Stages of Ecological Succession Explained with Real-World Examples
Ecological succession is the remarkable process by which an environment transforms from a lifeless or disturbed state into a thriving habitat teeming with diverse life forms. By understanding ecological succession, you can appreciate how species take turns colonising land, forming complex relationships, and ultimately stabilising their surroundings. This cycle not only highlights nature’s resilience but also emphasises the delicate balance that keeps every forest ecosystem and other habitats healthy.
Below, we dive deeper into the ecological succession stages, the types of ecological succession, some fascinating ecological succession examples, and how it all ties into broader ecological concepts such as the ecological pyramid. You will also find unique insights, a fun quiz, and tasks to enhance your understanding of ecological succession in ecosystem development.
Definition of Ecological Succession
Ecological succession is the gradual and predictable shift in the composition of species in a region as the environment changes over time. This shift usually begins with the colonisation of hardy species (often mosses or lichens on bare surfaces) and progresses to more complex life forms, culminating in a stable, mature community known as the “climax community.” The overarching goal of ecological succession is to reach a balanced state where all organisms coexist in harmony.
Why does Ecological Succession Happen?
Ecological succession occurs because both the living organisms and their environment are constantly interacting and modifying one another. When pioneers like lichens or mosses break down rocks into smaller particles, they help form soil suitable for grasses or small shrubs. Over time, these smaller plants enrich the soil further, paving the way for larger flora such as trees. Eventually, when the right conditions are set, a climax community emerges, maintaining a dynamic equilibrium.
Key Points to Remember:
Succession ensures the utilisation and recycling of nutrients.
Changing microclimates within a habitat can favour new species while discouraging existing ones.
This phenomenon highlights how ecosystems adapt to disturbances, whether natural or human-induced.
Types of Ecological Succession
The types of ecological succession explain how different scenarios shape the way life forms develop in an area. Each type showcases the adaptability of organisms and the speed at which they recolonise after disruptions.
1. Primary Succession
Definition: Occurs in regions devoid of life, such as bare rock or newly formed volcanic surfaces where soil is initially absent.
Process: Pioneer species like lichens and mosses break down rock and create the first thin layers of soil. Gradually, small plants and grasses appear, followed by shrubs and eventually trees.
Speed: Typically slow because it begins from scratch, with no pre-existing soil.
2. Secondary Succession
Definition: Happens when a previously occupied habitat is disturbed or destroyed (e.g., by fire, farming, or storms) but the soil remains intact.
Process: Weeds and grasses often appear first. Over time, shrubs and young trees establish themselves. Eventually, if undisturbed, the area may return to its former climax community.
Speed: Faster than primary succession since a base of nutrients and soil microbes already exists.
3. Cyclic Succession
Definition: A recurring change in ecosystem structure that happens in a cyclic fashion.
Example: Some plant species lie dormant most of the year and then bloom simultaneously, altering the habitat’s structure and the species interactions in a repeating cycle.
Stages of Ecological Succession (Seral Stages)
Ecological succession stages are often called seral stages, each representing a temporary community on the way to the final, stable climax community. Every seral stage modifies the environment, making it more conducive for the next stage of species.
Pioneer Stage: Dominated by hardy species capable of surviving in harsh, nutrient-poor conditions.
Intermediate Stages: As soil quality and organic matter improve, more species—typically grasses, shrubs, and small trees—colonise the area.
Climax Community: A stable, mature community that can persist until a disturbance resets the cycle.
When life starts from absolutely nothing, it’s primary succession; when it rebounds after destruction, it’s secondary succession. In both cases, seral communities serve as stepping stones toward equilibrium.
Seral Community
A seral community is any intermediate stage found within the succession process. It often has:
Simple food chains and minimal diversity.
Fewer species compared to a climax community.
Lower nutrient availability, gradually built up by successive communities.
The concept of seres applies to various conditions, such as:
Hydrosere: Succession in aquatic environments.
Xerosere: Succession in dry habitats.
Lithosere: Succession on bare rock.
Psammosere: Succession on sandy substrates.
