Carbon sequestration in forests at the DePauw Nature Park

Vanessa Fox, Amanda Hendricks, and Laura Robinson
DePauw University, Biology Department
October 29, 2008

Carbon Storage in the Forests

We estimate that the 120 hectares of forests at the Nature Park currently store 28,428 metric tons of carbon.  This is the result of 50 to 100 years of forest growth and subsequent storage.  This estimate includes storage in soils, organic debris, and trees, as follows:

12,348 metric tons stored in trees
15,708 metric tons stored in soil organic material
     372 metric tons stored in debris on the forest floor
28,428 metric tons total, 120 hectares of forest

Annual Carbon Uptake in the Forests

We estimate that the 120 hectares of forests at the Nature Park uptake 563 metric tons of carbon per year via photosynthesis.  This estimate represents new growth of trees on an annual basis.  The forests will continue to uptake this much carbon on a yearly basis for the foreseeable future.

Comparison to Published Values

Our estimates of carbon storage and carbon flux are directly comparable to published estimates for our region (Turner et al. 1995).

Implications

The carbon stored in the forests (28,428 metric tons) offsets the annual carbon emitted for electricity use on campus (23,507 metric tons).  However, the carbon stored in the forests represents 50 to 100 years of carbon accumulation and sequestration.  It doesn’t seem appropriate to use 50 to 100 years worth of carbon storage to offset one year of burning fossil fuels for electricity use on campus.

The annual uptake of carbon by the forests (563 metric tons) offsets 2.4% of the annual carbon emitted for electricity use (23,507 metric tons).

Other Portions of the Nature Park

The 120 hectares of forest comprises 62% of the total area of the Nature Park.  The other 38% of the Nature Park includes developed areas, prairies, fields, the quarry pond, and the quarry bottom. 

The vegetated areas (prairies, fields) also provide carbon storage, but not as much as the forests on a per hectare basis. 

The limestone floor of the quarry bottom effectively absorbs heat from solar radiation.  Plant growth is very low in this area, thus minimizing its role as a carbon sink. 

Methods

We followed these steps (Hoover et al. 2000) to estimate the amount of carbon sequestered in the forests:

1.)  We began an inventory of trees using standard methods.  During the past 3 ½ months, we have surveyed trees in a 1.31 ha portion of the Nature Park.  We plan to continue these surveys next spring and summer to cover more area.

2.)  We used data tables published by the USDA Forest Service to estimate the amount of merchantable volume per tree in cubic feet, based on the diameter of the trees at breast height (1.38 m above the ground). 

3.)  We converted the merchantable volume per tree to total volume (above- and below-ground) per tree in cubic feet using a conversion factor (conversion factor = 2.418, Table 1, Hoover et al. 2000). 

4.)  We converted the total volume per tree to pounds of carbon per tree using a conversion factor (conversion factor = 17.90, Table 2, Hoover et al. 2000). 

5.)  We used published values in Birdsey (1992) to estimate carbon storage in woody debris and soil. 

6.)  We converted all values from pounds per tree or pounds per acre to metric tons for the total area of forest at the Nature Park, 120 hectares. 

References

Birdsey, R. A. 1992.  Carbon storage and accumulation in United States forest ecosystems.  General Technical Report WO-59.  Washington, D.C., USDA Forest Service.

Hoover, C. M., R. A. Birdsey, L. S. Heath, and S. L. Stout.  2000.  How to estimate carbon sequestration on small forest tracts.  Journal of Forestry 98:  13-19.

Smith, J. E., L. S. Heath, and J. C. Jenkins.  2003.  Forest volume-to-biomass models and estimates of mass for live and standing dead trees of U.S. forests. General Technical Report NE-298.  Newtown Square, PA, USDA Forest Service, Northeastern Research Station. 

Turner, D. P., G. J. Koerper, M. E. Harmon, and J. J. Lee.  1995.  A carbon budget for forests of the conterminous United States.  Ecological Applications 5:  421-436.