ABSTRACT
Changes in land use and agricultural land management have been and are currently occurring in the United States (Kellogg et al., 1994; CTIC, 1998; Paustian et al., 1998). These changes can dramatically impact soil carbon stocks (Bruce et al., 1999; Buyanovsky and Wagner, 1998; Houghton et al., 1999; Lai et al., 1999; Paustian et al., 1997a; Paustian et al., 1997b). A means of estimating changes in terrestrial carbon storage at a national level is required to fulfill U.S. obligations under the United Nations Framework Convention on Climate Change (UNFCCC; UNFCCC, 1995). Furthermore, an accurate and defensible estimate of carbon storage in agricultural cropland soils is critical for the development of effective U.S. agricultural and environmental policies and strategies. The Intergovernmental Panel on Climate Change (IPCC) has developed a standardized inventory approach for monitoring greenhouse gas emissions (IPCC, 1997a). The approach was developed to be usable by any of the signatory nations of the UNFCCC. These include many developing countries in which data on land use and management and soil resources are limited.
