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TEACHING ALL VOLUMES SUBMIT WORK SEARCH TIEE
VOLUME 2: Table of Contents TEACHING ISSUES AND EXPERIMENTS IN ECOLOGY
EXPERIMENTS


Challenges to Anticipate and Solve:

  1. equipment availability: Students want to collect all kinds of data from this experimental plot. Much of it involves abiotic variables. The challenge is to come up with equipment to allow this data collection and to get students to collect data for which you have equipment. My strategy for this is both short and long term. In the short term, I require students to think about why they wish to collect any given data. This often leads them to realize they do not need that data. If they still feel they need this data and we do not have the equipment, I simply tell them that. If this data is important for the research they are proposing, I suggest they include this data collection as an experiment in their proposal. In the long run, I will purchase useful equipment that is not yet available in my department.

           A variety of equipment is easy to make, acquire, or purchase inexpensively. Equipment for quadrat, point, and line transect sampling of vegetation is easy to obtain or build. For example, 1 m2 quadrats can be built with 4 lengths of PVC pipe and 4-90o PVC corners. Larger quadrats for sampling larger scales (e.g. trees and shrubs) can be constructed with 4 stakes and string. Soil test kits for estimation of soil nitrogen, phosphorus, potassium, and pH are readily available from many sources (e.g. Hach, LaMotte, and local garden suppliers) and not expensive. Simple methods to visualize and estimate stomata density are found in Grant and Vatnick 2004 (TIEE Vol 1 - tiee.ecoed.net/v1/experiments/stomata/stomata.html). Although large scale destructive sampling is not appropriate in our experimental plot, students could selectively sample plants to develop allometric estimates of plant biomass (see Griffith and Forseth 2003)

           Students interested in ecophysiology may be out of luck due to the cost of equipment. Light meters and sensors for photosynthetically active radiation (PAR) are available from about $500 to $1000. Be sure to purchase a sensor that measure in units that can be related to photosynthesis (e.g. µmol · m-2 · s-1). Portable photosynthesis, gas exchange, and water relations measurement equipment like the LiCor 6400 costs about $10,000. Leaf area meters may cost from $2500 to $5000, but leaf area can be estimated using leaf sketches on graph paper.


  2. formulating questions: Many students struggle with formulating specific questions for their proposals. Students must propose questions with specific measurable dependent and independent variables. The challenge of the instructor is to provide support in this difficult and many times first time task, but not to tell students what questions to ask. I ask students what their dependent and independent variables are and if they are measurable. I also stress that there should be some relationship among their questions to create an integrated research proposal. It is this relationship among research questions that creates a broader context for the proposed research. In developing their research agenda, students may work from the specific questions to the broader conceptual questions or they may work from the broad concepts to the specific questions. I do not yet know which direction is preferable pedagogically.

           To date for my course, the ecological questions addressed by my student groups have generally concerned spatial and temporal patterns in plant population and community ecology. The broad concepts covered include mutualism and potential mechanisms of that mutualism, life history differences among grasses and forbs, seed germination strategies, competition and specific limiting factors leading to competition, environmental correlates of species diversity, and root competition.

           Here are 4 sets of questions showing a range of ecological concepts addressed. The broad concepts covered include mutualism and potential mechanisms of that mutualism, life history differences among grasses and forbs, seed germination strategies, competition and specific limiting factors leading to competition, environmental correlates of species diversity, and root competition. Although all of these hypotheses deal with spatial ecology, students should be able to address hypotheses / questions about changes in time, if they have an historical dataset of plant abundance and distribution from the experimental plot.

        a) Does Amaranthus sp. have a mutualistic relationship with Digitaria sp.? Does Digitaria sp. grow taller when growing close to Amaranthus sp.? Does Amaranthus sp. decrease wind speeds around its stems? Does Digitaria sp. grow more densely when growing close to Amaranthus sp.?

        b) Do grasses germinate earlier in the summer than plants with broad leaves and short stature (i.e. forbs)? Do forbs germinate better under low light conditions than thin leaved, tall plants (grasses)? Do forbs increase stem length more quickly in low light conditions than in high light conditions? For grasses that germinate in open canopies, does high light intensity increase phytochrome activity in the seeds?

        c) Does Oxalis sp. (wood sorrel) grow in lower abundance when growing in the presence of other plant species than when growing in the presence of other Oxalis sp. plants? Does Oxalis sp. grow in lower abundance when growing in low light levels? Does Oxalis sp. have lower stomatal apertures to increase CO2 uptake in low light levels? Does Oxalis sp. grow in lower abundance when growing in low soil nitrogen levels?

        d) Does species richness increase with increased incident light levels? Does species richness increase with increased soil moisture levels? Does total biomass of plants increase when fibrous root plants and tap root plants grow together, as compared to when fibrous root plants grow with fibrous root plants or tap root plants grow with tap root plants? Do fibrous root plants uptake soil nitrogen from more shallow soil depths than tap root plants?


