession-

(a)  Shrubs

(b)  Lichens

(c)   Trees

(d)  Mosses

3.     Stabilized community at the end in plant succession is called-

(a)  Ecotone

(b)  Seral community

(c)   Climax community

(d)  Ecosere

Please comment answers in the comment section