Students investigate the factors that control the rate at which CO2 is emitted from soil using simple soil chambers and soda lime in a field experiment. Students in small groups design and conduct their own experiments to investigate the effects of soil and microclimate factors on CO2 emission. The projects are typically conducted over two consecutive lab periods. During the first session students design their experiment and initiate their incubations. The incubation is ended after 24 to 48 hours and during the following lab period the final results are collected, the data are statistically analyzed, and a lab report is written as homework.
Jeffrey A. Simmons1
1 - Science Department, Mount St. Mary's University, Emmitsburg, MD 21727 (firstname.lastname@example.org)
Two three-hour lab sessions (plus, possibly, one lecture period).
OUTSIDE OF CLASS TIME
Students will spend 4 to 6 hours, primarily writing up the associated draft and final lab reports.
Group Experimental Design (1-2 pages)
This experiment was originally designed for forested ecosystems but is easily adapted to grassland or other terrestrial environments. Very steep or rocky terrain can be problematic for the incubation chambers. In cold weather or in waterlogged soils the emission of CO2 is usually too low to be detectable by this method. In these circumstances a modified version of the experiment can be conducted indoors or in a greenhouse.
This experiment has been used successfully in a freshman-level introductory Biology course (3-4 sections of 24 students each) and in an upper-level Ecology course (up to 18 students).
Four-year, private, small, liberal arts, primarily undergraduate institution.
This experiment is very flexible and is easily translatable to larger or smaller class sizes and to non-majors classes. It can be adapted for use in meadows, gardens, lawns, and construction sites. Users just need to be sure to remove any plants from under the chambers as they will absorb CO2. It can be used indoors or in a greenhouse by creating artificial soils in a plant tray or bin. The indoor setting gives experimenters greater control over environmental variables and allows them to manipulate the soil composition.
I learned this technique from Dr. Joseph Yavitt and Dr. Timothy Fahey as a graduate student at Cornell University. Funding for development and testing of the exercise was provided through a 2003 award from the National Science Foundation’s Course, Curriculum and Laboratory Improvement Program (#DUE-0410577) as part of the Collaboration through Appalachian Watershed Studies (CAWS) project.
Jeffrey A. Simmons. 23 February 2009, posting date. Decomposition and Soil CO2 Emission. Teaching Issues and Experiments in Ecology, Vol. 6: Experiment #2 [online]. http://tiee.ecoed.net/vol/v6/experiments/soil_respiration/abstract.html
This image shows the CO2 emission chamber and a jar of soda lime (white granules) at the beginning of an incubation in a forested habitat.
full size image