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Ecological Succession
Ecological Succession
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Ecological succession is the gradual change in a biological community over time after a new habitat forms or a disturbance resets an existing one. It matters because it explains how ecosystems recover, how biodiversity develops, and how soil, water, and climate interact with living things. Succession helps scientists predict what species may appear first and how communities become more complex. It also helps land managers restore damaged environments.
In primary succession, life begins on surfaces with no soil, such as bare rock left by lava or glaciers. In secondary succession, soil is already present, so recovery usually happens faster after events like fire, farming, or storms. Early species modify the environment by adding organic matter, holding moisture, and changing light levels, which allows later species to establish. Over time, the community often shifts toward a more stable and diverse mature ecosystem called a climax community.
Key Facts
- Primary succession starts without soil, while secondary succession starts with existing soil.
- Pioneer species are the first organisms to colonize a disturbed or newly exposed area.
- Lichens and mosses help form soil by weathering rock and adding organic material.
- Biodiversity and biomass usually increase during succession, especially in early to middle stages.
- Rate of succession depends on climate, soil quality, disturbance frequency, and seed availability.
- Net primary productivity = gross primary productivity - respiration
Vocabulary
- Ecological succession
- The gradual change in the species composition of a community over time.
- Primary succession
- Succession that begins in an area with no soil, such as bare rock.
- Secondary succession
- Succession that occurs after a disturbance in an area where soil remains.
- Pioneer species
- The first hardy organisms that colonize a new or disturbed habitat.
- Climax community
- A relatively stable, mature community that forms after many stages of succession.
Common Mistakes to Avoid
- Confusing primary and secondary succession, because students often ignore whether soil is present. Soil absence is the key feature of primary succession, while secondary succession begins with soil already in place.
- Assuming succession always ends in one permanent climax community, because real ecosystems can be changed again by fire, storms, climate shifts, or human activity. Succession is dynamic, not a guaranteed final endpoint.
- Thinking pioneer species are large plants or trees, because early colonizers must tolerate harsh conditions and low nutrients. Small hardy organisms like lichens, mosses, and grasses usually arrive first.
- Believing later stages always have faster change, because the biggest visible shifts often happen early when bare ground is first colonized. Later stages may change more slowly as competition and stability increase.
Practice Questions
- 1 A volcanic eruption leaves a bare rock surface with no soil. Name the type of succession and identify one likely pioneer species.
- 2 A field is abandoned after farming, and soil is still present. If grasses dominate after 3 years and shrubs appear after 10 years, what type of succession is this, and which stage comes later: grasses or shrubs?
- 3 Explain why secondary succession usually happens faster than primary succession using soil and seed availability in your answer.