Estimating CO2 flux of croplands for bottom-up carbon budgeting

Agricultural crops play a significant role in the diurnal and seasonal cycle of atmosphericCO2 over the growing season. The evolution of CO2 flux over space and timefor various crops need to be determined for establishing any (mid-)continental atmosphericCO2 budget as it is intended to be done in the North American Carbon Program.Flux towers and the ancillary measurements are critical for regional analysis andunderstanding of dynamics of CO2 and energy exchange. They provide ground-truthdata for remote sensing observations, information for verifying process-based modelsand for interpreting aircraft and tall tower concentration measurements. Several instrumentedtowers are monitoring CO2 and energy fluxes from agricultural crops suchas corn, wheat, soybean, sugar beet, rape seed, and rice paddies for various locationsthrough networks such as Ameriflux, CarboEurope, and Japanflux. Our objectives are(i) to prepare an exhaustive inventory of the eddy flux measurements carried out (pastand present) reporting the crop types, agro-climatic conditions, soil type and slope,management practices and type of measurements (fluxes and the so-called ancillaryones) along with any relevant methodological problems encountered in flux measurementsabove short canopy crop and (ii) to compare different temporal series (30-min,daily, 10 days) of flux measurements acquired through the growing season in order tostress the commonalities and the differences in the functional response of the variouscrops in relation to climate, and management practices.