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 donít 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.
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.
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.
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.
The following comments could be shared with students, as part of their introduction to the lab.
There are many ways to discuss the activity. After comparing the results of each groupís 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 groupís game sequences and outcomes different from each other.
Essentially, the outcome of the game is greatly affected by chance events.
Answer — The species that tend to move ahead, i.e., become more abundant, during no disturbance in the game are all ďLate SuccessionalĒ types.
Answer — The outcome of interactions in the game is different for early and late species.
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.
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.
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.
Answer — Six as opposed to tens or hundreds.
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.
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.
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.
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.
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, studentsí 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.
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.