EarthLabs > Climate and the Carbon Cycle: Unit Overview > Lab 1: Living in a Carbon World > 1A: Trees: The Carbon Storage Experts!

Living in a Carbon World

Part A: Trees: The Carbon Storage Experts

Sequoia National Park Sentinal Tree. Courtesy, Daniel Mayer

Have you ever stood next to a Giant Sequoia tree in California and wondered how this tree got to be so big? Some Giant Sequoias are more than 2000 years old and can weigh over 2 million pounds (987,185 Kg) and grow to be over 300 ft tall. Think about it! That's a lot of biomass [Biomass is a measure of the mass of carbon compounds remaining in a tree after the tree's wood has been dried and water removed. These carbon compounds are comprised of carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur atoms. ] added as the tree grows from a tiny Sequoia seed to a mature tree! Where does all that biomass come from?

Watch scientists taking measurements of the second largest giant sequoia in this National Geographic video then, read the accompanying Giant Sequoia article.

Discussion

With a partner, write down where you think the biomass of the Giant Sequoia tree comes from as it grows. Share your list with the class. As you look at the class list, are there any sources of the tree's biomass that make more sense than others? Why?


After your discussion, watch this TedEd video: Where Do Trees Come From? In the video, people are asked for their hypotheses as to where tree growth comes from. As you watch, make note of the hypotheses that people suggest.

Note: Make sure that you watch the video in full screen format by clicking on the full screen logo in the bottom right hand corner of the screen.

Discussion

In the video, were there any major misconceptions that people had about where the biomass of a tree comes from as it grows? If so, do they match any of the hypotheses on the class list?

What is a tree really made of?

Trees, like all living organisms, are made of a lot of water. If we remove the water and dehydrate the tree, the left-over dry mass (dry weight) of the tree is referred to as the tree's biomass. A tree's biomass consists of organic carbon-compounds Includes most molecules containing both carbon and hydrogen atoms and are made by living things. All living things make and are thus made of organic carbon-compounds. Carbon-compounds such as carbon dioxide (CO2) and calcium carbonate (CaCO3) do not contain both carbon and hydrogen atoms and are called "inorganic carbon compounds." the tree has created in order to grow. As you can see in the image on the right, the biomass of a tree is mostly made of wood and bark. And, the wood and bark is mostly made of cellulose and lignan molecules, two important organic carbon-compounds made by the tree as it grows. If you look at the image of the cellulose molecule below right, you can see that the cellulose is made of carbon atoms (gray), oxygen atoms (red) and hydrogen atoms (white). The carbon atoms in the cellulose originally come from the carbon atoms in the glucose sugar molecule you can see in the image below left. Glucose is a carbohydrate sugar (C6H12O6) produced by plants via photosynthesis and is a vital component for most life on earth. Organisms use energy contained in the carbon-carbon and carbon-oxygen bonds of glucose molecules to provide their cells with energy. Glucose sugar molecules that are not burned for energy are used instead to build new organic carbon-compounds. is a carbohydrate sugar (C6H12O6) produced by plants via photosynthesis and is a vital component for most life on earth. Organisms use energy contained in the carbon-carbon and carbon-oxygen bonds of glucose molecules to provide their cells with energy. Glucose sugar molecules that are not burned for energy are used instead to build new organic carbon-compounds such as the cellulose molecule.



Checking In

Where do you think the carbon atoms in the glucose sugar molecule come from?
The carbon atoms in the glucose sugar come directly from carbon dioxide molecules (CO2) taken in from the air during photosynthesis. This means that ALL of the billions and billions of carbon atoms in a tree originally came from the air.


How does a sequoia tree build itself from the tiny seed in the image on the right?

Trees, like all other plants, grow by building billions of different types of organic carbon-compounds such as proteins, carbohydrates, fats and oils, and nucleic acids (DNA and RNA.) For example, glucose and cellulose are just two of many different types of carbohydrates produced by a tree. Carbon atoms form the structural backbone of all organic carbon-compounds but other types of atoms are needed as well. These key atoms include hydrogen, nitrogen, oxygen, phosphorus and sulfur. Collectively, the key atoms needed to build trees and all living organisms are referred to as CHNOPS. CHNOPS is a acronym used to list the most important types of atoms that are used to build organic carbon-compounds, the molecules of life! These include carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. Other types of atoms such as potassium, calcium, magnesium and iron are also important but are needed in very small quantities.
Where do these key atoms come from?