  3. experimental plot: While my experimental plot was off campus, this may or may not be a challenge for some departments. Some schools do not provide transportation resources. In this case, any appropriately sized plot of vegetated land on campus will do for motivation. For example, the faculty of Cedar Crest College, Allentown, PA maintain a research plot on campus which is a small piece of land that has not been mown for many years. The faculty have kept a time series of data from ongoing sampling of the plot. Alternatively, most grassy lawns are not monocultures and so contain considerable diversity. This surprising amount of diversity leads to interesting questions. For example, given the strict and routine management of lawns, how do we explain the distribution and abundance of plant species on these lawns?


  4. working in groups: At the University of Mary Washington there is an explicit honor code that reads, in short, as follows, “I hereby declare, upon my word of honor, that I have neither given nor received unauthorized help on this work.” Students raise many questions about what work can be done as a group and what must be produced individually. The instructor needs to be clear from the onset about these group vs. individual issues. I will give two examples of the differences between group and individual work. First, data from the experimental garden (e.g. plant abundance, plant distribution, maps of rare plants, soil moistures, and soil textures) has been collected by different groups in the class. This is simply an efficient way of collecting data useful to the whole class. For example, if there are 6 groups in the class, the experimental garden can be split into six smaller sections for each group to sample plant abundance. This data must, in turn, be shared among all six groups. Once the data is shared each individual should have a copy of all data collected by each group for their use. Each individual should create appropriate data presentations and write titles and captions for the presentations. It may be difficult or impossible to verify that each student has created his/her own graphs and tables. I would say though that you can expect significant differences among the titles and captions of graphs and tables when you assess their data presentations. Second, annotated bibliographies are assessed individually, but they emerge from the work of the group. I believe it is sensible and efficient for the members of a group to share their literature search efforts. This shared effort has several purposes. Students will have different levels of experience with literature searches. Thus, the group can work together and learn from each other. At UMW, the whole class works in our “Science Literacy Center,” a dedicated computer room in the science building. Each student can do literature searches at his/her own computer and work side-by-side with peers. The group can also share ideas about the appropriateness of papers as they find them. I have also allowed students to share the task of typing and formatting references. The task of writing reference annotations after reading papers is an individual task.

           In addition, group work invariably leads to personality conflicts in one or two groups. To a certain extent, I believe students should be encouraged to work out these conflicts among themselves. These people will likely work in teams during their careers and will run into the same kinds of conflicts in the future.

           Another group issue that may arise is whether or not all members of the group contribute equally. This is a difficult matter to track and I have not yet developed consistent measures to evaluate this equity issue. First, keep your eyes and ears open. As you work with and ask questions of research groups, note who answers questions and who does not. Challenge quiet students to respond to your questions as you interact with groups. You may have to explicitly ask more verbal students to remain silent. Ask individuals in a group about any tension you sense among members of the group. Second, carefully compare individual assignments among the individuals of each research group. Assignments like the annotated bibliography are sufficiently complex that there should be little similarity among individuals in a group. Third, ask students about their group’s dynamics and division of labor. Have they shared resources while gathering references for their research? Has each member contributed equitably to the organization and creation of oral presentations? The discussion on Formative Evaluation in the Teaching Section of this website provides some guidance on how to ask students to evaluate their performance and their peers’ performance in the group.


  5. in-class and out-of-class time commitment: The experiment schedule as presented in the class syllabus (see syllabus_fall2003.doc, 36kb) does not use laboratory class time as efficiently as is possible. The experiment is currently designed to have a significant amount of in-class time devoted to work such as library research, oral presentation development, and peer reviews of proposals. This decreases the amount of time that one might expect from students out of class. As I refine the details of this experiment, some of this in-class time will be reorganized. When I move some of this in-class work to out-of-class work, I anticipate inserting short term exercises during laboratory class time to supplement lecture concepts, computer modeling exercises, and / or discussions of research articles.
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Comments On the Lab Description:

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Comments On Questions for Further Thought:

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Comments On the Assessment of Student Learning Outcomes:

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Comments On the Evaluation of the Lab Activity:

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Comments On Translating the Activity to Other Institutional Scales:

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