A methodology to estimate carbon storage and flux in forestland using existing forest and soils databases

Sequestration of carbon through expansion and management of forestland can assist in reducing greenhouse gas concentrations in the atmosphere. Quantification of the amount of carbon presents an ongoing challenge that calls for new approaches. These new approaches must seek to simplify the science-based accounting of carbon storage and flux, while adhering to general principles of greenhous gas accounting. Quantifying change in carbon storage and carbon flux consists of two steps: developing a baseline of carbon storage, and measuring resulting storage and flux following a change of conditions. A methodology is proposed that accomplishes both steps, applicable to an aggregate-level analysis using the state of Iowa (U.S.A.) as a case study. The method combines existing databases from the U.S. Forest Service (USFS) and U.S. Department of Agriculture (USDA), and merges these with the methods of Birdsey (USDA. 1992. 1995: IPCC, 1997: EIIP, 1999) for partitioning carbon stocks into storage pools. Forested ecosystems in the study area contain approximately 137.3 metric tons organic carbon per hectare, or 114 million metric tons of carbon in aggregate. Of this total, 44.7 million tons are stored in biomass tissue, and 69.2 million tons of carbon are contained in soils. Carbon flux due to forests in the state of Iowa is estimated to be a net annual sequestration (removal from the atmosphere) of 4.3 million metric tons of CO2-equivalent, approximately 5% of the net annual CO2-equivalent emissions from the state (Ney et al.. 1996).