A practical approach for estimating the red edge position of plant leaf reflectance

The point of maximum slope on the reflectance spectrum of a plant leaf between red and near-infrared wavelengths is known as the red edge position (REP). The REP is strongly correlated with foliar chlorophyll content, and hence it provides a very sensitive indicator for a variety of environmental factors affecting leaves such as stress, drought and senescence. The REP is also present in spectra for vegetation recorded by remote sensing methods. Due to its importance for the application of inversion procedures, a number of techniques have been developed for determining the REP for foliar spectral reflectance. In this paper a new approach is proposed. It allows an unsupervised estimation of the REP. The accuracy of the new approach is evaluated by comparing REP estimates with values derived from measured spectral data for woody and herbaceous species available in the LOPEX (Leaf Optical Properties Experiment) database.