Succession and Nutrient Cycling in a Temperate Rainforest Ecosystem
OverviewStudents will examine succession in two forest ecosystems: a recently de-glaciated area and an established temperate rainforest. (Note: This lesson can be adapted to succession in any forest ecosystem.)
Objective(s)Students will examine the differences in throughfall, litterfall, and soil condition the two forests sites. Students will learn to design an experiment to investigate a well thought out hypothesis. Students will gain an understanding of nutrient cycling in a forest. Students will understand how outside influences, natural or human-made, can interfere with this cycle.
Read sections on Succession and Temperate Rainforest Ecology in this manual.
MaterialsYou will need at least one copy of the glacial succession reading and the temperate rainforest ecology reading.
You may want a full copy of "Forging Connections - An Educational Resource For Kenai Fjords National Park"
- Journals for each student
- 8-12 1x1 sq. meter litterfall catchers (Need 4- 1”x 2” x 3’ boards per catcher and 1 3’2”x3’2” piece of fi ne mesh screen per catcher)
- 6 Throughfall catchers (Need 8-12, 2 liter bottles and 8 -12, 2’ pieces of rebar or strong wood stake, duct tape, clear plastic cup and volume cylinder for measuring.)
- 6 Soil test kits (a set of 10 for each nitrogen, potassium, phosphorus, and pH) can be ordered online.
Homework includes reading the Succession and Temperate Rainforest Ecology sections of this manual (1), Experimental Design (2), and Dealing with Data (3). Students will need 7 days and some class time to complete Experimental Design. Following completion of each assignment, a classroom discussion will follow.
Day 1 - Optional Field Day
If time and transportation allow, the best scenario is to take the students to the two forest sites where they will eventually do their experiment and just let them spend time observing the ecosystem. Ask them to write the date and location and observations for the sites in their journals. Encourage observations of the plants, animals, and soil at each site and comparisons of the two sites. This part of the procedure can be skipped but it will diminish the student’s input.
Homework Assignment 1
Have students read the Succession and the Temperate Rainforest Ecology section of this manual. Ask them to take notes as they read and to be prepared to discuss local forest ecosystems the next day in class. Have them research vocabulary words: Canopy, Lichen, Litterfall, Nutrient Cycling, Nitrogen Fixation, pH, Substrate, Succession, and Throughfall.
Day 2 - Classroom Discussion
1) What are the requirements for a forest to grow? (sunlight, water, soil, seeds, nutrients)
2) Which of these might be less available in an area where a glacier has recently been? (soil, seeds, and water retention ability)
3) How do soil and seeds get to an area? (litterfall, animal transport, wind, rain)
4) What hypothesis could we propose comparing a more recently deglaciated area with one that has undergone years of succession?
Try to have students come up with a hypothesis which can be tested using one of the methods below. Use the following sheet as a homework assignment, allowing students a week to prepare the class experimental design.
A. Hypothesis: There is less soil in a more recently deglaciated area. There are less nutrients in a recently deglaciated area.
Test—Test soil nutrients with soil test kit.
B. Hypothesis: Soil composition and nutrient availability are better in an established forest due to long-term contribution from the forest canopy. Test—Measure litterfall in both ecosystems.
C. Hypothesis: Less rain hits the ground, hence less soil run-off occurs in an established forest.
Test—Measure throughfall in both ecosystems.
Homework Assignment 2: Experimental Design
From our classroom discussion, we came up with 3 hypotheses we would like to test in our forest ecosystems. Read the hypotheses stated below. With the scientific method in mind, write out methods for testing each of these 3 hypotheses. Be very exacting in your descriptions as we will use student designs for these experiments. Spend time determining the best testing scenario for each hypothesis.
Consider how data will be collected, what will be measured and quantified. Is there any qualitative data to be gathered? Write out your experimental design or methods for each hypothesis with an explanation of why you would do it this way. Talk with each other to expand on ideas, but do your own write up. Consider carefully where and why you might disagree with another student’s design.
1) The soil in a recently deglaciated area will not be as healthy as the soil in the established ecosystem. Consider: How do we define a healthy soil?
- How do we test soil health?
- Where should we test the forest’s soil?
- How often does this test need to be repeated?
- How do we prevent bias in this experiment?
2) The forest canopy is a major contributor to the soil of its ecosystem. Therefore, the litterfall is likely more diverse and more plentiful in the established ecosystem. Consider: How can we measure litterfall? Weight? Volume? Type?
- Should we sort litterfall to further define it?
- Where should we test litterfall?
- What outside influences may affect our results?
- How often should the data be gathered?
- How do we prevent bias in this experiment?
3) With a more developed canopy, less rain hits the ground (throughfall), hence less soil run-off occurs in an established forest. Consider: How do we measure throughfall?
- Where do we measure throughfall?
- How often should the data be gathered?
- What local and/or outside infl uences may aff ect our results?
- How do we prevent bias in this experiment?
Homework assessments are found lower on the page.
Day 3 Classroom Activity: Field Work Initial Set Up
This activity will vary depending on the distance to the field site, experimental design chosen, and data collection method chosen. Ideally, the whole class could walk to both sites at least once a week. Teams could collect litterfall, throughfall, and soil data on one site at each location each week and present data back in the classroom.
