Challenges to Anticipate and Solve

Overcoming student statistical misconceptions:

Through evaluation we have discovered that some students develop the misconception that plant community changes are unpredictable due to the randomness of the environment. It is important to explain what predictability means. Given knowledge of the probable changes in the environment, and knowledge of how species may respond to these changes, it is possible to predict changes in the community with some degree of certainty. You can remind students of the example of playing the game without disturbance cards. In that case you can make two predictions: 1) there will only be three species in the community, and 2) all three will be late successional species.

You could also discuss this type of ecological forecasting using the example of weather forecasting — the goal is to predict a statistical likelihood of a particular weather pattern such as will it rain or not. If the most likely event is rain, but it then turns out not to rain, that does not mean that the weather forecasting model was wrong. Many students do not understand this distinction, and this simulation is a good way to teach about statistical thinking.

Another way to address this would be to deliberately stack the decks of Event Cards among groups, if one has a larger class. Give some groups very few disturbance cards and give some groups lots of them, but don’t tell them ahead of time. Then, at the end when the among group discussion occurs, educe from them the suggestion that disturbance frequency may have differed to account for why one set of groups led to Early winners and in the other set the Late species won out.

Bringing students back to learning mode after playing:

This seems to be a common challenge when doing fun activities. The transition from game playing to filling out worksheets seems to work well in focusing students on the learning aspects of the game, it will work better if each student fills out their own individual worksheet. You could also use a cycle of guided discussions at this stage. First, have students discuss and write responses within groups, drawing their community diagrams on overheads or on the board. Students could then report their results to the class (2 mins/group). Then, you could lead a class-wide among group discussions to compare results.

Translating from the model system to real systems:

The game overstresses the role of chance in plant community dynamics. Be sure to discuss this with students. In real systems, disturbance regimes tend to have some level of predictability. Fire regimes, for example, can be tied to cycles of precipitation and lightning seasons. Periods of high rainfall, which result in high productivity, are followed by dry periods during which plants dry out and become easier to ignite when lightning strikes.

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Lab Description

Introducing the Lab to Your Students:

This activity has been used as an introduction to succession with little or no introduction to the activity. Simply distribute materials, read the rules with students, and walk them through the first round of playing. At the end of game playing, ask students to fill out worksheets. Distribute discussion questions for students to answer and use these to introduce the main concepts of succession and disturbance dynamics.

Activities in the Lab:

The following comments could be shared with students, as part of their introduction to the lab.

• On teaching succession: A common misconception of succession is that it always progresses the same way towards the same end community. That is, if a plant community is disturbed and then left alone, it will always return to its initial condition. In textbooks, succession is often depicted in this way, as a directional, deterministic process (Gibson, 1996). This view of succession as a singular pathway of progression from a cleared, recently disturbed site to mature climax vegetation is outdated. Current theories suggest that succession will not always create the same community that existed before the disturbance. There are multiple possible outcomes, depending on many factors including the order of arrival of colonizing species, which varies over time and space and can depend on chance (Diamond and Case, 1986). Also, because disturbances can re-occur frequently, the plant community might always be in a state of flux, never reaching a climax state (Pickett and White, 1985). This lesson attempts to address this misconception, and teach succession as a dynamic process that can be reasonably, but not completely, predictable. By teaching about succession through its mechanisms we can avoid teaching some of the misconceptions about climax communities.
• On using a game to teach succession: This game is a dynamic way to teach a dynamic subject. There is a body of literature on the use of games in learning (for a review see Ellington et. al., 1998). Games have been shown to increase student motivation, increase retention, and in some cases, shorten the time to teach concepts to naïve students (Randel et al., 1992). We decided to teach this topic using a game for several reasons. Games are fun. Students easily learn complicated sets of rules in order to play a game. We can use this to our advantage by making analogies between game rules and the theories and concepts we want to teach (Kaplan and Kaplan, 1982). As students play the game, they learn the rules, which are analogous to the mechanisms of succession. Students begin building their own conceptual model of the mechanisms of succession through game play. Also, even though games are no better than traditional teaching methods at teaching factual information (Randel et al., 1992), they seem to be more effective in teaching dynamics (Monroe, 1968). Third, it can take many years to observe succession in nature; the game condenses this time and allows students to watch plant community dynamics within a class period. Fourth, current curriculum about succession is limited in its applicability because it is designed to take advantage of regional examples such as old-field succession in temperate hardwood forests. Because it uses imaginary species, this game can be played anywhere in the world. And last, we wanted to create a system where students could interactively explore the plant community dynamics, rather than just observe them. They can experiment with the plant community by manipulating the disturbance processes, and observe the changes that occur as a result of their actions.

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Questions for Further Thought

There are many ways to discuss the activity. After comparing the results of each group’s game, you could discuss what the movement across the board represents (the farther a character travels, the more individuals it has in the community). You could also talk about what made the different group’s game sequences and outcomes different from each other.