Halosere: Succession in saline conditions.
Senile (Saprosere): Succession on decaying organic matter.
Eosere: Broad-scale development of vegetation from an early geological era.
Explore, Food Chain & Food Web and the Differences between them
Ecological Succession Examples
Real-world ecological succession examples illustrate how these natural processes unfold:
Acadia National Park:
A devastating wildfire once stripped the land of its evergreen forest cover.
In the immediate years, only small shrubs, grasses, and wildflowers could grow on the depleted soil.
Over subsequent decades, deciduous trees like birch and aspen took root, reshaping the forest ecosystem into one more diverse than the original.
Coral Reef Succession:
Tiny coral polyps anchor themselves onto submerged rocks.
Over time, these corals expand into large colonies, attracting small fish and crustaceans.
Larger predators follow, culminating in a vibrant reef teeming with life.
Old Farmland Reclaimed by Nature (Unique Example):
Abandoned agricultural fields see quick growth of weeds and grasses.
Gradually, shrubs and pioneer trees emerge.
Eventually, the land may convert into a young forest ecosystem, reflecting a classic case of ecological succession in ecosystem restoration.
Role of Ecological Pyramids in Succession
An ecological pyramid visually represents the distribution of energy or biomass across different trophic levels in a community. During the early seral stages, these pyramids might show fewer consumers because pioneer producers (like mosses or grasses) offer limited energy. As succession progresses and more diverse and abundant plant life emerges, the pyramid broadens at the base (producers) and subsequently at higher levels (herbivores and predators). Monitoring the ecological pyramid at various stages can help ecologists understand the energy flow dynamics and the overall health of the evolving community.
Importance of Ecological Succession in an Ecosystem
Ecological succession in ecosystem development is essential because:
It drives biodiversity, allowing various species to settle into niches over time.
It aids in soil formation and nutrient cycling.
It helps habitats recover from natural disasters and human-induced disturbances.
It maintains ecological balance, ensuring sustainable interactions among organisms.
Interactive Quiz: Test Your Knowledge!
What is the final, stable stage of ecological succession called?
Name one difference between primary and secondary succession.
Which organisms usually appear first in primary succession?
Give an example of cyclic succession.
Why does primary succession take longer than secondary succession?
Check Your Answers
Climax community
Primary succession starts with no soil; secondary succession begins with existing soil.
Lichens and mosses
Seasonal plant cycles, where dormant plants bloom all at once each year
Primary succession starts on bare rock or surfaces without soil, slowing colonisation and soil formation
FAQs on Ecological Succession: Understanding How Ecosystems Change
1. What is ecological succession and why is it important?
Ecological succession is the gradual and predictable process of change in the species structure of an ecological community over time. An area of bare rock, for instance, will not stay barren forever. It will be colonised by pioneer species, which are gradually replaced by other species, leading through several seral stages until a stable climax community is formed. This process is important because it allows ecosystems to develop, mature, and recover from disturbances, leading to increased biodiversity and stability.
2. What is the main difference between primary and secondary succession?
The primary difference lies in the starting conditions of the environment.
- Primary Succession occurs in an area that is devoid of life and has no existing soil. It starts on bare surfaces like newly formed volcanic islands, cooled lava flows, or exposed rock after a landslide. This process is very slow as it requires the formation of soil first.
- Secondary Succession occurs in an area where a previous community existed but was removed by a disturbance, such as a forest fire, logging, or an abandoned farm. The key is that the soil and some life forms (like seeds or roots) already exist, making this process much faster than primary succession.
3. What are pioneer species and what is their specific role?
Pioneer species are the first organisms to colonise a barren or disturbed environment in the initial stage of succession. A classic example is lichens on bare rock. Their role is critical because they are hardy and can survive in harsh conditions. They perform two main functions:
- They help break down the rock surface to begin the process of soil formation.
- When they die and decompose, they add essential organic matter to the developing soil, making it possible for other, less hardy species like mosses and grasses to establish themselves.
