Module 9S1 Ecological Interactions

Explore

The changes that a community goes through as it ages are known as succession. For every biome, or micro-climate within a biome, there is a predictable succession of plant and animal species that will play their parts then disappear, from the first pioneer species to the final stable climax species that represents the completed succession. Communities are named by their climax species (e.g. aspen forest, black spruce forest). Why does succession occur? How does one species change the environment resulting in its replacement by another species? How does primary succession differ from secondary succession?

 

Read

Read p. 725-6 and 728 in the textbook.

 

Watch and Listen

Succession and Climax Communities

Description of Succession

 

Primary V.S. Secondary Succession

 

Self-Check

Alberta has significant forestation. Every year you hear about the forest fire hazard, and where fires are burning out of control. To review the role of fire in the ecosystem and how it affects the succession of communities, try the following self check. You may wish to score your answers, and be sure to add your work to your course folder.

Fire is a force of nature that has positive and negative roles to play in a healthy ecological community. In nature, the source of fire is lightning.

 

Research the following questions regarding the role of fire.

 

SC 1. What positive and negative roles do forest fires play in nature?

 

SC 2. Research and evaluate the practice of ‘controlled burns’ used in National Parks in terms of advantages and disadvantages. If fire terminates an existing succession and causes secondary succession to start over, isn’t a controlled burn interfering with natural processes?

 

SC 3. In the past, native aboriginal Albertans would purposely set prairie fires in the spring to begin a secondary succession. Why? (Remember what the primary food source was.)

 

SC 4. One of the first species to colonize burned forest is fireweed. What are some traditional uses of this plant by native aboriginals?

 

 

Try This

To review the types and conditions of succession, complete the following table for your course folder.

 

TR 1. Using your text fill out the following table:

	Starting Point (soil or bare rock)	Possible Causes (ecological disturbance)	Pioneer Species
Primary Succession
Secondary Succession

 

 

SC 5.

If producer species go through successions, consumer species must as well. As the food source changes, conditions favor the invasion of different animal species. For example, after a fire, the pioneer species of grasses favors the presence of seed eaters like mice and gopher. The lack of overhead cover suits them in that they can burrow to hide from predators overhead like hawks. When the soil is too cool and shady to germinate grasses, shrubs start to appear, and rabbits will tend to replace the mice and gophers.

 

Continue this central Alberta plant animal succession on the table below. You made need to do some research on Alberta food chains.

Producer succession	Consumer succession
Pioneer species: grass	Mice/gophers/coyotes
Low shrubs (berries)
High shrubs
Aspen poplar trees

 

 

 

 

 

 

Self-Check

Succession and Biodiversity

You will recall the significance of biodiversity from Biology 20, and from Unit D, Module 8. Consider how they might interact by completing the following assignment. There is opportunity to score your answer, but be sure to file your work in your course folder.

 

How does primary succession affect genetic biodiversity of communities?
Check out "Figure 20.21" on page 726 and answer the following questions.

 

SC 1. What is the effect of time on biodiversity in a succession? Why does this occur?

 

SC 2. Why is the number of species that can survive at the beginning of the succession so low?

 

SC 3. Why does the number of species level off towards the end of the succession?

 

SC 4. How many years did it take to complete this succession?