Note: All atoms have mass, thus all of the atoms mentioned above contribute to the growing mass of the tree. However, the billions of carbon compounds created by trees as they grow cannot be built without carbon atoms originally taken in from the air in carbon dioxide (CO2) molecules. In other words, a tree cannot gain mass without carbon atoms. So, here is what a tree must do to build itself:

  1. Absorb carbon dioxide (CO2) from the air via photosynthesis.
  2. Use the CO2 absorbed from the air and H2O drawn up from the roots to make glucose sugar molecules - a carbon-compound.
  3. Burn (oxidize) some of the glucose sugar molecules for the energy needed by the tree to carry out all of its life functions. Release some CO2 to the air as a by-product of cellular respiration.
  4. Break the remaining glucose sugar molecules apart and combine the carbon atoms with hydrogen, oxygen, nitrogen, phosphorus, and sulfur atoms to build complex organic carbon compounds such as carbohydrates, proteins and nucleic acids (DNA and RNA).
  5. Discussion

    Examine the image on the right of a small segment of a DNA molecule made by a tree. Click to enlarge. In the image, you will see carbon (grey), hydrogen(white), oxygen(red), nitrogen(blue) and phosphorus (orange) atoms.

    1. Which type of CHNOPS atom forms the structural backbone of this DNA molecule?

    2. Where would the tree get the atoms to build this DNA molecule?


    Checking In


    The dry biomass of a mature Giant Sequoia tree is about 550 metric tonnes (about 1,213,000 lbs). Check your understanding of where the dry mass of a growing tree comes from by selecting the correct answer for each question below. Then click the Check Answers button at the bottom of the list.
    1. How much of the dry biomass of a tree comes from water?
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    2. How much of the dry biomass of a tree comes from nutrients in the soil such as nitrogen and phosphorus?
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    3. How much of the dry biomass of a tree comes from the air?
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    4. How much of the dry biomass of a tree comes from the Sun?
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    5. How much of the dry biomass of a tree comes from the carbon atoms in carbon dioxide molecules?
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    Carbon In, Carbon Out and Carbon Stored.

    Carbon atoms are continually on the move into and out of air, trees and soil. Carbon atoms do not move as single atoms but instead move as part of carbon-compounds such as carbon dioxide (CO2 )or glucose (C6H12O6). Photosynthesis and cell respiration are critical to moving carbon atoms into and out of trees and other plants whereas biosynthesis is critical to building the biomass of trees and storing carbon.


Examine the diagram of the carbon cycle of a single tree, pictured above, and take a few minutes to trace where the carbon goes. When you are finished answer the Checking In questions below.

Checking In

Check your understanding of where carbon goes once it enters a tree by answering the questions below. Select all the answers that are correct, and then click the Check Answers button at the bottom of the list.
  1. Carbon dioxide (CO2) in the air enters a tree via the process(es) of ...
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  2. Once CO2 enters the leaves of a tree, where can the carbon atoms move to?
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  3. Under which of the following conditions would a tree add biomass and grow?
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  4. Carbon gets stored in the stems, branches, roots and leaves of trees by what process?
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Stop and Think

1. Using the diagram above to help you, explain why trees (and all plants) represent a small but complete carbon cycle. Draw your own diagram to help you illustrate your answer.


Plants and Food Webs: Passing the carbon on!

Carbon cycles cannot exist without plants and the food webs they support. Plants are autotrophs and thus make their own food in the form of glucose sugar. Heterotrophs, like ourselves, do not photosynthesize and must instead find and eat food. This food is made of proteins, carbohydrates, fats and oils and nucleic acids. Heterotrophs break these complex organic carbon-compounds down into smaller molecules and biosynthesize new organic molecules.

As carbon compounds in food pass through food webs,



Checking In

Check your understanding of how carbon moves through food webs by answering the questions below. Select all the answers that are correct and then click the Check Answers button at the bottom of the list.

  1. What process brings in carbon in from the air into the terrestrial food web?
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  2. Carbon compounds move from plants to animals via the process(es) of...
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  3. Which process(es) moves carbon from above-ground food webs to the food web in the soil?
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  4. Which process(es) releases carbon from food webs back into the air in the form of carbon dioxide?
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Put it all together by watching The Carbon Cycle


Stop and Think

2. Examine the Terrestrial Carbon Cycle food web diagram again. Describe how the carbon from carbon dioxide molecules in the atmosphere can end up in a coyote. Use a diagram to help you explain your answer if you need to.


Keeping track of tree carbon in your own neighborhood!

You may have a favorite tree nearby in your own backyard, outside your school or in your neighborhood. You can easily determine the amount of carbon stored in your favorite tree using simple materials and calculations. Watch this video Forest Carbon 101 produced by The Nature Conservancy to see how easy it can be and then start the activity below.
As you watch, make note of important data the narrator shares with you about trees and carbon storage.

