4.1.3. ECOLOGICAL SUCCESSION

Ecological Succession is the phenomenon or process by which a community progressively transforms itself until a stable community is formed. It is a fundamental concept in ecology, refers to more or less predictable and orderly changes in the composition or structure of an ecological community.

Ecological succession is a natural process where ecosystems change and develop over time. This process leads to the establishment of a stable community. It starts from a specific point, often after a disturbance or formation of a new area, and gradually develops into a mature ecosystem. The changes are predictable and occur in a specific order - for instance, after a volcanic eruption, new species will slowly appear, leading to the formation of a forest over many years.

Think of ecological succession like a garden that starts from bare soil. Initially, you may see a few weeds growing. Over time, these weeds give way to more established plants and flowers. Eventually, a full garden with various plants will develop. Just like in nature, starting from bare soil gradually results in a diverse and well-structured garden.

Succession may be initiated either by formation of new, unoccupied habitat (e.g., a lava flow or a severe landslide) or by some form of disturbance (e.g. fire, severe wind throw , logging) of an existing community. Succession that begins in areas where no soil is initially present is called primary succession, whereas succession that begins in areas where soil is already present is called secondary succession.

Succession can start in two main scenarios: primary and secondary succession. Primary succession occurs in places with no pre-existing soil, like after a volcanic eruption or glacier retreat, where new land is formed. On the other hand, secondary succession takes place in areas where soil is intact, but the community has been disturbed or destroyed (like after a fire). Both types lead to the regrowth of plant and animal communities, but the starting conditions and speed of recovery can vary significantly.

Imagine a new island forming after a volcanic eruption. At first, there's just bare rock. Over time, tiny plants and mosses start to grow, creating soil, which allows larger plants to take root. That’s primary succession. Alternatively, think of a forest affected by a wildfire. While the trees may be destroyed, the soil is still there. Plants can regrow more quickly than when starting from scratch - that’s secondary succession.

Clement's theory of succession had a powerful influence on ecological thought. According to Clement, succession is a process involving several phases: 1. Nudation 2. Migration 3. Ecesis 4. Competition 5. Reaction 6. Stabilization.

Clement's theory outlines the phases of ecological succession. 'Nudation' marks the start, where a bare area forms due to disturbance. Next, 'Migration' involves seeds and organisms moving into this area. 'Ecesis' occurs when these organisms establish and grow. As they grow, they enter the 'Competition' phase, where plants start competing for resources. During 'Reaction', environmental changes occur as the growing community alters the habitat, which eventually leads to 'Stabilization'—the establishment of a climax community, which remains stable over time.

You can visualize these phases like a group project. First, the team is formed (nudation). Then, everyone brings their ideas (migration), and ideas begin to take shape (ecesis). As more ideas compete for attention, some become more dominant (competition). The team's ideas may change and evolve as they develop (reaction), and finally, the project solidifies into a complete presentation (stabilization).

A seral community is an intermediate stage found in an ecosystem advancing towards its climax community. In many cases more than one seral stage evolves until climax conditions are attained.

Seral communities are the transitional stages that occur during ecological succession. As the ecosystem matures, different species dominate at various stages, known as seral stages. Each seral community prepares the ground for the next, eventually leading to a stable climax community. The type of seral community that develops depends on the environment, such as the presence of water, soil type, and climate.

Think of a school play. First, students practice their lines in small groups (seral stage), then they come together for rehearsals (another seral stage). Eventually, they perform the full play (climax community). Each step builds on the previous one, leading to a polished final performance. Similarly, seral communities evolve towards a mature ecosystem.

The final or stable community in a sere is the climax community or climatic vegetation. It is self-perpetuating and in equilibrium with the physical habitat.

A climax community represents the final stage of ecological succession. It is the most stable and enduring community, where species populations balance in harmony with their environment. Energy production and use reach equilibrium, meaning the amount of organic matter produced is roughly equal to what is used by organisms for growth and energy. Essentially, it becomes a self-sustaining ecosystem.

Consider a well-established forest. It houses a variety of mature trees, plants, and wildlife, functioning like a self-sufficient city. While trees grow and die, their nutrients benefit new growth. Just like a mature city maintains its infrastructure, the climax community maintains its balance of life.

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