The gradual, sequential regrowth of a community of species in an area is called ecological succession. You can see early stages of succesion in vacant lots, along roads, and even in sidewalks or parking lots where weeds are pushing up through cracks in the concrete.

Mt St Helens eruption and 12 years later

Is the development of a community in an area that has not supported life previously, such as bare rock, a sand dune, or an island formed by a volcanic eruption. Soil is not initially present.

Mt St Helens primary succession

Is the sequential replacement of species that follows disruption of an existing community. Disruption may stem from a natural disturbance, such as a forest fire or a strong storm, or from human activity, such as farming, logging or mining. Occurs where soil is already present.

A species that colonizes an uninhabited area and that starts an ecological cycle in which many other species become established Occurs in areas that been recently exposed to the elements and lack soil. Primary succession typically proceeds from lichens and mosses to a climax community

Occurs in areas where the original ecosystem has been cleared by a disturbance. Secondary succession typically proceeds from weeds to a climax community.

The traditional description of succession is that the community proceeds through a predicatable series of stages until it reaches a stable end point, called the climax community.

A recently abandoned agricultural field is being pioneered by weeds A recently abandoned agricultural field is being pioneered by weeds. Eventually, taller plants and shrubs will compete with the pioneers. If no further disturbances occur, a forest of pine or cottonwood may follow, succeeded by a hardwood forest. The whole process will take about 100 years.

Primary succession starts when bare rock is colonized by pioneer species such as lichens which build up soil.

Secondary succession starts when disturbance allows pioneer species such as weeds to grow in existing soil. These pioneers are later followed by shrubs and trees until a climax community is established.

Play Glacier Bay which took 200 years