Essentially, the outcome of the game is greatly affected by chance events.

Discussion Questions:

• Which species tend to get ahead during times of no disturbance? What life history traits do they have in common?

Answer — The species that tend to move ahead, i.e., become more abundant, during no disturbance in the game are all “Late Successional” types.

• How do early and late successional species differ from each other?

Answer — The outcome of interactions in the game is different for early and late species.

• Which life history traits might allow a species to respond well to a fire event? Which traits might make a species a better competitor?

Answer — Early successional plants thrive in recently disturbed environments; some traits they share include small seeds, fast growth, and tremendous dispersal capacity. They are also called colonizers, ruderals or weeds. Late successional plants often grow more slowly, live longer, are more shade tolerant, produce fewer and larger seeds, tend to allocate fewer resources to seed production than do early successional species. Late successionals generally only become prevalent long after the disturbance event.

• What would happen if we stacked the deck to reduce the relative number of Disturbance Cards?

Answer — By removing the Disturbance Cards, the total number of species in the diagram at the end of the game is reduced from 6 to 3. Without disturbances, none of the disturbance-adapted species leave the Start box, and you end up with a less diverse system, with only three species. The same happens if you remove all the periods of no-disturbance. You could then talk about what effect these outcomes might have on the birds or other animals that live in different plant communities.

• How might changes in the plant community affect other properties of the ecosystem?

Answer — Changes will affect wildlife; animals with different habitat preferences will prefer different plant communities. Changes may affect soil properties and movement of water and nutrients through the ecosystem; different types of plants have different nutrient-uptake and soil-stabilizing capacities and can affect infiltration rates differently.

• How does this imaginary system compare to real ecosystems in the number of species?

Answer — Six as opposed to tens or hundreds.

• In the game, events occur at random. Does this reflect how events, such as fires, occur in time in real ecosystems?

Answer — The disturbance regime of a particular environment describes disturbance timing, frequency and intensity (Pickett and White, 1985). Disturbances occur with some predictability, rather than completely at random.

• The outcome of interactions in the game is also random. How does this reflect real species interactions?

Answer — This can lead into a discussion of the effect of resource availability on interaction strength. The outcome of species-species interactions can be affected by the availability of resources, such as sunlight, water or nutrients (Diamond and Case, 1986). Also, you could discuss the mechanisms of species interactions, other possible interactions such as inhibition (Connell and Slayter, 1977.). Additionally you could discuss scenarios in which more than one type of interaction can occur simultaneously or at different times in the life history of plants (Quinn and Dunham, 1983). Maybe you could challenge more advanced students to create additional interaction cards or discuss how interactions could be made more realistic.

• In the game, demographic events, such as reproduction and mortality, are occurring independent of population size. Is this realistic?

Answer — You could discuss density dependence, i.e., the idea that populations behave differently at different population densities. The game actually sets the stage for density dependent effects since the further a plant type advances the higher is its relative density. Thus, the Event and Interaction Cards could take this into effect by for example forcing a consequence to be a fixed % of the spaces advanced rather than a fixed number of spaces, e.g. Grazing Disturbance: go back halfway to Start. Or, you could challenge your students to come up with other solutions to incorporating density dependence in the game as a separate activity.

• The game can also be used to talk about the concept of scale. In the game we are only observing a small space, as opposed to a larger landscape, which typically is composed of many vegetation types. By assigning each student group to be a specific land area, and aggregating the results of each group, one could simulate plant community outcomes for a larger landscape mosaic.

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Assessment of Student Learning Outcomes

See the section on Tools for Assessment in the "Lab Description." In addition to writing opinions on the scenario, you could also have students debate the scenario using evidence they gathered by playing the game.

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Evaluation of the Lab Activity

To evaluate the activity, we have quizzed students before and after the lesson to see if they learned what we hoped they would learn. A total of 39 non-majors were tested (28 in Bio 100 and 11 in Environmental Biology for non-majors) in the spring of 2003. The questions used for the evaluation are listed in Tools for Assessment section of the "Description" of the Experiment. Data was analyzed using pairwise t-tests. On average, students’ scores improved after participating in the activity from 7.6 out of 20 pts to 12.1 out of 20 pts (See Figure 12). For some questions, the scores improved more than for others (Figure 13). Students seem to learn more about how plants respond to disturbance and each other. They are less certain about applying concepts to real community changes, or predicting outcomes.

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Translating the Activity to Other Institutional Scales

This activity can be used with pre-college and college students in introductory courses as is, without including the extension activities. Extension activities add difficulty and depth and are appropriate for advanced undergraduate students. The main difference in conducting the activity with pre-college students as opposed to college students is in the depth of the post-activity discussion. For middle school students, we generally only discuss what happened during the game and how that relates to some examples of successional processes in local plant communities. We include more ecological concepts for high school and college students in the discussion. So far, we have only conducted the activity with non-science majors, but it could easily be adapted for science majors by adding some of the extension activities.