Primary and Secondary Succession
Learning Goal: To understand how human and natural interactions can change ecosystems, and how ecosystems respond to these changes.
There are two types of succession:
1) Primary succession:This is the process of an ecosystem development, and takes place in areas lacking soil (bare rocks, sand dunes, and cooled lava for example). It can be started by pioneer species like lichens.
2) Secondary succession: The process by which an ecosystem changes after it has been disturbed, for example by a forest fire. This succession represents the re-growth of a community.
1) Cleaning the forest floor: Fire removes low-growing underbrush, cleans the forest floor of debris, opens it up to sunlight, and nourishes the soil. Reducing this competition for nutrients allows established trees to grow stronger and healthier.
2) Providing habitat: Fire cleans wild lands of heavy brush, leaving room for new plant species that provide a habitat for wildlife.
3) Killing Disease: Fire kills diseases and insects that prey on trees and provides valuable nutrients that enrich the soil. More trees die each year from insect infestation and disease than from fire.
4) New Generations: Change is important to a healthy forest. Some species of trees and plants are actually fire dependent. They must have fire every 3-25 years in order for life to continue.
Click on the picture to go to a link to an interactive game on succession. Explore the game and try the check your understanding quiz at the end.
ACTION ITEM #2:
Succession can impact: soil composition, plant types, animal types, and amount of light in an ecosystem. With a partner, draw and label and illustrate a diagram demonstrating and explaining these changes. Make your thinking visible!
Click on the link below to complete your science journal:
Extra Learning Resources:
Over hundreds of years, vegetation changes from bare rock, to small annual plants and lichens (slow-growing plants that grow on rock), to grasses and herbs that come up each year, to larger trees.
After a forest fire, ecosystems travel through successions, eventually rebuilding the forest ecosystem.
Secondary succession refers to the concept of an ecosystem reviving itself after all or a portion has been destroyed. The concept refers primarily to plant life and can be the result of a natural or man-made event. The primary concept is that the life was previously on the soil, eliminating the need for deposition of new seeds or soil. Secondary succession is a much more rapid process than primary succession because the soil and nutrients are already available.
Examples of secondary succession include:
- The renewal of a forest after a fire: The fire itself destroys a majority of different types of trees and plant life. Because seeds and roots and other plant and tree parts remain in and on the soil, gradually the plants and trees begin to grow again and eventually returns to the state of the original ecosystem.
- The renewal of a crop after harvesting: A crop is completed harvested when it becomes ripe. Without new seeds being planted, the crop can regenerate the following year due to the plants and seeds that remained after harvesting.
- A forest renews after logging: A large amount of trees were chopped down by loggers in order to create building materials. Over time, trees grow in and the area returns to its previous state.
- A volcanic eruption: In an area where a volcano erupts, lava may cause some damage to the plant and tree life. Over a span of years, however, if there was land that had been affected by the eruption but not necessarily covered in new volcanic rock, the seeds and plant parts and roots in the soil could renew.
- On the island of Lawahii, several centuries ago, a fire erupted that caused the destruction of all plants and vegetation. Many years later, the plants and vegetation had grown back in, as the nutrients, seeds and soil remained.
- Renewal after disease: A plant population can be very negatively affected by a variety of infectious plant diseases. If the entire population dies, but the soil and roots remain, it is possible for secondary succession to occur and for the population of those plants to to return.
- A flood can ruin farmlands. However, because the soil remains after the waters recede, over the course of many years a natural secondary succession can occur and the vegetation that had previously grown there can grow again.
- Plants can be very susceptible to attack from pests, particularly if there is an overpopulation of those pests. When this occurs, the plant population in one area can be completely destroyed. However, when the pest overpopulation is resolved, the plants are able to live again and thrive in the soil in which they previously had lived.
- Potato scab is a tuber disease that grows on potatoes. If this disease affects a large amount of potatoes, the potatoes may not grow or may be harvested and thrown away. Over time, once the disease has been eradicated, healthy potatoes can grow again.
All of these examples of secondary succession help to show exactly what secondary succession is and how it works in the real world.