Discussion

List important carbon storage data from the Forest 101 video. Which data helps you to understand the importance of trees and forests in storing carbon? Why?


Activity: How Much Carbon is Stored in a Nearby Tree?

Adapted from an activity created by Maria Janowiak, Northern Institute of Applied Science , Michigan Technological University


Description:

Scientists studying the carbon cycle, forests and climate change are very interested in understanding how much carbon trees have absorbed from the air and stored in their leaves, stem, branches, and roots. In this activity, you will choose a species of tree in your neighborhood and calculate the approximate amount of carbon stored in your tree.

Learning objectives:

:


Materials/Resources:

for each group:

Instructions/Procedure: Measuring diameter and calculating biomass and mass of carbon in a tree.

Step 1: Watch this video on how to measure the diameter of trees with different shapes before going outside to select a nearby tree to study.

Step 2: Select a tree near your house or school to use in this investigation with a circumference of at least 38 cm (15 inches), if possible. Make sure that the species of tree you choose is in the Allometric Coefficients for Common North American Trees (Microsoft Word 2007 (.docx) 91kB Jan30 15) table.

  1. Take a picture and/or make drawings of the tree. You may want to include other information such as GPS location and environmental variables that might impact the growth of the tree (soil type, moisture and/or nutrients; light, temperature, moisture, pollution etc.)
  2. Identify the species of tree using a tree ID guide or a tablet APP. ___________________________
  3. Is this species Hardwood or Softword? (The resources you used to help identify your tree species should tell you if your tree is a hardwood or softwood.) ______________________

Step 3: Determine the diameter of your tree in centimeters (cm)

If using a regular tape measure or string, measure the circumference of the tree at 1.4 meters (4.5-4.6 feet) from the ground. If necessary, convert the circumference to centimeters(cm).

Measure the Circumference: ­­­­­­­­­­__________________(cm)

Calculate the Diameter: ______________________(cm) Note: To calculate diameter, divide the circumference by 3.14(Pi)

If using a diameter tape measure such as in the image on the right, measure the tree the same way but it is not necessary to calculate diameter since the diameter tape already does that for you. If necessary, convert to centimeters (cm).

Measure the Diameter: _______________________(cm)

Step 3.) Calculate the biomass(M) for your tree.

To calculate tree biomass, foresters use a standard allometric equation M=aDbwhere:

M= above ground dry weight biomass(kg) of the tree

D= diameter measured at 1.4 meters (4.6 feet above ground)

"a" and "b" are species-specific allometric coefficients. Locate these two coefficients for the species of your tree on the Allometric Coefficients for Common North American Trees (Microsoft Word 2007 (.docx) 91kB Jan30 15) table.
tree allometry

Biomass of tree (M): _____________(kg)

One team determines that the diameter of a nearby sugar maple tree has a diameter of 20 cm.

1. The coefficient values for a sugar maple tree are a = 0.21 and b = 2.53

2. Using the formula M=aDb

M = 0.21 (22 cm ^ 2.53) Exponent calculator link

M = 0.21 * 2490.75 = 2490. 75(kg0

The biomass (M) of this sugar maple tree weighs 2490.75 (kg). Remember that the tree's dry biomass contains hydrogen, oxygen, nitrogen, phosphorus and sulfur atoms in addition to carbon atoms.


Step 4. Calculate the approximate mass of carbon stored in your tree (in kg).

Foresters know that approximately half of a tree's biomass is made of carbon atoms. This value is slightly different in hardwood vs softwood trees. To determine the amount of carbon in your species of tree, choose one of the following:

Multiply tree biomass (M) by 0.521 for hardwood trees =__________________(kg) of carbon stored

or

Multiply tree biomass (M) by 0.498 for softwood trees = ___________________(kg) of carbon stored

The sugar maple tree is a hardwood. If the biomass (M) of a selected sugar maple tree is 2490.75 then:

Biomass(M) of sugar maple 2490.75(kg) * 0.521 = 1,297.68 kg of carbon in this tree.


Step 5. Calculate the approximate amount of CO2 dioxide absorbed by your tree to create its store of carbon.

Scientists have determined that 1 kg of carbon is equivalent to approximately 3.67 kg of CO2. Thus, multiplying the carbon stored (kg) in your tree by 3.67 will give you an approximate measure of CO2 taken in via photosynthesis and stored in the tree.

Approximate mass of carbon stored in tree ______________(kg) x 3.67 = _________________________(kg) of mass of CO2 absorbed.

