ABSTRACT

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.

AUTHORS

Jeffrey A. Simmons¹

1 - Science Department, Mount St. Mary's University, Emmitsburg, MD 21727 (simmons@msmary.edu)

CLASS TIME

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.

STUDENT PRODUCTS

Group Experimental Design (1-2 pages)
Lab report (8-12 pages, 2 drafts)

SETTING

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.

COURSE CONTEXT

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).

INSTITUTION

Four-year, private, small, liberal arts, primarily undergraduate institution.

TRANSFERABILITY

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.

ACKNOWLEDGMENTS

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.

CITATION

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