Earthlabs: Climate and the Carbon Cycle– Lab 5
http://serc.carleton.edu/eslabs/carbon/lab5.html
Name _________________________
Soil and the Carbon Cycle
PART A: Decomposition and soil respiration – A Tale of Microbes and Rot!
1. Explain why decomposition is important in the global carbon cycle.
Decomposition is a chemical and physical process that eventually breaks down dead
organisms into carbon compounds which become part of the soil. Thus, decomposition
moves carbon from one reservoir (the biosphere) into another reservoir (the
geosphere.)
2. How do decomposers change the amount of carbon in the soil and carbon dioxide in
the atmosphere?
Decomposers carry out decomposition. When dead organisms are broken down into
carbon compounds, the amount of carbon in the soil increases.
When soil microbes and other decomposers consume the dead material, they use some
of the carbon compounds for cell energy. This process is called cell respiration.
Respiration produces carbon dioxide gas, which is released to the atmosphere. This
can cause an increase in the amount of carbon dioxide in the atmosphere. Once in the
atmosphere, carbon dioxide acts like a greenhouse gas, warming the atmosphere.
Page 1 of 5
Earthlabs: Climate and the Carbon Cycle– Lab 5
http://serc.carleton.edu/eslabs/carbon/lab5.html
Part B. Permafrost – A Soil with a Past and an Uncertain Future.
1. Explain how a thawing permafrost creates ideal environments for methane-producing
microbes(methanogens).
Permafrost contains ice. When this ice melts, the surrounding ground becomes waterlogged. Methanogens live and thrive in an anoxic (low oxygen) environment. Waterlogged soils provide an anoxic environment.
2. How might permafrost microbes impact the current greenhouse effect if the
permafrost continues to thaw?
As more of the permafrost thaws, more dead plant and animal material will thaw out
– creating more food for permafrost microbes. As the microbes consume more of this
thawing food, cell respiration will increase, emitting increased amounts of carbon
dioxide and methane into the atmosphere. Because they are greenhouse gases,
carbon dioxide and methane will trap more infra red radiation, amplifying the
greenhouse effect and making the atmosphere warmer.
Earthlabs: Climate and the Carbon Cycle– Lab 5
http://serc.carleton.edu/eslabs/carbon/lab5.html
Earthlabs: Climate and the Carbon Cycle– Lab 5
http://serc.carleton.edu/eslabs/carbon/lab5.html
Earthlabs: Climate and the Carbon Cycle– Lab 5
http://serc.carleton.edu/eslabs/carbon/lab5.html