Effects of leaf water content on reflectance

Abstract

The aim of this project was to study how the reflectance spectra of leaves were affected by water content. Reflectance spectra of leaves were measured using a portable field spectrometer (ASD FieldSpecPro). The leaf water content was measured in the laboratory by measuring the fresh weight and the dry weight after heating in an oven. The leaf reflectance at several stages of drying was measured to determine the change in reflectance due to decreasing water content. The reflectance spectra were analyzed to determine specific spectra features that correlate well with the equivalent water thickness (EWT). The wavelengths that have high correlation with EWT are near the green peak at 550 nm, near the red edge at 730 nm and the water absorption band at 1440 nm. Correlation with EWT can be improved when ratios of reflectance at wavelengths where there is high correlation with EWT are taken. The results are useful in developing non-destructive methods of determining the water content of leaves.