Succession is a fancy word used to describe how things change in an ecosystem over time. An ecosystem is like a community where different types of animals and plants live together. Just like a community, an ecosystem is always changing. Succession happens in different stages, where certain animals and plants become better suited to live in the ecosystem. This means that some plants and animals will become less common, while others will become more common. Eventually, a new community will take over from the old one, and the cycle starts again. In short, succession is the process of one community taking over from another in an ecosystem.

What is primary succession?

Have you ever wondered how new plants and animals find their way to a barren land? This process is called primary succession, and it happens when new species gradually move into a newly exposed or formed area. New terrain can be formed in different ways. For example, when a volcano erupts, the hot magma cools and forms new rock surfaces. When the water level drops in a river or ocean, it reveals the riverbed or seabed. Even places that seem lifeless, like deserts or rocky coasts, can still have primary succession as long as new species are slowly moving in. It's like starting a new community from scratch, with each new species finding a place to call home.

What is secondary succession?

Sometimes, an environment that already has a stable ecosystem can suddenly and drastically change. This can present an opportunity for new species to come and recolonise the area. This process is known as secondary succession. For example, when land is cleared for agriculture, when forest fires occur or when a disease destroys fundamental species in an ecosystem. Secondary succession is similar to primary succession, but it usually happens much faster. When an area is cleared, there might still be some resources left, like a thick layer of soil full of seeds, spores, water, and nutrients. Also, the surrounding areas might provide new species that were not there before. Over time, the ecosystem can recover and support a new stable community with different species. It's like hitting the reset button on a community, and seeing what grows back in its place.

What are the stages of succession in biology?

Succession does not typically happen overnight; it occurs as a series of stages over a long period. At every stage, a new wave of species comes to colonise the area and makes additional changes to the environment, affecting the next wave of colonising species.

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Primary colonisation (pioneer species)

The process of succession starts when a new, inhospitable environment is colonised by primary colonisers, also known as pioneer species. At this stage, the environment is barren and not suited to support most forms of life. However, pioneer species have unique traits that allow them to colonise the area successfully. For example, they can reproduce asexually, which means that a individual a can nitrogen the atmosphere, allowing them to produce their food independently. Pioneer species can produce lots of seeds or spores that disperse and germinate quickly, and they can tolerate extreme conditions, also known as extremophiles.

Extremophiles are organisms that live in very extreme conditions that are largely inhospitable for most other organisms. For instance, halophiles live in areas with high salt concentrations, radiophiles live in areas with high levels of radiation, and acidophiles live in areas with an acidic pH. Even a rock can be considered an inhospitable environment, but organisms like lichens can grow on them. Lichens are composite organisms that arise from the symbiotic relationship between cyanobacteria and fungi. They are self-sustaining and can survive in a wide range of temperatures and humidity levels, making them excellent pioneer species.

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Symbiotic relationship: a mutual relationship between two organisms in which both benefit from the association.

Secondary colonisation

Lichens are known for their unique ability to survive in extremely harsh environments, such as on rocks, tree trunks, and even in the Arctic tundra. As they grow and spread, they can cause physical and chemical weathering of the substrate they are growing on, breaking it down into smaller particles and creating soil. This soil can then provide a suitable environment for other organisms to colonize and grow.

As lichens die, they decompose and release nutrients into the soil, which can support the growth of plantses This primary living transform an uninhabited environment to a more habitable one, can take centuries or even millennia.

Secondary succession, on the other hand, occurs when an already established ecosystem is disturbed, for example, by a wildfire or a forest clearing. In this case, the soil and other resources are already present, and the process of colonization and growth can occur at a much faster rate.

It is important to note that secondary colonisation should not be confused with secondary succession. Secondary colonisation is the process by which new species arrive in an already established ecosystem and begin to colonize it. These new species can be introduced through natural means, such as wind or water dispersal, or through human activities, such as the introduction of invasive species.

In conclusion, lichens play an essential role in the formation of soil and the creation of habitable environments for other organisms. While they may not be the most glamorous of organisms, they are crucial for the functioning of ecosystems and the survival of many different species.

Tertiary colonisation

As the layer of soil and organic matter grows thicker, it becomes more and more suitable for a wider variety of plants and animals to thrive. The arrival of fungal spores and seeds of small plants like grasses, carried in by the wind, water, or animals, marks the beginning of the tertiary colonization phase. These new arrivals can take advantage of the nutrients and shelter provided by the soil and other organisms, and begin to grow and reproduce.

