The gradual changing of species within an ecological community is succession. Usually applied to plants, succession begins with an area of no soil and eventually reaches a point where the region supports many plant species.

Environment

The physical environment of an area determines what life may exist within that area. Communities of organisms establish themselves within an area and succession begins.

Community

The ecological community of an area alters that area in ways that benefit different species more than the current species. A succession of communities takes place over time, each contributing factors that make the next community possible.

Predictability

Succession can be predicted because the area environment is continually modified by the current community to make it more suitable for the next. Trees that don't grow in shade, for example, create an environment suitable for trees that tolerate or do well in shade.

Climax Succession

Succession often ends in a stable community that changes little until another factor such as a landslide or forest fire sets the stage of succession back to an earlier stage. The stable community is called the ecological climax.

Climax Ecology

A diverse community of many species becomes ecologically stable. Each species supports the others in ways that are often symbiotic in nature. Until disaster occurs, the community changes very little.

Types

Primary succession begins in an area of no soil. Development of a community begins very slowly and few organisms are able to survive. Secondary succession begins when organic matter is present and greater numbers and species of organisms live there.

Source:

Indiana University of Pennsylvania: Ecological Succession

More Information:

Science Clarified: Succession

not sure