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Lesson

Defining  Succession:

Succession refers to the series of ecological changes that every community undergoes over long periods of time. The process of succession begins with relatively few  plants and the animals that are associated with these plants. The plant life serves as food, and often shelter for the animal life that can survive in a particular environment. The succession in the plant life is therefore matched by a succession in animal life.

 As a result of the process of succession, a primitive community develops. The organisms that make up the primitive community gradually change the environmental conditions so each successive community paves the way for the next. Each successive community develops through increasing complexity until it becomes a final, sustainable, stable community, of dominant organisms, known as a climax community.

Climax Community.....final stage of succession

In an ecosystem with a climax community, the conditions continue to be suitable for all the members of the community. The climax community is the final stage of ecological succession. This stage has the greatest diversity of organisms and very complex food chains and food webs.

Succession will occur whenever there are favorable circumstances. Over a long period of time(1000’s of years) an area can change from bare rock to a forest if the abiotic and biotic factors are favorable. This change would take place in a series of steps or stages:..........................

Stages or Steps to Succession.........

    Stage #1:...here comes the lichens

                                   

·         small hardy plants such as lichens  will gradually break down the surface of rock and soil will start to form

Stage #2:....here comes more soil

                     

·        as plants grow and die they add organic material (material from their bodies containing carbon) to the soil that is forming and worm and insects will start to move in.

Stage #3:....here comes the small plants

·         as a thin soil forms, other small plants such as grass and small shrubs will begin to grow, further adding to the soil as they grow and die as well.

Stage #4:....here comes the animals

·         Small animals such as mice and rabbits will move into area as more and more plants grow there  providing food and shelter.

Stage #5:.....here comes the larger plants

·         Over time, as the soil becomes rich and deeper, more larger plants will grow such as large shrubs.

Stage #6......climax community is forming

·         If the abiotic conditions are favorable, trees will grow and a forest will now be growing where once there was only bare rock.

Click here to view interactive video on succession

Succession can also occur when an ecosystem undergoes a drastic change such as when:

…..a forest burns down                                                                  

.....a farm is abandoned

In both cases, there is already a good soil present and the early stages of having only hardy plants present is bypassed. Also, in both of these cases, with enough time, the climax community will change if the factors are favorable.

Below, is another diagram showing the stages of succession from left to right. In an actual succession, only one stage is present at any given time.

Factors that contribute to ecological succession:

Climate....

The most important environmental conditions that affect succession include the climate such as temperature, precipitation, and availability of sunlight.

Soil....

characteristics such as salinity (amount of salt), fertility, moisture, and  texture, are also very important.

Geographical Features.....

such as latitude, altitude, and closeness to mountain ranges or large bodies of water are important.. For example, in a hot ,dry desert, the climax community will certainly be quite different from the climax community that would form in a humid but cool environment such as the forests of Newfoundland and Labrador.

What!!...no such thing as a Climax community????........

Some biologists argue that there is no such thing as a climax community because the entire Earth is in constant change or upset. The causes of upset include both:

Natural events such as floods, fires, volcanic activity, climate changes, species extinction, etc.),

Human influenced events such as acid rain, ozone depletion, enhanced global warming, pollution, habitat destruction, monoculture farming, clear-cut logging, and over-fishing, etc.).

Activity

Activity 1:

Search the web to find at least one example to illustrate succession. Prepare a brief research paper, including a sequence of diagrams or images, to describe the changes that occur during succession and lead to the formation of a climax community. Your series of diagrams or images should identify the different types of plant and animal life found at each stage in the process, and clearly identify the type of climax community formed at the end of the process of succession. You essay should include answers to each of the following questions:

• What is succession?
• What factors contribute to succession?
• What are the characteristics of a climax community?

Here are a few links to get you started:

• Link webpage on forest succession.
• Link to "Buell-Small Succession Study."
• Link to slide show by Dr. Collins, Biology Department, MUN.
• Link to some images related to succession.
• Outline notes - excellent images on succession.
• Farm to forest succession - shows stages.

Activity 2:

Imagine that a forest fire has wiped out all the trees and other plant life in an area near where you live. Predict what plants and animals will move into the area after the fire over a long period of time( say 400 years) by compiling a list.

Activity 3:

Plan a field trip to an area where evidence of succession is occurring, ex: pond with grass growing in it

Test Yourself

1. What is succession?
   1. one community type replaces another over time
   2. a forest is destroyed and replaced by a pond
   3. a climax community is destroyed forever
   4. a series of natural changes leading from climax community to the early beginnings of a community
2. What factors might result in succession?
   1. A forest is destroyed by fire.
   2. A farmer plants different crops each year.
   3. Pollution causes rapid plant growth in ponds.
   4. An island is formed by volcanic activity.
3. What is a climax community?
   1. The final stable community in succession.
   2. Bare rock represents the climax community.
   3. The first types of plants and animals to be established.
   4. The point when all life forms become extinct.
4. Which statement is true of succession?
   1. The  organisms which first arrive represent the dominant forms of plant life.
   2. Lichens will make up the climax community.
   3. Succession will occur whenever there are favorable circumstances.
   4. Succession occurs over a short period of time
5. Which is a probable correct order in which organisms appear in a community undergoing succession?
   1. trees--->lichens--->worms--->shrubs
   2. worms--->lichens--->shrubs--->trees
   3. lichens--->worms--->shrubs--->trees
   4. shrubs--->trees--->lichens--->worms