title: Cropland carbon fluxes in the United States: increasing geospatial resolution of inventory-based carbon accounting.
abstract: Net annual soil carbon change, fossil fuel emissions from cropland production, and cropland net primary production were estimated and spatially distributed using land cover defined by NASA's moderate resolution imaging spectroradiometer (MODIS) and by the USDA National Agricultural Statistics Service (NASS) cropland data layer (CDL). Spatially resolved estimates of net ecosystem exchange (NEE) and net ecosystem carbon balance (NECB) were developed. The purpose of generating spatial estimates of carbon fluxes, and the primary objective of this research, was to develop a method of carbon accounting that is consistent from field to national scales. NEE represents net on-site vertical fluxes of carbon. NECB represents all on-site and off-site carbon fluxes associated with crop production. Estimates of cropland NEE using moderate resolution (approximately 1 km2) land cover data were generated for the conterminous United States and compared with higher resolution (30-m) estimates of NEE and with direct measurements of CO2 flux from croplands in Illinois and Nebraska, USA. Estimates of NEE using the CDL (30-m resolution) had a higher correlation with eddy covariance flux tower estimates compared with estimates of NEE using MODIS. Estimates of NECB are primarily driven by net soil carbon change, fossil fuel emissions associated with crop production, and CO2 emissions from the application of agricultural lime. NEE and NECB for U.S. croplands were -274 and 7 Tg C/yr for 2004, respectively. Use of moderate- to high-resolution satellite-based land cover data enables improved estimates of cropland carbon dynamics.
authors.affiliation: Environmental Sciences Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6335, USA. westto@ornl.gov
authors.forename: Tristram O
authors.initials: TO
authors.lastname: West
authors.forename: Craig C
authors.initials: CC
authors.lastname: Brandt
authors.forename: Latha M
authors.initials: LM
authors.lastname: Baskaran
authors.forename: Chad M
authors.initials: CM
authors.lastname: Hellwinckel
authors.forename: Richard
authors.initials: R
authors.lastname: Mueller
authors.forename: Carl J
authors.initials: CJ
authors.lastname: Bernacchi
authors.forename: Varaprasad
authors.initials: V
authors.lastname: Bandaru
authors.forename: Bai
authors.initials: B
authors.lastname: Yang
authors.forename: Bradly S
authors.initials: BS
authors.lastname: Wilson
authors.forename: Gregg
authors.initials: G
authors.lastname: Marland
authors.forename: Richard G
authors.initials: RG
authors.lastname: Nelson
authors.forename: Daniel G
authors.initials: DG
authors.lastname: De la Torre Ugarte
authors.forename: Wilfred M
authors.initials: WM
authors.lastname: Post
mesh_terms: D000383:Agriculture; D018533:Biomass; D002244:Carbon; D005579:Fossil Fuels; D012987:Soil; D014481:United States
chemical_list: D005579:Fossil Fuels; D012987:Soil; D002244:Carbon