Can Canopy Radiometric Temperature Be Used as an Alternate of Air Temperature to Predict Ecosystem Carbon Fluxes

Net ecosystem carbon dioxide (CO₂) exchange (NEE) and ecosystem respiration (R_eco) were determined in an alfalfa (Medicago sativa L) crop in Taiyuan basin, Shanxi province of China, using the closed chamber technique. Gross primary production (GPP) was calculated as the sum of NEE and R_eco. The results showed that the coefficients of determination (r²) of the GPP and NEE with canopy radiometric temperature (T_c) were significantly higher than those with air temperature (T_a) on diurnal scales. The R_eco was closely correlated to both Ta and Tc on all measurement dates on a diurnal scale. The coefficients of determination (r²) values between R_eco and T_s were lower than those between R_eco and both T_a and T_c on diurnal scale. Those results suggest that at the plot scale T_c is a better predict factor for ecosystem carbon fluxes estimate than both T_a and T_s are. Those results give us some implications for linking remotely sensed infrared temperature of canopy to ecosystem carbon flux estimate.