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Education: The Carbon Question

Project 2: Carbon in a Local Ecosystem: Measuring Carbon Storage

The Institute on Climate and Planets (ICP) at NASA's Goddard Institute for Space Studies (GISS) is calling for "Young Science Investigators" to research carbon in a local ecosystem. The aim is to collect carbon storage data around the world. Because of the important role of land (vegetation and soils) in the cycling of global carbon and in the carbon budget, scientists are seeking to quantify the amount of carbon held in forests.

The GISS Carbon Research Team has begun collecting data in Cornwall, New York at Black Rock Forest, approximately 50 miles north of New York City. Two habitats were studied in this deciduous forest, an upland and lowland area. For background on Black Rock Forest, see the Black Rock Forest Consortium's web site. Also available are ICP's past team plans and results. Other studies are ongoing in northeastern deciduous forests, including:

  1. Harvard University's Harvard Forest in north-central Massachusetts
  2. The USDA's Hubbard Brook Experimental Forest, New Hampshire
  3. The Institute of Ecosystem Studies in New York

Since many of the methods now used by scientists to measure carbon collect regional-scale data, it is imperative that researchers collect field data so that satellite and flux tower data can be checked for accuracy. We are especially looking for teams to collect data that will reveal the degree of variability within and between forested ecosystems since it is difficult to measure with other methods. This research will improve our understanding of the behavior of carbon in terrestrial ecosystems. In addition, it will be both timely and extremely important to other climate and ecosystem scientists.

Student investigators should be well informed about the scientific justification for the study. They should understand why and how the carbon data is collected and what it can reveal about ecosystems, carbon storage and their relationship to global climate.

The investigation should explore ways to quantify a local natural ecosystem with methods that are objective, testable and repeatable in the tradition of "good" and true scientific investigation. Part of the challenge faced by student researchers in this investigation will be to consider hypothetical situations that link natural and human-caused ecosystem changes with carbon storage.

Students will explore the following questions to contribute to our understanding of the variability in terrestrial carbon storage:

  1. How much carbon is stored in the trees in two habitats in Black Rock Forest (a northern temperate deciduous forest)?
  2. How might changes in the environment affect the amount of carbon an ecosystem can store?
  3. How does the carbon storage at Black Rock Forest compare to the carbon storage in a forest near you?

Young researchers will begin by investigating whether the amount of carbon stored in the trees at an upland dry forest site differs from the amount stored in the trees at a moist, lowland site. Then use the ICP team's data from Black Rock Forest to develop two possible future scenarios concerning how ecological change and land management may affect carbon storage. The final part of the research is to collect and analyze carbon storage data for a local forest ecosystem near where student researchers live, and to compare it to the results of the GISS Carbon Team.

Part 1: Carbon Hidden in a Northeastern Deciduous Forest

Guiding Question: What factors contribute to the variability in above-ground carbon storage in forested ecosystems?

The data collected by the ICP team in Black Rock Forest, along with their calculations, is provided for you to analyze. Download the 2002 Black Rock Forest Carbon Data Set (Excel spreadsheet).

Answer the following questions and write a report to summarize your findings. Include graphs that illustrate and defend your results.

  1. Using the data, calculate which tree species store the most carbon in the upland site. Which species store the most carbon in the lowland site?
  2. What abiotic factors contribute to the kinds of tree species located in both sites?
  3. What is the average diameter of each species at each site and how does this measurement affect carbon storage? What else can diameter at breast height (DBH) tell you about a tree?
  4. What other components of the two habitats should be considered when quantifying the total carbon storage in each?
  5. How does an understanding of species-specific growing conditions and species-specific carbon storage help you to understand the relationship between climate and carbon storage?

Part 2: Your Powers of Prediction.Two Possible Scenarios

Guiding Question: How can different ecosystem-wide events affect the amount of carbon stored in the trees in a forest ecosystem?

It is important to measure how much carbon is stored in the trees in temperate regions because many types of events emit carbon into our atmosphere. These include: a forest fire, forest logging (trees cut and sold as lumber or land) or land clearing for agriculture or housing developments. The state of an ecosystem can change very quickly. As an example of how development can impact a forest ecosystem, read the Earth Observatory's feature on Escaping Carbon, that shows you the subtle but significant changes that have occurred in a forest in Brazil over the period 2000 to 2002.

Using the ICP Black Rock Forest data set above, investigate two different scenarios that result in a change in forest composition. Write two short reports on how you think the two scenarios would affect carbon storage in the trees over time. Be sure to include sample calculations from your research and any graphs that help to illustrate and defend your conclusions. Download and use this Carbon Storage Worksheet (Excel spreadsheet) for the calculations required in the two scenarios below.

Scenario 1: Logging Impacts in Black Rock Forest

"What If" the two sites at Black Rock Forest are selectively logged? All of the trees with diameters of 25cm or greater are removed from the sites. What is the immediate affect of this action on the carbon stored in the two sites? Which habitat loses more carbon?