Step 6 (optional) Convert the mass of carbon stored in your tree to metric tons and pounds (lbs).

1 metric ton = 1000kg = 2,205 lbs. Use the worldwide metric calculator to easily make these conversions.

Mass of carbon stored_____________(kg)

= _______________metric tons of carbon stored

= _______________lbs of carbon stored


Discussion

Throughout this module, you will explore how the carbon cycle is changing and how those changes can affect the environment and climate. One important change that you will explore in Lab 3 is the increase of carbon dioxide in our atmosphere and its relationship to a warming climate. Click on the graph on the right and take a few minutes to examine the data.

Fossil fuels are hydrocarbons - carbon compounds that are comprised of hydrogen and carbon atoms. When burned as an energy source, fossil fuels such as oil, natural gas and coal release carbon dioxide molecules into the air.

1. Think about the amount of carbon stored in your tree and the amount of carbon that could be stored in an entire forest. As carbon dioxide levels continue to increase in the atmosphere, how might trees and entire forests respond to this change in the carbon cycle?

2. Think about the carbon storage data your class has collected and the skills you have gained to collect that data. How might tree carbon storage data and your new skills be useful to your community? What could you do to increase tree carbon storage in your community?

Carbon storage in trees and forests. Why care?

You have now learned that trees are true carbon storage experts! Of all land plants, trees have the greatest capacity to store carbon because of their size and the denseness of their wood. Depending on the species of tree, approximately 50 - 80% of a tree's weight is made of carbon. And, all that carbon comes from the air into the tree in the form of CO2. If just one tree like the Giant Sequoia can store four million pounds of carbon in the cells and tissues of its leaves, trunks, branches and roots, think how much carbon a forest can store! But why should we care about trees and forests storing carbon? Here are some FAQs:

CO2 Fertilization, Carbon Storage and Forests.

Will forests continue to absorb and store large amounts of the extra CO2 produced from burning fossil fuels - or will there be limits? To answer this important question, scientists carried out 15 year-long experiments measuring the effects of adding extra CO2 to plots of trees in forests. In the Free CO2 Enrichment Experiments (or FACE for short), scientists used large pipes to blow in extra CO2 over the plots of trees that you see in the the image on the right. Measurements of carbon storage over time revealed that trees did absorb the extra carbon and grow more, but that tree carbon uptake and growth was limited by important soil nutrients including nitrogen, phosphorus, sulfur and others such as iron, manganese, potassium, copper, manganese, molybdenum and zinc. This finding illustrates how the carbon cycle is tightly linked with biogeochemical cycles A biogeochemical cycle or nutrient cycle is a pathway by which a chemical element or molecule moves through both biotic (biosphere) and abiotic (lithosphere, atmosphere, and hydrosphere) compartments of Earth. Examples of important biogeochemcial cycles are the nitrogen cycle, oxygen cycle, phosphorus cycle etc. of other elements and molecules such as nitrogen and phosphorus that cycle through the biosphere and geosphere. For an advanced understanding of the relationship between The Carbon Cycle, CHNOPS and Biogeochemical Cycles , watch this ten minute video from Bozeman science.

Lab 5 on soil and Lab 6 on oceans will continue to explore this relationship between the carbon cycle and other biochemical cycles - such as the nitrogen cycle and the phosphorus cycle.


Extensions (Optional)

Use ScienceDaily to research the latest research on carbon storage/sequestration in trees and forests, forests and soil nutrients, soil nutrients and CO2 fertilization. Here is an example: Soil Nutrition Affects Carbon Sequestration in Forests-The FACE Study

Read this essay Terrestrial Primary Production: Fuel for Life on Net Primary Production(NPP), a measure of net carbon uptake and storage in plants.

Read about how the Amazon forest's ability to take in extra carbon dioxide from the atmosphere is weakening over time in Amazon Forest is Becoming Less of a Climate Safety Net

You can review the photosynthesis process in this animation on photosynthesis.

Watch this NASA video on Seeing Photosynthesis from Space

Explore visualizations of forests and vegetation created with data from the new NASA NPP Suomi satellite. NASA visualizations of forests and vegetation

Read about how scientists use remote sensing to map carbon in forests in Seeing Forests for the Trees and the Carbon; Mapping the World's Forests in Three Dimensions

Read about San Francisco's Urban Forest Map. Does your community and/or state have a forest mapping or tree planting initiative? Find out!

Watch these videos for an advanced understanding of The Nitrogen and Phosphorus Cycle and the Hydrologic Cycle and the Carbon Cycle from CrashCourse

Explore these NASA Visualizations and others on the free NASA Viz app for IPhone and IPAD




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