County-level Estimates for Carbon Distribution in U.S. Croplands, 1990-2005

Tristram O. West
Environmental Sciences Division, Oak Ridge National Laboratory

Net Primary Productivity (NPP) for croplands can be estimated using a statistical method that includes factors for dry weight, harvest indices, and root:shoot ratios multiplied by yield data from the National Agricultural Statistics Service (NASS). This method has been documented and published by Prince et al. (2001), Hicke and Lobell (2004), and Hicke et al. (2004). We expanded this method by including factors for more crops and by using an estimated carbon content of 0.45 for agricultural crops to estimate (a) total net carbon uptake, (b) carbon in aboveground biomass, (c) carbon in belowground biomass, (d) carbon harvested and transported off site, and (e) the amount of carbon remaining on the surface following harvest. These five variables are included with their respective Federal Information Processing Standards (FIPS) codes for all counties in the contiguous U.S. from 1990-2005. A mean harvest efficiency of 0.95 was assumed across all crops. Total cropland NPP for the U.S. ranges from 378-527 Tg C yr^-1 within years 1990-2005, and total carbon harvested and removed ranges from 161-228 Tg C yr^-1 within years 1990-2005.

Users of these data are encouraged to read papers cited above and listed in the reference section. These papers provide information on the initial collection and analysis of USDA-NASS data and on data gaps and potential errors in the NASS data.

Data are provided in two file formats. A comma-delimited format (CSV) is provided for use with common spreadsheet software. An ArcGIS shapefile (SHP) is provided for spatial delineation of the county data within GIS software. Shapefiles consist of six separate files, all of which are provided as a single zip file.

Metadata:	Web page	PDF file
Legend:	Web page	PDF file

Cropland carbon for years 1990-1995:
CSV (663Kb)		Excel (1.34Mb)		ArcGIS (1.17Mb)
Cropland carbon for years 1996-2000:
CSV (558Kb)		Excel (1.13Mb)		ArcGIS (1.11Mb)
Cropland carbon for years 2001-2005:
CSV (551Kb)		Excel (1.11Mb)		ArcGIS (1.11Mb)

References

• Brady, N.C. and R.R. Weil. 1996. The nature and properties of soils. 11th edition. Prentice-Hall, Inc., Upper Saddle River, New Jersey.
• Hicke, J.A. and D.B. Lobell. 2004. Spatiotemporal patterns of cropland area and net primary production in the central United States estimated from USDA agricultural information. Geophysical Research Letters 31, L20502, doi:10.1029/2004GL020927,2004.
• Hicke, J.A., D.B. Lobell, and G.P. Asner. 2004. Cropland area and net primary production computer from 30 years of USDA Agricultural Harvest Data. Earth Interactions 8, Paper No. 10.
• Prince, S.D., J. Haskett, M. Steininger, H. Strand, and R. Wright. 2001. Ecological Applications 11(4): 1194-1205.