Regional uptake and release of crop carbon in the United States
1Joint Global Change Research Institute, Pacific Northwest National Laboratory and University of Maryland, College Park, MD 20740, USA
2Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
3Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO 80523, USA
Abstract. Carbon fixed by agricultural crops in the US creates regional CO2 sinks where it is harvested and regional CO2 sources where it is released back to the atmosphere. The quantity and location of these fluxes differ depending on the annual supply and demand of crop commodities. Data on the harvest of crop biomass, storage, import and export, and on the use of biomass for food, feed, fiber, and fuel were compiled to estimate an annual crop carbon budget for 2000 to 2008. With respect to US Farm Resource Regions, net sources of CO2 associated with the consumption of crop commodities occurred in the Eastern Uplands, Southern Seaboard, and Fruitful Rim regions. Net sinks associated with the production of crop commodities occurred in the Heartland, Northern Great Plains, and Mississippi Portal regions. The national crop carbon budget was balanced to within 0.3 to 6.1 % yr−1 during the period of this analysis.