This is because primary succession is newly formed logs that are colonized by living things. Seconday succession is there were living things there once but due to disturbance life is lost and started over which could take decades.
One of the oldest arguments in the history of psychology is the Nature vs Nurture debate. Each of these sides have good points that it's really hard to decide whether a person's development is predisposed in his DNA, or a majority of it is influenced by this life experiences and his environment.
