Hello,

Primary Succession can be defined as the process of growth in an area that was previously uninhabited, barren, unoccupied and there was no initial vegetation.

Secondary Succession can be defined as the growth of the community in such area which was previously occupied, inhabited and that has primary vegetation but got disturbed or damaged due to some external or internal factors.

• The primary succession occurs in areas which are lifeless or barren, whereas the secondary succession occurs in areas which were previously inhabited or recently denuded.
• The primary succession takes around 1000 years or more to complete, whereas the secondary succession takes around 50 - 200 years.
• In primary succession, humus is absent in the starting as there is no soil, whereas, in secondary succession, humus is present due to the previous occupants and their decomposition.
• There are many intermediary seral communities primary succession, whereas there are many intermediary seral communities in secondary succession.
• Examples of primary succession are Bare rock, ponds, desert, etc. and examples of secondary succession are the areas affected by natural calamities, covered under deforestation, etc.

Best Wishes.