Initial site selection will take time. The site must be chosen (remember to remove bias from site selection) and equipment set up. You will need 6 teams to collect data for the 3 experiments (soil nutrients and pH, litterfall, and throughfall) with two replicas at both forest sites:
- Sites 1 and 2: Successional Forest Edge Sites
- Sites 3 and 4: Successional Forest Mid Sites
- Sites 5 and 6: Successional Forest Deep Sites
- Sites 7 and 8: Temperate Forest Edge Sites
- Sites 9 and 10: Temperate Forest Mid Sites
- Sites 11 and 12: Temperate Forest Deep Sites
If only one pair or small group of students can visit the site each week, eliminating the mid-forest sites would cut down on the work. Data collection could also be reduced to once every two weeks. In the scenario above, one group of students would test for each variable at sites 1 and 7.
Before field work gets started be sure the exact number of data collection dates, stations, and analysis is known by all students. Help the class to establish a clear, concise way of organizing data in their notebooks. One example follows, but this will vary depending on your design.
|Date||Sites 1 & 2||Sites 3 & 4||Sites 5 & 6|
Make necessary adjustments to the data collection as needed, but aim for at least one collection of data every other week to be shared with the class. Students should have access to all data collected so that they can keep track of the information in their journals and participate in interpreting the entire project’s results. Continue sampling the sites for 2-3 months. Each time students visit the sites, they should be gathering data as well as listing observations (such as weather, animal disturbance to equipment etc.) about the site. All data should be posted after each site visit on classroom charts or graphs so that each student has access to every team’s results.
Homework Assignment 3: Dealing with Data, or, Now What Do We Know?
Complete this worksheet within your journal.
- Review the data charts in your journal. Based on trends you see in the data, decide how best to graph your results. Complete graphs for each site and each part of the experiment (soil, litterfall, throughfall). If any data is left out, explain your reason. To be certain graphs can be interpreted by anyone, remember to title the graph and clearly label the axis and scale. Graphing of various sites can be combined so long as labeling is clear.
- Did you notice any irregularities in the data? If so, do you know how these occurred? If there is not a known explanation can you make an educated guess?
- Write a conclusion for each experiment. Be thorough and explain how your hypothesis was proven or disproved. As a part of your conclusion be sure that you answer the following questions:
Where does the soil show the best quality for plant growth needs?
What soil had the poorest nutrient quality?
Where is the greatest amount of litterfall? The least?
Where is throughfall the highest? lowest?
At which site did plant growth appear to be thickest? Did this correlate to any of the things you were testing for?
What can you say about the relationship between the 3 things you were testing for? In other words, do you think the amount of throughfall correlates to the amount of litterfall or to the quality of the soil? 9/23/09 Site 1 Site 2 Site 3 Site 4 Site 5 Site 6
- Now that you have completed this experiment, what would you do to change it if you were to re-run it in the future?
- Has this experiment generated any new questions about the two ecosystems being examined?
- Now think on a larger scale and write down how human influences or natural phenomena might manipulate each of the ecosystems you studied.
Homework assessment is found below.
Classroom Discussion on Experimental Design
This will occur 7-9 days after Homework Assignment 2 is given. If possible, use the experimental design of the students in the actual field work; ideally drawing from the work of three students (one each for throughfall, litterfall and nutrient availability).
Prior to beginning field work, discuss the chosen designs with the class and see if anyone can discover any flaws in the design. If you see a flaw but can get data even with this fl aw, leave it as a learning tool for students later on. Discuss bias with the students and look at ways bias might infl uence the designs chosen. Be certain to mention site selection bias and determine a way to eliminate it. For example, a hoola hoop toss over the shoulder is a good unbiased way to chose a site within a given area. After bias has been covered, determine methodology for each part of the experiment. Remind students that hypothesis, methods, data, observations, and conclusion will all be important in their journal write-ups of their field work.
Homework Assignment 2 Assessment
- Did the student do a design for each of the 3 hypotheses?
- Was the design well thought out?
- Were variables considered?
- Were multiple trials or data replicates considered?
- Was bias considered?
Homework Assignment 3 Assessment
The student’s ability to make sense of these questions in their journal will thoroughly evaluate the thought put into this project. Pay close attention to:
- Graphed results—can you read and understand them? Are they organized well?
- Observations of possible data errors—if there were discrepancies, what did the student do?
- The answers to Question 3 in this assignment contain the real conclusions where all items can be compared. It should be weighted heavily. The final three questions assess the student’s ability to take knowledge from this project and apply it to other projects and to their understanding of the workings of the world.
Add additional questions to the Classroom Discussion on Experimental Design (step 4, above):
If you were a resource management professional in a national park tasked with allowing the public to observe the resources but also with conservation of those same resources, how would you allow for viewing of these two ecosystems? What if you were tasked with adding a trail to your park, which ecosystem do you think could better withstand visitation and why?
Additional ResourcesThese websites contain additional information or supplies useful in the lesson plan.
Ancient Forests of the Pacifi c Northwest by Elliot A. Norse, Island Press, 1989
Carolina Biological Supply sells Rapitest 66-5404 kits that will run 10 soil samples each for nitrogen,
phosphorus, potassium, and pH. http://www.carolina.com/product/rapitest+soil+test+kit.do?keyword=rapitest+66-5404&sortby=bestMatches
VocabularyLichens, Litterfall, Nitrogen Fixing, Nutrient cycling, Photosynthesis, Precipitation,
Soil pH, Substrate, Succession, Temperate Rainforest, Throughfall.