Scenario 2: Deer Population Explosion in Black Rock Forest

"What If" over the next several hundred years all of the trees that are currently present will die and begin to decompose while new seedlings germinate and grow up into the canopy. Suppose that, at the same time, there is a deer population explosion and the huge deer population selectively eats all of the young oak seedlings. Calculate how the carbon storage in the Black Rock Forest sites would change if all the oak species were eliminated and their habitat became dominated by other species. You can run this scenario several times based on different species taking a new dominant position in the forest. Remember that some tree species are never dominant forest species so you will need to research and separate the other non-oak trees into 'possible dominants' and 'always under-story' species.

To conclude Part 2 of the project, write a summary stating your opinion about the different ways that land management can affect carbon storage. Use evidence from calculations you have done to back up your arguments. You will also need to research different forestry management techniques so that you can determine how they might affect the composition of a forest (i.e. selective logging of species, selective logging of trees of a certain size, no logging or clearing, allowing forest to reach old-growth stage, suppressing forest fire, prescribing controlled forest fires, etc.). Your report could include information concerning the possible effects of pest outbreaks or disease on forest carbon storage.

Part 3: What about carbon storage in the trees near you?

Guiding Question: What is the variability of carbon storage in different ecosystems in North America?

This part of the research gives you the opportunity to repeat the field research done by the ICP team in a local ecosystem where you live. In doing so, you will help achieve greater scientific understanding of carbon storage in the terrestrial United States.

Prepare a series of science questions you hope to address in your study. Be sure to include one about tree species so you can compare your results with the ICP carbon data.

Choose a site that exemplifies a forest ecosystem in your area. Be sure to record the biotic and abiotic characteristics that define your site. Research and include past climate data and information about land management concerning your site. One of the best ways to organize the data you will collect is in a spreadsheet which you can design and create to suit your needs (and which you can include as the appendix in your research report).

Methodology for Carbon Data Collection

Research Task Protocol
Define the boundaries of your field site. Locate the center point of your site.

Lay down two lengths of string measuring 42.5 meters in an "X" formation, with the strings intersecting at 90 degree angles. Be sure that the center point of your site is at the point of intersection of the two strings.

The end points of the two strings mark the four corners of a square. The perimeter of this square demarks your field site's area. (30 meters along each side).

Map locations and species of your trees. Once the perimeter is identified, each individual tree within the square should be given an identification number.

Prepare a diagram of the locations of the numbered trees on a grid (e.g. graph paper) and write down the total number of trees.

Identify and note each tree species.
Create a spreadsheet. Use the format in the spreadsheets you used in Part 1 and Part 2 above to create your own spreadsheet to record your data and make your calculations.
Determine: How big are the trees?

π = 3.14159 (pi)
Tree circumference should be measured at a height of 1.3 meters from the ground (this is considered Breast Height) using a 150 cm cloth measuring tape.

Each tree's diameter at breast height (DBH) is calculated by using the circumference (DBH = circumference/π). Alternatively, you can use a special DBH tape measure, eliminating the need to determine the circumference.

All tree location coordinates, species and circumferences must be recorded in a data table that you create.
Determine: How heavy are the trees?

Equation terms:

LN = Natural Logarithm

DAGBIG = Dry Above Ground Biomass in Grams

a and b = Constants used to define the relationship between tree diameter and actual weight of specific tree species.

DBH = Diameter at Breast Height
Total above ground biomass for a site is found by using the allometric equation:

    LN(DAGBIG)=a+b[LN(DBH)]

The terms of this equation are defined at the left.

(Equation reference: Pastor, 1985 and Whittaker, 1974).

Use the information in the next table to make this calculation
Calculate how much carbon is in the trees?

π = 3.1416 (pi)
1. Diameter at Breast Height (DBH) = circumference/π
2. Tree Biomass: LN(DAGBIG) = a + b[LN(DBH)]
3. Above Ground Carbon (AGC) = (50%)DAGBIG
4. Root Biomass = (20%)DAGBIG
5. Root Carbon = (50%)Root Biomass
6. Add together the Above Ground Carbon and the Root Carbon to see how much carbon the trees in your site are storing.

Table for Calculating Total Above Ground Biomass. How heavy are the trees?

Tree Species a b
Red maple* 4.5893 2.4300
Sugar maple* 5.0249 2.4285
Yellow birch* 5.1428 2.3729
Black birch 5.1428 2.3729
Red oak* 4.9967 2.3944
White oak** 2.3058 2.1666
Chestnut oak** 2.3948 2.1900
Other species* 4.938 2.406

*from Pastor et al., 1984
**from Whittaker et al, 1974

If you would like to find specific constants for species other than those at Black Rock Forest, additional constants can be obtained from an article by Ter-Mikaelian and Korzukhin (1997).

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