Ecological successions is of two types; they are primary and secondary succession. The primary succession are that which formed on bare rocks or uninhabited areas. Where as the secondary successions are formed in the areas where they are previously inhabited and then destroyed by human or certain natural calamities. The formation of secondary succession is more rapid than the primary successions. That is why new successions are fastly formed in a forest devastated by fire(secondary succession) than on the bare rocks(primary succession). Similarly secondary succession is formed in an abandoned land after flood which is faster than the succession formed on bare rock.