Succession

Standard B1.39

 

What is succession? The series of predicable changes that occur in community over time.

      Changes cause older inhabitants to gradually die out and new organisms to move in causing more change.

 

Primary succession: the colonization of surfaces where no soil exists.

Examples:  volcanic eruptions, lava flows, silt deposits, bare rock exposed when glaciers melt.

   

 

     First colonized by a pioneer species, usually a lichen (a combination of a fungus and an algae).

       

     As the lichens grow they break up the rock into soil.

     As the lichens die, they add nutrients and organic material to the soil.

     Other less hardy species can begin to colonize the area such as mosses, grasses, weeds and shrubs.

       

     The area finally reaches a mature, stable community that does not undergo further succession called the climax community.

 

      The type of climax community is usually dependant on the climate of the area.

      Climate is determined by the average precipitation and average temperature.

      Examples of climax communities are tropical rain forests, temperate grasslands, boreal forests, temperate forests or tundra.

 

     

Secondary succession: the colonization of a community after a disturbance of some kind changes the community without removing the soil.

Examples:  forest fires, hurricanes, tornados, farming a field, floods

 

           

 

     After a disaster, the community will usually return to the original climax community unless there is a change in climate or the introduction of a non-native new species. Standard B1.40

     Sometimes random, unpredictable events may influence the path of succession.