Ecological Succession

Ecological Succession

Definition

• Ecological succession is the observed process of change in the species structure of an ecological community over time. The time scale can be decades for example, following a wildfire, or millions of years after a mass extinction.

Types of Succession

• There are two main types of ecological succession: primary succession and secondary succession.
• Primary succession occurs in essentially lifeless areas, where the soil is incapable of sustaining life like newly formed volcanic islands or lands left from retreating glaciers.
• Secondary succession is a process started by an event, such as a forest fire, that reduces an already established ecosystem, but not to such an extent that the soil is incapable of sustaining life.

Stages of Succession

• Ecological succession generally progresses through a series of stages: nudation (the creation of a new site), invasion (arrival of species), stabilisation or climax (when changes in community structure are minor).
• The final or climax community is seen as a stable endpoint of this succession process. Climax communities are relatively stable and constitute the end point of succession, e.g., mature oak forest or sagebrush desert.

Pioneer Species

• Early in the process after a significant event like a forest fire, the community is dominated by few very fast growing species, often referred to as pioneer species. These hardy species are often simple plants like mosses, lichens, and grasses that are adapted to be the first colonisers in these disturbed areas.

Seral Stages and Climax Community

• As succession progresses through different seral stages, more complex species such as shrubs and trees will begin to appear. The exact sequence of species will depend on the specific conditions and species available in the area.

Factors influencing rate and trajectory of succession

• Succession is influenced by a variety of factors, both internal (biotic factors, species interactions), and external (abiotic environmental conditions). So-called facilitation, when earlier species make conditions more favourable for others, plays a crucial role in the process.
• Disturbances, such as fire, can also influence the rate and pathway of succession.

Succession and Ecosystem

• The processes of succession and maturation lead to increases in the biodiversity of a community as well as to changes in community structure and function. They are key to understanding how communities recover from disturbance and are essential for conservation and ecosystem management.