Lahar Ecosystem Activity

Goal: To compare disturbances and patterns of succession in three ecosystem plots on the Mount St. Helens lahar. (This activity should be preceded by Classification: A Life Skill and School Site Ecosystem Activity.)

Objectives: Students will demonstrate ability to

  1. Identify at least seven (more, if most of the plants in the area are familiar to students) individual plant species in each of the three designated ecosystem study plots, using a dichotomous key
  2. Understand and differentiate survivor and pioneer or immigrant plants
  3. With the aid of a key to animal signs, identify animal species that frequent each of the three plots and their associated food chains.
  4. Summarize major differences among the three ecosystems, drawing from those differences predictions of future changes likely to occur.

Key Concepts: Although life has been catastrophically disturbed, it persists. Surviving plants create habitat for colonizing pioneer plants, while both serve to contribute to a food chain that sustains surviving animal life and hastens recoloniz ation by animals. It is at the margins of disturbances that the greatest abundance and diversity of life may be found.

Summary: Students use plant-type and animal-sign keys to identify and tally numbers of survivor and pioneer plants and animals in three ecosystem plots maintained in the lahar area of Mount St. Helens National Volcanic Monument: two each on the l ahar, at the edge of the lahar, and in the forest margin. They describe soil differences, assess plot similarities and differences, identify the characteristics of survivor species, and predict future ecological changes.

Content Areas: Science (all categories,) creative writing (extension activity)

Materials Needed:

Handouts:

  1. Lahar Ecosystem Observation Record
  2. Lahar Ecosystem Observation Record Key
  3. Animal Signs
  4. Plant Identification Guide
  5. Plants of the Mount St. Helens Lahar-Worksheet
  6. Plants of the Mount St. Helens Lahar-Key
  7. Transect Map of EcosystemPlots
  8. paper and pencil
  9. clipboards or notebooks
  10. three pairs of ecosystem study plots, maintained and marked with signs near Lahar Viewpoint at Mount St. Helens National Volcanic Monument
  11. See also articles on animal life in Classroom Supplements and suggested resources at the end of this lesson

Evaluation: Successful identification of a specified number of plant species, and differentiation between surviving and pioneer plants and animals, as demonstrated by completion of the Lahar Ecosystem Observation Record.

Instructional Sequence:

  1. Review ecosystem topics, referring to prior Disturbance Ecology classroom activities, via question-and-answer period just prior to field experience

  2. Remind students of the fragility of the St. Helens ecosystem in general, and these study plots in particular. Students are to work at the margins, only, without entering or in any way altering the ecosystem plots.

  3. Select an example of a survivor plant. Pose questions about the ability of a plant to survive an eruption. Discuss how to identify survivor plants. Discuss ways of recognizing pioneer plants (those that have colonized on site since 1980.) Compare and contrast, focusing on root structure and size of plant.

  4. Explain procedure for this activity:

    1. Provide directions to, or walk students to and point-out, the three pairs of ecosystem plots. Note how they are identified on the handout

    2. Assign a small group to each plot (you will rotate them at intervals of 20 minutes to a half hour to cover all three types)

    3. Distribute and explain the Record Sheet, and the Plant Identification Guide for use as supplementary reference. Point-out the questions at the bottom of Record Sheet, which they should be prepared to discuss or elaborate-upon in writing at the end of the activity

    4. Following their investigation of the plots, bring the groups together. Discuss questions at the bottom of the page. Draw inferences/conclusions regarding:

      1. soil comparisons among ecosystems

      2. numbers and diversity of plants

      3. locations of survivors vs. pioneers

      4. number and diversity of animal life signs noted.
Extension Activity:
  1. In small groups, students will create a plant or animal lifeform capable of surviving a major eruption of the future. In words, illustrations, dramatizations, etc., the group will then present its created survivor to the rest of the class. Allow ple nty of time for preparing a detailed description, visual aids, and a presentation plan. Groups may then combine their mythical survivor-species to design a detailed, complete new ecosystem, that illustrates the kinds of complex relationships and interdep endencies that might assure the survival of that ecosystem in the event of a future mudflow, other natural catastrophe, or major human-made disturbance.

References.

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Living Lab Curriculum

Mount St. Helens