4. Can you provide some real-world examples of ecological succession?
Certainly. Here are some common examples:
- Primary Succession Example: The colonisation of a new volcanic island like Surtsey off the coast of Iceland. Initially barren volcanic rock, it was first colonised by lichens and mosses, followed by grasses, and eventually, small shrubs and trees.
- Secondary Succession Example: An abandoned agricultural field. Initially, weeds and grasses will dominate. Over years, they will be replaced by shrubs, then fast-growing trees like pine, and finally, a stable hardwood forest (the climax community) may develop.
5. What are the key processes or stages involved in ecological succession?
Ecological succession is a continuous process driven by several mechanisms:
- Nudation: The creation of a bare, lifeless area, either by natural disturbances (like volcanic eruption) or human activities.
- Invasion: The arrival of seeds or spores (migration) of pioneer species, followed by their germination and establishment (ecesis).
- Competition and Co-action: As the population of species grows, they begin to compete for resources like light, water, and nutrients. They also interact with each other (co-action).
- Reaction: The living organisms modify their own environment. For example, plants add humus to the soil and alter light conditions, making the habitat unsuitable for themselves but suitable for new species.
- Stabilisation: This is the final stage where a relatively stable climax community is formed, which is in equilibrium with the local climate.
6. How do key ecosystem attributes like biomass and species diversity change during succession?
During ecological succession, several ecosystem attributes change in a predictable way. As the community progresses from pioneer to climax stages:
- Species Diversity: It generally increases. Pioneer stages have few species, while later stages support a wide variety of plants, animals, and decomposers.
- Biomass: The total amount of living organic matter (biomass) increases significantly as small, simple life forms (like lichens) are replaced by larger, more complex ones (like shrubs and trees).
- Nutrient Cycling: It becomes more efficient and 'closed'. In early stages, many nutrients are lost from the ecosystem. In the climax stage, nutrients are effectively recycled within the community, ensuring long-term stability.
7. Does ecological succession always end in a forest? What determines the climax community?
No, a forest is not always the endpoint. The type of climax community is primarily determined by the regional climate. While a temperate forest might be the climax community in a region with high rainfall and moderate temperatures, other climax types exist. For example:
- In regions with low rainfall, the climax community might be a grassland or a desert scrub.
- In cold, high-altitude or high-latitude regions, the climax community is often tundra.
8. Why are seral communities considered crucial, not just temporary steps?
Seral communities (the intermediate stages) are crucial because they actively facilitate the progression of succession through a process called reaction. Each seral stage modifies the environment in ways that make it less favourable for itself but more favourable for the next stage. For example, grasses in an old field add nitrogen and organic matter to the soil, which helps nutrient-demanding shrubs to grow. The shrubs then shade out the grasses. Without these transitional stages and their environmental modifications, the climax community could not be established.
9. How does succession in water (hydrosere) differ from succession on land (xerosere)?
While both follow the same principle of community change, the environments and species are different.
- Hydrosere (in water): Starts in a water body like a pond. The pioneer species are tiny phytoplankton. These are followed by submerged plants, then floating plants, and reed swamps. Over time, sediment and organic matter fill the pond, turning it into a marsh, then scrubland, and potentially a climax forest. The trend is from a hydric (wet) to a mesic (moderate moisture) condition.
- Xerosere (on dry land): Starts on a dry, barren surface like rock. The pioneers are lichens and mosses. They create soil, allowing herbs, shrubs, and finally trees to grow. The trend is from a xeric (dry) to a mesic condition.
10. How can human activities influence the natural process of ecological succession?
Human activities can profoundly impact succession in two main ways:
- Interrupting or Reversing Succession: Actions like deforestation, agriculture, and urbanisation destroy climax or late-stage communities, resetting the successional clock to an earlier stage (initiating secondary succession). Pollution can also alter environmental conditions so severely that natural succession is inhibited.
- Accelerating Succession: Humans can also speed up the process. Through ecological restoration efforts like reforestation (planting trees) or enriching depleted soil, we can help a disturbed ecosystem reach its climax stage faster than it would naturally.
