The 2017-18 School Year is the 2nd year of our NOAA sponsored “Climate Resiliency Fellows” Program.  Our aim is to “Create a dynamic community of informed teachers committed to involving their students in learning about and engaging in local climate change issues and climate resiliency projects.”  Many thanks to all of our hard working teachers and students! 

How to Measure Carbon Sequestration

Tree Measurements:

To calculate carbon sequestration, our team determined the tree species, diameter at breast height (DBH) and height of the tree.  To find the DBH, you take the diameter tape and start at 4 ½ feet (breast height). Dig one end of the diameter tape into the tree then, walk around the tree holding it at breast height till u come back to where u digged it in and record the measurement. Record this number, and then move on to taking clinometer measurements.  Before using the clinometer, walk 100 hundred feet away from the tree. Next, use the clinometer by looking at the stump height (base of the tree) to take your first reading. When looking through the clinometer at this height, record the number that reaches the top of the tree using the number signified on the right side scale. Then, move the clinometer to the very top of the tree (by looking up) to take the second reading. Record the number that is determined slightly lower than the very top of the tree. Calculate the difference between the two numbers that you have recorded in order to get the total tree height. The picture above shows several students taking these calculations with D-tape and clinometer in order to find the height and diameter of the tree we are focusing on.

Calculations:

After determining the height in feet from the clinometer measurement, and measuring the DBH in inches, these measurements need to be converted into meters (height) and meters (diameter). In order to do this, the height in feet needs to be divided by 3.28 ft/m to equal the height in meters. For DBH, the measurement in inches needs to be multiplied by the conversion factor of 2.54 cm in order to get the diameter in meters (the decimal needs to be moved over three places after the calculation).

 

In the example below, the unconverted DBH was 12.9in. And the height was 38ft.

height= 38ft ÷3.28ft/m =11.585m

diameter=12.9in. 2.54cm=32.766cm=.3276m

 

Next, the volume of the tree needs to be determined.

The volume equation depends on whether a tree is hardwood or softwood.

The softwood equation is: tree height (m) diameter 2 (m2) 0.7854/3

• For hardwoods, this equation is the same, EXCEPT the number is not divided by three at the end.

In the example below, the tree calculations were for a Red Cedar (softwood).

V=11.585m .3276m2 0.7854 3 = 0.3255m3

 

After the volume is calculated, the green mass of the tree needs to be calculated.

The equation for Tree Mass is: Tree Mass (kg) = volume of the tree (m3) density of wood (kg/m3)

For softwood trees, the density is 400kg/m3, and for hardwood it is 700kg/m3.

 

In the example below, the tree (Red Cedar) is a softwood.

Tree Mass= 0.3255m3400kg/m3 =130.2 kg/tree

The next step is to calculate the Carbon Dioxide stored in each individually measured tree.

The calculation is: tree mass 65% (solid dry mass) 50% (carbon %) 3.67 (conv. factor) 120% (conv. factor)

Carbon dioxide in tree=130.2 kg/tree 65% (solid dry mass)50% (carbon %) 3.67 120%= 186.36 kg/tree

Generalizations from “How is Carbon Stored in Trees and Wood Products”, from Forest Learning:

• 35% of a tree is green mass, 65% is solid dry mass
• 50% of tree dry mass is carbon
• 20% tree biomass is in the roots of a tree (120% multiplication factor)
• 3.67 is a conversion factor to find the equivalent amount of Carbon Dioxide

 

This resulting number is the amount of carbon sequestered by the measured tree.