Initial Publication Date: July 7, 2011

Lab 5: Soil and The Carbon Cycle


Do you ever think about the soil under your feet when you walk to school? Did you know that a teaspoon of rich soil can contain over 5000 different species and strains of bacteria? Perhaps your family or school has a compost pile and you already know the importance of soil microbes in creating rich, dark soil. Farmers certainly know the importance of good, rich soil in growing healthy, robust crops.

Soil seems fairly simple to understand yet soil is one of the most complicated reservoirs of the carbon cycle. Soil and soil microbes are very important to scientists who study the carbon cycle and climate change. This is because soils store a lot of carbon! As a matter of fact, more carbon is stored in the world's soils than is currently present in the atmosphere. Scientists agree that there are many unknowns about how soil and soil microbes might respond to regional climate change and how any resulting changes might impact global climate change. For this reason, research is on-going in many areas of the world.

In Part A of this Lab, you will explore the relationship between soil and the carbon cycle by focusing on soil carbon storage and the role of microbes in decomposition and soil respiration. Then, you will design and carry out an experiment to determine how temperature affects the rate of soil respiration. Finally, you will investigate what ranchers are doing to create carbon-rich healthy soil, a process that has the potential to mitigate climate change. In Part B, you will learn about soil respiration dynamics in permafrost, a frozen soil with the potential to further unbalance the carbon cycle if it thaws.

By the end of this Lab, you should be able to:

  • describe how carbon is stored in soil;
  • describe the role of soil microbes, decomposition and soil respiration in transferring carbon from the soil to the atmosphere; and
  • describe the possible impact of a warming climate on permafrost carbon.

Keeping Track of What You Learn

Throughout these labs, you will find three kinds of questions.
  • Checking In questions are intended to keep you engaged and focused on key concepts and to allow you to periodically check if the material is making sense. These questions are often accompanied by hints or answers to let you know if you are on the right track.
  • Stop and Think questions are intended to help your teacher assess your understanding of the key concepts and skills you should be learning from the lab activities and readings.
  • Discuss questions are intended to get you talking with your neighbor. These questions require you to pull some concepts together or apply your knowledge in a new situation.
Your teacher will let you know which answers you should record and turn in.