An important and often misunderstood concept in ecology is succession. Succession refers to the series of changes observed in a plant community following a disturbance event (Connell and Slayter 1977). A disturbance event, such as a wildfire, flood, landslide or hurricane, is an event that changes ecosystem structure and resource availability (Pickett and White 1985). For an example of succession, think of a severe forest fire that kills many trees. What was once a closed canopy forest with very little light reaching the ground is now a very open and bright place. Plants and seeds that were in the shade can take advantage of the new available resources, including sunlight. The plant species that will thrive in the new, open environment may be different from those that grew under the closed forest canopy. These plants are called early successional plants because they thrive in recently disturbed environments. They are also called colonizers, ruderals or weeds. Over time, as colonizers grow, they change the environment again (by shading, or changing soil conditions), which creates opportunities for a different set of plant species. These plant species that establish after the early successional species are called late successional species. They are generally less tolerant of disturbance events. These species also often grow more slowly and live longer than early successional species and only become prevalent a while after the disturbance event. Plant communities can be thought of as going through cycles of disturbance followed by succession followed by disturbance and so on. This is not to say that these cycles, and the resulting communities, are ever identical or exactly repeatable.
In this lab, students explore the dynamics of plant communities, that is, how plant communities change over time and space as a result of interactions between plants, their biotic and abiotic environment, and chance events. The concepts of succession and disturbance dynamics are timely given the extent to which human-caused disturbances, such as logging and land development, are influencing global ecosystems and the extent to which natural disturbances, such as fires and floods, are actively managed. Informed voters and citizens should know about disturbance and succession in plant communities. Knowledge of these processes will help them make decisions about land conservation, wildlife habitat restoration and natural resource management practices.
In the game, each student plays the role of one of six different imaginary plant species. The student with the most plants of his or her species in the community wins the game. As students play the game, they learn that the six plants respond differently to the disturbances. They also learn that plants interact with each other. Each round begins with an event card randomly drawn from a deck of cards. All the players then move across the playing board based upon that one event and the response of their given plant species. When two or more players land on the same spot, they must draw an interaction card for each pair of interacting players.
The rules handout explains how to play, step by step. The game ends when a player reaches the Finish square. At the end of the game, students count the event cards that were played, and record the number of each event type on their worksheet (Figure 8). Students also record the position of the players on the playing board. Using the sample diagram (Figure 9), have students diagram what their plant community looked like at the end of the game (based on the premise that the further a player travels on the board, the greater the number of individuals of their species). If any players are at the Start box at the end of the game, their species has zero plants in the diagram. After an initial discussion following the first game, ask students to predict the results of a game played without the Disturbance Event cards. They can play again and test their prediction. To evaluate their learning, ask students to “manage” disturbance by stacking the event deck to favor a particular species. Then have them test the results of their management by playing a game with the stacked deck.
Number of players: 6
Object of the game: First player to reach the “Finish” square wins.
Step 1: Choose a dealer.
Step 2: All players, including the dealer, choose a game piece. Place game pieces in the “Start” square.
Step 3: Dealer shuffles Event Cards and places them face down in Future Events spot on the playing board. Shuffle and place the Interaction Cards face down in their spot, and deal one Character Card to each player.
Step 4: The dealer draws the first Event Card and places it face up in the Current Event spot.
Step 5: Each player then plays according to the Event and Character Card directions, starting with the dealer and going clockwise.
Step 6: After all players have their turn, check the board for players who landed on the same square. These players are interacting.
Step 7: Repeat Steps 4-6 until a player wins. Record the order of the players and the number of each type of event that occurred during the game.
Some possible discussion questions include:
After initially diagramming their community and answering discussion questions within their group, you could have students share their results with the class. You could also jigsaw the teams and ask all the truffula trees to compare their data, all the lorax trees to compare their data, etcetera, to demonstrate that the same species don’t always have the same successional outcome.
With advanced students, you can introduce other concepts in plant population biology and community ecology. For example:
You can have students turn in written answers to the discussion questions. I have also used the following questions to assess student learning. Specifically, we quizzed students before and after the lesson to see if they learned what we hoped they’d learn.
Figures 10 & 11: Photos for formative evaluation pre and post activity quizzes.
From: Hastings and Turner, The Changing Mile, 1968.
Figure 10: Red Rock Canyon, Patagonia, Arizona 1895.
Figure 11: Red Rock Canyon, Patagonia, Arizona 1965.
Other assessment options include having students apply what they have learned by asking them to try to stack the Event Cards deck to favor a specific species. Have students report their findings. You could have students decide on the grading standards for this report. By creating their own grading rubric, students feel more ownership in and take more responsibility for writing a good report. Ask them what a good report should include, and what parts of the report are essential, without which the report is not satisfactory. These criteria provide the scale from A to F.
“Environmentalists of the group Earth Brigade are asking the government to ban all grazing in Lorax National Forest. They believe that if the park manager continues to allow cattle to graze in the forest, that soon there will be no Borogrove grass in the forest. The rancher who owns the cattle that are in the forest has told the government that grazing is good for the forest. Grazing encourages the Grickle grass to grow, and the Grickle grass helps the Borogrove grass. The park manager at Lorax National Forest has been telling his boss and others in the government, that grazing makes no difference. Who is right? What happens if we remove grazing? If the decision is made to allow grazing, how often should it happen?”
The evaluation of this activity is tied to the assessment. Specifically, we quiz students before and after the lesson to see if they learn what we hope they learn, and see how to revise steps in the instruction for next time.
To see results of our evaluation, go to the Comments on the Evaluation of the Activity in the "Notes to Faculty" section.
An extensive discussion on Evaluation appears in the Teaching section of this site.