Mechanism of ecological succession

MECHANISM OF ECOLOGICAL SUCCESSION

Nudation

Beginning of vegetation growth in the bare area is called as Nudation, which depends on following factors;

1.         Topographic:  Topography of any region is important for vegetation and according to this topography growth begins.  Eg. growth and attachment of lichens on rocks, growth of phytolanktons in lakes or bryophytes in cold desert.

2.         Climatic factor:  The rate of plant growth depends on climatic factor of the region as light, temperature and rainfall.  If factor is favorable, then rate of succession will be more.

3.         Biotic factors:  When vegetation startes growing then struggle starts among different species.  This struggle may be positive or negative.

Invasion

When species invade any new area, then it shows following processes :

Migration

Temporary transference of species from any other area to newly developed area is called as migration.  Due to migration, species increases its dispersal area.

Ecesis

Process of establishment of a species in the new area is called as ecesis.  During species development it shows positive or negative relationship with other species.  If positive relationship is there then species can be better established.

Aggregation

When slowly many species aggregate in the area then struggle takes place among them and the species, which get well established during this struggle, is sown in the form of effective species.  This species are found in a group.

Competition and Co-action

When many species aggregate at the same place, then among them either a struggle takes place for shade and nutrients, it is called as competiton or species positively associate with each other to benefit each other, it is called as reaction.

Reaction

When plants grow in the bare area then it affects soil and climate, it is called as reaction.

Stabilization

When continuous changes are taking place in the community, then a stage comes, when the community becomes stable, it is called as climax and the process is called stabilization.

Current Concepts of Succession

Succession pattern is a serial process, which takes place in definite steps.  Following steps are important for primary succession :

Table 1.3: Life history

Xerarc	Mesarch	Hydrarch
Crustose lichen Foliose lichen Moss stage -- -- Herb stage Shrub stage Climax stage	Grassland -- -- -- -- Herb stage Shrub stage Climax stage	Phytoplankton Submerged Free floating Reed swamps Marsh meadow Herb stage Shrub stage Climax stage

Two models have been given for primary succession of plants.

1.        Relay floristic model:  In it, when next community develops then this area is formed.  The first community disappears, while in the second model all community adds new community and develops together.

2.         Initial floristic model:  A model has also showed Autogenic mechanism for succession, which are mainly based on three processes;

 a. Facilitation:  

This process indicates adopted species in the distributed area.

 b.Tolerance:  

This process indicates that by changing environment, there is no effect of it on the species or, if there

is, then very small because species can tolerate this environment.

c. Inhibition:  

When environment is modified by early species, then it is not suitable for early species and

this species inhabits growth and due to which, growth of another species get increased.