# Living in a Carbon World

## × General Sherman Sequoia, Sequoia National Park.Courtesy: Wikicommons/Jim Bahn Part A: Trees - The Carbon Storage Experts

Have you ever stood next to a tree and wondered how this tree got to be so big? In California, some Giant Sequoia trees are more than 2000 years old and grow to be over 300 feet tall. General Sherman pictured in the image on the right, is the largest tree in the world by volume and is estimated to weigh over a million kilograms of mass (2,204,622 pounds). Where does all that mass come from?

Think about the question above as you watch scientists taking measurements of The President, the second largest giant sequoia in this National Geographic Video 'Magnificent Giant Tree: Sequoia in a Snowstorm.'

If the video does not load, you can view the video at this link Magnificent Giant Tree: Sequoia in a Snowstorm - YouTube

## Discuss

With a partner, write down ideas of where you think the mass of the Giant Sequoia tree comes from as it grows and then create a class list of all possible ideas:

• What ideas about the source of the tree's mass are you more confident about? Why? Hint: Remember that mass is a measurement of matter, and matter is made of atoms.

Next, watch Derek Muller of Veritasium ask people where they think a tree's mass comes from. As you watch, make note of the hypotheses suggested by people being interviewed and be prepared to compare your notes with the class.

If the video does not load, you can view the video at this link Where Do Trees Get Their Mass From? - YouTube.

## Discuss

Compare and discuss people's hypotheses from the video with your class's ideas about where the mass of a tree comes from.

• Which items on both lists are misconceptions about how a tree grows and adds mass.
• Where does a tree actually get most of its mass from?

### Trees use the carbon from carbon dioxide to make sugar molecules

Trees, like all organisms, grow by adding mass . Carbon is the central ingredient in making that new biomass. Tree biomass is comprised of all parts of the tree; leaves, stems, branches, roots, tree trunks. The biomass of the woody tissue in the tree pictured on the right is made mostly of , a carbon compound. In a process called , plants transform CO2, an into .

Plants use organic carbon compounds for energy, growth and metabolism. Examine the images of glucose and cellulose pictured below. Then, answer the checking in questions below. NOTE: Carbon atoms are grey, hydrogen atoms are white and oxygen atoms are red. Click on the images for a larger view.

## Checking In

1. Where do you think the carbon atoms in the glucose molecule originally came from? Choose all that apply.

2. Where do you think the carbon atoms in the cellulose molecule originally came from? Choose all that apply.

### Carbon atoms cycle throughout the Geosphere and Biosphere as part of millions of different types of carbon compounds

Carbon atoms are continually on the move, cycling into and out of different components of the Biosphere and Geosphere. Carbon atoms do not cycle as single atoms but instead move as part of carbon compounds. Changing from one type of carbon compound to another as carbon cycles and is stored is a key feature of the carbon cycle. You will learn more about carbon compound transformations in Lab 1C.

### The amount of CO2 trees absorb from air influences climate

Like all plants, trees are an important component of the Earth System primarily because they absorb so much carbon dioxide from the atmosphere and store the carbon in their biomass. As a , carbon dioxide (CO2) plays an important role in regulating Earth's climate. By reducing the amount of atmospheric CO2, trees have the capacity to influence climate. You will learn more about carbon dioxide's role in regulating Earth's climate in Lab 3.

### The amount of carbon stored in biomass depends on the balance of carbon input via photosynthesis and carbon output via respiration

There are three important carbon cycle processes that cycle carbon compounds into and out of trees, and into storage in biomass:

If the carbon input from photosynthesis is greater that the carbon output from respiration, trees will biosynthesize more biomass resulting in greater carbon storage. Measures of NPP will be higher. Conversely, if the carbon output of respiration is greater than the carbon input of photosynthesis, less carbon will be stored and measures of NPP will be lower.

### × Carbon Cycle of a Single Tree. Credit: Valerie Martin, TERC

1. Examine the diagram of the carbon cycle of a single tree, pictured on the right.
2. 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. Check all that apply.

1. Carbon dioxide (CO2) in the air enters a tree via the process(es) of .......?

2. Once CO2 enters the leaves of a tree, the carbon atoms can eventually move to........?

3.   Under which of the following conditions would a tree add biomass and grow?

4.   Carbon atoms get stored in new organic carbon compounds created by what process?

5.   The source of a tree's biomass is mostly from...?