Using Reflectance Measurements to Determine Light use Efficiency in Corn

This study examines the ability of narrow band vegetation indexes to detect spectral changes associated with stress and relate them to light use efficiency (LUE) over the course of a day as well as through the growing season. In a corn field in Beltsville, MD, carbon flux measurements were made at a flux tower using eddy covariance techniques. At this site on six days during the 2007 growing season hyperspectral reflectance measurements were collected at hourly intervals. LUE was determined at the time of the reflectance measurements from carbon fluxes measured at the flux tower. The measured LUE values were compared with a number of spectral indices that have been shown to be related to a number of leaf characteristics including: the status of the xanthophyll cycle; solar induced fluorescence; leaf water content; and concentrations of pigments such as chlorophyll, carotenoids, and anthocyanins. We found that several of these indices provide good estimates of both diurnal and seasonal LUE variability.