Ecological
succession
Introduction
• Succession can be defined as the Natural change in structure and species composition
of a community.
• It can be defined in terms of following parameters .
1. It is the orderly process of community changes , which is directional and therefore
predictable.
2. It results from modification of the physical environment by the community.
3. It ends in the establishment of a stable ecosystem at any given site.
• Bare area--------→ climax community / climax stage
Causes of succession
Cilmatic causes: plants cannot adjust with the long variations in the climate.
The fluctuating climate sometimes leads the vegetation towards total or partial destruction and as
a result a bare area develops which becomes occupied by such plants which are adapted for
changed climatic conditions.
Droughts, heavy rainfall, hails etc.are some of the important factors destruction of vegetation.
Topographic causes
These are concerned with the changes in soil.
these are two important soil factors.
• Erosion of soil:
soil erosion by a number of agents such as wind water currents and rainfall leads to exposure
of new / bare area in which new plant communities begin to appear one after another.
b) Soil deposition :
it is one of the important cause that initiates succession . Soil deposition results owing to
heavy storms , glaciers snowfalls and landslides.
If the deposition of the soil takes placeover an area which is already , vegetated the plants
occurring over there maybe suppressed and destroyed.
Deposition results in new bare area on which succession of vegetation starts.
Iii) BIOTIC CAUSES:
Grazing, cutting , cleaning, cultivation, harvesting and deforestation all
caused by living agencies are responsible for vegetational change.
parasitic plants and animals also affect vegetation and destroy it.
Types of succession:
Primary Secondary
succession succession
• Begins on a sterile area such as newly exposed rock where conditions of
existence may not be favorable initially.
Primary succession:
Secondary succession
• This refers to development of community
on sites which were occupied by well
developed communities.
• These sites maybe rich in nutrients with
favorable survival conditions.
• This type of succession is called as
Heterotrophic succession.
ECOLOGICAL NICHE
• An important principle of ecology is that each species has a specific
role to play in the ecosystem where it is found.
• Scientists describe the role that a species plays in its ecosystem as its
ecological niche.
• It is a species way of life in a community and includes everything that
affects its survival and reproduction , how much water and sunlight it
needs , how much space it requires, what it feeds on and the
temperature and other conditions it can tolerate.
• A species niche should not be confused with its habitat, which is the
place where it lives . Its niche is the pattern of living.