As the plant communities become more established, they can support herbivores, which are also known as primary consumers. These herbivores feed on the plants and help to maintain the balance of the ecosystem. They, in turn, become sources of food for even larger animals, such as carnivores and omnivores, which are known as secondary consumers.

As the ecosystem continues to develop, the number and diversity of species increases. This is known as biodiversity, and it is an essential component of a healthy ecosystem. Biodiversity helps to ensure the stability of the ecosystem, as different species are able to fill different niches and provide different ecosystem services.

Overall, the process of colonization and succession is a slow and gradual one, taking place over hundreds or thousands of years. However, it is a critical process that helps to create and maintain the incredible diversity of life on our planet.

Shrubland

As the ecosystem continues to develop, the layer of soil deepens and becomes enriched with more nutrients from the decomposition of dead plants and animals. This creates a more fertile environment that is capable of supporting larger and more complex plants.

The plants and fungi in the ecosystem also develop extensive root systems that help to keep the soil in place and prevent erosion. These roots can penetrate deep into the soil, helping to anchor the plants and hold the soil in place during heavy rain or wind.

As the soil becomes deeper and more nutrient-rich, it is able to store more water and support larger plants like shrubs and small trees. These plants provide more shelter and resources for animals, which leads to even more biodiversity and complexity in the ecosystem.

Eventually, over time, the ecosystem may develop into a mature forest, with a rich and diverse community of plants and animals. This process of colonization and succession is essential for the creation and maintenance of healthy ecosystems, and it highlights the incredible resilience and adaptability of life on our planet.

Climax community

Now, the ecosystem has become much more complex than it initially was, allowing large species to come and colonise the area. The final species to colonise the ecosystem will play a dominant role in the area, bringing in new resources and habitats and allowing a diverse range of species to live together; large species of trees, such as oaks in deciduous woodlands or dipterocarps in rainforests, will often fill this niche. The final, stable community formed is known as the climax community.

What is the significance of ecological succession?

We can see several common themes emerging at each stage of succession. Firstly, the abiotic environment usually becomes less hostile to organisms. The environment collects and produces more nutrients, soil is formed, water is retained, and plants and other structures provide shelter. These create new habitats and niches for organisms to fill, which allow the environment to support more biodiversity and more complex food webs.

Ecosystems are particularly diverse and have very high biomasses during the intermediate or middle stages of succession. However, as they approach climax, dominant species can bring about changes in the abiotic features of the environment that make it less hospitable towards the previous species. For instance, large, dominant trees can block out sunlight and prevent smaller trees and shrubs from getting enough sunlight to survive. These are thus eliminated from the community, reducing the overall biodiversity but leading to a more stable ecosystem overall.

Succession and conservation

Understanding the stages of succession is very important for the conservation of habitats, particularly for maintaining high levels of biodiversity in a habitat. Read our article on Conservation to find out more!

Succession - Key takeaways Succession refers to the changes in the species that occupy a particular area over time. Succession makes habitats more hospitable to organisms. Primary succession occurs when new species gradually colonise a newly exposed or formed terrain. Secondary succession occurs when land undergoes drastic changes, and new species can recolonise. Succession occurs in a series of stages. These include the primary colonisation by pioneer species, secondary colonisation, tertiary colonisation, shrubland and the climax community. Pioneer species have traits that allow them to colonise not hospitable land to life. These traits include being able to reproduce asexually and fix nitrogen. The final, stable community formed after the stages of succession is known as the climax community.

Succession

What is succession in biology?

Succession refers to the changes in the species that occupy a particular area over time. Succession makes habitats more hospitable to organisms.

What is the order of succession in biology?

Succession occurs in a series of stages. These are:Primary colonisation by pioneer speciesSecondary colonisationTertiary colonisationShrublandClimax community

What is secondary succession in biology?

Secondary succession can occur when a stable habitat is suddenly cleared and new species recolonise the land. Secondary succession occurs at a faster rate than primary succession because the cleared habitat usually still has some of the resources it accumulated during primary succession.

What is primary succession in biology?

Primary succession occurs when a newly exposed or formed terrain is gradually colonised by new species.

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