Regional uptake and release of crop carbon in the United States.

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 into 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 Crescent, Northern Great Plains, and Mississippi Portal regions. The national crop carbon budget was balanced to within 93 to 99% yr^-1 of total carbon uptake during the period of this analysis. [ABSTRACT FROM AUTHOR]