Ecology of disturbance: Implications
for the water and nitrogen cycles
Grade Levels: 9th-12th grade
Length of Lesson Sequence: 1-50 minute lesson
Brief Description:
The purpose of this lesson is to introduce students to using data in Excel,
specifically in the context of how humans impact different natural processes. The
exercise uses data from Hubbard Brook Experimental Forest to show the impacts of
clear cutting on stream flow and nutrient dynamics. Students will be walked through an
exercise using Excel to make graphs of changes in stream flow (Figure 1) and then
asked to examine the impacts of the same experiment on nitrogen dynamics (Figure 2).
Uses of short- versus long-term data will be covered, as will different ways of graphing
data and the use of control/reference sites in ecological manipulations. At the end of
the lesson, students should be able to make graphs using data from scientific studies
and develop interpretations based on those graphs about the impact of humans on
nitrogen and water cycling.
Streamflow (mm/area/year)
Streamflow, 1965-1979
1800.00
1600.00
1400.00
1200.00
1000.00
800.00
600.00
400.00
200.00
0.00
1964
clearcut
reference
1966
1968
1970
1972
Year
Figure 1.
1974
1976
1978
1980
Nitrate concentration (mg/L)
Nitrate Flux, 1965-1979
60.00
50.00
40.00
clearcut
30.00
reference
20.00
10.00
0.00
1964
1966
1968
1970
1972
1974
1976
1978
1980
Year
Figure 2.
Content Statements/Standards Covered:
Standard B3: Interdependence of living systems and the environment
L3.p4 Human Impact on Ecosystems (prerequisite)
L3.p4A Recognize that, and describe how, human beings are part of
Earth’s ecosystems. Note that human activities can deliberately or
inadvertently alter the equilibrium in ecosystems.
B3.3 Element Recombination
B3.3b Describe environmental processes (e.g., the carbon and nitrogen
cycles) and their role in processing matter crucial for sustaining life.
B3.4 Changes in Ecosystems
B3.4A Describe ecosystem stability. Understand that if a disaster such as
a flood or fire occurs, the damaged ecosystem is likely to recover in
stages of succession that eventually result in a system similar to the
original one.
B3.4C Examine the negative impact of human activities
Objectives of Lesson:
At the conclusion of the lesson, students will be able to:
 Graph data in Microsoft Excel
 Understand the importance of ecosystem-scale experiments
 Look for patterns in long-term datasets from scientific studies
 Interpret these patterns based on previous knowledge of the nitrogen
cycle
 Understand the importance of long-term datasets (i.e. conclusions based
on short-term versus long-term responses can be completely different)


Understand the tight coupling of the nitrogen cycle in forested ecosystems
Understand that human disturbance can alter the nitrogen cycle (i.e.
accelerating the export of nitrate from this ecosystem study)
Materials and Resources
1. computers with Microsoft Excel
2. computer with projector
3. internet access to download watershed data
Strategy
Inquiry cycles: finding and explaining patterns in data (arguments from evidence)
- TOPE: techniques-observations-patterns-explanations
Observations, patterns, and explanations
Observations or
experiences (examples,
phenomena, data)
Long-term Hubbard Brook
watershed nitrate data
Patterns (laws,
generalizations, graphs,
tables, categories)
Develop graphs of watershed
nitrate data
Explanations (models,
theories)
Relate patterns back to
conceptual model of nitrogen
cycle
Application: Model-based Reasoning
Inquiry: Finding and Explaining Patterns in Experience
Activities of the Session
5 minutes –introduction/anticipatory set: show students a picture of a clear-cut forest
and ask students to discuss possible impacts to the watershed
5 minutes – introduction to the Hubbard Brook Experimental System and the small
watershed concept
10 minutes – exploration of a stream flow dataset from Hubbard Brook, one fellow
leading on projected computer, second one answering questions/troubleshooting
throughout the classroom.
20 minutes – individual/partner exploration of the nitrogen data from Hubbard Brook,
graphing data and discovering trends. Halfway through they will be given/directed to a
data expansion that includes more years and asked to see if longer term data makes a
difference.
10 minutes- wrap-up/concluding activities: discussion of the importance of scale,
long term data & spatial, discussion of this as a demonstration of human impacts,
discussion of relevant content standards. Depending on time, possible extensions to
this exercise using related data that are available at the Hubbard Brook website
(www.hubbardbrook.org). In addition, please see the MSU GK-12 website for additional
graphing ideas with this same dataset.
References
Likens, G. E., F. H. Bormann , R. S. Pierce, and W. A. Reiners. 1978. Recovery of a
deforested ecosystem. Science 199: 492-496.
Likens, G. E., F. H. Bormann, N. M. Johnson, D. W. Fisher, and R. S. Pierce. 1970.
Effects of forest cutting and herbicide treatment on nutrient budgets in the Hubbard
Brook watershed-ecosystem. Ecological Monographs 40:23-47.
Welman, A., C. Berger, M. Krasny and the Ecological Society of America. 2004.
Hubbard Brook streamflow response to deforestation. Teaching Issues and
Experiments in Ecology 1:1-13 (www.tiee.ecoed.net).