Abstract
Net annual soil carbon change, fossil fuel emissions from cropland production, and cropland net primary productivity were estimated and spatially distributed using land cover defined by the Moderate Resolution Imaging Spectroradiometer (MODIS) and by the Cropland Data Layer (CDL). Spatially resolved estimates of net ecosystem exchange (NEE) and net ecosystem carbon balance (NECB) were developed. 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 (~1km2) land cover data were generated for the conterminous US and compared with higher resolution (30m) estimates of NEE and with direct measurements of CO2 flux from croplands in Illinois and Nebraska. Estimates of NEE using the CDL (30m 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 US croplands were -274 and 7 Tg C yr-1 for 2004, respectively. Use of moderate to high resolution satellite-based land cover data enables improved estimates of cropland carbon dynamics.
