Basic Units of Measurement and Conversions - Basic Mathematics for Water and Wastewater Operators - page 82

Calculation
Due to rounding, performing the calculations given in the equations below may not
return the exact results show.
(23.2 lb C per tree) × (44 units CO 2 ÷ 12 units C) × (1 metric ton ÷ 2204.6 lb) = 0.039
metric ton CO 2 per urban tree planted.
Acres of U.S. Forests Storing Carbon for One Year
Growing forests accumulate and store carbon. Through the process of photosyn-
thesis, trees remove CO 2 from the atmosphere and store it as cellulose, lignin, and
other compounds. The rate of accumulation is equal to growth minus removals (i.e.,
harvest for the production of paper and wood) minus decomposition. In most U.S.
forests, growth exceeds removals and decomposition, so the amount of carbon stored
nationally is increasing overall.
Calculation for U.S. Forests
The Inventory of U.S. Greenhouse Gas Emissions and Sinks (USEPA, 2012b) pro-
vides data on the net change in forest carbon stocks and forest area. Net changes in
carbon attributed to harvested wood products are not included in the calculation.
Annual net change in carbon stocks per area in year n = (Carbon stocks ( t +1) - Carbon
stocks t ) ÷ (Area of land remaining in the same land-use category)
1. Determine the carbon stock change between years by subtracting carbon
stocks in year t from carbon stocks in year ( t + 1). (This includes carbon
stocks in the above-ground biomass, below-ground biomass, dead wood,
litter, and soil organic carbon pools.)
2. Determine the annual net change in carbon stocks (i.e., sequestration) per
area by dividing the carbon stock change in U.S. forests from step 1 by the
total area of U.S. forests remaining in forests in year ( n + 1) (i.e., the area of
land that did not change land-use categories between the time periods).
DID YOU KNOW?
Forest land in the United States includes land that is at least 10% stocked
with trees of any size, or, in the case of stands dominated by certain western
woodland species for which stocking parameters are not available, at least
5% crown cover by trees of any size. Timberland is defined as unreserved
productive forest land producing or capable of producing crops of industrial
wood. Productivity is at a minimum rate of 20 ft 3 of industrial wood per acre
per year. The remaining portion of forest land is classified as “reserved forest
land,” which is forest withdrawn from timber use by statute or regulation, or
“other forest land,” which includes forests on which timber is growing at a
rate less than 20 ft 3 per acre per year (Smith et al., 2010).