Visualizing Succession

When learning about the parts and interactions in an ecosystem, it is essential to understand the dynamic nature of living things. However, despite understanding how living things change, students often perceive ecosystems themselves as stable and unchanging. Because of this, learning about succession is an important part of understanding ecology. 

Succession is change in an ecosystem. It often occurs after a disturbance of some type. The disturbance can be human-induced, such as clear-cutting a forest, but can also be from natural influences. The Earth itself is dynamic, which means that change is a constant. Lightning causes forest fires, winds can flatten trees, and volcanic activity can change the landscape entirely.  Succession restores the ecosystem through a series of biological communities.

There are two types of succession, primary and secondary. Primary succession takes much more time because it occurs in an area where there is no soil. A granite outcrop or fresh lava flow would seem devoid of life, however, lichens and mosses are pioneer species that can break down rock and create soil. With the help of erosion, over time, these areas can become fertile ecosystems. To see primary succession first-hand, my classes venture outdoors to examine sidewalks and parking lots for signs of life. We discuss how if left alone, the action of wind, water, and living things would break down the rock and gravel into soil.

While outside, we also look for signs of secondary succession. Secondary succession occurs in areas where soil is present, but a disturbance has taken place. In certain areas, an abandoned field can become a forest once again as blackberry bushes and pine saplings create conditions necessary to germinate oak and hickory tree seedlings. Unlike primary succession, which can take hundreds to thousands of years, secondary succession can occur over a period of one to two hundred years.  My classes observe the edge of a forest and discuss how a field can change if undisturbed. 

A discussion of secondary succession leads us to the topic of forest fires. My students are surprised to find out that many forests are actually fire-dependent. As humans have suppressed forest fires, leaf and wood debris have built up and created unhealthy forests that may be subject to intense burns. When natural fires are allowed or prescribed fires are used, fuel is burnt that would otherwise lead to a large uncontrollable fire later. 

These topics are fascinating, but difficult to understand from within a classroom. To help, my students view videos and manipulate computer models. They also create flipbooks to illustrate ecosystem change. The lessons below can help you teach your students about the complex changes of succession.

Succession Lessons and Activities:

Investigating the Process of Plant Succession 

In this lesson students learn about secondary succession in plants. They discuss the role maintenance plays in the diversity and stability of ecosystems.

Ecological Succession in Pond Water Cultures  

Students analyze a pond ecosystem in this lesson. They gather samples of pond water, grass, and soil. They make predictions about the pond water cultures. They compare their expected results with the observed results.

Pond Succession Mural

As part of this lesson, students create a mural depicting the three stages of pond succession. They discuss what changes would occur in a pond over time, and show what it would look like.

Primary and Secondary Succession in America's Forests

Students learn about succession in the forest environment and classify organisms according to where they come from, and how they are interrelated.