Ecological Succession

Ecosystems, even when undisturbed by people, are not static but change over time. This is one characteristic of all communities and ecosystems—their structures change constantly in response to changing environmental conditions. This natural recovery can occur if the damage is not too great. Studying the patterns of the changes in ecosystems in response to natural or human disturbance is an important tool for learning how to restore lands damaged by people.

If fundamental requirements for life are available, areas on Earth without life are soon filled with living things. Over time, ecosystems undergo patterns of development called ecological succession. Ecological succession is of two types: primary and secondary.

Primary succession is initial establishment and development of an ecosystem. Begins with bare rock exposed by geologic activity

       Example: Rock -> lichen -> moss -> grass -> shrub -> trees -> oak hickory forest

Secondary succession is reestablishment of an ecosystem. Begins on soil from which previous community has been removed (by fire, agriculture, etc.)

 Example: grass -> shrub -> trees -> oak hickory forest 

      

Fig.: Primary succession 

   

Fig: Secondary succession