Ecological Succession-Primary and Secondary

Ecological Succession

Ecological succession is the gradual change in an ecological community after a disturbance or when life begins colonizing a new habitat. Over time, succession can transform newly formed or damaged areas into ecosystems with established plant communities.

Primary Succession

Primary succession occurs in newly formed or severely disturbed areas where little or no soil remains. For example, lava flows can create new land, and volcanic eruptions can leave areas nearly stripped of life.

As soil develops, plants begin to grow, and the ecosystem may gradually return as a forest or grassland. The first organisms to colonize an area are called pioneer species; lichens and mosses are common examples.

Secondary Succession

Secondary succession occurs when an existing ecosystem is disturbed or damaged but the soil remains. Fires and floods are examples. Because soil is still present, recovery can proceed differently from primary succession.

A typical progression after a fire is:

1. Fire removes much of the existing plant growth but leaves the soil.
2. Grasses and other plants grow back first.
3. Small bushes and trees begin to establish themselves.
4. Fast-growing evergreen trees mature while shade-tolerant trees grow beneath them.
5. Larger deciduous trees eventually grow, producing an ecosystem similar to—but not necessarily identical to—the original.

Disturbance and Ecosystem Management

Disturbances can benefit an area over time and may contribute to increased biodiversity. Park services use controlled burns to manage weeds and other growth and to reduce wildfire risk. Fire can also destroy nutrients and help create conditions for more desirable plant growth later.

Speaker

• Narrator: The video’s single speaker, who explains ecological succession and its examples.