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 2000 tonsthat's four million pounds of mass added as the tree grows! Where do all those millions of pounds of mass 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

Write down a hypothesis as to how a Giant Sequoia tree can add over four million pounds of mass as it grows from a small seed to a fully grown tree. Share your hypothesis with the class. As you look at the list of class hypotheses, are there any hypotheses 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 mass of a tree comes from as it grows? If so, do they match any of the hypotheses on the class list?

Checking In

Check your understanding of where the mass of trees comes from 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. Think about a large tree that is close to where you live and imagine that this tree weighs 100,000 pounds. The tree gained most of its 100,000 pounds of mass from...?
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Carbon In, Carbon Out: Photosynthesis and Cell Respiration

Trees are 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 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!

Photosynthesis and cell respiration are key carbon cycle processes that move carbon atoms into and out of trees and all other plants. Plants take in carbon dioxide (CO2) from the air via photosynthesis and return CO2back to the air via respiration. The tree uses some of the carbon atoms it takes in to build millions of carbon-based biomolecules such as proteins, carbohydrates, lipids (fats and oils) and nucleic acids (DNA, RNA). These carbon-compounds make up the cells and tissues of the tree. You will learn more about about the molecular nature of photosynthesis and respiration in Lab 1B. You can review the photosynthesis process in this animation on photosynthesis.

Next, examine the diagram of the carbon cycle of a single tree, pictured on the right, 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 go?
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  3. Under which of the following conditions would a tree add mass and grow?
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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. Closely examine the image of a terrestrial carbon cycle below. Then, answer the three Checking In questions below the image.


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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Plants are called producers because they use carbon dioxide from the air and water from the soil to produce their own fooda carbohydrate sugar. Plants use this sugar in two ways:

When a consumer eats (ingests) a plant, the consumer is eating the plant's carbohydrates, proteins, fats and oils and DNA. In this way, the carbon is passed on from plant to consumer and then from consumer to consumer. Consumers use these biomolecules in two ways:


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.


Carbon storage in trees and forests. Why care?

Trees are 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:

Next, watch this video Forest carbon 101, produced by The Nature Conservancy. As you watch the video, think about the discussion questions below.

Discussion

  • Why should we care about trees and forests storing carbon?
  • What solutions can you think of to increase carbon storage in your community?
  • Can trees and forests keep absorbing and storing ever-increasing amounts of CO2in the air? If not, what might limit carbon uptake and storage in trees?

What limits carbon storage and growth in trees?

To answer this 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 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 soil nutrients.

All organisms have certain requirements to survive, grow and reproduce, for example - food, space, water, light, and nutrients.

These requirements are called limiting factors. Not enough of any one of these limiting factors can limit growth and reproduction and in some cases cause early death. In elementary school, you most likely learned about two important limiting factors for plants - light and water. In the experiment you are about to begin, you will be exploring the limiting effects of nutrients on plant growth, carbon uptake from photosynthesis and carbon storage(sequestration). These nutrients include nitrogen, phosphorus, iron, manganese, potassium, copper, manganese, molybdenum and zinc. The most important plant nutrient in this list is nitrogen. These nutrients are typically found in soil but you will be growing the corn hydroponically. Here is your research question and experiment synopsis.

Experiment Title: What is the Effect of Nutrients on Carbon Dioxide Uptake and Carbon Storage in Corn Plants Grown in Hydroponic Conditions: A Systems Thinking Approach.

Research Question:

How does the availability of important nutrients such as nitrogen, phosphorus, and magnesium affect carbon uptake and storage in hydroponically grown corn plants?

Experiment Synopsis:

In this experimental design, you will be using hydroponics – a soil-less method for growing corn plants. You will also be using "systems thinking" strategies and language to think about your experiment and the changes you observe.

The "Corn Plant Growth Systems" you will use in this experiment consist of corn seeds/plants grown in hydroponic growth chambers exposed to different concentrations of nutrient solutions. As the corn plants grow, you will be observing and measuring changes to the system. Specifically, you will be measuring how much carbon the corn plant growth system gains from the air as it grows. The experiment takes two - four weeks. During that time, you will keep a written and/or photo journal of your observations. When the experiment is complete, you will follow the instructions on the experimental protocol sheet to determine the percent (%) change in mass and the approximate amount of carbon stored.

  1. Open the Experiment Protocol for Hydroponic Corn Growth Systems (Microsoft Word 2007 (.docx) 4.6MB Nov11 13)
  2. Read the protocol, gather your materials, and begin. Good Luck!

Content extensions:

Read about the FACE carbon dioxide enrichment experiments

Determine the amount of carbon in a tree near you. Use this simple tree carbon calculator http://www.northsydney.nsw.gov.au/carbon/carbon.html

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

Research various programs to plant trees such as the "Plant a Billion Trees" program at The Nature Conservancy.



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