Ecological succession is a natural process of change in the species composition of an ecosystem over time. One of the forms of succession is primary autotrophic succession, which begins with the creation of a bare area and ends with the formation of a stable, self-maintaining community of plants and animals known as the climax community. This article will provide a step-by-step guide to the complete process of primary autotrophic ecological succession.

1. Nudation

The process of ecological succession begins with the formation of a bare area, also known as nudation. Nudation can occur due to several reasons, including natural disasters such as volcanic eruptions, landslides, floods, erosion, and fire, as well as human activities such as construction, stone quarrying, burning, and digging. In some cases, large areas of land may also be flooded to form reservoirs, resulting in the creation of new, lifeless bare areas.

2. Invasion

The next step in the process of primary autotrophic succession is the invasion of the new or bare area by various organisms. The first invaders in any area are plants, also known as pioneers, as animals depend on them for food. The invasion of the area includes the following three steps:

A. Dispersal or migration

The first step in the invasion process is the movement of the reproductive bodies or propagules of the species to the new area. This movement can occur through the agency of air, water, or animals. The entire process, from the time the propagule leaves the parent plant to the time it arrives in the new area, is known as migration.

B. Ecesis

The next step in the invasion process is the successful establishment of the migrated plant species in the new area. This step includes the germination of the seeds or propagules, growth of seedlings, and the starting of reproduction by adult plants. However, only a few immigrant propagules are capable of surviving and thriving in the harsh conditions of the new area, and most will disappear.

C. Aggregation

The final stage of the invasion process is the aggregation of the successful immigrant species. As their numbers increase through reproduction, they come together and form a large population in the area. The individuals of the species come close to each other, resulting in the formation of a community.

3. Competition and Reaction

As the number of individuals of a species increases, competition for space and nutrition begins, both between individuals of the same species and between different species. All individuals also interact with the environment, and as a result of increased intra- and interspecific competition and other biotic and abiotic interactions, the environment is modified. The existing community is eventually replaced by new invaders or another community (seral community), which finds the modified environment more suitable. This results in a balance among the species, with the former species being reduced to a subdominant status or completely eliminated.

The addition of organic matter, nutrients, and moisture in the substratum by small plants makes it suitable for larger ones. The increased availability of food also allows various animals to join the community, and the resulting interactions further modify the environment and pave the way for fresh invasion by other species of plants and animals.

4. Stabilization or Climax

Eventually, the process of succession reaches a stage where the final community is more or less stabilized for a longer period of time. The community can maintain itself in an equilibrium or steady state with the local climate. This last stage, known as the climax community, is characterized by an equilibrium between gross primary production and total respiration, the energy captured from sunlight and the energy released by decomposition, and the uptake and return of nutrients by litter fall.

The climax community is characterized by a wide diversity of species, a well-developed spatial structure, complex food chains, and a steady state of living biomass. It is mature, self-maintaining, self-reproducing, and relatively permanent, with vegetation that is tolerant of the environmental conditions it has imposed on itself. The climax community represents the endpoint of succession, where the ecosystem has reached a stable, self-sustaining state.