Ecological Succession

Ecological succession is the process of change that occurs in a forest or in any type of vegetation system, starting from an early and immature stage, moving toward a mature and stable stage (Figure 8-3). Some plant species are only present during the immature period (pioneer species) and are replaced by other species as the community matures. Succession may initiate after a disturbance has occurred (e.g., fire) or when the area is new for colonization. The mature stage of a forest and its biotic community was previously known as a climax community. Currently, the term shifting-mosaic steady state is used instead because all individuals in an ecological community will not likely be at the final stage of maturity at the same time. It is possible that portions of a community will suffer a fire, flooding, or other disturbances. Therefore, succession is not homogenous throughout the community because some portions of the biotic community will be in different successional stages.

 

Figure 8-3. Forest succession. The first line in the age of the site in years. The second line is the community type across the years. The third line is the type of vegetation you may find in each community type.
Credit: Robert Tjaden and Julia Klapproth. General Forestry Correspondence Course.

 

Succession is divided into two categories: primary and secondary. Primary succession occurs in a site without previous vegetation and soil (e.g., a new island) or following a disturbance resulting in a barren landscape (e.g., after a lava flow). Secondary succession occurs in a site previously occupied by living organisms, where soil is present. Secondary succession also occurs in places where initial succession has been disrupted naturally, such as in a burned forest or a forest hit by a hurricane, or by human intervention, such as at an abandoned agricultural site.

 

As plant communities change, the wildlife associated with those successional stages change as well. Wildlife are adapted to different stages of ecological succession. Meadow voles are found in grasslands, while yellow-breasted chats are found in shrublands and box turtles are associated with mature woods. Some species rely on more than one plant community such as bobwhite quail which utilize fields, shrubs and open woods.