Meaning

• Primary succession is the process by which an area first changes from bare rock into a functioning ecosystem. Secondary succession is the process by which an ecosystem that has been destroyed gradually regains its former appearance and function.
  
  

Possible Number of Occurrences

• Secondary succession can occur in the same area any number of times. Because it is defined as the first time ecological succession occurs, primary succession can only happen once to any given area.
  
  

Number of Seral Stages

• Primary succession has more stages--called "seral stages"--than secondary succession. Primary succession includes seral stages where lichens and moss break rock down into soil; in areas undergoing secondary succession, soil already exists.
  
  

Shared Seral Stages

• The later stages of primary succession--once rock has been broken down into soil--are essentially the same as the entire process of secondary succession.
  
  

Duration

• The entire process of primary succession takes thousands of years to complete. Secondary succession can be completed in as little as one hundred years.