Ecological succession is a process in which plant (and then animal) species in a community are progressively replaced over time due to the changing conditions that the plants themselves create.
Primary succession begins in areas that have not yet been colonized, such as on bare rock. Lichens are pioneer species that can attach to bare rock surfaces. As they grow and die over the years, soil begins to form and accumulate, allowing mosses to move in.
Soil builds up over time, allowing larger plants to move in—first small herbs and grasses and later, small shrubs.
Sun-tolerant trees such as pine and cedar move in when there is enough soil to support large root systems.
Taller plants produce shade, changing conditions and favoring different plant species.
Secondary succession describes a similar process that occurs in an area that once held life but has been damaged somehow, such as by fire.
The level of damage an ecosystem suffers determines what stage of plant community moves in after the damage. For example, a forest with extensive damage may start again with small herbs and grasses. This community would yield to small shrubs, followed by a young forest, followed by a mature forest.
Secondary succession is much faster than primary succession because soil already exists at the site.
Identify the typical stages of primary succession by dragging the images and labels into the correct order.