Successional Dynamics

Along with physical factors and competition among species, another important factor affecting the distribution of vegetation on a site at a given time is the history of the site, i.e. when was the last disturbance such as a fire, flood, or landslide?  The process of recovery from disturbances is called ecological succession (because one vegetative community tends to replace or “succeed” another through time).

Succession is a dynamic that occurs in all natural systems.  It is ecological change that occurs after a disturbance, generally following a predictable path, and often repeating.  For example, when you mow (or “disturb”) the lawn, you generally expect the grass to grow back.  Mowing the lawn is a repeated disturbance to which the grass has a predictable response.

vegetation growing on gravel bars
NPS Photo / Uwe Anders

In Denali, a more fitting example is the cycle of vegetation growth on gravel bars.  The powerful rivers and streams of Denali are excellent disturbance agents, grabbing sediment (gravel and sand) from certain areas, in a process called erosion, and dropping (or depositing) it onto other areas.  Once sediment has been deposited, it becomes potential substrate for new vegetation, and the succession of a vegetation community begins.  However, erosion and deposition constantly occur as long as a stream flows, resulting in a frequent disturbance of those vegetation communities, and a frequent resetting of the succession cycle.

Continue on to Vegetation Patterns Across the Landscape